Search

Our objective was to determine the impact of rate of overwinter gain in March-born yearling heifers on pre- and post-breeding growth rates and reproductive performance. Red Angus x Simmental crossbred beef heifers [n = 182; weaning body weight (BW) = 242 kg ± 23 kg] were utilized in a 3-yr study conducted at the University of Nebraska, Gudmundsen Sandhills Laboratory (GSL) near Whitman, NE. Using 3-d BW averages collected in January, heifers were stratified by BW and randomly assigned to one of two treatments: 1) to achieve a low overwinter rate of gain at 0.34 kg/d (LO, n = 106), or 2) to achieve a high overwinter rate of gain at 0.68 kg/d (HI, n = 76). To achieve gains, heifers were managed together and had individual access to a dried distillers grain supplement via a C-lock Smart Feeder (Rapid City, SD). Each year, treatments were initiated in January and ended in May (111 ± 4 d). Heifer BW was collected at the start of trial (January), end of the trial (May), pre-breeding (May), pregnancy diagnosis (October), and pre-calving (February). Heifer body condition score (BCS) was collected at pregnancy diagnosis (October) and pre-calving (February; Yr 1 and 2). Before the breeding season, two blood samples were collected 10-d apart via coccygeal venipuncture to determine the percentage of heifers cycling. At breeding, HI-fed heifers had a greater (P < 0.01) BW than LO-fed heifers (813 and 788 kg, respectively; Table 1). However, heifer BW at pregnancy diagnosis and precalving were not impacted (P ≥ 0.16) by supplemental treatment. Additionally, there were no differences (P ≥ 0.16) in BCS at pregnancy diagnosis and pre-calving among treatments. Furthermore, rate of gain did not influence (P ≥ 0.38) the percent pubertal prior to the breeding season, pregnancy rates, or the percent that calved in the first 21-d of the calving season. Moreover, rate of gain did not impact (P = 0.89) subsequent calf BW at birth. There was a significant treatment x year interaction (P < 0.01) for subsequent calving date, where HI treatment heifers calved 7-d earlier than LO treatment heifers in Yr 1. This study implies that producers can develop heifers at a less overwinter rate of gain without impacting reproductive performance or subsequent calf birth weight. [ABSTRACT FROM AUTHOR]

Reproductive performance is the most critical factor affecting production efficiency in the cow-calf industry. Heifers with low reproductive efficiency may fail to become pregnant during the breeding season or maintain a pregnancy. The cause of reproductive failure often remains unknown, and the non-pregnant heifers are not identified until several weeks after the breeding season. Therefore, improving heifer fertility utilizing genomic information has become increasingly important. One approach is using microRNAs (miRNA) in the maternal blood that play an important role in regulating the target genes underlying pregnancy success and thereby in selecting reproductively efficient heifers. Therefore, the current study hypothesized that miRNA expression profiles from peripheral white blood cells (PWBC) at weaning could predict the future reproductive outcome of beef heifers. To this end, we measured the miRNA profiles using small RNA-sequencing in Angus-Simmental crossbred heifers sampled at weaning and retrospectively classified as fertile (FH, n = 7) or subfertile (SFH, n = 7). In addition to differentially expressed miRNAs (DEMIs), their target genes were predicted from TargetScan. The PWBC gene expression from the same heifers were retrieved and co-expression networks were constructed between DEMIs and their target genes. We identified 16 differentially expressed miRNAs between the groups (p-value =0.05 and absolute (log2 fold change =0.05)). Interestingly, based on a strong negative correlation identified from miRNA-gene network analysis with PCIT (partial correlation and information theory), we identified miRNA-target genes in the SFH group. Additionally, TargetScan predictions and differential expression analysis identified bta-miR-1839 with ESR1, bta-miR-92b with KLF4 and KAT2B, bta-miR-2419-5p with LILRA4, bta-miR-1260b with UBE2E1, SKAP2 and CLEC4D, and bta-let-7a-5p with GATM, MXD1 as miRNA-gene targets. The miRNA-target gene pairs in the FH group are over-represented for MAPK, ErbB, HIF-1, FoxO, p53, mTOR, T-cell receptor, insulin and GnRH signaling pathways, while those in the SFH group include cell cycle, p53 signaling pathway and apoptosis. Some miRNAs, miRNA-target genes and regulated pathways identified in this study have a potential role in fertility; other targets are identified as novel and need to be validated in a bigger cohort that could help to predict the future reproductive outcomes of beef heifers. [ABSTRACT FROM AUTHOR]

Reproductive failure is a major contributor to inefficiency within the cow-calf industry. Particularly problematic is the inability to diagnose heifer reproductive issues prior to pregnancy diagnosis following their first breeding season. Therefore, we hypothesized that gene expression from the peripheral white blood cells at weaning could predict the future reproductive potential of beef heifers. To investigate this, the gene expression was measured using RNA-Seq in Angus–Simmental crossbred heifers sampled at weaning and retrospectively classified as fertile (FH, n = 8) or subfertile (SFH, n = 7) after pregnancy diagnosis. We identified 92 differentially expressed genes between the groups. Network co-expression analysis identified 14 and 52 hub targets. ENSBTAG00000052659, OLR1, TFF2, and NAIP were exclusive hubs to the FH group, while 42 hubs were exclusive to the SFH group. The differential connectivity between the networks of each group revealed a gain in connectivity due to the rewiring of major regulators in the SFH group. The exclusive hub targets from FH were over-represented for the CXCR chemokine receptor pathway and inflammasome complex, while for the SFH, they were over-represented for immune response and cytokine production pathways. These multiple interactions revealed novel targets and pathways predicting reproductive potential at an early stage of heifer development. [ABSTRACT FROM AUTHOR]

Herein, we evaluated the hepatic lipid metabolic profiles of bovine fetuses in response to maternal vitamin and mineral supplementation (VMSUP; supplemented (VTM) or not (NoVTM)) and two different rates of gain (GAIN; low gain (LG), 0.28 kg/d, or moderate gain (MG), 0.79 kg/d). Crossbred Angus heifers (n = 35; initial BW = 359.5 ± 7.1 kg) were randomly assigned to a 2 × 2 factorial arrangement, resulting in the following treatment combinations: NoVTM-LG (n = 9), NoVTM-MG (n = 9), VTM-LG (n = 9), and VTM-MG (n = 8). Heifers received their treatments until d 83 of gestation, when they were ovariohysterectomized. Fetuses were harvested and liver samples were analyzed via ultrahigh-performance liquid chromatography–tandem mass spectroscopy to characterize lipid profiles and abundances. We identified 374 biochemicals/metabolites belonging to 57 sub-pathways of the lipid metabolism super-pathway. The majority of the biochemicals/metabolites (n = 152) were significantly affected by the main effect of GAIN. Maternal moderate rates of gain resulted in greater abundances (p ≤ 0.0001) of ω-3 fatty acids (eicosapentaenoate, docosapentaenoate, and docosahexaenoate) and lower abundances (p ≤ 0.0001) of ω-6 fatty acids. Further, MG resulted in the accumulation of several diacylglycerols and depletion of the majority of the monoacylglycerols. Concentrations of nearly all acylcarnitines (p ≤ 0.03) were decreased in VTM-LG fetal livers compared to all other treatment combinations, indicating a greater rate of complete oxidation of fatty acids. Levels of secondary bile acids were impacted by VMSUP, being greater (p ≤ 0.0048) in NoVTM than in VTM fetal livers. Moreover, NoVTM combined with lower rate of gain resulted in greater concentrations of most secondary bile acid biochemicals/metabolites. These data indicate that maternal diet influenced and altered fetal hepatic lipid composition in the first trimester of gestation. Maternal body weight gain exerted a greater influence on fetal lipid profiles than vitamin and mineral supplementation. Specifically, lower rate of gain (0.28 kg/d) resulted in an increased abundance of the majority of the biochemicals/metabolites identified in this study. [ABSTRACT FROM AUTHOR]

Reproductive performance is the most critical factor affecting production efficiency in the cow-calf industry. Heifers with low reproductive efficiency may fail to become pregnant during the breeding season or maintain a pregnancy. The cause of reproductive failure often remains unknown, and the non-pregnant heifers are not identified until several weeks after the breeding season. Therefore, improving heifer fertility utilizing genomic information has become increasingly important. One approach is using microRNAs (miRNA) in the maternal blood that play an important role in regulating the target genes underlying pregnancy success and thereby in selecting reproductively efficient heifers. Therefore, the current study hypothesized that miRNA expression profiles from peripheral white blood cells (PWBC) at weaning could predict the future reproductive outcome of beef heifers. To this end, we measured the miRNA profiles using small RNA-sequencing in Angus-Simmental crossbred heifers sampled at weaning and retrospectively classified as fertile (FH, n = 7) or subfertile (SFH, n = 7). In addition to differentially expressed miRNAs (DEMIs), their target genes were predicted from TargetScan. The PWBC gene expression from the same heifers were retrieved and co-expression networks were constructed between DEMIs and their target genes. We identified 16 differentially expressed miRNAs between the groups (p-value ≤0.05 and absolute (log2 fold change ≥0.05)). Interestingly, based on a strong negative correlation identified from miRNA-gene network analysis with PCIT (partial correlation and information theory), we identified miRNA-target genes in the SFH group. Additionally, TargetScan predictions and differential expression analysis identified bta-miR-1839 with ESR1, bta-miR-92b with KLF4 and KAT2B, bta-miR-2419-5p with LILRA4, bta-miR-1260b with UBE2E1, SKAP2 and CLEC4D, and bta-let-7a-5p with GATM, MXD1 as miRNA-gene targets. The miRNA-target gene pairs in the FH group are over-represented for MAPK, ErbB, HIF-1, FoxO, p53, mTOR, T-cell receptor, insulin and GnRH signaling pathways, while those in the SFH group include cell cycle, p53 signaling pathway and apoptosis. Some miRNAs, miRNA-target genes and regulated pathways identified in this study have a potential role in fertility; other targets are identified as novel and need to be validated in a bigger cohort that could help to predict the future reproductive outcomes of beef heifers.

Fall-calving primiparous crossbred beef females [body weight (BW): 451 ± 28 (SD) kg; body condition score (BCS): 5.4 ± 0.7] were allocated by fetal sex and expected calving date to receive either 100% (control; CON; n = 13) or 70% (nutrient restricted; NR; n = 13) of metabolizable energy and metabolizable protein requirements for maintenance, pregnancy, and growth from day 160 of gestation to calving. Heifers were individually-fed chopped poor quality hay and supplemented to meet targeted nutritional planes based on estimated hay intakes. Dam BW, BCS, backfat, and metabolic status were determined pre-treatment, every 21 d (BW and metabolic status) or 42 d (BCS and backfat) during gestation, and post-calving. At birth, calf BW and size were measured, and total colostrum from the most full rear quarter was collected pre-suckling. Data were analyzed with nutritional plane, treatment initiation date, and calf sex (when P < 0.25) as fixed effects. Gestational metabolites included day and nutritional plane × day as repeated measures. During late gestation, CON dams gained (P < 0.01) maternal (non-gravid) BW and maintained (P ≥ 0.17) BCS and backfat, while NR dams lost (P < 0.01) maternal BW, BCS, and backfat. Circulating glucose, urea N, and triglycerides were less (P ≤ 0.05) in NR dams than CON at most late gestational timepoints after treatment initiation. Circulating non-esterified fatty acids were greater (P < 0.01) in NR dams than CON. Post-calving, NR dams weighed 63.6 kg less (P < 0.01) and were 2.0 BCS less (P < 0.01) than CON. At 1 h post-calving, NR dams had less (P = 0.01) plasma glucose and tended to have less (P = 0.08) plasma triglycerides than CON. Nutrient restriction did not affect (P ≥ 0.27) gestation length, calf birth weight, or calf size at birth. Colostrum yield was 40% less (P = 0.04) in NR dams than CON. Protein and immunoglobulin concentrations were greater (P ≤ 0.04), but free glucose and urea N concentrations were less (P ≤ 0.03), in colostrum of NR dams than CON. Colostrum total lactose, free glucose, and urea N were less (P ≤ 0.03) in NR dams than CON, but total protein, triglycerides, and immunoglobulins were not affected (P ≥ 0.55). In summary, beef heifers experiencing late gestational nutrient restriction prioritized partitioning nutrients to fetal growth and colostrum production over maternal growth. During undernutrition, fetal and colostral nutrient demands were largely compensated for by catabolism of maternal tissue stores. [ABSTRACT FROM AUTHOR]

This experiment investigated the effects of diet composition on rumen, vaginal, and uterine microbiota of beef heifers. Fifteen rumen-cannulated, pubertal Angus-influenced heifers were used in a replicated 3 × 3 Latin square design (28-d periods and 21-d washout intervals). Dietary treatments included diets based on (as-fed) 100% grass hay (HF), 60% grass hay + 40% corn-based concentrate (INT), or 25% grass hay + 75% corn-based concentrate (HG). Treatments were offered individually to heifers once daily at 2% body weight. Rumen, vaginal, and uterine samples were collected on days 0 and 28 of each period. Data were analyzed using orthogonal contrasts (linear and quadratic), using results from day 0 as independent covariates and heifer as the experimental unit. Ruminal pH on day 28 decreased linearly (P < 0.01) as concentrate inclusion increased. Uterine and vaginal pH on day 28 were not affected by treatments (P ≥ 0.35). Within the rumen samples, Bacteriodetes was the most abundant phylum and its relative abundance linearly decreased (P ≤ 0.01) with the inclusion of concentrate. Prevotella was the most abundant genus within the rumen but was not affected by treatments (P ≥ 0.44). Genera with relative abundance ≥1% (average across treatments) in the rumen that were impacted by treatments (P ≤ 0.01) included Bacteroides , Pedobacter , Dysgonomonas , Caloramator, and Ruminococcus. Firmicutes was the most abundant phylum in the vagina and uterus, but it was unaffected by treatments (P ≥ 0.16). Prevotella was the most abundant genus in the vagina, and its relative abundance increased (P < 0.01) with the inclusion of concentrate. Other genera with relative abundance ≥1% that were significantly affected (P ≤ 0.05) by treatments were Clostridium, Pedobacter , Roseburia, Oscillospira, Faecalibacterium, Caloramator, Paludibacter, Rhodothermus, and Porphyromonas. In uterine samples , Prevotella was the most abundant genus but was unaffected by treatments (P ≥ 0.29). Genera with relative abundance ≥1% in the uterus that were significantly affected (P < 0.01) by treatments were Caloramator , Paludibacter , and Thalassospira. Collectively, inclusion of concentrate in the diet altered the bacterial composition within the rumen as well as shifting bacterial populations within the vagina and uterus. Research is warranted to further understand the impacts of these diet-induced microbiota changes on reproductive function and performance of beef heifers. [ABSTRACT FROM AUTHOR]

Our objectives were to determine the impact rumen undegradable protein (RUP) supplementation prior to and during the breeding season had on growth rates and reproductive performance in May-born yearling range heifers. This study was conducted over a 3-yr period at the University of Nebraska, Gudmundsen Sandhills Laboratory (GSL) near Whitman, NE and utilized May-born Red Angus x Simmental crossbred heifers [n = 192; weaning body weight (BW) = 200 kg ± 28 kg]. Heifers were randomly assigned by pre-breeding BW to one of two treatments: 1) received 0.908 kg of a dried distillers grain supplement (DDGS; Supp, n = 66) pre-breeding through the breeding season or 2) received no supplement (NoSupp, n = 138). Each year, treatments were initiated in July and ended in August (55 ± 3 d). Using a C-Lock Smart Feeder (Rapid City, SD) heifers had individual access to their allotted DDGS supplementation. On average, NoSupp heifers consumed 0.09 kg/d (yr 1) and 0.02 kg/d (yr 2 and 3); whereas, Supp heifers averaged 0.59, 0.74, and 0.76 kg/d in yr 1, 2, and 3, respectively. Heifer BW was collected pre-trial (May), pre-breeding (July), breeding (August), pregnancy diagnosis (October), and pre-calving (April). Body condition score (BCS) was collected at pregnancy diagnosis (October) and pre-calving (April; Yr 1 and 2). Before each breeding season, two blood samples were collected 10 d apart to determine pubertal status. Heifers were synchronized with a single 5 mL intramuscular injection of prostaglandin F2 alpha (Lutalyse, Zoetis, Parsippany, NJ) 5 d after bull turnout during a 30 d natural service breeding season. Pregnancy diagnosis was determined via rectal ultrasound in October. No differences (P > 0.12) in BW were noted among treatments for all measurement timepoints. Moreover, SUPP heifers had greater (P < 0.02) average daily gain (ADG) from pretrial to pregnancy diagnosis compared with NoSUPP heifers. However, there was no differences (P = 0.11) in ADG from pregnancy diagnosis to pre-calving. At pregnancy diagnosis (October), a treatment x year interaction (P = 0.02) for BCS was present where Supp heifers had a greater BCS than NoSupp heifers in yr 3. Heifer BCS pre-calving was not affected (P = 0.12) by treatment. There was a greater percentage (P < 0.01) of SUPP heifers cycling compared with NoSUPP heifers. However, there were no differences (P > 0.24) in pregnancy rates, the percentage that calved in the first 21 d, calf birth BW, or subsequent calving date. Ultimately, this study implies that providing a RUP supplement prior to and during the breeding season will increase the percentage of heifers that are cycling before breeding and have a greater ADG through pregnancy diagnosis; however, supplementation will not impact other reproductive parameters or BW gains. [ABSTRACT FROM AUTHOR]

Heifer reproduction management research is being conducted at the NDSU–Dickinson Research Extension Center. Using crossbred heifers, the objective was to evaluate reproductive performance and economic efficiencies comparing a drylot synchronized fixed-time AI protocol with clean-up bulls to two grazing systems using a fixed-time AI protocol without clean-up bulls. Synchronization protocol:14-d CIDR-PG-GnRH (TAI 66 h ± 2 h). Fixed-time AI treatments: 1) Drylot Control (DLOT) with clean-up bulls, 2) Integrated diverse crop-heifer annual forage grazing (IAF, no clean-up bulls), and 3) Native range grazing (NR, no clean-up bulls). Following pregnancy ultrasound on d 85, non-pregnant heifers continued to bale-graze until late November, when they were transferred to the University of Wyoming SAREC feedlot, finished, harvested at Cargill Meat Solutions packing plant, Ft. Morgan, CO, and grid marketed. Data were analyzed using the MIXED procedure of SAS. Year 1 and 2 grazing days were 121, and 149, respectively. Synchronized TAI pregnancy rates yr 1 and 2 for DLOT, IAF, and NR were 59.4, 43.8, and 62.5%; 68.8, 46.9, and 34.4%, respectively. Total DLOT control pregnancy rates yr 1 and 2 were 90.6 and 100%. Grazing heifer feedlot performance Yr 1 did not differ for starting body weight (BW; 452 vs 436 kg, P = 0.29), ending BW (610 vs 600 kg, P = 0.74), gain (157 vs 164 kg, P = 0.69), average daily gain (ADG; 1.42 vs 1.48 kg, P = 0.70), dry matter (DM) feed intake (15.0 vs 14.7 kg, P = 0.73), F:G (4.81 vs 4.56 kg, P = 0.42), daily feed cost ($7.45 vs $9.47, P = 0.73), feed cost/ kg BW gain ($3.11 vs $2.95, P = 0.51), and feed and yardage cost ($3.41 vs $3.24, P = 0.55). Year 2 grazing heifer feedlot performance for the IAF and NR were starting BW (501 vs 456 kg, P = 0.007), ending BW (670 vs 604 kg, P = 0.004), feedlot finishing gain (143 vs 123 kg, P = 0.05), ADG (1.08 vs 0.93 kg/day, P = 0.06), daily DM feed intake (20.1 vs 20.1 kg/d, P = 0.98), feed to gain ratio (7.13 vs 8.22 kg/d, P = 0.11), daily feed cost ($9.61 vs $9.54/d, P = 0.94), feed cost/ kg BW gain ($4.05 vs $4.67/kg, P = 0.11), and feed and yardage cost/kg gain ($4.45 vs $5.13/kg, P = 0.092). IAF and NR Yr 1 HCW (P = 0.83), dressing % (P = 0.69), marbling score (P = 0.78) did not differ. Year 2, except for hot carcass weight (HCW; 379 vs 341 kg, P = 0.004), dressing pct (P = 0.99), fat depth (P = 0.29), marbling score (P = 0.94) did not differ. Systems 2-yr mean net return for DLOT, IAF, and NR were $592, $296, $379, respectively. Systems net return profitability was very good for all management comparisons, but reduced for IAF and NR due to IAF farming, finishing, and transportation costs, and NR finishing and transportation costs. [ABSTRACT FROM AUTHOR]

Genome-wide association studies (GWAS) have accelerated the identification of functional trait loci in cattle and identified single nucleotide polymorphisms (SNPs) in candidate genes associated with fertility and production traits in high milk yield dairy cattle. The fertility of Hanwoo (Korean native beef cattle) has declined after the adaptation of a selection program for high quantity and quality meat. However, there are few GWAS studies of fertility in beef cattle. We performed a genome-wide association study of 40 Korean native beef cattle heifers with imputed 770 K genotype and identified 12 significant SNPs within seven regions on three chromosomes (BTA 8, BTA 16 and BTA 24) associated with services per conception (SPC). Five SNPs were located in the ABCA1, BRINP3 and ESRRG genes, which are involved in early embryo development. In addition, 27 proximal genes were identified within 1 Mb of the candidate SNPs, which are involved in muscle cell differentiation and muscle structure development. However, we did not find any previously reported SNPs related to fertility in Holstein cows. Taken together, we identified SNPs associated with SPC and their proximal genes using gene-based analysis and the candidates were different from SNPs associated with subfertility of dairy cattle. [ABSTRACT FROM AUTHOR]

Simple Summary: Developing and raising replacement beef heifers requires a large capital investment for producers. Therefore, it is imperative to discover traits and management practices to eliminate subfertile heifers prior to breeding and pregnancy determination. In this study, four years of data was analyzed from a centralized heifer development yard in the Midwest of the United States. The objective of this study was to analyze various heifer physical characteristics and management practices in order to quantify their impact on pregnancy and date of conception. Physical measurements can be used to improve the ability to select and develop heifers for improved reproductive longevity. Veterinarians have an opportunity to work with their clients to utilize this information to select replacements that fit the ranch environment. This should result in increased reproductive efficiency and cost optimization for the replacement heifer enterprise. Developing and raising replacement heifers requires a large capital investment for producers. Therefore, it is imperative to discover traits and management practices to eliminate subfertile heifers prior to breeding and pregnancy determination. In this study, four years of data was analyzed from a centralized beef heifer development yard in the Midwest of the United States. The objective of this study was to analyze various heifer physical characteristics and management practices in order to quantify their impact on pregnancy and date of conception. Logistic regression models were built to investigate risk factors associated with conception to artificial insemination (AI), pregnancy by natural service after AI exposure, and pregnancy in the first 21-days of the breeding season. Age at entry, average daily gain from entry to breeding, pelvic width, and year were associated with AI pregnancy (p < 0.05). On the second model, average daily gain from entry to yearling weight, weight at breeding, weight at pregnancy diagnosis, and age at AI were significantly associated with pregnancy. There were no associations with reproductive tract score with any of the response variables analyzed. These results indicate there are physical measurements that can be used to improve the ability to select and develop heifers for improved reproductive performance. [ABSTRACT FROM AUTHOR]

Reproductive failure remains a significant challenge to the beef industry. The omics technologies have provided opportunities to improve reproductive efficiency. We used a multistaged analysis from blood profiles to integrate metabolome (plasma) and transcriptome (peripheral white blood cells) in beef heifers. We used untargeted metabolomics and RNA-Seq paired data from six AI-pregnant (AI-P) and six nonpregnant (NP) Angus-Simmental crossbred heifers at artificial insemination (AI). Based on network co-expression analysis, we identified 17 and 37 hub genes in the AI-P and NP groups, respectively. Further, we identified TGM2, TMEM51, TAC3, NDRG4, and PDGFB as more connected in the NP heifers' network. The NP gene network showed a connectivity gain due to the rewiring of major regulators. The metabolomic analysis identified 18 and 15 hub metabolites in the AI-P and NP networks. Tryptophan and allantoic acid exhibited a connectivity gain in the NP and AI-P networks, respectively. The gene–metabolite integration identified tocopherol-a as positively correlated with ENSBTAG00000009943 in the AI-P group. Conversely, tocopherol-a was negatively correlated in the NP group with EXOSC2, TRNAUIAP, and SNX12. In the NP group, α-ketoglutarate-SMG8 and putrescine-HSD17B13 were positively correlated, whereas a-ketoglutarate-ALAS2 and tryptophan-MTMR1 were negatively correlated. These multiple interactions identified novel targets and pathways underlying fertility in bovines. [ABSTRACT FROM AUTHOR]

Our aim was to investigate the effects of maternal (F0) body weight (BW) gain during the first 84 d of gestation on body composition, ovarian reserve, and hormonal and metabolic parameters of breeding-age F1 heifers, as well as the body weight and morphometry of F2 fetuses. The study also evaluated the effect of maternal body weight gain (F0) on the mRNA relative abundance of the small intestine of both F1 heifers and F2 fetuses. Crossbred Angus heifers (F0; n = 100) were managed to gain 0.20 kg/d (low gain [LG], n = 50) or 0.75 kg/d (moderate gain [MG], n = 50) for the first 84 d of gestation. Subsequently, F0 dams were managed on a common forage-based diet for the rest of gestation until the weaning of the F1 offspring. At 15 months of age a subset of F1 heifers was randomly selected for the current experiment (n = 8 LG and n = 8 MG). Heifers were bred via artificial insemination (AI; d 0), then harvested on d 84 of gestation. On d -10, 42, and 84, BW was recorded, and blood was collected and analyzed for concentrations of glucose, non-esterified fatty acids, progesterone, insulin, and insulin-like growth factor-1. Weight of F1 carcasses, organs, gravid uteri, and F2 fetuses and organs were recorded at harvest. Visible follicles were counted on F1 ovaries at harvest, and histology was used to count microscopic follicles. Liver and jejunal samples from F1 heifers were collected to measure tissue oxygen consumption and jejunal samples from F1 heifers and F2 fetuses were collected for mRNA relative abundance analysis. Body weight of F1 heifers from MG dams tended to be 12 kg greater (P = 0.06) than for F1 heifers from LG dams. Concentrations of glucose were greater (P = 0.03) in F1 heifers from the MG group, with no differences in other blood metabolites or follicular populations (P ≥ 0.16). Interestingly, mammary glands were heavier (P = 0.05) and placentas and body depth tended to be heavier and greater, respectively (P ≤ 0.10), for F2 fetuses from F0 LG heifers. Oxygen consumption in the liver and jejunum, as well as mRNA relative abundance in the jejunum of F1 heifers, were not affected by F0 rate of gain (P ≥ 0.16). However, the NDUFC1, SDHA, UQCR1, and PPARG genes were upregulated (P ≤ 0.05) in the jejunum of F2 fetuses from the LG group. In conclusion, BW gain of F0 heifers during early gestation exerts subtle effects on pre-breeding BW and blood metabolites in F1 offspring, with impacts present in F2 placenta, mammary gland, and intestine., (© The Author(s) 2024. Published by Oxford University Press on behalf of the American Society of Animal Science. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Simple Summary: Cow-calf operations rely mostly in forage-based systems. Different supplementation strategies are used by beef producers in order to overcome nutrient deficiencies and achieve targeted growth or reproductive performances. This study provides information on the impacts of feeding pregnant replacement heifers with vitamin/mineral and protein/energy supplements on heifer performance and fetal outcomes. Our study shows that moderate rates of gain (achieved via protein/energy supplementation) resulted in fetuses with heavier femurs and reduced liver mass relative to fetal body weight. Moreover, vitamin and mineral supplementation increased fetal liver mass, and vitamin and mineral supplementation combined with moderate gain treatments resulted in greater fetal intestinal weights. These findings indicate that replacement heifer nutrition during early gestation can alter the development of organs in the fetus that are relevant for future offspring performance. Liver and intestines are key organs related to energy metabolism; therefore, this study shows that compensatory mechanisms are in place in the developing conceptus that can alter the growth rate of key metabolic organs possibly in an attempt to increase or decrease energy utilization. Thirty-five crossbred Angus heifers (initial BW = 359.5 ± 7.1 kg) were randomly assigned to a 2 × 2 factorial design to evaluate effects of vitamin and mineral supplementation [VMSUP; supplemented (VTM) vs. unsupplemented (NoVTM)] and different rates of gain [GAIN; low gain (LG), 0.28 kg/d, vs. moderate gain (MG), 0.79 kg/d] during the first 83 d of gestation on dam hormone and metabolic status, fetal tissue and organ mass, and concentration of glucose and fructose in fetal fluids. The VMSUP was initiated 71 to 148 d before artificial insemination (AI), allowing time for mineral status of heifers to be altered in advance of breeding. At AI heifers were assigned their GAIN treatment. Heifers received treatments until the time of ovariohysterectomy (d 83 ± 0.27 after AI). Throughout the experiment, serum samples were collected and analyzed for non-esterified fatty acids (NEFA), progesterone (P4), insulin, and insulin-like growth factor 1 (IGF-1). At ovariohysterectomy, gravid reproductive tracts were collected, measurements were taken, samples of allantoic (ALF) and amniotic (AMF) fluids were collected, and fetuses were dissected. By design, MG had greater ADG compared to LG (0.85 vs. 0.34 ± 0.04 kg/d, respectively; p < 0.01). Concentrations of NEFA were greater for LG than MG (p = 0.04) and were affected by a VMSUP × day interaction (p < 0.01), with greater concentrations for NoVTM on d 83. Insulin was greater for NoVTM than VTM (p = 0.01). A GAIN × day interaction (p < 0.01) was observed for IGF-1, with greater concentrations for MG on d 83. At d 83, P4 concentrations were greater for MG than LG (GAIN × day, p < 0.01), and MG had greater (p < 0.01) corpus luteum weights versus LG. Even though fetal BW was not affected (p ≥ 0.27), MG fetuses had heavier (p = 0.01) femurs than LG, and VTM fetuses had heavier (p = 0.05) livers than those from NoVTM. Additionally, fetal liver as a percentage of BW was greater in fetuses from VTM (P = 0.05; 3.96 ± 0.06% BW) than NoVTM (3.79 ± 0.06% BW), and from LG (p = 0.04; 3.96 ± 0.06% BW) than MG (3.78 ± 0.06% BW). A VMSUP × GAIN interaction was observed for fetal small intestinal weight (p = 0.03), with VTM-MG being heavier than VTM-LG. Therefore, replacement heifer nutrition during early gestation can alter the development of organs that are relevant for future offspring performance. These data imply that compensatory mechanisms are in place in the developing conceptus that can alter the growth rate of key metabolic organs possibly in an attempt to increase or decrease energy utilization. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Animal Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Bacterial communities play major roles in rumen and uterine function toward optimal animal performance and may be affected by changes occurring during heifer development such as nutritional supplementation for optimal growth and the attainment of puberty. The effect of different levels of protein supplementation on ruminal and uterine bacterial communities following weaning was examined through first breeding of heifers. Angus heifers (n = 39) were blocked by initial body weight (BW) and randomly assigned to one of three 163-day (d) crude protein (CP) supplementation diets including control (10% CP, n = 14), 20% CP (n = 11), or 40% CP (n = 14) treatment groups. Growth and development were monitored by body weight, with blood progesterone concentration determined every 14 d to determine pubertal status. Uterine flush and rumen fluid were collected on d 56, 112, and 163 relative to the start of supplementation. Bacterial DNA was extracted from fluid samples, the V1–V3 hypervariable region of the 16S rRNA gene was amplified, and amplicons were sequenced then processed in R 4.1. Statistical analyses were performed in SAS 9.4 with a GLIMMIX procedure utilizing fixed effects of protein, month, pubertal status, and interactions, with random effects including BW, interaction of BW and protein, and heifer within the interaction, and repeated measures of day. In the uterus, pubertal status and day of supplementation affected the observed amplicon sequence variants (ASVs) and led to clustering of samples in a principal coordinate analysis (PCoA; P < 0.05), but no effect of protein supplementation was observed. Ruminal samples clustered in PCoA (P = 0.001), and observed ASVs were impacted over time (P < 0.0001), but no effect of protein supplementation was detected. In contrast, protein supplementation, pubertal status, and day of supplementation affected the abundance of multiple phyla and genera in the uterus and rumen (P < 0.05). Temporal and pubertal status effects on the heifer’s uterine bacterial communities potentially indicate a maturing uterine microbiome. Protein supplementation did not impact microbial diversity measures but did affect the abundance of individual bacterial phyla and genera that may provide future opportunities to manipulate bacterial community composition and maximize productivity.

Maternal nutrition during pregnancy influences postnatal life of animals; nevertheless, few studies have investigated its effects on the productive performance and reproductive development of heifers. This study evaluated the performance, reproductive development, and correlation between reproduction × fat thickness and performance × ribeye area (REA) traits of heifers. We also performed an exploratory genomic association during the rearing period in heifers submitted to fetal programming. The study comprised 55 Nellore heifers born to dams exposed to one of the following nutritional planes: control, without protein-energy supplementation; PELT, protein-energy last trimester, protein-energy supplementation offered in the final third of pregnancy; and PEWG, protein-energy whole gestation, protein-energy supplementation upon pregnancy confirmation. Protein-energy supplementation occurred at the level of 0.3% live weight. After weaning, heifers were submitted to periodic evaluations of weight and body composition by ultrasonography. From 12 to 18 months, we evaluated the reproductive tract of heifers to monitor its development for sexual precocity and ovarian follicle population. The treatments had no effect (p > 0.05) on average daily gain; however, the weight of the animals showed a significant difference over time (p = 0.017). No differences were found between treatments for REA, backfat, and rump fat thickness, nor for puberty age, antral follicular count, and other traits related to reproductive tract development (p > 0.05). The correlation analysis between performance traits and REA showed high correlations (r > 0.37) between REA at weaning and year versus weight from weaning until yearling; however, no correlation was found for reproductive development traits versus fat thickness (p > 0.05). The exploratory genomic association study showed one single-nucleotide polymorphism (SNP) for each treatment on an intergenic region for control and PEWG, and the one for PELT on an intronic region of RAPGEF1 gene. Maternal nutrition affected only the weight of the animals throughout the rearing period. [ABSTRACT FROM AUTHOR]

Herein, we evaluated the hepatic lipid metabolic profiles of bovine fetuses in response to maternal vitamin and mineral supplementation (VMSUP; supplemented (VTM) or not (NoVTM)) and two different rates of gain (GAIN; low gain (LG), 0.28 kg/d, or moderate gain (MG), 0.79 kg/d). Crossbred Angus heifers (n = 35; initial BW = 359.5 ± 7.1 kg) were randomly assigned to a 2 × 2 factorial arrangement, resulting in the following treatment combinations: NoVTM-LG (n = 9), NoVTM-MG (n = 9), VTM-LG (n = 9), and VTM-MG (n = 8). Heifers received their treatments until d 83 of gestation, when they were ovariohysterectomized. Fetuses were harvested and liver samples were analyzed via ultrahigh-performance liquid chromatography–tandem mass spectroscopy to characterize lipid profiles and abundances. We identified 374 biochemicals/metabolites belonging to 57 sub-pathways of the lipid metabolism super-pathway. The majority of the biochemicals/metabolites (n = 152) were significantly affected by the main effect of GAIN. Maternal moderate rates of gain resulted in greater abundances (p ≤ 0.0001) of ω-3 fatty acids (eicosapentaenoate, docosapentaenoate, and docosahexaenoate) and lower abundances (p ≤ 0.0001) of ω-6 fatty acids. Further, MG resulted in the accumulation of several diacylglycerols and depletion of the majority of the monoacylglycerols. Concentrations of nearly all acylcarnitines (p ≤ 0.03) were decreased in VTM-LG fetal livers compared to all other treatment combinations, indicating a greater rate of complete oxidation of fatty acids. Levels of secondary bile acids were impacted by VMSUP, being greater (p ≤ 0.0048) in NoVTM than in VTM fetal livers. Moreover, NoVTM combined with lower rate of gain resulted in greater concentrations of most secondary bile acid biochemicals/metabolites. These data indicate that maternal diet influenced and altered fetal hepatic lipid composition in the first trimester of gestation. Maternal body weight gain exerted a greater influence on fetal lipid profiles than vitamin and mineral supplementation. Specifically, lower rate of gain (0.28 kg/d) resulted in an increased abundance of the majority of the biochemicals/metabolites identified in this study.

Maternal nutrition during pregnancy influences postnatal life of animals; nevertheless, few studies have investigated its effects on the productive performance and reproductive development of heifers. This study evaluated the performance, reproductive development, and correlation between reproduction × fat thickness and performance × ribeye area (REA) traits of heifers. We also performed an exploratory genomic association during the rearing period in heifers submitted to fetal programming. The study comprised 55 Nellore heifers born to dams exposed to one of the following nutritional planes: control, without protein-energy supplementation; PELT, protein-energy last trimester, protein-energy supplementation offered in the final third of pregnancy; and PEWG, protein-energy whole gestation, protein-energy supplementation upon pregnancy confirmation. Protein-energy supplementation occurred at the level of 0.3% live weight. After weaning, heifers were submitted to periodic evaluations of weight and body composition by ultrasonography. From 12 to 18 months, we evaluated the reproductive tract of heifers to monitor its development for sexual precocity and ovarian follicle population. The treatments had no effect (p > 0.05) on average daily gain; however, the weight of the animals showed a significant difference over time (p = 0.017). No differences were found between treatments for REA, backfat, and rump fat thickness, nor for puberty age, antral follicular count, and other traits related to reproductive tract development (p > 0.05). The correlation analysis between performance traits and REA showed high correlations (r > 0.37) between REA at weaning and year versus weight from weaning until yearling; however, no correlation was found for reproductive development traits versus fat thickness (p > 0.05). The exploratory genomic association study showed one single-nucleotide polymorphism (SNP) for each treatment on an intergenic region for control and PEWG, and the one for PELT on an intronic region of RAPGEF1 gene. Maternal nutrition affected only the weight of the animals throughout the rearing period.

Interest is growing in methods to apply precision nutritional supplements strategically during the peri-conceptual period to enhance progeny performance of beef females. Studies where supplemental methionine (MET) was provided to bovine females in the peri-conceptual period demonstrated epigenetic modifications in muscle of the progeny. Guanidinoacetic acid (GAA) has been fed directly to livestock to increase creatine synthesis, but has not been evaluated for use in fetal programming. We fed MET and GAA to crossbred heifers during the peri-conceptual period as a 2 x 2 factorial design to influence carcass characteristics of their steer calves. It was, therefore, important to determine if the interactions of dietary MET and GAA in the peri-conceptual period would alter reproductive efficiency. The null hypothesis was that these supplements would not alter reproductive efficiency of beef heifers when fed in the peri-conceptual period. Heifers were divided into four breeding groups for management purposes. On day -63, heifers (n = 20/diet, age = 384.1 ± 1.1 d) were assigned HeatTime collars and individually fed MET (10 g/d), GAA (40 g/d), the combination (MET + GAA), or ground corn carrier (CON) for 126 days. On day -9, heifers received 100 mg of gonadotropin releasing hormone and a CIDR. On day -2, the CIDR was removed and luteolysis was initiated with 25 mg of prostaglandin F2a. All heifers were inseminated with male sexed semen from a single sire and administered a second 100 mg injection of gonadotropin releasing hormone on day 0. On day 63, a blood sample was collected from all pregnant heifers (CON n = 10; MET n = 8; GAA n = 7; MET + GAA n =10) to evaluate circulating progesterone concentrations. Reproductive tracts were collected to determine CL weight, gravid uterine weight, and placentome number. Data were analyzed using the MIXED procedure of SAS with group, MET, GAA, and the interaction of MET and GAA as fixed effects. Days to first estrus were greater and number of estrus events prior to synchronization were fewer in CON heifers compared with supplemented heifers (P < 0.05). Luteal weight tended to be greater in heifers supplemented with MET compared with CON and GAA heifers (P = 0.09), but peak intensity of estrus, concentration of progesterone at day 63 of pregnancy, gravid uterine weight, and placentome number did not differ due to diet (P > 0.10). Supplementation with MET or GAA may improve onset of puberty but does not negatively alter reproductive performance in crossbred beef heifers. These supplements can be used for fetal programming of muscle development in steer progeny without negatively impacting reproductive performance in the breeding herd. USDA is an equal opportunity provider and employer. Funded in part by USDA-NIFA-AFRI # 2022-67015-36196. [ABSTRACT FROM AUTHOR]

Objective: This study investigated the effect of melatonin administration in combination with the CoSynch‐56 protocol on the conception rate after artificial insemination (AI) in beef heifers. Methods: Eighty‐six beef heifers were allocated to four treatments in combination with CoSynch‐56 treatment. All heifers, excluding the control group (CTR = 25), were injected with melatonin on day 1. The melatonin (MT = 20) and MT + human chorionic gonadotropin (MT + hCG = 21) groups received no further treatment with melatonin. Each heifer was treated with gonadotropin‐releasing hormone (GnRH) on day 4, prostaglandin F2α (PGF2α) on day 11, and GnRH and AI 56 h later. The fourth group (2MT = 20) was injected again with melatonin concurrent with AI, and the MT + hCG group received hCG on day 19. Pregnancy diagnosis was performed using transrectal ultrasonography 45 days after AI and blood samples were collected via caudal venipuncture on days 0–1, 14–15, 24 and 59. Concentrations of progesterone (P4) and the activities of oxidative stress‐related enzymes were determined using enzyme‐linked immunosorbent assay. Results: The conception rate was greater in the 2MT group (75%) than in the other groups, while there was no significant difference among the CTR (44%), MT (45%) and MT + hCG (38.1%) groups. Treatment with melatonin increased superoxide dismutase and glutathione peroxidase activities and decreased malondialdehyde concentrations but did not significantly affect the concentration of P4. Conclusion: Our results indicate that the administration of melatonin twice during the CoSynch‐56 protocol may increase conception rates in beef heifers. [ABSTRACT FROM AUTHOR]

Thirty-five crossbred Angus heifers (initial BW = 359.5 ± 7.1 kg) were randomly assigned to a 2 × 2 factorial design to evaluate effects of vitamin and mineral supplementation [VMSUP; supplemented (VTM) vs. unsupplemented (NoVTM)] and different rates of gain [GAIN; low gain (LG), 0.28 kg/d, vs. moderate gain (MG), 0.79 kg/d] during the first 83 d of gestation on dam hormone and metabolic status, fetal tissue and organ mass, and concentration of glucose and fructose in fetal fluids. The VMSUP was initiated 71 to 148 d before artificial insemination (AI), allowing time for mineral status of heifers to be altered in advance of breeding. At AI heifers were assigned their GAIN treatment. Heifers received treatments until the time of ovariohysterectomy (d 83 ± 0.27 after AI). Throughout the experiment, serum samples were collected and analyzed for non-esterified fatty acids (NEFA), progesterone (P4), insulin, and insulin-like growth factor 1 (IGF-1). At ovariohysterectomy, gravid reproductive tracts were collected, measurements were taken, samples of allantoic (ALF) and amniotic (AMF) fluids were collected, and fetuses were dissected. By design, MG had greater ADG compared to LG (0.85 vs. 0.34 ± 0.04 kg/d, respectively; p < 0.01). Concentrations of NEFA were greater for LG than MG (p = 0.04) and were affected by a VMSUP × day interaction (p < 0.01), with greater concentrations for NoVTM on d 83. Insulin was greater for NoVTM than VTM (p = 0.01). A GAIN × day interaction (p < 0.01) was observed for IGF-1, with greater concentrations for MG on d 83. At d 83, P4 concentrations were greater for MG than LG (GAIN × day, p < 0.01), and MG had greater (p < 0.01) corpus luteum weights versus LG. Even though fetal BW was not affected (p ≥ 0.27), MG fetuses had heavier (p = 0.01) femurs than LG, and VTM fetuses had heavier (p = 0.05) livers than those from NoVTM. Additionally, fetal liver as a percentage of BW was greater in fetuses from VTM (P = 0.05; 3.96 ± 0.06% BW) than NoVTM (3.79 ± 0.06% BW), and from LG (p = 0.04; 3.96 ± 0.06% BW) than MG (3.78 ± 0.06% BW). A VMSUP × GAIN interaction was observed for fetal small intestinal weight (p = 0.03), with VTM-MG being heavier than VTM-LG. Therefore, replacement heifer nutrition during early gestation can alter the development of organs that are relevant for future offspring performance. These data imply that compensatory mechanisms are in place in the developing conceptus that can alter the growth rate of key metabolic organs possibly in an attempt to increase or decrease energy utilization.

Developing and raising replacement heifers requires a large capital investment for producers. Therefore, it is imperative to discover traits and management practices to eliminate subfertile heifers prior to breeding and pregnancy determination. In this study, four years of data was analyzed from a centralized beef heifer development yard in the Midwest of the United States. The objective of this study was to analyze various heifer physical characteristics and management practices in order to quantify their impact on pregnancy and date of conception. Logistic regression models were built to investigate risk factors associated with conception to artificial insemination (AI), pregnancy by natural service after AI exposure, and pregnancy in the first 21-days of the breeding season. Age at entry, average daily gain from entry to breeding, pelvic width, and year were associated with AI pregnancy (p < 0.05). On the second model, average daily gain from entry to yearling weight, weight at breeding, weight at pregnancy diagnosis, and age at AI were significantly associated with pregnancy. There were no associations with reproductive tract score with any of the response variables analyzed. These results indicate there are physical measurements that can be used to improve the ability to select and develop heifers for improved reproductive performance.

Reproductive failure remains a significant challenge to the beef industry. The omics technologies have provided opportunities to improve reproductive efficiency. We used a multistaged analysis from blood profiles to integrate metabolome (plasma) and transcriptome (peripheral white blood cells) in beef heifers. We used untargeted metabolomics and RNA-Seq paired data from six AI-pregnant (AI-P) and six nonpregnant (NP) Angus-Simmental crossbred heifers at artificial insemination (AI). Based on network co-expression analysis, we identified 17 and 37 hub genes in the AI-P and NP groups, respectively. Further, we identified TGM2, TMEM51, TAC3, NDRG4, and PDGFB as more connected in the NP heifers’ network. The NP gene network showed a connectivity gain due to the rewiring of major regulators. The metabolomic analysis identified 18 and 15 hub metabolites in the AI-P and NP networks. Tryptophan and allantoic acid exhibited a connectivity gain in the NP and AI-P networks, respectively. The gene–metabolite integration identified tocopherol-a as positively correlated with ENSBTAG00000009943 in the AI-P group. Conversely, tocopherol-a was negatively correlated in the NP group with EXOSC2, TRNAUIAP, and SNX12. In the NP group, α-ketoglutarate-SMG8 and putrescine-HSD17B13 were positively correlated, whereas a-ketoglutarate-ALAS2 and tryptophan-MTMR1 were negatively correlated. These multiple interactions identified novel targets and pathways underlying fertility in bovines.

To determine the effects of Follicle Stimulating Hormone (FSH) treatment and subsequent withdrawal on uterine proliferation and estrogen receptor (ESR), Brahman crossbred heifers (n = 12) were twice daily injected with FSH (4, 3, and 2 mg/injection) on Days 17-19 of the estrous cycle (FSH 3 days) and (4 and 3 mg/injection) on Days 17-18 (FSH 2 days) and withdrawal with saline on Day 19 and (4 mg/injection) on Day 17 (FSH 1 day) and withdrawal with saline on Days 18-19. Uterine tissue was subjectively collected on Day 20 and microscopically classified to four regions: endometrial stroma (ES), surface endometrial gland (EG), deep endometrial gland (DG), and myometrium (Myo). The cell proliferation marker, Ki-67, was quantified as labeling index (LI) in uterine regions, and tissues were immunostained to detect ESR2 followed by image analysis. The LI of ES, EG, and DG was greater (P = 0.0018, P = 0.0005, and P = 0.0103; respectively) in heifers received FSH for 3 days. The expression of ESR2 protein on ES and EG was greatest (P < 0.0001 and P = 0.0036, respectively) in FSH 3 days-treated group. Thus, FSH administration during proestrus stimulates uterine cell proliferation, and ESR2 expressions are affected by FSH during proestrus and differentially distributed in the uterine regions. [ABSTRACT FROM AUTHOR]

Length of the menstrual cycle was positively associated with antral follicle number in women. If this pattern is consistent in cattle, a value-added benefit to using automated activity monitors to determine estrous status could be the ability to predict antral follicle count (AFC). We, therefore, hypothesized that as inter-estrous interval increased ultrasonographic AFC would be greater in crossbred beef heifers. Over 3 yr, crossbred beef heifers ( n  = 1,394) were fitted with automated activity monitors for 81 d. From days 42 to 46, heifers were submitted for ultrasonographic examination to determine AFC. From days 60 to 81, heifers were visually observed twice daily for 45 min for signs of behavioral estrus. Heifers that had a behavioral estrus that coincided with a sensor-based estrus and had a previous sensor-based estrus between 15 and 26 d earlier were used for the analysis ( n  = 850). A combination of regression analyses and correlation analyses were applied to understand the association between data collected by sensors and follicle number determined by ultrasonographic examination. Antral follicle count was analyzed using the GLM procedure of SAS with estrous cycle length (15 to 26 d) as a fixed effect. Estrus was more likely to initiate in the early morning hours and peak activity was greater ( P  < 0.0001) when estrus initiated between 0200 and 0800 hours then when estrus initiated at other times of the day. Antral follicle count did not differ due to length of the estrous cycle ( P  = 0.87). Thus, length of the estrous cycle obtained from three-axis accelerometers cannot be used to predict follicle number in crossbred beef heifers; however, machine learning approaches that combine multiple features could be used to integrate parameters of activity with other relevant environmental and management data to quantify AFC and improve reproductive management in beef cows., Competing Interests: The authors declare no conflicts of interest., (Published by Oxford University Press for the American Society of Animal Science 2024.)

The objectives of the present study were (experiment 1) to characterized development and dynamics of the dominant follicles (DF) and the corpus luteum (CL) to determine patterns of two (W2) and three (W3) follicular waves in beef heifers, and (experiment 2) to determine gene expression of growth factors gene expression in follicular cells of W2 and W3 heifer. Twenty‐eight Braford heifers were used. Dominant follicular and CL were monitored daily by ultrasonography to identify the development W2 and W3 in heifers. Pre‐ovulatory DF were aspirated on day 19 in W2 and on day 22 in W3 heifers. In W2 and W3, follicular cells (FC) of gene expression of growth differentiation factor 9, bone morphogenetic protein 15 (BMP15), fibroblast growth factor basic, transforming growth factor beta receptor 1, bone morphogenetic protein receptor type IB and fibroblast growth factor receptor 2 were evaluated. The regression of the DF of the first follicular wave and the emergency of the DF of the second follicular wave began later in the heifers W2 than in W3 (p =.02 and p <.01). The regression of the CL began earlier in the W2 than in W3 group (p <.01). Gene expression of growth factors and receptors was similar between groups. However, higher relative levels of BMP15 was observed in W2 group (p =.07). Results propose that wave patterns were regulated by the development time of the DF in the first wave and the life of the CL. Furthermore, higher levels of BMP15 could produce shorter life of CL. The present work suggest that ultrasonography associated with molecular assays could be used as an easy and effective tool to characterize follicular wave patterns. [ABSTRACT FROM AUTHOR]

The value of carinata, a non-food oilseed crop, has been demonstrated as a high-quality jet fuel alternative and successful cover crop in the southeastern U.S.; however, research is limited regarding carinata as an alternative for commonly used protein sources in livestock. Eighty-four Angus crossbred heifers were used in a generalized randomized block design to evaluate the effects of supplementing carinata meal compared with cottonseed meal on performance, intake, and digestibility in a backgrounding corn silagebased diet. Treatments included: corn silage only (CS), corn silage + Brassica carinata meal (BCM) at 10% (BCM10) or 20 % (BCM20) inclusion, or corn silage + cottonseed meal at 10% inclusion (CSM). Protein sources were mixed with corn silage prior to delivery and provided ad libitum, with individual intake measured using the GrowSafe system. Data were analyzed using Proc Glimmix of SAS. An effect of treatment was observed (P < 0.01) for final body weight (BW), average daily gain, and gain to feed ratio, where CS was least. Dry matter intake (DMI; kg/d) was greatest (P = 0.01) for BCM10 compared with CS, yet BCM20 and CSM did not differ from CS or BCM10. No effect of treatment was observed on DMI as a percentage of BW (P = 0.35) or residual feed intake (P = 0.94). Heifers receiving CSM had the greatest (P < 0.01) intake of dry matter (DM), organic matter (OM), neutral detergent fiber (NDF), and acid detergent fiber (ADF). Intake of crude protein (CP; P < 0.01) was least for CS and greatest for BCM20 and CSM, with BCM10 intermediate. Digestibility of all nutrients was least (P < 0.01) for CS, and greatest (P < 0.01) for BCM20 in CP and NDF, only, where BCM10 and CSM did not differ. Digestibility of DM, OM, and ADF was less (P < 0.01) in BCM10, greater in BCM20, while CSM did not differ between BCM10 and BCM20. Carinata supplemented at 10% diet DM performed similarly to cottonseed meal in backgrounding beef heifers fed a corn silage-based diet, thereby enhancing its value in the southeastern U.S. [ABSTRACT FROM AUTHOR]

Recent research has demonstrated that feeding rumen protected methionine (MET) products increases circulating methionine while feeding guanidinoacetic acid (GAA) may result in a methyl deficiency. Therefore, we hypothesized that maternal MET or GAA supplementation from 63 days before breeding until d 63 of gestation would increase fetal hepatic methyl donors or result in a fetal hepatic methyl donor deficiency, respectively. Eighty MARC II heifers (n = 20 per treatment; initial BW = 344 ± 8 kg; day -63) were weighed and assigned to one of four breeding groups and four treatments stratified by age and starting weight. Heifers were fed a total mixed ration to gain 0.68 kg/d and received 100 g of one of four treatments top dressed: control supplement of ground corn (CON), MET (10 g/d) in a ground corn carrier, GAA (40 g/d) in a ground corn carrier, or MET + GAA (10 g/d MET + 40 g/d GAA) in a ground corn carrier. At breeding (d 0), all heifers were bred to a single sire using male sexed semen. At d 63 of gestation, 35 heifers (CON n = 10, MET n = 8, GAA n = 7, MET + GAA, n = 10) confirmed pregnant with bull calves were humanely slaughtered and fetal liver tissues were collected and sent to Metabolon Inc. for global metabolomics analysis. Data were analyzed as a 2 x 2 factorial with 2 levels of GAA and 2 levels of MET with breeding group included in the model. For this abstract, only metabolites from the methionine cycle and adjacent pathways will be reported and only metabolites with significant P-values will be discussed (P ≤ 0.05). There were no main effects or interactions for the abundance of methionine, GAA, creatine, SAM, SAH or homocysteine. Glycine was decreased and sarcosine increased in fetuses from MET supplemented dams. Serine was affected by a MET x GAA interaction being decreased in livers of CON, MET, and MET + GAA fetuses compared with GAA. Cystathione, S-methylcysteine, s-methylcysteine sulfoxide, and hypotaurine were greater in fetuses of MET supplemented heifers and pyridoxal phosphate was reduced in fetal liver of MET supplemented heifers. The abundance of urea was greater in GAA supplemented fetuses. These results indicate that fetuses from dams fed methionine may be able to maintain balance in methionine supply by shunting methionine through adjacent pathways including the transsulfuration pathway. We also interpret these data to imply that excess methionine is not utilized by the fetus and is metabolized to products that can be excreted. Lastly, GAA did not alter the fetal methyl supply. USDA is an equal opportunity provider and employer. Funded by (USDANIFA-AFRI # 2022-67015-36196). [ABSTRACT FROM AUTHOR]

This experiment evaluated the physiological and reproductive responses of beef heifers reared at a high stocking density and provided with access to an exercise area. Ninety Angus × Brahman heifers were ranked by age (257 ± 2 days), body weight (BW; 216 ± 2 kg), and temperament score on day 0 and assigned to a) 1 of 6 drylot pens (10x14 m pens; 10 heifers/pen) resulting in a stocking density of 14 m2/heifer (DENS), or b) 1 of 3 paddocks (2-ha paddocks; 10 heifers/paddock) resulting in a stocking density of 2,000 m2/heifer (CON). On day 15, 3 DENS pens were randomly selected and given access to an exercise area (DENS-EX) for 1 hour three times weekly. Negligible forage was available for CON heifers, whereas all heifers received the same limit fed diet which averaged 13 kg/heifer daily of a corn-based diet. Heifer shrunk BW was recorded after 16 h of feed and water withdrawal on days -3 and 225 for average daily gain calculation. On day 0, heifers were fitted with a pedometer behind their shoulder and an ear tag (CowManager, Select Sires, Plain City, OH) to record behavioral responses. Each week, pedometer results were recorded, and blood samples were collected for puberty evaluation via plasma progesterone. Heifers from CON had more (P < 0.05) steps per week compared with DENS and DENS-EX, and DENS-EX heifers had more (P < 0.05) steps per week compared with DENS. Heifers from CON spent more (P < 0.05) time ruminating and eating compared with DENS and DENS-EX. No treatment effects (P = 0.12) were detected for heifer BW gain or temperament variables. Heifers from DENS experienced delayed puberty attainment given a greater (P < 0.05) proportion of CON heifers were pubertal by day 98 compared with DENS and DENS-EX, whereas a greater (P < 0.05) proportion of DENS-EX heifers were pubertal by day 154 compared with DENS heifers (treatment × day interaction, P < 0.01). Collectively, results from this experiment demonstrate that providing heifers reared at a high stocking density access to an exercise area does not result in similar reproductive responses as those reared on pasture at a low stocking density. This work is supported by the USDA National Institute of Food and Agriculture (#2021-67015-34083). [ABSTRACT FROM AUTHOR]

In an effort to better understand the consequences of early weaning (EW) for replacement beef heifers, a two-phase experiment was conducted investigating the impact on metabolic function and documenting reproductive characteristics. In phase 1, Angus×Simmental heifers (n=35) were stratified by BW and sire, and randomly assigned to either a normal weaning (NW, n=18) or EW (n=17) treatment. EW heifers were weaned at 107±3 days of age and provided access to a concentrate-based ration ad libitum with limit-fed mixed grass hay. NW heifers remained with their dams until 232±3 days of age, at which point heifers from both treatments were comingled and grazed on mixed summer pasture. Following NW, weekly blood samples were collected from all heifers for progesterone analyses used to determine the onset of puberty. Pelvic and ovarian size was measured before breeding. All heifers were subjected to an estrous synchronization protocol with timed artificial insemination (AI) at 437±4 days of age. During phase 2 of the experiment, a subset of pregnant heifers (n=16) were divided into two replicates and subjected to a glucose tolerance test, epinephrine challenge and progesterone clearance analysis. Neither age nor BW at puberty differed between EW and NW heifers. Likewise, no differences in pelvic area or ovarian size were observed. Thus, it appears that the reproductive maturity of EW and NW heifers was similar. Heifers studied during phase 2 of the experiment were restricted to those that had become pregnant to their first AI. Within this cohort, EW heifers tended to have lower overall circulating progesterone concentrations than those that were NW (P=0.14). Aspects of glucose and insulin dynamics were also altered, as EW heifers tended to have lower baseline glucose concentrations (P=0.10) despite similar baseline insulin concentrations. Compared with NW heifers, EW heifers had lower insulin area under the curve (P

Fat supplementation has potential to improve reproductive performance and increase pregnancy rates in cattle by increasing the energy density of the diet. However, some of the positive effects of fat seem to be influenced by the type of fatty acid fed. Docosahexaenoic acid (DHA, 22:6n-3) and eicosapentaenoic acid (EPA, 20:5n-3) are long-chain n-3 poly-unsaturated fatty acids (PUFA) that have important biological effects on reproduction through their involvement in hormone and series 3 prostaglandin synthesis. Ruminant tissues are naturally almost devoid of n-3 long-chain PUFA, specifically EPA and DHA. Algae biomass provides a consistent source of DHA and EPA that could be fed to alter hormonal profiles and improve reproduction of beef heifers. Eighty-eight Angus × Simmental heifers (427 ± 1.8 kg body weight [BW]) were blocked by BW and allotted to 2 treatments (44/treatment, 4 pens/treatment, 11 heifers/pen). Control heifers were fed a diet that contained (dry matter [DM] basis) 52.8% mixed grass silage, 32% corn silage, and 15.2% concentrate. DHAgold (49% fat; 21.8% DHA; DSM Inc.) was included in the algae diet at 1.65% DM, replacing equal parts of corn and DDGS. Diets were formulated to contain 12% crude protein and 0.85 Mcal/kg net energy for gain (NEg). Heifers were fed treatment diets from 54 d prior to the breeding season through the first trimester. Follicular fluid was collected on day 47 for hormonal analysis. Artificial insemination (AI) was from days 54 to 77. Heifers that did not get pregnant to AI were removed from the study on day 109 and placed with a bull. The study ended on day 180. Data were analyzed using the MIXED procedure of SAS. During the pre-breeding period, algae heifers had lesser dry matter intake (P = 0.006) compared to control heifers. Heifers supplemented with algae had a greater average daily gain (P = 0.03) during the breeding period and BW tended (P = 0.06) to be greater for algae compared to control heifers on day 98 and was greater on day 180 (P = 0.03). Dominant follicle diameter and follicular estrogen concentration were unaffected by treatment (P ≥ 0.12). Follicular insulin-like growth factor-1 was greater in algae compared to control heifers (P = 0.03). First service conception rate did not differ between treatments (P = 0.67); however, second service and overall conception were lesser (P ≤ 0.03) in algae compared to control heifers. These data suggest supplementing DHA-rich algae improved growth but decreased conception rates of primiparous beef females., (© The Author(s) 2024. Published by Oxford University Press on behalf of the American Society of Animal Science. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Our study objectives were to evaluate the effects of divergent rates of body weight (BW) gain during early gestation in beef heifers on F0 performance, metabolic and endocrine status, colostrum immunoglobulins, and subsequent F1 calf characteristics, growth performance, concentrations of hormones and metabolites, and response to vaccination. Angus-based heifers (n = 100; BW = 369 ± 2.5 kg) were adapted to individual feeding for 14 d and bred using artificial insemination with female-sexed semen. Heifers were ranked by BW and assigned to either a basal diet targeting 0.28 kg/d gain (low [LG], n = 50) or the basal diet plus an energy/protein supplement targeting 0.79 kg/d gain (moderate gain [MG], n = 50) until day 84 of gestation. Dam BW and blood samples were collected at 6 time points during gestation; body composition was evaluated on days -10 and 84; and fetal measurements were taken on days 42, 63, and 84. At calving (LG, n = 23; MG, n = 23), dam and calf BW were recorded; and colostrum, calf body measurements, and blood samples were collected. Cow-calf pairs were managed on a common diet from calving to weaning, followed by a common postnatal development period for all F1 female offspring. Growth performance, hormone and metabolite profiles, feeding behavior, and reproductive performance were assessed from birth to prebreeding in F1 heifers. Offspring were vaccinated against respiratory disease and bovine viral diarrhea pathogens on days 62.3 ± 4.13 and 220.3 ± 4.13 postcalving. By design, MG dams were heavier (P < 0.0001) than LG on day 84, and the BW advantage persisted until subsequent weaning of F1 calves. Concentrations of serum IGF-1 and glucose were increased throughout gestation (P < 0.001) in MG dams, whereas concentrations of NEFA were decreased (P < 0.001) in LG dams. Calves from MG dams were 2.14 kg heavier (P = 0.03) and had larger chest circumference (P = 0.04) at birth compared with LG cohorts. Heifers from MG dams continued to have greater (P ≤ 0.03) BW gain and feed efficiency during the development period, but no differences were observed (P ≥ 0.13) in body composition, concentrations of hormones and metabolites, feeding behavior, puberty attainment, and response to vaccination in F1 offspring. Hence, early gestation rate of gain impacted BW and concentrations of glucose and IGF-1 throughout gestation in the F0 dam, resulting in altered F1 calf BW and measurements at birth and increased gain and efficiency during the development period., (© The Author(s) 2024. Published by Oxford University Press on behalf of the American Society of Animal Science. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

An experiment was designed to evaluate the effect of extending duration of the presynchronization treatment in a long-term progestin-based estrus synchronization protocol. Heifers were assigned to either an 18 d (Day 0–18) or 14 d (Day 4 to Day 18) CIDR® treatment (1.38 g progesterone controlled internal drug release insert; Zoetis, Madison, NJ), with prostaglandin F 2α (PG; 250 μg im cloprostenol sodium) administered 16 d after CIDR® removal (Day 34). Heifers at two locations (location one, n = 193; location two, n = 649) were assigned to treatment based on reproductive tract score (RTS; Scale 1–5) and body weight. Heifers that were assigned RTS 1 were not retained for the trial (n = 6). Estrus detection aids (Estrotect®) were applied at PG. Split-time artificial insemination (STAI) was utilized and AI performed based on expression of estrus at 66 h. Expression of estrus was defined as removal of ≥50% of the grey coating from the Estrotect® patch. Heifers that expressed estrus at 66 h were inseminated then and heifers that had not expressed estrus were inseminated at 90 h. Only heifers that failed to express estrus by 90 h received gonadotropin-releasing hormone (GnRH; 100 μg im gonadorelin acetate) at the time of AI. At location one, blood samples were collected at PG and AI (66 h or 90 h) from all heifers to determine E 2 concentration by radioimmunoassay, and transrectal ovarian ultrasound was performed to detail ovarian structures on a subset of heifers (n = 73) at both time points. The proportion of heifers expressing estrus did not differ between treatments, either by 66 h (60%) or in total by 90 h (84%) after PG. Pregnancy rate to STAI did not differ between treatments (P = 0.3; 52%, 14-d CIDR®-PG; 50%, 18-d CIDR®-PG), or at the end of the 60 d breeding season (P = 0.2; 86%, 14-d CIDR®-PG; 82%, 18-d CIDR®-PG). No differences were detected in mean diameter of the dominant follicle at PG (P = 0.6; 10.9 ± 0.4 mm, 14-d CIDR®-PG; 11.0 ± 0.4 mm, 18-d CIDR®-PG) or at STAI (P = 0.3; 12.6 ± 0.4 mm, 14-d CIDR®-PG; 13.2 ± 0.4 mm, 18-d CIDR®-PG), nor were any differences observed between treatments in concentrations of E 2 at PG (P = 0.8; 1.1 ± 0.19 pg/ml, 14-d CIDR®-PG; 1.1 ± 0.19 pg/ml, 18-d CIDR®-PG) or STAI (P = 0.6; 3.8 ± 0.19 pg/ml, 14-d CIDR®-PG; 3.6 ± 0.19 pg/ml, 18-d CIDR®-PG). These data indicate that duration of CIDR® treatment can be extended from 14 to 18 d, thus providing flexibility in scheduling without compromising reproductive outcomes. • Extending length of the presynchronization period was evaluated in replacement beef heifers using a long-term progestin based protocol and split-time artificial insemination (STAI). • Estrous response rates following prostaglandin were similar among heifers assigned to a 14 day or 18 day CIDR treatment, with prostaglandin administered 16 days after CIDR removal. • Pregnancy rates resulting from (STAI) were similar among heifers assigned to a 14 day or 18 day CIDR treatment, with prostaglandin administered 16 days after CIDR removal. • Length of CIDR treatment can be extended from 14 to 18 days, thus providing flexibility in scheduling without compromising reproductive outcomes. [ABSTRACT FROM AUTHOR]

Fixed-time and split-time AI were compared following the melengestrol acetate (MGA®) prostaglandin F 2α (Experiment 1) and 7-d CO-Synch + controlled internal drug release (CIDR®) protocols (Experiment 2). Heifers in Experiments 1 (n = 524) and 2 (n = 456) were assigned within pen to balanced treatments based on weight and reproductive tract score (RTS; Scale 1–5). In Experiment 1, MGA® (0.5 mg∙animal−1∙d−1) was fed for 14 d, and prostaglandin F 2α (PG; 250 μg im cloprostenol sodium) was administered 19 d after MGA® withdrawal. In Experiment 2, gonadotropin-releasing hormone (GnRH; 100 μg gonadorelin acetate) was administered coincident with CIDR® (1.38 g progesterone [P 4 ]) insertion. Inserts were removed after 7 d, and PG (250 μg im cloprostenol sodium) was administered at CIDR® removal. In both experiments, estrus detection aids (Estrotect®) were applied at the time of PG administration. Estrous status was recorded at FTAI or STAI. Estrus was defined as removal of ≥ 50% of the grey coating from the Estrotect® patch. Heifers assigned to FTAI treatments received GnRH and were artificially inseminated at the standard time for FTAI for each protocol: 72 or 54 h after PG administration for the MGA-PG or 7-d CO-Synch + CIDR® protocol, respectively. In the STAI treatments, only heifers that expressed estrus prior to the standard time of FTAI were artificially inseminated at that time. For heifers failing to express estrus, AI was postponed 24 h. Only heifers that failed to exhibit estrus by the delayed time received GnRH concurrent with AI. In both experiments, estrous response prior to the standard time of FTAI did not differ between treatments. Total estrous response was increased (P < 0.01) among heifers assigned to STAI in Experiment 1 (88%, STAI; 72%, FTAI) and 2 (74%, STAI; 47%, FTAI). In Experiment 1, pregnancy rates resulting from AI were greater (P < 0.04) for heifers assigned to STAI compared with FTAI (55% vs 46%, respectively). In Experiment 2, pregnancy rates resulting from AI were similar between treatments (48% and 46%, respectively; P = 0.6). In summary, when compared with FTAI, STAI resulted in greater estrous response following both the MGA®-PG and 7-d CO-Synch + CIDR® protocols. The increased estrous response through use of STAI was associated with a corresponding increase in pregnancy rates to AI following the MGA®-PG protocol; however, a similar improvement in pregnancy rates was not observed following the 7-d CO-Synch + CIDR® protocol. • Estrous response and pregnancy rates resulting from AI were improved among beef heifers assigned to split-time versus fixed-time AI treatments following administration of the MGA-PG protocol. • Estrous response using split-time AI was improved among heifers following administration of the 7-day CO-Synch + CIDR protocol, however the improvement in estrous response did not translate into improved pregnancy outcomes compared to heifers that were inseminated at the pre-determined fixed time. • These experiments highlight the effectiveness of STAI for improving timed AI pregnancy rates following long-term progestin-based protocols for beef heifers across varying pubertal classes, and raise interesting questions pertaining to use of long- versus short-term progestin-based protocols to synchronize estrus in replacement beef heifers. [ABSTRACT FROM AUTHOR]

Fescue toxicosis is a multifaceted syndrome common in cattle grazing endophyte-infected tall fescue. The objective of this study was to evaluate the impact of the slick hair trait on physiological and reproductive parameters in heifers experiencing fescue toxicosis. Angus × Senepol heifers (n = 31) were blocked by weight (393.5 ± 17.3 kg) and phenotype relative to hair coat at birth, and randomly fed novel endophyte fescue (EN) or endophyte-infected fescue (EI) haylage in a total mixed ration for 91 d. Weekly measurements were collected to monitor heifer growth and response during ergot alkaloids exposure. Following 28 d of treatment, estrus was synchronized and heifers were inseminated. Ovary mapping and AI pregnancy rate were examined via transrectal ultrasonography. Blood samples were taken for genotyping: slick (S) or wildtype (W). Data were analyzed using repeated measures in PROC MIXED of SAS including fescue treatment (EN vs. EI), genotype (S vs. W), and sample collection time as main effects. Body condition scores were decreased for W heifers compared with S heifers (5.48 vs. 5.66, respectively; P < 0.0001). Surface temperature was greater for EI-W heifers (37.2 °C) compared with other groups (36.4, 36.6, 36.7 °C for EN-S, EN-W, EI-S, respectively; P < 0.05). Serum PRL concentrations were reduced for EI heifers compared with EN heifers (133.5 vs. 163.1 ng/mL, respectively; P < 0.05). The average number of 2 to 4 mm follicles were greater in EI-W heifers (13.8 follicles) compared with other groups (12.2, 10.6, and 11.1 for EN-S, EN-W, and EI-S, respectively; P < 0.0001). However, the average number of preovulatory follicles (≥9 mm) were reduced in EI-W heifers (0.52 follicles) compared with other heifer groups (0.94, 0.88, and 0.85 ± 0.04 for EN-S, EN-W, and EI-S, respectively; P < 0.05). Ovulatory follicle size was smaller in EI-W heifers compared with EN-W heifers (9.14 vs. 11.57 mm, respectively; P = 0.05). Corpus luteum area was reduced in EI-W heifers (235.1 mm2) compared with other heifer groups (297.2, 272.7, and 276.8 mm2 for EN-S, EN-W, and EI-S, respectively; P < 0.05). Concentrations of P4 were greater for EN heifers compared with EI heifers (2.7 vs. 1.8 ng/mL, respectively; P < 0.05). Pregnancy was not established in EI-W heifers (0%) compared with other heifer groups (37.5%, 57.1%, and 62.5% for EN-S, EN-W, and EI-S, respectively; P < 0.05). Overall, the slick hair mutation appears to aid in offsetting the physiological symptoms associated with fescue toxicosis and helps to improve reproductive performance. [ABSTRACT FROM AUTHOR]

Fescue toxicosis is a multifaceted syndrome common in cattle grazing endophyte-infected tall fescue. The objective of this study was to evaluate the impact of the slick hair trait on physiological and reproductive parameters in heifers experiencing fescue toxicosis. Angus × Senepol heifers (n = 31) were blocked by weight (393.5 ± 17.3 kg) and phenotype relative to hair coat at birth, and randomly fed novel endophyte fescue (EN) or endophyte-infected fescue (EI) haylage in a total mixed ration for 91 d. Weekly measurements were collected to monitor heifer growth and response during ergot alkaloids exposure. Following 28 d of treatment, estrus was synchronized and heifers were inseminated. Ovary mapping and AI pregnancy rate were examined via transrectal ultrasonography. Blood samples were taken for genotyping: slick (S) or wildtype (W). Data were analyzed using repeated measures in PROC MIXED of SAS including fescue treatment (EN vs. EI), genotype (S vs. W), and sample collection time as main effects. Body condition scores were decreased for W heifers compared with S heifers (5.48 vs. 5.66, respectively; P < 0.0001). Surface temperature was greater for EI-W heifers (37.2 °C) compared with other groups (36.4, 36.6, 36.7 °C for EN-S, EN-W, EI-S, respectively; P < 0.05). Serum PRL concentrations were reduced for EI heifers compared with EN heifers (133.5 vs. 163.1 ng/mL, respectively; P < 0.05). The average number of 2 to 4 mm follicles were greater in EI-W heifers (13.8 follicles) compared with other groups (12.2, 10.6, and 11.1 for EN-S, EN-W, and EI-S, respectively; P < 0.0001). However, the average number of preovulatory follicles (≥9 mm) were reduced in EI-W heifers (0.52 follicles) compared with other heifer groups (0.94, 0.88, and 0.85 ± 0.04 for EN-S, EN-W, and EI-S, respectively; P < 0.05). Ovulatory follicle size was smaller in EI-W heifers compared with EN-W heifers (9.14 vs. 11.57 mm, respectively; P = 0.05). Corpus luteum area was reduced in EI-W heifers (235.1 mm2) compared with other heifer groups (297.2, 272.7, and 276.8 mm2 for EN-S, EN-W, and EI-S, respectively; P < 0.05). Concentrations of P4 were greater for EN heifers compared with EI heifers (2.7 vs. 1.8 ng/mL, respectively; P < 0.05). Pregnancy was not established in EI-W heifers (0%) compared with other heifer groups (37.5%, 57.1%, and 62.5% for EN-S, EN-W, and EI-S, respectively; P < 0.05). Overall, the slick hair mutation appears to aid in offsetting the physiological symptoms associated with fescue toxicosis and helps to improve reproductive performance. [ABSTRACT FROM AUTHOR]

Highlights • Red osier dogwood (ROD) is a native shrub plant and contain high phenolic compounds. • Replacing silage with ROD up to 100 g/kg diet linearly increased feed digestibility in finishing beef heifers. • Feeding ROD improved immune response and blood antioxidant activity of beef heifers. • Feeding ROD performed better or at least equal to antibiotics currently used in beef cattle rations. Abstract Red osier dogwood (ROD; Cornus sericea) is an abundant native shrub plant across North America and it is rich in bioactive compounds with total phenolic concentration up to 220 g/kg dry matter (DM) depending on the season. The phenolics include anthocyanins, gallic acid, ellagic acid, quercetin, and cyanin, which have both antioxidant and antimicrobial properties. The objective of this study was to determine the effect of increasing substitution of ROD for barley silage in a high-grain diet on DM intake, ruminal pH and fermentation, digestibility in the total digestive tract, blood metabolites and acute phase response in beef heifers. Five ruminally cannulated Angus heifers (averaged body weight of 660 ± 40.8 kg; initial age of 18 months) were used in a 5 × 5 Latin square design with 21-d periods including 14 d for adaptation to new diets and 7 d for data collection. Treatments were a control diet containing 150 g/kg barley silage and 850 g/kg barley concentrate mix (DM basis), the control diet substituted with 30, 70 or 100 g/kg of ROD for equal proportions of barley silage, respectively, and the control diet supplemented with antibiotics (330 mg monensin + 110 mg tylosin/heifer/d). Apparent digestibility was determined using Cr 2 O 3 as external marker by sampling feces from the rectum. Intake of DM quadratically (P < 0.02) increased with increasing the substitution of silage for ROD. Mean ruminal pH were not affected by diets, and no effects of diets on total volatile fatty acid (VFA) concentration were observed. However, ruminal NH 3 -N concentration linearly (P < 0.01) decreased with increasing ROD feeding. Digestibility of DM linearly (P < 0.04) increased with increasing dietary ROD. Increasing ROD feeding also linearly increased plasma concentration of haptoglobin (P < 0.01) and concentration of serum amyloid A (P < 0.06). Compared with antibiotic group, feeding ROD resulted in greater (P < 0.01) intake and digestibility of DM, and greater (P < 0.05) VFA concentration. These results indicate greater feed value of ROD versus barley silage in high-grain diets. Feeding ROD potentially improves immune status and antioxidant activity in finishing beef heifers. Beef cattle fed ROD performed better or at least equal to antibiotics currently used in beef cattle rations and it could be used as a natural alternative for beef cattle production. [ABSTRACT FROM AUTHOR]

The objective of this experiment was to assess the effects of eprinomectin, an extended-release injectable parasiticide, on fescue toxicosis and its impacts on beef heifer performance and reproduction. Fall-born Angus × Simmental heifers (age = 246.3 ± 22.4 d; 264.8 ± 21.1 kg body weight [BW]) were randomly assigned to one of two treatments: extended-release eprinomectin injection (ERE; n = 100) or control (CON; saline; n = 99). Treatments were administered at a rate of 1 mL/50 kg BW. Prior to experiment, heifers were dosed with oral fenbendazole to minimize parasite load. All heifers grazed endophyte-infected tall fescue as a single group and were offered a 50:50 supplement mix of corn gluten feed and soybean hulls (2.7 kg as fed per heifer per day). Body condition scores (BCS), BW, hair coat score (HCS), blood, and fecal samples were collected throughout the experiment. A subset of 40 heifers were randomly selected (20 per treatment) to assess respiration rate (RR). On d 138, heifers began a 14-d controlled internal drug release + prostaglandin synchronization protocol. Following artificial insemination (AI), heifers were exposed to five bulls for 71 d. On d 214 and 291, AI and overall pregnancy rates, respectively, were determined. There was a treatment × time interaction (P < 0.01) for BW, BCS, and average daily gain (ADG). The ERE heifers had greater (P < 0.04) BW and BCS compared to CON heifers from d 55 and 112, respectively. In addition, ERE heifers had greater (P ≤ 0.04) ADG from d 0 to 56, 56 to 112, 112 to 171, and 171 to 214; however CON heifers had greater (P < 0.01) ADG from d 214 to 291. There was no treatment × time interaction or treatment difference (P ≥ 0.27) for HCS, RR, and serum prolactin concentrations. However, serum prolactin decreased (P < 0.01) in all heifers over time. There was a treatment × time interaction (P< 0.01) for fecal egg counts (FEC). The FEC did not differ (P ≥ 0.32) on d −1 or 55; however, ERE heifers had decreased (P < 0.01) FEC compared with CON heifers on d 111 (1.52 vs. 13.56 eggs per gram). The ERE heifers tended (P = 0.10) to have greater AI pregnancy rates (69% vs. 58%) and had greater (P = 0.01) overall pregnancy rates (84% vs. 68%) than CON heifers. Spring administration of extended-release eprinomectin improved BW, ADG, BCS, and AI and overall pregnancy rates in fall-born beef heifers. However, the underlying mechanism is still unclear, as there were minimal to no differences in HCS, RR, serum prolactin, and FEC. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Animal Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The objective of the experiment was to examine and evaluate growth performance and physiological changes of cattle raised under normal roof versus a modified roof. Ten Hindu Brazil x Brahman heifers were used in the experiment. The animals were divided randomly into two groups. They were used to evaluate the effects of modified roofing on the subjects’ physiological responses to heat stress and performance under hot humid conditions. It was found that the modified roof (MR) offered a more efficient way to lower heat stress in the cattle than the normal roof (NR). The difference was sufficient to enable the NR at 14:00 p.m. to have a THI higher (P

A non-traditional forage-based protocol was employed to evaluate replacement heifer growth, fertility, and economics between small frame (SF, 3.50; n = 50) and large frame (LF, 5.56; n = 50) heifers using three increasing gain growth phases. Preceding an 85 d growing-breeding period (Phase 3; P3) the heifers were managed as a common group for Phases 1 and 2 (P1 and P2). During P1, heifers grazed common fields of unharvested corn and corn residue (total digestible nutrients [TDN] 56%) with supplemental hay. For P2, heifers grazed early spring crested wheatgrass pasture (CWG; TDN 62%) that was followed by the final P3 drylot growing and breeding period (TDN 68%). Small frame heifers were lighter at the end of P1 in May and at the start of P3 breeding in August (p = 0.0002). Percent of mature body weight (BW) at the end of P1 (209 d) was 48.7% and 46.8%, respectively, for the SF and LF heifers and the percent pubertal was lower for SF than for LF heifers (18.0% vs 40.0%; p = 0.02). At breeding initiation (P3), the percentage of mature BW was 57.8 and 57.2 and the percentage pubertal was 90.0 and 96.0 (p = 0.07) for the SF and LF heifers, respectively; a 5-fold increase for SF heifers. Breeding cycle pregnancy on days 21, 42, and 63, and total percent pregnant did not differ (p>0.10). In drylot, SF heifer dry matter intake (DMI) was 20.1% less (p = 0.001) and feed cost/d was 20.3% lower (p = 0.001), but feed cost/kg of gain did not differ between SF and LF heifers (p = 0.41). Economically important live animal measurements for muscling were measured in May and at the end of the study in October. SF heifers had greater L. dorsi muscle area per unit of BW than LF heifers (p = 0.03). Small frame heifer value was lower at weaning (p = 0.005) and the non-pregnant ending heifer value was lower for SF heifers than for the LF heifers (p = 0.005). However, the total development cost was lower for SF heifers (p = 0.001) and the net cost per pregnant heifer, after accounting for the sale of non-pregnant heifers, was lower for SF heifers (p = 0.004). These data suggest that high breeding efficiency can be attained among March-April born SF and LF virgin heifers when transitioned to a more favorable May-June calving period through the strategic use of grazed and harvested forages resulting in a lower net cost per pregnant SF heifer.

Although antral follicle count is a repeatable parameter across life that is positively associated with fertility, its use at weaning as a tool to discard less fertile heifers has not been extensively evaluated. The hypotheses of this work are: 1) maximum antral follicle count (MAFC) is repeatable between weaning and pre breeding evaluations, allowing selection of more fertile heifers at an early age, 2) heifers with high MAFC have growth and development parameters linked to an earlier puberty and pregnancy, 3) MAFC has a positive correlation with AMH concentrations, so that both could be used inter changeably. In this study, Hereford (n = 42 and n = 50) and Braford (n = 40 and n = 50) females were used in years 1 and 2; respectively, in a completely randomized experimental design. Heifers were examined for five to ten days at two different moments (post weaning and pre service), to determine MAFC. The concentrations of Anti müllerian hormone (AMH) were evaluated on the day of MAFC assessment. Growth and development parameters were evaluated post weaning and pre service. The repeatability of MAFC between post weaning and pre service evaluations was poor in three cases (Hereford Year 1 = 0.36 and 2 = 0.39 and Braford, Year 2 = 0.32) but it was high for Braford in Year 2 (0.72). The AMH repeatability between post weaning and pre service evaluations was high in one case (Braford Year 2 = 0.72) and moderate in the others (Year 1, Hereford = 0.50 and Braford = 0.52 and Year 2, Hereford = 0.50). In Year 2, Braford heifers with greater MAFC attained puberty at an earlier age (r 2  = 0.129; P = 0.0196). Also, diminished MAFC corresponded with decreased growth and development, thus less Braford heifers with low MAFC were inseminated (2/16), compared to those with medium (12/17) and high MAFC (7/17; P < 0.01). Moreover, Braford heifers with low AFC had less progesterone in the cycle post insemination but pregnancy rate was not affected. In Braford heifers in Year 2, there was a high correlation between MAFC and AMH concentrations (0.85 P < 0.001). The results of these experiments indicate that post weaning MAFC and AMH concentrations may be applied to select those Braford heifers that attain puberty at an early age, but these tools are not useful in Hereford heifers. [ABSTRACT FROM AUTHOR]

Two experiments were conducted to evaluate the effects of a high concentrate, s.c. PGF2α compared with a conventionally concentrated, i.m. PGF2α in estrus synchronization protocols for heifers. In Exp. 1, 869 Angus-based beef heifers were enrolled at 8 locations. All heifers were exposed to the 7-d CO-Synch + controlled internal drug release (CIDR) estrus synchronization protocol. On day 7 of the protocol heifers received 100 pg of GnRH i.m., and a CIDR insert for 7 d. On day 0, at CIDR removal, estrous detection patches were applied to heifers and, within location, heifers randomly received 1 of 2 PGF2α treatments: 5 mL of Lutalyse i.m. (CONTROL; n = 434) or a 2 mL of Lutalyse HighCon s.c. (HiCON; n = 435). A second GnRH injection was administered at 54 ± 2 h and heifers were fixed-time AI (TAI). Heifers were evaluated for estrous activity at TAI by determining the activation of estrous detection patches. Pregnancy rates to AI (PR/AI) were diagnosed by transrectal ultrasonography between 35 and 55 d after TAI. The percentage of heifers exhibiting estrus between day 0 and TAI did not differ (P = 0.68) between CONTROL and HiCON treatments (47 vs. 46 ± 4%, respectively). Additionally, PR/AI were similar (P = 0.65) between CONTROL and HiCON treatments (46 vs. 45 ± 3%). In Exp. 2, 190 Angus-based beef heifers were enrolled at 2 locations. Heifers were exposed to the melengestrol acetate (MGA)--PGF2α protocol where they were offered 0.5 mg MGA per day from days 1 to 14. On day 33, heifers were randomly assigned to receive CONTROL (n = 95) or HiCON (n = 95) treatment, and estrous detection aids were applied. Heifers were exposed to AI 12 h after detection of estrus. Heifers not detected in estrus at location 1 received a second PGF2α injection 6 d after the initial PGF2α injection and were placed with fertile bulls. Heifers at location 2 that did not express estrus were administered 100 pg of GnRH i.m. and exposed to TAI 96 h after the initial PGF2α injection. Transrectal ultrasonography was used to diagnose PR/AI between 51 and 57 d after the initial PGF2α injection. The percentage of heifers exhibiting estrus during the estrus detection period was similar (P = 0.40) between CONTROL and HiCON treatments (82 vs. 87 ± 4%). Furthermore, PR/AI were similar (P = 0.62) between CONTROL and HiCON treatments (60 vs. 65 ± 5%). In summary, the 2 concentrations and corresponding routes of administration of PGF were similar in 2α efficacy at synchronizing estrus in beef heifers. [ABSTRACT FROM AUTHOR]

To determine the effects of administration of 25 mg of PGF2α7 d prior to the initiation of the 7-d CO-Synch + controlled internal drug release (CIDR) fixed-time AI (TAI) protocol, 985 Bos taurus beef heifers were enrolled in a completely randomized design at 9 locations from April to July of 2016. Within location, all heifers were randomly assigned to 1 of 2 treatments: 1) CONTROL (n = 496); 100 pg injection of GnRH and a CIDR insert for 7 d [day 7], administration of 25 mg of PGF2α at CIDR removal [day 0], followed by a second injection of GnRH and TAI 54 ± 2 h later; or 2) PRESYNCH (n = 489); same as CONTROL but heifers received an additional injection of 25 mg of PGF2α 7 d prior [day 14] to CIDR insertion. Estrous detection patches were applied to all heifers on day 14 and were evaluated for estrual activity on day 7. Similarly, estrus alert patches were placed on all heifers on day 0 and evaluated for estrual activity at the time of TAI. Pregnancy was diagnosed via transrectal ultra-sonography between 35 and 55 d after TAI. The percentage of heifers exhibiting estrus between days 14 and 7 was greater (P < 0.001) for the PRESYNCH (70.1 ± 2.4%) than the CONTROL (41.1 ± 2.3%) treatment, whereas the percentage of heifers exhibiting estrus between day 0 and TAI was greater (P < 0.001) for the CONTROL (55.6 ± 2.4%) than the PRESYNCH (39.7 ± 2.5%) treatment. Estrus response rates differed (P < 0.001) among locations. Pregnancy rates to TAI differed (P = 0.023) among locations; however, they did not differ (P = 0.739) between CONTROL and PRESYNCH treatments (45.4 ± 2.5 vs. 43.2 ± 2.5%, respectively). Final breeding season pregnancy rates did not differ (P = 0.811) between treatments. Therefore, an injection of PGF2α 7 d prior to initiation of the 7-d CO-Synch +" CIDR protocol failed to improve pregnancy rates to TAI in replacement beef heifers. [ABSTRACT FROM AUTHOR]

Contents: Two experiments were conducted to determine (i) factors influencing calf temperament at weaning, (ii) association between heifer–calf temperament at weaning and temperament at breeding and (iii) effect of heifer–calf temperament on pregnancy rate per artificial insemination (P/AI). In experiment 1, beef cows and their calves (n = 285) from three farms were used. Sire docility estimated progeny difference (EPD) score, birth type (normal or assisted), calf gender, calf behaviour (during 1st 4 weeks) and calf health status (until weaning) were recorded. Cows and calves were assigned a temperament score (0—calm; 1—excitable), and all cows were given a body condition score (BCS, 1–9; 1—emaciated; 9—obese) at weaning. Calf's illness (p < .05), low sire docility EPD score (p < .05), altered gait (p < .05), altered resting behaviour (p < .01), reduced/no play behaviour (p < .05) and cow excitable temperament (p < .001) increased calf excitable temperament at weaning. In experiment 2, replacement heifer–calves (n = 758) from 12 farms were assigned a temperament score at weaning and later at breeding. Blood from 40 calves at weaning and 31 heifers at initiation of synchronization (same animals) was collected by coccygeal venipuncture for determination of circulating cortisol and substance P concentrations. Heifers were assigned a BCS and reproductive tract score (RTS, 1–5; 1—immature, acyclic; 5—mature, cyclic), synchronized for fixed time AI, observed for oestrus and were artificially inseminated. Cortisol concentrations were increased in excitable heifer–calves compared to calm heifer–calves at weaning (p < .05), and substance P was increased in excitable compared to calm females both at weaning and breeding (p < .05). Low sire EPD docility score (p < .01), heifer–calf excitable temperament at weaning increased excitable temperament at breeding (p < .01). Controlling for BCS categories (p < .01), oestrous expression (p < .0001) and temperament at breeding by oestrous expression (p < .05), the calf's excitable temperament at weaning (p < .001) reduced P/AI (Calm, 62.7 (244/389) vs. Excitable, 53.4% (197/369); p < .01). In conclusion, selection of docile cows and sires with greater docility EPD score should be given consideration to reduce calf excitement. Temperament in beef female can be detected earlier in their life and could be used as a tool in the selection process and to improve their performances. [ABSTRACT FROM AUTHOR]

To determine the effects of estrus synchronization (ES) and fixed-time artificial insemination (TAI) on calving distribution in Bos indicus influenced heifers, 751 Bos taurus × Bos indicus beef heifers were enrolled in a completely randomized design at 2 locations from January to May of 2016. Within location, all heifers were randomly assigned to one of two treatments: 1) SYNCH (n = 371); heifers were exposed to the 5-day CO-Synch + CIDR protocol where they were treated with 100 μg of GnRH, 25 mg of PGF 2α , and a controlled internal drug releasing insert (CIDR) on d 0; heifers received 50 mg of PGF 2α at CIDR removal on d 5, and were treated with 100 μg of GnRH and TAI 66 ± 2 h later on d 8; or 2) CONTROL (n = 380); heifers were exposed to natural service without ES or TAI. On d 9, all heifers were exposed to bulls for the remainder of the breeding season at each location. Blood samples were collected on d −9 and on d 0 to determine pretreatment estrous cyclicity (progesterone ≥ 1.0 ng/mL). Pregnancy was diagnosed via transrectal ultrasonography 54 d after TAI by determining the presence of a viable fetus. Fetal age was estimated based on fetal size and structural features at the time of pregnancy diagnosis. Pregnancy rates on d 54 differed ( P < 0.001) between locations, but did not differ ( P = 0.777) between CONTROL and SYNCH treatments. Pregnancy rates on d 54 were greater ( P < 0.001) in cycling compared with non-cycling heifers (63.9 vs 42.4%). A greater ( P < 0.05) proportion of SYNCH heifers became pregnant in the first 19 d of the breeding season compared with CONTROL heifers (52.2 vs 46.4%). Overall breeding season pregnancy rates did not differ ( P = 0.982) between treatments. In summary, ES and TAI increased the percentage of heifers that conceived in the first 19 d of the breeding season, and therefore, potentially altered the calving distribution by ensuring that more heifers calve early during the subsequent calving season. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine the effect of stockpiled forage type and protein supplementation on VFA production, serum metabolites, and BW in yearling beef heifers. Over 2 yr, spring-born, Angus crossbred yearling beef heifers (n = 42; 305 ± 2.9 kg initial BW) were randomly assigned to 1 of 3 forage pasture types: 1) endophyteinfected tall fescue [TF; Schedonorus arundinaceus (Schreb.) Dumort], 2) a big bluestem (Andropogon gerardii Vitman) and indiangrass (Sorghastrum nutans L.) combination (BI), or 3) switchgrass (SG; Panicum virgatum L.). Each pasture was then randomly assigned to receive either 1 of 2 isonitrogenous CP treatments: 1) 0.68 kg·heifer-1·d-1 of dried distiller's grains with solubles (DDGS; 28% CP and 88% TDN) or 2) 0.22 kg·heifer-1·d-1 of blood meal and fish meal (BF; 72.5% CP and 69.5% TDN), resulting in a 3 × 2 factorial arrangement of treatments. Treatments were initiated in January and terminated in April in both years of the study. Body weights and blood samples were collected approximately every 28 d from initiation of grazing until the end of the trial. Heifer BW change from January to February and overall BW change were greater (P < 0.01) for TF heifers. However, BW change from March to April was not different (P = 0.84) among forage types. Supplement type did not influence (P ≥ 0.13) BW or BW change from January to February and from January to April; however, heifers fed DDGS had greater (P = 0.03) BW gain from March to April. Heifer BW change from February to March exhibited (P < 0.05) a forage type × supplement interaction, with BF-fed heifers gaining more BW on BI pastures than DDGSfed heifers. Serum glucose concentrations, ruminal acetate, and the acetate:propionate ratio were greater (P ≤ 0.04) for SG heifers. However, circulating serum NEFA and urea N (SUN) concentrations were not different (P ≥ 0.85) among forage types. Serum glucose and NEFA concentrations were not influenced (P ≥ 0.61) by supplement type. Circulating SUN concentrations were greater (P < 0.01) in BF-supplemented heifers. Ruminal acetate tended to be greater (P = 0.09) and butyrate concentrations were greater (P < 0.01) for BF-supplemented heifers. The acetate:propionate ratio was not influenced (P = 0.15) by supplement type. These results suggest that a compensatory gain period prior to breeding would be needed for these native warm-season species to be a viable opportunity for growing and developing replacement heifers in the southeastern United States. [ABSTRACT FROM AUTHOR]