Search

Simple Summary: Environmental indices are commonly used for detecting heat stress in dairy cattle; however, most studies have only focused on the productivity traits of dairy cattle in response to heat stress and have not considered their health and reproductive characteristics simultaneously. In this study, we aimed to determine the effects of heat stress on the production and reproduction performances of Thai–Holstein dairy cattle and the impact of the genetics of dairy cattle on their heat tolerance. We observed that heat stress significantly reduced milk yield and negatively affected the milk fat-to-protein ratio. Additionally, conception rates declined under heat stress, highlighting the challenges of finding an effective genetic approach for hot and humid regions, including Thailand. Genetic analysis revealed differences in heat tolerance among cows, indicating that the genetic improvement approach used in this study is suitable for planning future genetic improvements in dairy cattle. Heat stress severely affects dairy cattle production and reproduction performances in tropical regions. Genetic selection to maintain adequate yield and reproductive performance while enhancing their ability to withstand heat is essential for improving the genetics of dairy cows. Therefore, in this study, we aimed to estimate genetic parameters affecting production and reproduction performances under heat stress conditions in dairy cattle and to investigate the threshold point of heat stress for milk yield (MY), milk fat-to-protein ratio (FPR), and conception rate (CR) in Thai–Holstein dairy cattle. The data included 168,124 records related to MY and milk FPR and 21,278 records of CR in Thai–Holstein dairy cattle, covering the period from 1990 to 2007. A multiple-trait threshold-linear random regression model based on a Bayesian approach via Gibbs sampling was used to estimate variance components, genetic parameters (heritability values, and genetic correlations), and decline rates for each studied trait. The threshold point of heat stress was identified as a temperature and humidity index (THI) of 76. At THI76, a decline was observed in the MY, milk FPR, and CR of Thai dairy cattle. The heritability estimates for MY, milk FPR and CR were 0.347 ± 0.032, 0.293 ± 0.021, and 0.032 ± 0.001, respectively. The genetic correlation between MY and milk FPR and MY and CR were −0.24 and −0.53, respectively, whereas those between milk FPR and heat tolerance as well as between CR and heat tolerance were −0.48 and −0.49, respectively. In addition, the decline rates in MY, milk FPR, and CR were found to be associated with a high percentage of Holstein genetics. In conclusion, the results obtained in this study reveal that the simultaneous consideration of the MY, milk FPR, CR, and heat tolerance traits of Thai–Holstein dairy cattle is possible. In addition, developing a genetic model that incorporates THI is essential for sustainably addressing heat stress problems. [ABSTRACT FROM AUTHOR]

This document discusses the importance of dairy cattle in economic development and their multifaceted interactions with humans throughout history. It highlights the advancements in reproductive technologies for dairy cattle and their potential applications in other mammalian species. The document emphasizes the significance of effective reproductive management for the economics of herds, cow health and welfare, and reducing greenhouse gas emissions. It also provides a summary of the articles included in the Special Issue on "Advances in Dairy Cattle Reproduction," which cover various strategies to improve reproductive parameters and optimize assisted reproductive technologies. The document concludes by stating that further research and understanding of the reproductive function of cows can lead to improved health, welfare, productivity, and sustainability in dairy production systems. [Extracted from the article]

Copyright of Journal of Central European Agriculture is the property of Journal of Central European Agriculture 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.)

Background: The genetic progress of fertility and reproduction traits in dairy cattle has been constrained by the low heritability of these traits. Identifying candidate genes and variants associated with fertility and reproduction could enhance the accuracy of genetic selection and expedite breeding process of dairy cattle with low-heritability traits. While the bovine LAP3 and SIRT1 genes exhibit well-documented associations with milk production traits in dairy cattle, their effect on cow fertility have not yet been explored. Eleven single nucleotide polymorphisms (SNPs), comprising five in the promoter (rs717156555: C > G, rs720373055: T > C, rs516876447: A > G, rs461857269: C > T and rs720349928: G > A), two in 5'UTR (rs722359733: C > T and rs462932574: T > G), two in intron 12 (rs110932626: A > G and rs43702363: C > T), and one in 3'UTR of exon 13 (rs41255599: C > T) in LAP3 and one in SIRT1 (rs718329990:T > C) genes, have previously been reported to be associated with various traits of milk production and clinical mastitis in Sahiwal and Karan Fries dairy cattle. In this study, the analysis primarily aimed to assess the impact of SNPs within LAP3 and SIRT1 genes on fertility traits in Sahiwal and Karan Fries cattle. Association studies were conducted using mixed linear models, involving 125 Sahiwal and 138 Karan Fries animals in each breed. The analysis utilized a designated PCR-RFLP panel. Results: In the promoter region of the LAP3 gene, all variants demonstrated significant (P < 0.05) associations with AFC, except for rs722359733: C > T. However, specific variants with the LAP3 gene's promoter region, namely rs722359733: C > T, rs110932626: A > G, rs43702363: C > T, and rs41255599: C > T, showed significant associations with CI and DO in Sahiwal and Karan Fries cows, respectively. The SNP rs718329990: T > C in the promoter region of SIRT1 gene exhibited a significant association with CI and DO in Sahiwal cattle. Haplotype-based association analysis revealed significant associations between haplotype combinations and AFC, CI and DO in the studied dairy cattle population. Animals with H2H3 and H2H4 haplotype combination exhibited higher AFC, CI and DO than other combinations. Conclusions: These results affirm the involvement of the LAP3 and SIRT1 genes in female fertility traits, indicating that polymorphisms within these genes are linked to the studied traits. Overall, the significant SNPs and haplotypes identified in this study could have the potential to enhance herd profitability and ensure long-term sustainability on dairy farms by enabling the selection of animals with early age first calving and enhance reproductive performance in the dairy cattle breeding program. [ABSTRACT FROM AUTHOR]

Introduction: Optimizing the management of dairy cattle reproduction can reduce postpartum ovarian disease in high-yielding dairy cows and thus enhance ranch economic benefit. The hypothesis of this study was that the Double-Ovsynch (DO) protocol in high-producing dairy cows would result in a lower incidence of follicular cysts but a higher incidence of luteal cysts compared to those undergoing the Presynch-Ovsynch (PS) protocol. Methods: In this experiment, 384 cows (204 primiparous and 180 multiparous) were allocated to the DO group, which followed the protocol: GnRH-7d-PGF2α-3d-GnRH-7d-Ovsynch-56 h (GnRH-7d-PGF2α-56 h-GnRH-16hTAI), starting on 39 ± 3 days in milk (DIM). Additionally, 359 cows (176 primiparous and 183 multiparous) were assigned to the PS group, which followed the protocol: PGF2α-14d-PGF2α-12d-Ovsynch-56 h, starting on 31 ± 3 DIM. In DO, B-mode ultrasound examinations were conducted 1 day after the GnRH-7d-PGF2α-3d-GnRH protocol to diagnose the presence of ovarian diseases followed by reexamination after 7 days of suspected cases. In PS, B-mode ultrasound examinations were conducted 1 day after the PGF2α-14d-PGF2α protocol to diagnose the presence of ovarian diseases followed by reexamination after 7 days. For all cows confirmed to having ovarian diseases, a second B-mode ultrasound examination was conducted at the time of the second GnRH and timed artificial insemination (TAI). If the ovary showed a normal developing follicle in combination with normal ovulation, the ovarian disease was considered to be cured. Results: The current study revealed no significant difference in the overall incidence and cure rate of postpartum ovarian diseases between DO and PS (incidence rate: 3.9% vs. 6.7%, cure rate: 50% vs. 41.7%, DO vs. PS). Also, there was no significant difference in the incidence and cure rate of luteal cysts between DO and PS (incidence rate: 2.9% vs. 2.2%, cure rate: 50.0% vs. 50.0%). The incidence of follicular cysts was significantly lower in the DO group than in the PS group (0.8% vs. 2.8%, DO vs. PS, p = 0.037), but there was no significant difference in the cure rates (66.7% vs. 50%). The occurrence of inactive ovary was lower in DO compared to PS (0.2% vs. 1.7%, p = 0.047). There was no significant difference in the pregnancy rate between the DO and PS groups (48.2% vs. 41.8%), although the DO group had a higher rate. What is different from our assumption is that PS did not effectively reduce the incidence of postpartum luteal cysts. [ABSTRACT FROM AUTHOR]

In this study we investigated the genetic variability, the inbreeding and allele frequencies of monogenic traits in seven herds of Holstein breed and provided insight to farmers on the value of genomic management of reproduction in their herds. A total of 3,953 Holstein cows were sampled and genotyped with the Neogen GGP Bovine 100K SNP chip within the activities of the Regione Lombardia funded GO-PEI project 'GENOmic tool for the management of reproduction in dairy cattle and for the control of inbreeding – GENORIP'. Principal component analysis was applied for analysing the genetic variability within and among farms using the SVS software of Golden Helix. Run of Homozygosity (ROH) and the genomic inbreeding were obtained with the detectRUNS package of the R software. Genotype frequencies for mendelian disease, fertility and production traits were also obtained. A total of 458,267 ROH were identified and ROH were distributed on all autosomes with an average length of 2,703,811 bp covering 12.7% of the genome. Several genomic regions appear under selection, while a specific region on BTA4 was identified in one herd, harbouring genes mainly related to the specific selection strategy of the farmer. The FROH values obtained considering ROH greater than 16 Mb, varied from 0.004 to 0.325, with the highest FROH average value of 0.136. Among mendelian heritable diseases, the Haplotype Cholesterol Deficiency was the one with the largest proportion of carrier animals, i.e. 5.6%. A herd-tailored process to assist farmers in genomic management of reproduction was released. The ROH distribution within herd, together with the genotype frequencies for disease, fertility and production mendelian traits, suggest that similar directional selection is occurring across herds. This study released to each farmer the genomic make-up of their herd used jointly with the gEBV estimated by their national breeders' association (ANAFIBJ) for herd reproductive management. All females of 7 herds have been genotyped with the GGP 100K SNP chip. Genomic information on all females can be used by farmers in the process to manage reproduction, selection and genetic herd variability. The availability of genomic information on the whole herd allowed to release to each farmer the genomic make-up of their herd. The ROH distribution together with the genotype frequencies for disease, fertility and production mendelian traits, made it possible to identify genomic regions under selection according to farmer strategies. [ABSTRACT FROM AUTHOR]

Simple Summary: This review focuses on two crucial aspects of cattle breeding: the reproduction of dairy cows and the health status and body condition of cows during the periparturient period, as well as the immunity of newborn calves. The energetic importance of fat in ruminant nutrition and lipids metabolism in the rumen, the regulatory role of n-3 fatty acids in the reproduction of ruminants, their importance in fetus developmental programming and embryo development, as well as the role of n-3 fatty acids a key component in the building of the immunity of newborn calves, are discussed. This paper focuses on the role of n-3 fatty acids as a nutrient crucial to the proper functioning of reproductive and immune systems in cattle. Emphasis was placed on the connection between maternal and offspring immunity. The summarized results confirm the importance and beneficial effect of n-3 family fatty acids on ruminant organisms. Meanwhile, dietary n-3 fatty acids supplementation, especially during the critical first week for dairy cows experiencing their peripartum period, in general, is expected to enhance reproductive performance, and the impact of its supplementation appears to be dependent on body condition scores of cows during the drying period, the severity of the negative energy balance, and the amount of fat in the basic feed ration. An unbalanced, insufficient, or excessive fatty acid supplementation of cows' diets in the early stages of pregnancy (during fetus development) may affect both the metabolic and nutritional programming of the offspring. The presence of the polyunsaturated fatty acids of the n-3 family in the calves' ration affects not only the performance of calves but also the immune response, antioxidant status, and overall metabolism of the future adult cow. [ABSTRACT FROM AUTHOR]

Simple Summary: The bacterium C. burnetii, causing Q fever in humans and animals, is widespread worldwide, but the true extent of C. burnetii spread is not always known. Q fever in ruminants is mainly associated with abortions and reproductive disorders. However, there is a lack of research on what happens to animals after abortion and whether reproduction and productivity in animals with C. burnetii-related abortions differs from those with abortions that are unrelated to C. burnetii. In our study, we compared data on abortions, outcome of the animals after abortions both related and unrelated to Coxiella burnetii, and the reproduction and productivity data for animals which had aborted to the herd average parameters. We found that C. burnetii-related abortions are more often observed in older cows, but there were no significant differences between groups for the other compared indicators. We found that abortions, both related and unrelated to C. burnetii are economically unprofitable due to a high culling rate and due to the reproductive problems caused by abortions resulting in the absence of new pregnancies. When comparing the productivity data of animals that had aborted to the herd average, we found it to be lower if the animal had started a new lactation after an abortion. C. burnetii is a widespread pathogen, causing abortions and reproductive disorders in ruminants. The study aimed to evaluate animal reproductive capacity and productivity after abortion, related and unrelated to C. burnetii. We compared data about the abortion time, the outcome of the animals after an abortion, further reproduction, and productivity for C. burnetii-positive (n = 148) and C. burnetii-negative (n = 149) aborted dairy cows and heifers. C. burnetii-positive animals had a positive serological response or presence of C. burnetii DNA at the time of abortion. C. burnetii-positive animals had a significantly higher number of lactations at the time of abortion. However, in the other indicators, we observed no significant differences between the groups. Comparing indicators of all the aborted animals, we found that if animals started a new lactation after abortion, they had a significantly lower milk yield, lower fat, protein, and somatic cell counts (SCCs) in milk during the standard lactation for both primiparous and multiparous cows compared to herd averages in each group. Lower SCCs can be due to animals with a high SCC being culled earlier. We found an economic disadvantage to aborting, not only because of the loss of offspring, but also because of the high culling rate and lower productivity in both primiparous and multiparous cows. [ABSTRACT FROM AUTHOR]

Postpartum (PP) reproduction anomalies (increased calving interval and semen doses, pregnancy loss, infertility culling rate) are mostly caused by postpartum uterine diseases. The aim of this study was to find diagnostic symptoms (signs) help in identifying animals having possible subclinical endometritis. As a logical first step, analyzing a database with several thousand transrectal postpartum palpations and ultrasonic findings of the genital tract and production data of dairy cows (CATUS) seemed reasonable. Healthy (H) cows and animals with clinical endometritis (CE) both are in this database. We thought that statistical analysis of large amount of H and CE animals' data should help in identifying signs or reasonable suspicion for recognizing cows with subclinical endometritis (SCE) in the future as well. During this work palpation and ultrasound data of healthy and CE cows were compared. Totally, data of 10683 cows were evaluated by chi-square test. These results show distinct differences in distribution of uterine size (volume) and ovarian phenomena in the two groups. As a sign of inappropriate involution large-sized uterus (32.9 % vs. 64.9 %) and uterine fluid content (6.1 % vs. 31.1 %) were significantly higher (p<0.0001) in CE group. Abnormal ovarian ovulatory phenomena (corpus luteum /CL/ with cavity: 8.0 % vs. 13.1 %; or cystic CL: 4.2 % vs. 27.4 %) also were detected in significantly higher numbers in animals with CE signs (p<0.0001). These results induce further examinations to compare them with SCE animals' data for identifying diagnostic signs which are typical for the examiners. [ABSTRACT FROM AUTHOR]

The purpose of the research was to assess changes in the lactation activity of cows and their impact on the level of reproduction, as well as to study their fluctuations with respect to genetic and environmental factors. A sample of 807 cows of various ages was formed for the study. The cows were kept on a commercial farm in Kharkiv region, Ukraine. Data from DairyPlan C21 software were used in the study. It was revealed that the parameters of the Wood lactation curve model were significantly influenced by the calving season, days open, and cow's origin; lactation persistency of cows was more influenced by environmental factors (parity, calving season, days open) than by the sire. In order to improve the level of reproduction in dairy herds, it is advisable to take into account the lactation persistency of cows, since it has negative relationship with days open (r = -0.074). To improve lactation persistency it is necessary to use for insemination of cows semen of sires with high breeding values for this trait. [ABSTRACT FROM AUTHOR]

Heat stress has negative consequences for milk production and reproduction of dairy cattle. These adverse effects are likely to increase because of climate change and anticipated increases in milk yield. Some of the variation among cows in ability to resist effects of heat stress is genetic. The current objective of this observational study was to assess the effectiveness of the Australian breeding value for heat tolerance (ABVHT) based on the decline in milk yield with heat stress for predicting cow differences in effects of heat stress on regulation of body temperature, milk production, and reproductive function. Genomic breeding values for heat tolerance were calculated for 12,487 cows from a single California dairy farm. Rectal temperature in the afternoon (1100–2045 h) was measured on a subset of 626 lactating cows with ABVHT ≥102 (heat tolerant) or <102 (heat sensitive). Rectal temperature was 0.12°C lower for heat-tolerant cows than heat-sensitive cows. Vaginal temperatures were measured every 15 min for 5 d in 118 cows with ABVHT ≥108 (extreme heat tolerant) or <97 (extreme heat sensitive). Vaginal temperature was 0.07°C lower for extreme heat–tolerant cows than extreme heat–sensitive cows. Lactation records for 4,703 cows with ABVHT were used to evaluate seasonal variation in first 90-d milk yield, fat percent, and protein percent for each ABVHT quartile. Overall, cows with higher ABVHT had lower milk yield, fat percentage, and protein percentage and higher first service pregnancy rate. There was no summer depression in production or reproduction or interactions between season and ABVHT quartile. We observed that ABVHT can successfully identify heat-tolerant cows that maintain lower body temperatures during heat stress. The lack of a pronounced seasonality in milk production or reproduction precluded evaluation of whether ABVHT is related to the magnitude of effect of heat stress on those traits. [ABSTRACT FROM AUTHOR]

Simple Summary: Female fertility has gained significant attention and is incorporated in dairy cattle breeding objectives worldwide. Currently, age at first calving (AFC) and calving interval (CI) are the only traits used as indicators of fertility in the genetic evaluations of South African dairy cattle, but these traits are greatly affected by the breeder's decisions and calving interval is available late in an animal's life which delays selection decisions. This study investigated the possible use of additional fertility traits derived from artificial insemination records. The fertility traits examined in this study could be used in addition to age at first calving and calving interval to select for improved fertility in dairy cattle. This study aimed to derive additional fertility traits from service data and estimate their genetic parameters for their possible inclusion in the South African Holstein cattle breeding programs. Service records (n = 64,464) were collected from 18 South African Holstein herds using on-farm automated milk recording systems. Using a multivariate model, the data were used to estimate heritabilities and correlations among several fertility traits. The pedigree data consisted of information on 18,592 animals born between 1981 and 2013. Heritability estimates observed were low to moderate (0.02 ± 0.00 to 0.24 ± 0.00), indicating that there is some genetic basis for the explored fertility traits to warrant selection. The genetic correlations observed between fertility traits were generally favorable, with some high correlations between age at first service (AFS) and services per conception for heifers (SPCh) (0.73 ± 0.00) and between days from calving to first service (CFS) and services per conception for cows (SPC) (0.90 ± 0.01). Positive genetic correlations indicate that improvement in one trait is coupled with a correlated genetic increase in another trait. The studied fertility traits could be used in addition to AFC and CI to serve as a basis for the selection of reproduction in dairy cattle to minimize selection bias. [ABSTRACT FROM AUTHOR]

The purpose of this study was to determine the sensitivity of Staphylococcus aureus and Escherichia coli isolated from the reproductive tract of dairy cows during estrus to tetracycline, gentamicin, amoxicillin, and ciprofloxacin. Isolation and identification of E. coli and S. aureus from 24 cervical mucus samples resulted 15 samples containing E. coli and one sample containing S. aureus. Sensitivity test was performed using Kirby-Bauer (disc diffusion) method and interpreted using the Clinical and Laboratory Standards Institute (CLSI, 2017) guidelines. The sensitivity test of 15 isolates of E. coli showed 100% sensitivity to ciprofloxacin and tetracycline. For gentamicin, 14 (93.3%) isolates were sensitive, and 1 (6.7%) isolate was resistant, while for amoxicillin, 14 (93.3%) isolates were sensitive, and 1 (6.7%) isolate were intermediate. The sensitivity test of one isolate of S. aureus showed 100% sensitivity to ciprofloxacin, gentamicin, and amoxicillin; as for tetracycline 100% isolates were declared resistant. [ABSTRACT FROM AUTHOR]

The aim of this study was to assess the lactation, reproductive performance, and disorders of dairy cows in Waliso and Ilu districts. A total of 122 respondents who participated in the production of dairy cattle were chosen at random and proportional to their size. The collected data were analyzed using Statistical Package for Social Sciences (SPSS) version20. Descriptive statistics were used to summarize the results such as overall means, standard error (SE), graphs, tables, frequency, and percentage. Daily milk yield of local breed cow was1.890±0.05liters/per/cow/day, while cross breed dairy cows7.410±0.31liters/ cow/day. Cross breed dairy cows produced (1978.4597±0.98) liters/ lactation/cow and native breed cows produced (429.78±17.10) liters /lactation/cow on average. Results showed that local and cross breed dairy cows had lactations length of 7.58±0.05 and 8.90±0.29 months per lactation per year. The average reproductive performance of local and cross breed dairy cows was (AFS) 44.88±0.57and 24.43±0.29 months, (AFC)53.94±0.56and 33.43±0.29 months, (CI)14.35±0.41) and 14.35±0.41months, (DO)161±0.41 and 140±0.49) days, and (NSPC)1.69±0.06 and1.70±0.10 times, respectively. Daily milk yields, average milk yields, and lactation lengths were significantly (P0.05) different between the two Districts. The overall percentages of stillbirths, dystocia, retained fetal membranes, abortions, and mastitis were 8%, 6.35 %, 6.66 %, 12.15 %, and 11.8%, respectively. In inclusion, it could be concluded that the productive lactation, reproductive performance and disorder are relatively low. Thus, indicating that it is an urgent need for well-coordinated efforts of all concerned bodies to boost the productive and reproductive performance there by enhances the livelihood of the dairy farmers. [ABSTRACT FROM AUTHOR]

In our previous GWAS of Chinese and Nordic dairy cattle, genes CACNB2 , SLC39A12, and ZEB1 locating on BTA 13 were suggested as candidate genes for reproduction. In this study, validation of these associations was performed in an independent population with records of nine reproductive traits. More importantly, functions of these genes in the reproductive process were verified by employing the expression data of ovarian follicles. The potential variants within the three genes were firstly detected in 68 Chinese Holstein bulls, and then screened in 1,588 Chinese Holstein cows using the KASP (Kompetitive allele-specific PCR) method. There were nine variants with polymorphisms in CACNB2 , five in SLC39A12, and four in ZEB1 , respectively, of which one SNP was in the upstream regulatory region, two in exon region, four in downstream regulatory region, and 11 SNPs in intronic regions. Amongst the 18 variants, g.33267056T/G in CACNB2 explained the largest phenotypic variance for age at first calving (0.011%), interval from first to last insemination (0.004%), and calving ease (0.002%), while g.32751518G/A in SLC39A12 contributed the most to stillbirth in heifers (0.038%). Two haplotype blocks were constructed for CACNB2 while one each for SLC39A12 and ZEB1 , which were significantly associated with five reproductive traits, including age at the first service, age at the first calving, calving ease in heifers and cows, and the interval from calving to the first insemination. We then studied the profile of gene expression in granulosa cells isolated from four developmental stages of ovarian follicles from eight dairy cows. All three genes were differentially expressed between ovarian follicles with different sizes (p < 0.05), indicating their potential roles in the reproductive process of dairy cows. This study successfully demonstrated the associations of three BTA 13 genes CACNB2 , SLC39A12, and ZEB1 with reproduction and further examined their expression levels in ovarian follicles directly. These findings can be beneficial for the ongoing genomic selection program for reproductive traits which have long been considered as traits that are difficult to achieve genetic improvement due to the lack of efficient genetic markers. [ABSTRACT FROM AUTHOR]

Background: Genetic progress for fertility and reproduction traits in dairy cattle has been limited due to the low heritability of most indicator traits. Moreover, most of the quantitative trait loci (QTL) and candidate genes associated with these traits remain unknown. In this study, we used 5.6 million imputed DNA sequence variants (single nucleotide polymorphisms, SNPs) for genome-wide association studies (GWAS) of 18 fertility and reproduction traits in Holstein cattle. Aiming to identify pleiotropic variants and increase detection power, multiple-trait analyses were performed using a method to efficiently combine the estimated SNP effects of single-trait GWAS based on a chi-square statistic. Results: There were 87, 72, and 84 significant SNPs identified for heifer, cow, and sire traits, respectively, which showed a wide and distinct distribution across the genome, suggesting that they have relatively distinct polygenic nature. The biological functions of immune response and fatty acid metabolism were significantly enriched for the 184 and 124 positional candidate genes identified for heifer and cow traits, respectively. No known biological function was significantly enriched for the 147 positional candidate genes found for sire traits. The most important chromosomes that had three or more significant QTL identified are BTA22 and BTA23 for heifer traits, BTA8 and BTA17 for cow traits, and BTA4, BTA7, BTA17, BTA22, BTA25, and BTA28 for sire traits. Several novel and biologically important positional candidate genes were strongly suggested for heifer (SOD2, WTAP, DLEC1, PFKFB4, TRIM27, HECW1, DNAH17, and ADAM3A), cow (ANXA1, PCSK5, SPESP1, and JMJD1C), and sire (ELMO1, CFAP70, SOX30, DGCR8, SEPTIN14, PAPOLB, JMJD1C, and NELL2) traits. Conclusions: These findings contribute to better understand the underlying biological mechanisms of fertility and reproduction traits measured in heifers, cows, and sires, which may contribute to improve genomic evaluation for these traits in dairy cattle. [ABSTRACT FROM AUTHOR]

Background: Global warming has increased the frequency of heat stress in livestock. Although heat stress directly leads to negative effects on production and reproduction traits in dairy cattle, the transgenerational transition of these changes is poorly understood. We hypothesized that heat stress in pregnant cows might induce epigenetic modifications in the developing embryo germ cells, which, in turn, might lead to phenotypic effects in the offspring. Here, we examined whether transgenerational effects of heat stress contribute to the phenotypic expression of economic traits in Israel dairy cattle. Since heat stress in Israel occurs specifically between June and October, first we examined the association of the month of birth of F1 cows (pregnancy of the F0 dam) with the performance of the F2 and F3 female offspring. Then, we calculated an annual heat stress index and examined the association of the heat stress index during the pregnancy of the F0 dam with the performance of her F2 and F3 offspring. Finally, we examined intergenerational interactions of heat stress by comparing the performance of F3 cows according to the pregnancy seasons of the F0 and F1 animals. Results: We found a significant association of the month of birth, season of pregnancy, and heat stress index of F0 females, with the performance of their F2 and F3 progenies, which suggests a true transgenerational effect. The most significant transgenerational effects were on fat yield and concentration, dystocia, still-birth, and maturation. Conclusions: These findings suggest that heat stress during pregnancy affects the performance of offspring, regardless of life circumstances in at least the last three generations. Therefore, heat stress can reduce selection efficiency in breeding programs and may have economic significance in livestock. [ABSTRACT FROM AUTHOR]

Artificial reproduction in dairy cattle is challenged by summer temperatures in tropical environments. We describe a treatment based on mild temperature increases to induce thermotolerance and improve the embryo's performance under heat stress conditions. A protocol was established to induce upregulation of heat shock protein A (HSPA, formerly known as HSP70) but not impair embryonic development. Thermal treatment (TT) had no effect on morula/blastocyst rate or blastocyst quality (cell number and apoptosis). Heat shock given one day after TT revealed higher (P = 0.00) survival rates in TT blastocysts compared with Control. Treated embryos were transferred to recipients and no detrimental effects were observed regarding pregnancy rates, length, fetal growth or calf weight. Our results demonstrated that the established TT protocol could induce a thermal response by the embryo and is safe for further development. Heat stress negatively affects reproduction and ways to mitigate the effects are needed. Survival pathways can be activated to increase cell tolerance to elevated temperatures and we present a mild thermal treatment developed to induce protective mechanisms in embryos before exposure to heat stress conditions. Thermal treatment of embryos may be an interesting strategy to mitigate the effects of heat stress on reproduction. [ABSTRACT FROM AUTHOR]

Dustin Oedekoven, a jis president of Clifford Veterinary Illilif# Il Pierre, South Dakota, Dr. Charlie Dr. Dustin Consulting. Dr. Baysinger is the North American re, Young Swine Veterinarian of the Year ..6 V-i. animal welfare lead for Merck Animal 1, t<:-Dr. Chris Sievers (Iowa State '16), ~ '~ Health. JAVMA News People AMERICAN ASSOCIATION OF SWINE VETERINARIANS EVENT make science-based recommendations, and willingness to 52nd annual meeting, held virtually, Feb. 27-March 2 share knowledge. [Extracted from the article]

Heat stress has been widely studied in relation to its effects on the production and reproduction of dairy cattle. However, the long-term effects of heat stress during intrauterine development on adult cows have been scarcely considered. Thus, the aim of this study was to evaluate possible changes in the reproductive performance of Holstein cows gestated under different values of the Temperature-Humidity Index (THI) during their intrauterine development. Data collected from a database of reproductive and productive records of 10,790 Holstein cows from the central region of Argentina and the THI data from the agrometeorological station of the Instituto Nacional de Tecnología Agropecuaria (INTA) EEA Rafaela, Santa Fe, Argentina, were used. The gestation of the cows evaluated was divided into trimesters, in which the highest THI cycles (sum of three or more consecutive days of exposure to a THI ≥72 during each trimester) and number of days with a THI ≥ 72 were calculated. The calving-to-conception and calving-to-first-service intervals of the cows evaluated were considered as reproductive variables associated with their first lactation. Generalized Linear Mixed Models were used, considering the cow's dairy farm as a random factor within the model. The exposure of the animals to environments with a THI ≥72 during the first trimester of gestation had a negative impact on the reproductive efficiency parameters analyzed. The results obtained indicate that the exposure of pregnant females to high THI values has a long-term impact on their daughters, which may contribute to a decrease in their reproductive performance, possibly through inherited epigenetic characteristics that remain in later generations through fetal programming. • Exposure to high THI values during the first third of gestation has a negative impact on cattle progeny. • Heat stress during gestation negatively affects the CCI and CFSI of the resultant offspring. • The first trimester of gestation is critical for reproductive development of cattle. [ABSTRACT FROM AUTHOR]

Webinars are commonly organized in the dairy industry to remotely deliver information on a specific topic to a live audience. The information presented is simplified, current, based on scientific research, and delivered by experts that are not available at the home university. The objective was to utilize this popular source of information in an Animal Science course and evaluate the sources of webinar used, webinar delivery format, webinar themes, and student impressions obtained from the reflection assignment. Students (n =30) in a dairy production management course were required to attend a live or recorded webinar on the topic of their interest. Overall, 32% of the students used webinars hosted by private industry, 46% used university extension webinars, and 22% used professional society webinars. Altogether, 25% of the students used topics in dairy cattle nutrition, 18% used webinars related to milk quality, 25% used webinars on current industry status, 25% attended animal health webinars, and 7% used dairy cattle reproduction webinars. Overall, 58% of the students responded that they learned at least one new concept that was not discussed in the class. A qualitative thematic analysis of the student reflections indicated that students enjoyed learning about the practical application of classroom concepts, liked learning from experts about recent developments in the industry, and appreciated the flexibility associated with the webinars. We conclude that students prefer university extension webinars in topics directly applicable on farms. The webinars provide broader opportunities for students to learn the classroom concepts from experts in the field while offering flexible options to learn in an undergraduate course. [ABSTRACT FROM AUTHOR]

The seasonality of reproduction in most mammals is dictated by photoperiod, temperature and nutrition. Melatonin, mainly synthesized in the pineal gland, is generally accepted as the active mediator of photoperiod responses including reproduction. While non-pregnant heifers and cows show continuous sexual activity and are therefore not seasonal breeders, it has been suggested that photo-periodicity may influence the appearance of puberty in heifers and the onset of parturition. Further, the light/dark ratio may influence endocrine patterns of gestation and a shorter light period correlates with the incidence of twin pregnancies. This review considers specific aspects of the effects of photoperiod and melatonin on reproduction in dairy cattle and discusses the clinical applications of melatonin. [ABSTRACT FROM AUTHOR]

Background. The production of milk and dairy products and their placement on the market represent a constant profit for the farmers/producers in Bosnia and Herzegovina (BH). The profitable operation of the dairy farms is influenced by the reproductive performance of the lactating animals. This study assessed individual animal reproductive characteristics in selected dairy farms and described their reproductive performance indicators. Results. The median age at first insemination was 493 days (5th–95th percentile range 429–840), while the age at first calving was 802 days (5th–95th percentile range 708–1168). The median pregnancy proportion at first insemination was 40% (5th–95th percentile range 17–62), while the cumulative pregnancy rate calculated at day-60, day-80, day-100, and day-120 showed that approximately 64% of all pregnancies happened before day-120. The calculated interservice intervals showed that approximately 69% of the repeat breeding animals came back to the oestrus in the period of 18 to 24 days. This is an indication of very good oestrus detection in selected dairy farms. The mean number of services per pregnancy was 2.61 (range 1–12). The median calving-to-first-insemination interval was 62.5 days (5th–95th percentile range 16–408). The calving-to-conception interval was 101 day (5th–95th percentile range 36–506). Finally, the calving interval was 385 days (5th–95th percentile range 329–773). Conclusions. There is a need for an organised, regular, and more comprehensive recording system for the reproduction of dairy cattle among dairy farms in Una-Sana Canton. The calculated reproductive measures indicated an undulant trend in reproductive performance among selected dairy farms in Una-Sana Canton. Knowing the apparent reproductive indicators described in this study, the farmers and veterinary authorities may identify and correct areas in their management that contribute to the reproductive underperformance. [ABSTRACT FROM AUTHOR]

Abstract The objective of the present study was to assess the effects on ovulation and reproductive performance of a single injection of either GnRH or hCG applied 9 days before the start of the seasonal breeding period in anovulatory anoestrus cows compared with a 7-day progesterone-Ovsynch protocol. The study was conducted on four grass-based seasonal calving dairy herds in Ireland. The total number of cows in the herds was 2112, of which 488 were diagnosed as anoestrus based on absence of behavioural oestrus during a 30 day period. Ovarian structures and the uterus were examined by transrectal ultrasound on all 488 presumptive anestrus cows 9 days before mating start date (MSD). The number of corpora lutea (CL), number of large follicles (≥10 mm) and uterine reproductive tract score were recorded. Only cows that had no CL, ultrasound reproductive tract score ≤2 and were ≥30 days in milk (DIM) were enrolled in the study (n = 214). Cows were blocked by parity, DIM and body condition score and randomly assigned to one of four treatments: i.m. injection of gonadotropin releasing hormone analogue [GnRH; (n = 57)], i.m. injection of human chorionic gonadotropin [hCG; (n = 48)], 7-day Progesterone-Ovsynch protocol [P4OV; (n = 60)] and Control (no hormonal intervention, n = 49). A second ultrasound examination was performed 7 days after treatment to determine ovulatory response. There was a treatment effect on ovulation rate (P < 0.0001), whereby Control cows had a lesser ovulation rate compared with GnRH-, hCG- and P4OV-treated cows. Submission rate during the first 21 days of the breeding period [SR21; (P = 0.74)], pregnant to first service [P/AI1; (P = 0.24)], pregnant within 42 days after the onset of breeding [P42; (P = 0.73)], and pregnant within 84 days after the onset of breeding were not affected by treatment. A tendency was observed (P = 0.07) for greater likelihood of pregnancy within 21 days after the onset of breeding (P21) for P4OV and Control cows compared with GnRH- and hCG-treated cows. GnRH- and hCG-treated cows tended (P = 0.10) to have greater P/AI1 when first service events occurred after day 21 of the breeding period compared with Control cows. P4OV cows had shorter MSD to first service interval (P = 0.0001) and shorter MSD to conception interval (P = 0.02) compared with Control, GnRH- and hCG-treated cows. In conclusion, treatment of anestrous cows with GnRH or hCG resulted in an increase in ovulation rate compared with untreated Control cows, but did not improve reproductive performance during the first 21 days of the breeding season. The best reproductive performance results were obtained with the P4OV treatment, but this treatment has the greatest cost, and has the greatest number of interventions. The observation of good P/AI1 in hCG- and GnRH- treated cows when the first insemination occurred later than day 21 after MSD warrants further investigation, and suggests that these interventions should be applied earlier than 9 days before the farm MSD. Highlights • A single injection of GnRH or hCG increased ovulation rate compared with untreated Control cows. • GnRH or hCG treatment did not improve overall reproductive performance. • P4 Ovsynch is recommended treatment for anoestrous cows. [ABSTRACT FROM AUTHOR]

Abstract The objective of present study was to determine the effect of plasma progesterone (P4) on oocyte recovery, oocyte quality, and early in-vitro developmental competence of embryos in Bos indicus dairy cows. The ovaries were collected in an abattoir. These ovaries (n = 750) were divided into two groups: 1) estrous CYCLIC (n = 318), and 2) estrous ACYCLIC (n = 432). Mean serum concentrations of P4 in a subset of (n = 85; 4.21 ± 0.4 ng/ml compared with 0.5 ± 0.2 ng/ml; P < 0.05) were greater in estrous CYCLIC as compared to ACYCLIC cows, respectively. The mean number of oocytes recovered per ovary (6.5 ± 0.5 compared with 4.0 ± 0.2; P < 0.05) was greater for estrous CYCLIC than ACYCLIC cows, respectively. The oocytes with grade I_+_II quality (55.3% compared with 47.6%; P < 0.05) were greater, whereas, there was lesser percentage with grade III_+_IV quality (44.5% compared with 52.4%; P < 0.05) from estrous CYCLIC as compared with ACYCLIC cows, respectively. Cleavage rate (70.9% compared with 52.8%; P < 0.05) was greater for embryos derived from estrous CYCLIC than ACYCLIC cows, respectively. Similarly, the embryo developmental rates to the 8- (38.5% compared with 20.8%; P < 0.05) and 16- (20.0% compared with 10.9%; P < 0.05) cell stage were greater for embryos derived from estrous CYCLIC as compared to ACYCLIC cows, respectively. In conclusion, the presence of greater plasma P4 has a beneficial effect on oocyte recovery, oocyte quality, and early IVEP outcomes in Bos indicus dairy cows. [ABSTRACT FROM AUTHOR]

Abstract This study evaluated the effect of equine chorionic gonadotropin (eCG) on reproductive performance, when incorporated into the first Ovsynch + P4 synchronization following planned start mating (PSM) in pasture-based lactating dairy cows. Two synchrony programs were compared in a randomized controlled trial in Queensland, Australia. Lactating cows from a single dairy herd (n = 782) were randomly allocated to Control and eCG groups. Control cows had their estrous cycles synchronized by treatment with 100 μg gonadotropin releasing hormone (GnRH; im) and insertion of a progesterone (P4) releasing intravaginal device that contained 1.0 g of P4 on Day 0; removal of P4 device and administration of 500 μg of an analogue of PGF2α on Day 7 (cloprostenol; im); 100 μg im of GnRH on Day 9, and fixed-time artificial insemination (FTAI) on Day 10. The eCG group were treated the same as the Control group except for the addition of 400 IU of eCG, im on Day 7 of the first synchronized estrous cycle. Following the first insemination, non-pregnant cows from both groups had their estrous cycles synchronized with the same treatment protocol without using eCG. The effects of eCG on 42d cumulative incidence of pregnancy and pregnancy per AI (P/AI) were determined using logistic regression models. The effect of eCG on time to pregnancy was determined using Kaplan-Meier survival analysis and Cox proportional hazards models. Adjusted 42 d cumulative incidence of pregnancy for eCG and control groups were 47.2 and 39.3% respectively (Odds ratio [OR] = 1.38, 95% CI: 1.01–1.88). Hazard of pregnancy tended to be higher in eCG cows overall (Hazard ratio [HR] = 1.18, 95% CI: 0.99–1.41) and was significantly higher when restricting to the first 42 days after PSM (HR = 1.31, 95% CI: 1.04–1.64). Hazards of pregnancy were not different between groups when restricting to > Day 42 post PSM (HR = 1.00, 95% CI: 0.77–1.31). P/AI tended to be higher in eCG treated cows at the first AI (44.0 vs 37.7%, OR = 1.30, 95% CI: 0.94–1.78). P/AI for second and third AIs were not significantly different between groups. In this herd, a single treatment of eCG at the first synchronized estrus after PSM improved reproductive performance in the short term, but not at subsequent inseminations. Highlights • A research trial compared the effects of including eCG into a FTAI program in pasture-based dairy cows in Qld, Australia. • Treatment with eCG at the first synchrony improved short-term reproductive performance, but did not have lasting benefits. • Treatment with eCG significantly increased adjusted 42 d pregnancy risk (47.2 vs. 39.3%, OR=1.38, 95% CI: 1.01–1.88). • Treatment with eCG tended to increase P/AI at the first AI (44.0 vs 37.7%, OR = 1.30, 95% CI: 0.94–1.78). [ABSTRACT FROM AUTHOR]

Optimal reproductive function in dairy cattle is mandatory to maximise profits. Dairy production has progressively improved milk yields, but, until recently, the trend in reproductive performance has been the opposite. Nutrition, genetics, and epigenetics are important aspects affecting the reproductive performance of dairy cows. In terms of nutrition, the field has commonly fed high-energy diets to dairy cows during the 3 weeks before calving in an attempt to minimise postpartum metabolic upsets. However, in the recent years it has become clear that feeding high-energy diets during the dry period, especially as calving approaches, may be detrimental to cow health, or at least unnecessary because cows, at that time, have low energy requirements and sufficient intake capacity. After calving, dairy cows commonly experience a period of negative energy balance (NEB) characterised by low blood glucose and high non-esterified fatty acid (NEFA) concentrations. This has both direct and indirect effects on oocyte quality and survival. When oocytes are forced to depend highly on the use of energy resources derived from body reserves, mainly NEFA, their development is compromised due to a modification in mitochondrial β-oxidation. Furthermore, the indirect effect of NEB on reproduction is mediated by a hormonal (both metabolic and reproductive) environment. Some authors have attempted to overcome the NEB by providing the oocyte with external sources of energy via dietary fat. Conversely, fertility is affected by a large number of genes, each with small individual effects, and thus it is unlikely that the decline in reproductive function has been directly caused by genetic selection for milk yield per se. It is more likely that the decline is the consequence of a combination of homeorhetic mechanisms (giving priority to milk over other functions) and increased metabolic pressure (due to a shortage of nutrients) with increasing milk yields. Nevertheless, genetics is an important component of reproductive efficiency, and the incorporation of genomic information is allowing the detection of genetic defects, degree of inbreeding and specific single nucleotide polymorphisms directly associated with reproduction, providing pivotal information for genetic selection programs. Furthermore, focusing on improving bull fertility in gene selection programs may represent an interesting opportunity. Conversely, the reproductive function of a given cow depends on the interaction between her genetic background and her environment, which ultimately modulates gene expression. Among the mechanisms modulating gene expression, microRNAs (miRNAs) and epigenetics seem to be most relevant. Several miRNAs have been described to play active roles in both ovarian and testicular function, and epigenetic effects have been described as a consequence of the nutrient supply and hormonal signals to which the offspring was exposed at specific stages during development. For example, there are differences in the epigenome of cows born to heifers and those born to cows, and this epigenome seems to be sensitive to the availability of methyl donor compounds of the dam. Lastly, recent studies in other species have shown the relevance of paternal epigenetic marks, but this aspect has been, until now, largely overlooked in dairy cattle. [ABSTRACT FROM AUTHOR]

Contents: In two experiments, we studied (a) the changes of LH secretion in heifers under different feeding schedules and (b) total ghrelin concentration at oestrus in cows and heifers. In experiment one, synchronized heifers were allocated in three groups (R, regularly fed controls; F, fasted; and F‐F fasted‐fed). One day after the completion of the oestrous induction protocol, group F and F‐F animals stayed without feed for 24 hr; thereafter, feed was provided to R and F‐F cattle; 2 hr later, GnRH was administered to all animals. Blood samples were collected for ghrelin, progesterone, LH and cortisol concentrations. Fasting caused increased ghrelin concentrations in groups F and F‐F, while in response to GnRH, LH surge was significantly attenuated in groups F and F‐F compared to R. In experiment 2, lactating cows and heifers were used. On day 9 of a synchronized cycle, PGF2α was administered, and blood samples were collected twice daily until the third day after oestrus and analysed for progesterone, estradiol, ghrelin, glucose and BHBA concentrations. No difference was recorded between groups in steroids and BHBA concentrations. In comparison to mid‐luteal values, ghrelin concentrations significantly increased at perioestrual period in cows, but not in heifers. This study provides evidence that starving‐induced elevated ghrelin concentrations can have suppressing effect on LH secretion, even after ghrelin's restoration to basal values and that during oestrus, ghrelin secretion is differently regulated in cows and heifers, likely being independent from oestradiol concentrations. Further research is required to identify the determining factors that drive the different regulation of ghrelin secretion in cows and heifers. [ABSTRACT FROM AUTHOR]

The aim of this study was to examine the effect of twin pregnancy, fetal laterality, the number of corpora lutea (CL) and cavitary CL on pregnancy losses in Holstein-Friesian cows with a positive pregnancy diagnosis based on ultrasonography between days 29–42 after AI. Pregnancy was confirmed by transrectal palpation between days 57–70 after AI and at the time of drying-off as well. Twin pregnancy rate was 8.4% at the time of the early pregnancy examination. Pregnancy loss did not differ between singleton- and twin-carrying animals either between days 57–70 of gestation or at drying-off. More losses occurred in singletons between days 29–42 and 57–70 in cows with cavitary than in cows with noncavitary CL (12.1% vs. 3.6%; P < 0.05) and in cows with double CL than in cows with single CL (7.3% vs. 3.6% %; P < 0.05). Between days 57–70 of gestation and drying-off this difference was still significant (20.7% vs. 3.7%; P < 0.001), while it was non-significant between cows with one CL (5.7%) vs. double CL (3.7%). Cavity occurrence was not affected by hormone therapy prior to AI (either PGF2α or OvSynch; 4.4% vs. 5.4%, respectively); however, the number of CL was reduced by the treatments (11.6 vs. 19.6%; P < 0.0005). In twin pregnancies there was no difference in the pregnancy losses between bilateral and unilateral pregnancies at any time point. The length of gestation was 278.2 ± 10.5 (singleton) and 267.4 ± 31.2 (twin) days, respectively (P < 0.01). The stillbirth ratio was higher in twin carriers than in singleton carriers (19.5% vs. 5.3%; P < 0.001). [ABSTRACT FROM AUTHOR]

Abstract The objective of this study was to evaluate the effect of administration of scopolamine (a parasympatholytic drug) immediately after delivery, on uterine involution in dairy cows. The cows were divided into two groups: group T (treated with scopolamine butylbromide 40 mg/100 kg P.V., within 24 h of delivery) and group C (treated with 2 ml/q of saline solution). The cows were monitored at T0, within 24 h of delivery, T7, T14, T28 and T40 respectively 7th, 14th, 28th and 40th day postpartum, by measuring the levels of hydroxyproline (HYP), an important marker of uterine involution; by ultrasound examination for the measurement of the diameter of uterine horns and of blood flow in the middle uterine artery; and by evaluation of reproductive indices. HYP showed higher concentrations in the T group than in the C group at all times, but the difference was significant at T7 and T40. Uterine diameters were reduced from T7 to T40, with lower values in the T group, as compared to the C group; the pulsatility index (PI) of the middle uterine artery increased in the T group compared to the C group, with a statistically significant difference at T7. There was a better conception-delivery interval and higher pregnancy rate in the T group compared to the C group. It is likely that scopolamine blocked the uterine contractions in postpartum, for the duration of its half-life. After cessation of its pharmacological effect, the uterus may have started to contract more effectively. These results suggested that scopolamine could be useful as a pharmacological approach to postpartum management. Highlights • We evaluated the effect of scopolamine on uterine involution in dairy cows. • Postpartum scopolamine administration resulted in higher serum hydroxyproline concentrations. • Scopolamine affected the uterine vascularization and ameliorated the delivery-conception interval. • It is hypothesizable that the uterus may have started to contract more effectively. • These results suggested that scopolamine could be useful to postpartum management. [ABSTRACT FROM AUTHOR]

Abstract Two experiments were conducted to investigate the effects of dietary supplementation with live yeast culture on hormonal profile, ovarian follicular dynamics and reproductive performance of lactating dairy cows exposed to high ambient temperature. In Expt. 1, Holstein cows were fed a diet with (n = 6) or without (n = 6) 4 g yeast/h/d from 21 d before expected calving date until 8 weeks postpartum. Concentrations of glucose, insulin, insulin like growth factor-I (IGF-I), estradiol-17β (E−17β) and progesterone (P4) were determined in plasma, and transrectal ultrasonography was used to monitor ovarian follicular dynamics. In Expt. 2, 150 Holstein cows (75/dietary group) received same diets as Expt. 1 with the exception that diets were fed from d 1 to d 70 postpartum. The effect of dietary treatments on reproductive performance was examined. In Expt. 1, plasma IGF concentrations during dietary treatment were higher (P = 0.05) in cows fed diets supplemented with yeast. On d 60 postpartum, average plasma concentrations of glucose (48.3 vs. 41.0 mg/dL) and insulin (0.90 vs. 0.23 μU/mL), were also greater in cows fed diets supplemented with yeast compared to that in cow fed diets without supplementation. Similarly, plasma concentrations of E−17β at estrus (P = 0.016) and P4 on d 10 of the estrous cycle (P = 0.021) were greater in yeast-supplemented cows. Moreover, yeast supplementation resulted on average in an estrous cycle 2.6 d shorter (P = 0.05) and in the development of larger ovulatory follicles (18.4 vs. 17.2 mm in diameter; P < 0.01). In Expt. 2, days open were fewer and the proportion of pregnant cows at 120 and 150 d postpartum were greater (P < 0.01) in cows fed diets supplemented with yeast compared to those receiving diets without yeast. In summary, cows fed diets supplemented with yeast had greater plasma IGF-I, E−17β and P4 concentrations, larger ovulatory follicles, shorter estrous cycles, and improved reproductive performance. Therefore, live yeast dietary supplementation could enhance lactating dairy cow's fertility during heat stress through improvement in hormonal profile and development of larger ovulatory follicles. Highlights • Probiotic supplementation during d −21 to +60 d improved reproductive performance of dairy cows in hot season. • Level of glucose, insulin and IGF-I were higher in probiotic group, suggesting positive effect of it on somatotropic axis. • Feeding probiotic increased ovulatory follicle's diameter and steroid hormone profile. • Elevated serum level of IGF-I probably contributed to the development of larger ovulatory follicles. [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.)

Reproductive efficiency of dairy cows is evaluated directly considering the calving interval, which is affected by nutrition, irregular estrus cycle, prolonged anestrus, and reproductive diseases. Reproductive diseases cause economic losses due to diagnosis and treatment costs, and reduction in milk production. Thus, the objective of this study was to report the occurrence of the main reproductive disorders in dairy cows of the Southwest of Paraná, South of Brazil. Data of ultrasound diagnoses were collected from 2274 cows of 70 rural properties in the municipalities of Realeza, Planalto, Capanema, Pérola do Oeste, and Santa Isabel do Oeste from January 2014 to May 2015. Reproductive disorders were found in 24.50% (557/2274) of the animals evaluated; ovarian cysts (follicular, and luteal) were the most significant disorders, found in 16.13% (367/2274) of the cases. Other disorders were found less frequently. The occurrence of follicular and luteal cysts was observed especially in primiparous animals in months of pasture transition. [ABSTRACT FROM AUTHOR]

Lameness in dairy cattle is a significant problem in intensive dairy industries around the world, causing production losses. This trial was undertaken to determine some reproductive and productive parameters of dairy cows after lameness treatment to anticipate their future performance. Twenty Holstein dairy cows were divided into: Ten healthy cows used as a control group and ten cows after treatment of lameness as treated group. Serum samples at the first estrous detection were collected for biochemical analysis. The results showed significant increase P˂0.05 in serum nitric oxide level (NO), lysozyme activity (LA), Serum progesterone (P4), total protein (TP) and globulin (GL) concentrations in the treated group compared to the control one. Also, there was significant increase P˂0.05 in the days open, days to first estrous detection, days to 1st insemination and number of services\conception in the treated group compared to the control group. The body weight (BW) has a significant decrease P˂0.05 in the treated than the control cows after one month post-partum. The milk yield in 1st and 2nd month's, Milk fat at 4th, 5th and 6th months and Milk lactose at 5th month post-partum showed significant decrease P˂0.05 in the treated group compared to the control group. In conclusion, lameness despite treatment somewhat disturb reproduction and milk production even if the locomotion score was apparently normal so, our decision should depend on benefit risk ratio and individually in each case. [ABSTRACT FROM AUTHOR]

Minimising the impact of lameness on dairy cattle is a crucial part of a dairy veterinarian's role. One of the most important parts of lameness management is the management of the pain resulting from lameness. This needs a multimodal approach focusing on claw trimming, the use of blocks and the use of analgesics. Despite being one of the most important causes of pain in dairy cattle, the literature on pain management in lameness is far from extensive, and the limited evidence suggests that we have a long way to go before we can claim that we have effective pain management strategies for lame cattle [ABSTRACT FROM AUTHOR]

This review discusses the effects of starch and fat before and after calving on metabolism, energy balance (EB), milk production, and reproduction in dairy cows. The shift in dairy cows from a pregnant nonlactating state to a non-pregnant lactating state induces physiological changes, which affect the metabolic and endocrinal axes to redirect body energy stores towards the mammary gland for milk production. Overfeeding high starch and fat levels during the dry period after calving may result in cows failing to adapt to the negative energy balance (NEB) because of major liver and rumen dysfunction. Alternatively, keeping dry cows on high-forage/low-energy diets adjusts dry matter intake (DMI) to optimize the rumen function and decrease the severity of the NEB during transition. These periparturient biological improvements in dairy cows showed real benefits such as fewer postpartum health complications (e.g. milk fever, ketosis, mastitis, metritis), decreased body condition loss and improved reproductive axis in the subsequent lactation. Adding dietary starch and/or fat to diets of dairy cows following parturition increased milk yield. In addition, milk protein of dairy cows increased with glucogenic diets, but decreased with lipogenic diets. Inversely, milk fat usually increases after feeding lipogenic diets, but it decreases when feeding glucogenic diets to dairy cows. Glucogenic and lipogenic nutrients can affect the cow's metabolism and its EB status positively, as is evidenced by plasma non-esterified fatty acids (NEFA), β-hydroxybutyrate (BHB), glucose, amino acids, insulin, insulin-like growth factor-I (IGF-I), growth hormone (GH), gonadotropin hormones, and progesterone (P4) levels. These metabolites (NEFA, BHB, glucose, amino acids) and hormones (insulin, IGF-I, GH, P4) have been shown to affect folliculogenesis, ovulation, conception, and pregnancy success. Feeding a starchbased diet to dairy cows can lead to acidosis and increase glucose and insulin levels, while decreasing NEFA and BHB levels. Furthermore, an insulinogenic diet favours an early resumption of ovarian activity, but has adverse effects on the quality of oocytes. In contrast, keeping dairy cows on a fat-based diet elevates NEFA and BHB levels and decreases glucose and insulin levels. Additionally, a lipogenic diet increases the plasma P4 levels and improves the quality of oocytes. These evidences suggest that reproductive performances in dairy cows can be enhanced by feeding an insulinogenic diet until the resumption of the ovarian cycle then switching to a lipogenic diet from mating period onwards. Since long-term field studies on fertility are limited and the reproduction process in dairy cows is multi-factorial, further research is needed on the pre- and postpartum effects of starch and/or fat as well as their combinations on reproduction axis and thus to draw conclusions on reproductive performances. [ABSTRACT FROM AUTHOR]

With the expansion of herds and the desire to improve offspring, cows are more covered by bulls but are artificially inseminated after their observation in heat. The quantitative data of reproduction studied farm showed that the rate of pregnancy in these cows is far from optimal. This is due essentially to a lack of experience of farmers especially in detecting cows in heat negatively affecting the economics of the operation. Although cattle industry plays a crucial role in the agricultural sector and in the Tunisian economy, he continues to use the traditional methods, especially in the identification of the heat. During this work system analysis and imagery has been applied for the obsevability of a dairy cattle. [ABSTRACT FROM AUTHOR]

The objectives of the experiment were to evaluate the effects of feeding diets with distinct dietary cation-anion difference (DCAD) levels and supplemented with 2 sources of vitamin D during the prepartum transition period on postpartum health and reproduction in dairy cows. The hypotheses were that feeding acidogenic diets prepartum would reduce the risk of hypocalcemia and other diseases, and the benefits of a negative DCAD treatment on health would be potentiated by supplementing calcidiol compared with cholecalciferol. Cows at 252 d of gestation were blocked by parity (28 nulliparous and 52 parous cows) and milk yield within parous cows, and randomly assigned to 1 of 4 treatments arranged as a 2 × 2 factorial, with 2 levels of DCAD, positive (+130 mEq/kg) or negative (−130 mEq/kg), and 2 sources of vitamin D, cholecalciferol or calcidiol, fed at 3 mg for each 11 kg of diet dry matter. The resulting treatment combinations were positive DCAD with cholecalciferol (PCH), positive DCAD with calcidiol (PCA), negative DCAD with cholecalciferol (NCH), and negative DCAD with calcidiol (NCA), which were fed from 252 d of gestation to calving. After calving, cows were fed the same lactation diet supplemented with cholecalciferol at 0.70 mg for every 20 kg of dry matter. Blood was sampled 7 d before parturition, and at 2 and 7 d postpartum to evaluate cell counts and measures of neutrophil function. Postpartum clinical and subclinical diseases and reproductive responses were evaluated. Feeding a diet with negative DCAD eliminated clinical hypocalcemia (23.1 vs. 0%) and drastically reduced the incidence and daily risk of subclinical hypocalcemia, and these effects were observed in the first 48 to 72 h after calving. The diet with negative DCAD tended to improve the intensity of oxidative burst activity of neutrophils in all cows prepartum and increased the intensity of phagocytosis in parous cows prepartum and the proportion of neutrophils with killing activity in parous cows postpartum (58.5 vs. 67.6%). Feeding calcidiol improved the proportion of neutrophils with oxidative burst activity (60.0 vs. 68.7%), reduced the incidences of retained placenta (30.8 vs. 2.5%) and metritis (46.2 vs. 23.1%), and reduced the proportion of cows with multiple diseases in early lactation. Combining the negative DCAD diet with calcidiol reduced morbidity by at least 60% compared with any of the other treatments. Cows with morbidity had lower blood ionized Ca and serum total Ca concentrations than healthy cows. Treatments did not affect the daily risk of hyperketonemia in the first 30 d of lactation. Despite the changes in cow health, manipulating the prepartum DCAD did not influence reproduction, but feeding calcidiol tended to increase the rate of pregnancy by 55%, which reduced the median days open by 19. In conclusion, feeding prepartum cows with a diet containing a negative DCAD combined with 3 mg of calcidiol benefited health in early lactation. [ABSTRACT FROM AUTHOR]

The reliable detection of estrus is an important scientific and practical challenge in dairy cattle farming. Female vocalization may indicate reproductive status, and preliminary evidence suggests that this information can be used to detect estrus in dairy cattle. The aim of this study was to associate the changes in the vocalization rate of dairy heifers with behavioral estrus indicators as well as test the influence of the type of estrus (natural estrus vs. superovulation-induced estrus). We analyzed 6 predefined estrus-related behavior patterns (standing to be mounted, head-side mounting, active mounting, chin resting, being mounted while not standing, and active sniffing in the anogenital region) and vocalization rates in the peri-estrus period (day of estrus ± 1 d) of 12 German Holstein heifers using audio-visual recordings. Each heifer was observed under natural estrus and a consecutive superovulation induced by FSH and cloprostenol. Estrus was determined by behavioral patterns and confirmed by clinical examination (vaginoscopy and ultrasound imaging of the ovaries) as well as by the concentration of peripheral progesterone. Estrus behavior and vocalization rates were analyzed in 3-h intervals (an average of 19 intervals for each heifer), and an estrus score was calculated based on the 6 behaviors. The interval with the highest estrus score (I0) was considered the estrus climax. We demonstrated similar time courses for the estrus score and vocalization rate independent of estrus type. However, in natural estrus, the maximum vocalization rate (±SE) occurred in the interval before estrus climax (I-1; 42.58 ± 21.89) and was significantly higher than that in any other interval except estrus climax (I0; 27.58 ± 9.76). During natural estrus, the vocalization rate was significantly higher within the interval before estrus climax (I-1; 42.58 ± 21.89 vs. 11.58 ± 5.51) than under superovulation. The results underscore the potential use of vocalization rate as a suitable indicator of estrus climax in automated estrus detection devices. Further studies and technical development are required to record and process individual vocalization rates. [ABSTRACT FROM AUTHOR]

We determined the threshold proportion of polymorphonuclear leukocytes (PMNs) for a diagnosis of cytological endometritis (CEM), the risk factors for this condition, and its impact on reproductive performance in dairy cows. Uterine cytology was performed on 407 Holstein cows 4 weeks postpartum to determine the proportions of endometrial cells and PMNs. A receiver operator characteristics curve was used to determine the threshold above which the PMN proportion affected the likelihood of cows conceiving by 200 days postpartum. The optimal threshold was = 14% PMN (sensitivity, 31.3%; specificity, 81.7%; p < 0.05). The farm identity, retained placenta (odds ratio [OR] = 1.87), and septicemic metritis (OR = 3.07) were risk factors for CEM (p < 0.05). Cows with CEM were less likely to resume cyclicity (OR = 0.58) and to conceive by 200 days postpartum (hazard ratio = 0.58). Cows with CEM tended (p < 0.1) to be less likely to become pregnant after their first insemination (OR = 0.65) and to require a greater number of inseminations per conception (2.3 vs. 2.2). In conclusion, a PMN threshold of 14% defined the presence of CEM at 4 weeks postpartum. The farm, retained placenta, and septicemic metritis were risk factors for CEM, which reduces subsequent reproductive performance. [ABSTRACT FROM AUTHOR]

Contentious issues in calf rearing include milk feeding practices and single versus group housing. The current study was performed on a high producing 170 Holstein cow dairy farm, to investigate the impact of nutrition and housing on growth and reproduction. Heifer calves (n = 100) were allocated in birth order to one of two commonly used management strategies. All calves received 3–4 litres of dam specific colostrum within 6 hours of birth. Group A calves were group housed from birth and fed milk replacer (MR) ad libitum via a computerised machine utilising a single teat, with weaning commencing at 63 days of age. Group R calves were initially housed in individual pens and received 2.5 litres of MR twice daily via a bucket until 21 days of age when they were group housed and fed 3 litres of MR twice daily via a group trough with weaning commencing at 56 days. From 12 weeks of age onwards, calves in both dietary groups were subject to common nutritional and husbandry protocols. All breeding of heifers was via artificial insemination with no hormonal intervention. Calves were weighed, body condition scored and morphometric measures recorded weekly up till 12 weeks of age then monthly until conception. Pre-weaning growth rates (kg/day) were significantly higher in Group A calves compared to Group R (0.89, 95% CI 0.86–0.93 vs 0.57, 95% CI 0.54–0.6 kg/day P < 0.001) with the most marked differences observed during the first three weeks of life (0.72, 95% CI 0.61–0.82 vs 0.17, 95% CI 0.08–0.26 P < 0.001). Whilst Group A calves gained body condition score (BCS) throughout the pre-weaning phase, Group R calves lost BCS during the first 4 weeks of life. Data suggested that Group R calves supported skeletal growth during this period by catabolising body tissue. Group A calves had a greater risk of disease than group R calves during the pre-weaning phase (diarrhoea: odds ratio 3.86, 95% CI 1.67–8.9; pneumonia: odds ratio 5.80, 95% CI 2.33–14.44) although no calves died during this period. Whilst pneumonia had a significant impact on growth during the study duration (P = 0.008), this was not the case for diarrhoea. Whilst univariate analysis failed to show any statistically significant group differences (P > 0.050) in any of the mean values of measured reproductive parameters, multivariable Cox regression suggested that there was a weak trend (P = 0.072) for Group A animals to achieve first service earlier than their Group R counterparts (62.6 weeks versus 65.3 weeks). Irrespective of dietary group, the hazard for achievement of all measured reproductive parameters, apart from time to puberty, was 20–40% less for heifers borne from multiparous dams compared to heifers from primiparous dams. [ABSTRACT FROM AUTHOR]

This study compares the effects of inducing ovulation using human chorionic gonadotropin (hCG) or gonadotropin releasing hormone (GnRH) at the end of a 5-day progesterone(P4)-based protocol for fixed-time artificial insemination (FTAI) in lactating dairy cows on ovarian dynamics and fertility. A P4 intravaginal device (PRID) was fitted for five days and GnRH administered upon PRID insertion and a double dose (24 h apart) of prostaglandin F 2α upon PRID removal. Cows received either GnRH (GnRH group; n = 98), 1000 IU hCG (hCG-1 group; n = 97), or 3000 IU hCG (hCG-2 group; n = 104) 36 h after PRID removal and were inseminated 50–56 h after PRID removal. Based on Tukey-Kramer tests, cows in hCG-1 and hCG-2 showed a larger follicle diameter at AI than cows in GnRH (P < 0.05). HCG-2 treatment increased corpus luteum (CL) size on Day 7 post-AI compared with the GnRH and hCG-1 treatments (P < 0.05). Based on odds ratios, the likelihood of ovulation failure decreased with increasing follicle diameter at AI (P = 0.002). Cows in hCG-1 or hCG-2 that did not become pregnant were more likely to return to estrus than cows in GnRH (P < 0.01). A larger CL size post-AI was related to an increased conception rate at FTAI (P = 0.003). Cows given hCG-2 treatment showed a 1.9-fold cumulative pregnancy rate after two rounds of AI compared to cows receiving GnRH. Our results indicate that hCG treatment hCG treatment used to induce ovulation at the end of a short protocol for FTAI improves follicular/luteal dynamics compared to GnRH treatment. Of the two hCG treatments tested, better results were obtained with the 3000 IU dose. [ABSTRACT FROM AUTHOR]

This study uses a survey of dairy farmers in Michigan and Pennsylvania to examine self-reported antibiotic use and use of natural therapies to treat mastitis on dairy farms, comparing Amish and Mennonite (Plain) farmers to others. Plain farmers represent a large minority of U.S. farmers, and their proportion is projected to increase. Scholars suggest a unique environmental ethic amongst Plain farmers, and we extend this to examine antibiotic use. Antibiotic use is a key component of sustainability on dairy farms. Regarding environmental sustainability, imprudent antibiotic use is associated with the risk of antibiotic resistance and drug residues. Regarding economic sustainability, antibiotic use is associated with increased costs and lost production. Results suggest that Plain farmers use antibiotics less frequently than others and rely more frequently on natural therapies. However, Mennonite farmers more closely resemble non-Plain peers. This suggests the need to recognize the distinctiveness of Plain farmers and that Plain farmers may offer lessons on sustainable practices that could be extended to other farmers. [ABSTRACT FROM AUTHOR]

This research paper addresses the hypothesis that dietary pioglitazone (PGT), as synthetic and specific ligand for PPAR-γ or walnut meal (WM) as a natural ligand for PPAR-γ, affect plasma metabolites and reduce the oxidative status in high body condition score (BCS) dairy cows (≥4 BCS). Total of 36 multiparous Holstein cows were randomly assigned to one of the dietary treatments: 1- Control (basal diet; CTR), 2- Walnut meal (9·45% walnut meal of DMI; WM), and 3- Pioglitazone (6 mg/kg BW; PGT). The experimental diets were fed from parturition time to 21 d postpartum. Results showed that the PGT supplementation increased dry matter intake (DMI) (22·95 kg/d) compared to the CTR (21·45 kg/d) and WM (21·78 kg/d) groups. Results showed that milk yield and milk composition were not affected by the experimental diets. Body condition score losses tended to be higher in the CTR group compared to the PGT and WM cows. The PGT group had higher plasma insulin compared to the CTR group (11·84 vs. 10·68 mIU/l), and WM cows had intermediate plasma insulin. The PGT cows had lower plasma non esterified fatty acid (NEFA) and tended to have lower β-hydroxy butyric acid (BHBA) than the CTR group. Feeding pioglitazone decreased plasma malondialdehyde (MDA) and increased plasma total antioxidant capacity (TAC) and superoxide dismutase (SOD) compared to the CTR and WM groups. It was concluded that dietary pioglitazone had positive effects on DMI, BCS change, blood metabolites and oxidative status in fresh dairy cows with high pre-calving BCS. The anti-oxidant effects of walnut meal were not supported by the present data. [ABSTRACT FROM AUTHOR]

The aims of the study reported in the Research Communication were to evaluate changes of macrominerals and major calcitropic hormone concentrations in 51 healthy dairy cows over the peripartum period, and to compare those cows with 51 cows subject to subclinical hypocalcaemia (SCH) on calving day. The results showed that serum calcium (Ca) and potassium (K) concentrations were lowest in the healthy periparturient dairy cows at parturition, while sodium (Na) and parathyroid hormone (PTH) concentrations were highest. Serum magnesium (Mg), chloride (Cl) and phosphorus (P) concentrations were highest 1 wk prepartum, however, the concentration of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] was highest 1 wk postpartum. The dairy cows with subclinical hypocalcaemia (SCH) had significantly lower serum levels of Ca, K, Na, Mg, Cl, 1,25(OH)2D3 and glucose and had significantly higher levels of serum P, non-esterified fatty acids (NEFA) and β-hydroxybutyrate (BHBA) than their healthy counterparts on calving day. However, the serumcalcitonin and PTH concentrations were not significantly different between the two groups. These data demonstrated that the concentrations of macrominerals and major calcium regulating hormones of cows change dramatically over the peripartum period. Furthermore, SCH was associated with a risk of the development of ketosis and fatty liver. [ABSTRACT FROM AUTHOR]