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Excessive abdominal fat might be associated with more severe metabolic disorders in Holstein cows. Our hypothesis was that there are genetic differences between cows with low and high abdominal fat deposition and a normal cover of subcutaneous adipose tissue. The objective of this study was to assess the genetic basis for variation in visceral adiposity in US Holstein cows. The study included adult Holstein cows sampled from a slaughterhouse (Green Bay, WI, USA) during September 2016. Only animals with a body condition score between 2.75 and 3.25 were considered. The extent of omental fat at the level of the insertion of the lesser omentum over the pylorus area was assessed. A group of 100 Holstein cows with an omental fold <5 mm in thickness and minimum fat deposition throughout the entire omentum, and the second group of 100 cows with an omental fold ⩾20 mm in thickness and with a marked fat deposition observed throughout the entire omentum were sampled. A small piece of muscle from the neck was collected from each cow into a sterile container for DNA extraction. Samples were submitted to a commercial laboratory for interrogation of genome-wide genomic variation using the Illumina BovineHD Beadchip. Genome-Wide association analysis was performed to test potential associations between fat deposition and genomic variation. A univariate mixed linear model analysis was performed using genome-wide efficient mixed model association to identify single nucleotide polymorphisms (SNPs) significantly associated with variation in a visceral fat deposition. The chip heritability was 0.686 and the estimated additive genetic and residual variance components were 0.427 and 0.074, respectively. In total, 11 SNPs defining four quantitative trait locus (QTL) regions were found to be significantly associated with visceral fat deposition (P <0.00001). Among them, two of the QTL were detected with four and five significantly associated SNPs, respectively; whereas, the QTLs detected on BTA12 and BTA19 were each detected with only one significantly associated SNP. No enriched gene ontology terms were found within the gene networks harboring these genes when supplied to DAVID using either the Bos taurus or human gene ontology databases. We conclude that excessive omental fat in Holstein cows with similar body condition scores is not caused by a single Mendelian locus and that the trait appears to be at least moderately heritable; consequently, selection to reduce excessive omental fat is potentially possible, but would require the generation of predicted transmitting abilities from larger and random samples of Holstein cattle. [ABSTRACT FROM AUTHOR]

This experiment compared 2 long-term controlled internal drug release (CIDR)-based protocols to synchronize estrus before fixed-time artificial insemination (FTAI) in postpartum beef cows. Cows were assigned to treatments by age, BCS, and days post-partum. Cows assigned to the 14-to 19-dCIDR-PGF2α protocol (n = 196) received CIDR inserts (1.38 g pro-gesterone [P4]) from d 0 to 14 and PGF2α (25 mg, i.m.) 19 d after CIDR removal on d 33. Cows assigned to the 14-to-16-d CIDR-PGF2α protocol (n = 195) received CIDR inserts from d 3 to 17andPGF2α 16 d after CIDR removal on d 33. Cows were artificially inseminated on d 36, 72 h after PGF2α, with GnRH (100 μg, i.m.) at FTAI. Cows were exposed for natural service 14 d after FTAI for 75 d. Blood samples for P4 were collected at d -10 and 0 to determine pretreatment estrous cyclicity status and again at PGF2α. Blood samples for estradiol (E2) were collected at PGF2α and FTAI. HeatWatch estrus detection transmitters were used from CIDR removal until FTAI to determine onset of estrus after CIDR removal and PGF2α. Dominant follicle diameter was determined at PGF2α and FTAI. Pregnancy diagnosis was performed 70 d after FTAI and confirmed at d 140 of gestation. Estrous response after CIDR removal was similar between treatments. Cows in both treatments had similar size dominant follicles on d 33 at PGF2α and d 36 at FTAI. Progesterone at PGF2⓪ was greater (P = 0.03) for 14-to-16-d compared to 14-to-19-d treated cows. Mean concentrations of E2 at PGF2Q were similar between treatments but were greater (P = 0.01) at FTAI for 14-to-16-d compared to 14-to-19-d treated cows. Estrous response after PGF2α was greater {P <0.01) for 14-to-19-d compared to 14-to-16-d treated cows (47.4 vs. 29.7%, respectively). Pregnancy rate resulting from FTAI was affected by the treatment x age group interaction (P = 0.08). Pregnancy rate after FTAI among cows >4 yr tended to be greater (P = 0.06) for 14-to-19-d compared to the 14-to-16-d treated cows, suggesting that the 14-to-19-d schedule works better for older age cows compared with the 14-to-16-d schedule. Final pregnancy rates were similar between the 2 treatments. In summary, these data indicate that a range in intervals from CIDR removal to PGF2n may be feasible when using long-term CIDR-based protocols in cows and raise questions that warrant further study regarding the benefits of extending this interval based on cow age. [ABSTRACT FROM AUTHOR]

Progesterone-containing controlled internal drug release (CIDR) inserts are used to synchronize the estrous cycle before PGF2α is administered for timed AI (14dCIDR-PGF2α program). The program, initially designed for beef cattle, was recently shown to be efficacious in dairy heifers. We hypothesized that the 14-d CIDR treatment would synchronize the estrous cycle in dairy heifers and result in a uniformly sized corpus luteum (CL) and largest follicle (LF) at the time of PGF2α treatment. Holstein (n = 110) or Holstein x Guernsey (n = 4) dairy heifers were assigned to 2 treatments: (1) 14dCIDR-PGF2α [CIDR in for 14 d, CIDR out for 16 d, PGF2α and AI after observed estrus (n = 57)] or (2) control [PGF2α and AI after observed estrus (n = 57)]. Regardless of treatment, additional PGF2α injections were administered at 14-d intervals to heifers that were not seen in estrus. Ovarian ultrasonography and blood sampling were done on d 0 (CIDR administered), 14 (day CIDR removed), 19 (5 d after CIDR removed), 30 (PGF2α administered), and 44 (second PGF2α dose administered to heifers that were not detected in estrus after the first PGF2α). Compared with control (untreated), more CIDR-treated heifers were categorized as having a small CL (≤9.9 mm) and large LF (15.0--19.9 mm) on d 14 (CIDR removal) and, as expected, a greater percentage of CIDR-treated heifers were in estrus during the 5 d after the CIDR removal compared with control heifers (75.4 vs. 22.8%, respectively). On d 19, the CIDR-treated heifers had apparently ovulated based on disappearance of LF and appearance of small CL. On d 30 (PGF2α administration), 89% of 14dCIDR-PGF2α heifers had CL that were ≥20 mm in diameter compared with 55% for control. Presence of larger CL on d 30 was associated with greater concentrations of plasma progesterone in 14dCIDR-PGF2α compared with control (10.5 ± 0.5 vs. 5.0 ± 0.6 ng/mL, respectively). The percentages of heifers with LF in the smallest category (≤9.9 mm) tended to be less (5.3 vs. 16.6%) and the percentage of heifers with LF in the medium-size category (10.0 to 14.9 mm) tended to be greater (84.2 vs. 69.1%) for 14dCIDR-PGF2α versus control, respectively, on d 30. More heifers were detected in estrus within 5 d after the first PGF2α (86.0 vs. 56.1%) and conception rate to AI using sexed semen tended to be greater (61.2% vs. 40.6%) for 14dCIDR-PGF2α compared with control (respectively). Treating dairy heifers with a CIDR for 14 d was an effective method to synchronize an estrous cycle before PGF2α was administered. [ABSTRACT FROM AUTHOR]

Progesterone-releasing (controlled internal drug release, CIDR) devices inserted for 14 d are used to presynchronize the estrous cycle for timed artificial insemination (TAI) in beef heifers (14-d CIDR-PGF2α program). The objective was to test a similar program in dairy cows by measuring first-service conception rates (FSCR), pregnancy rates after 2 AI, and time to pregnancy compared with a control (AI after observed estrus). Postpartum cows (Holstein, Jersey, or crossbred; n = 1,363) from 4 grazing dairy farms were assigned to 1 of 2 programs: 14dCIDR_TAI [CIDR in for 14 d, CIDR out, PGF2α injection at 19 d after CIDR removal, GnRH injection 56 h later, and then TAI 16 h later; n = 737] or control [AI after observed estrus; reproductive program with PGF2α (cycling cows) and CIDR (noncycling cows) to synchronize estrus with the start of the breeding season; n = 626]. Body condition was scored (1 to 5; thin to fat) at the start of the trial. The interval from the start of the breeding period (final PGF2α injection of either program) to first AI was shorter for 14dCIDR_TAI compared with the control (3.0 ± 0.2 vs. 5.3 ± 0.2 d; mean ± SEM) but 14dCIDR_TAI cows had lesser FSCR than controls (48 vs. 61%). Farm affected FSCR (50, 51, 67, and 58% for farms 1 to 4). The BCS affected FSCR (50, 55, and 62% for BCS = 2, 2.5, and 3, respectively). Cows that either calved the year before (carryover) or that calved early in the calving season had greater FSCR than cows that calved later in the calving season (55, 61, and 42%, respectively). The percentage of cows pregnant to AI (first and second inseminations within 31-d breeding season) was similar for 14dCIDR_TAI and control (64 vs. 70%) cows, but farm (64, 62, 80, and 69%) and time of calving (70, 76, and 56%: carryover, early, and late, respectively) affected the percentage. Survival analyses showed an initial advantage for 14dCIDR_TAI (more cows inseminated and more pregnancies achieved early in the breeding season) that was not maintained over time. Conclusions were that the 14dCIDR_TAI pro-gram achieved acceptable FSCR (48%) and overall AI pregnancy rates (64%), but did not surpass a control program that used AI after observed estrus (61 and 70%, respectively). [ABSTRACT FROM AUTHOR]

Progesterone-containing devices can be inserted intravaginally for 14 d to presynchronize the estrous cycle for timed artificial insemination (TAI) in beef heifers ("14-day CIDR-PG" or "Show-Me-Synch" program). The progesterone treatment is effective for presynchronization because cattle develop a persistent dominant follicle during treatment that ovulates within 3 d after progesterone removal. The subsequent estrous cycle can be effectively used for a TAI program. Some cattle will retain a functional corpus luteum (CL) for the entire 14-d treatment period and will not be synchronized effectively because the interval to ovulation depends on the lifespan of their existing CL. The objective was to test the effect of a luteolytic dose of PGF2α at progesterone removal for improving synchrony of estrus after treatment and increasing conception rate to a subsequent TAI in dairy cows. Postpartum cows (n = 1,021) from 2 grazing dairy herds were assigned to 1 of 2 presynchronization programs that used a controlled internal drug releasing (CIDR) device containing progesterone: 14dCIDR (CIDR in, 14 d, CIDR out; n = 523) or 14dCIDR+PGF2α (CIDR in, 14 d, CIDR out, and PGF2α; n = 498). Cows were body condition scored (BCS; 1 to 5, thin to fat) and tail painted at CIDR removal. Paint score (PS) was recorded after CIDR removal [PS = 0 (all paint removed, indication of estrus), PS = 3 (paint partially removed), or PS = 5 (no paint removed; indication of no estrus)]. At 19 d after CIDR removal, all cows were treated with PGF2α, 56 h later treated with GnRH, and then 16 h later were TAI. Treating cows with PGF2α at CIDR removal increased the percentage with PS = 0 within 5 d (58.1% vs. 68.9%; 14dCIDR vs. 14dCIDR+PGF2α). We found no effect of treatment, however, on conception rate at TAI (41.1% vs. 43.6%; respectively). The TAI conception rate increased with increasing BCS and was greater for cows that had PS = 0 within 5 d after CIDR removal. In summary, treating cows with PGF2α at CIDR removal increased the percentage of cows with all tail paint removed but did not increase percentage of pregnant cows after TAI. [ABSTRACT FROM AUTHOR]

Two long-term estrus synchronization protocols were evaluated among Bos indicus-influenced and Bos taurus beef heifers on the basis of estrous response and pregnancy rate resulting from fixedtime artificial insemination (FTAI). Estrus was synchronized for 1139 heifers in three locations, and heifers were assigned to one of two treatments within each location based on reproductive tract score (RTS; 1-5 scale). Heifers assigned to the 14-d CIDRPG protocol received a controlled internal drug release (CIDR) insert (1.38 g progesterone) on Day 0 with removal on Day 14, administration of prostaglandin F2α (PG; 25 mg im) on Day 30, and administration of gonadotropin-releasing hormone (GnRH; 100 µg im) concurrent with FTAI 66 h after PG. Heifers assigned to the 9-d CIDR-PG protocol were administered PG concurrent with CIDR insertion on Day 5, PG concurrent with CIDR removal on Day 14, PG on Day 30, and GnRH concurrent with FTAI 66 h after PG. Estrus detection aids were applied at CIDR removal and PG to evaluate estrous response. Mean RTS differed (P < 0.0001) based on biological type, with higher rates of estrous cyclicity (RTS 4 and 5) among Bos taurus heifers (72%) than Bos indicus-influenced heifers (27%). The proportion of heifers expressing estrus following CIDR removal was greater (P = 0.01) among heifers assigned to the 14-d CIDR-PG (88%) compared to the 9-d CIDR-PG protocol (83%). Estrous response following CIDR removal was higher (P < 0.0001) among Bos taurus (95%) compared to Bos indicus-influenced (75%) heifers. Rate of estrous response prior to FTAI did not differ based on treatment but was higher (P < 0.0001) among Bos taurus heifers (60%) than Bos indicus-influenced heifers (45%). However, biological type did not affect estrous response when RTS was included in the model, as RTS affected (P < 0.0001) the rate of estrous response at CIDR removal and prior to FTAI. Heifers that expressed estrus prior to AI achieved higher (P < 0.0001) AI pregnancy rates than heifers failing to express estrus. Pregnancy rates to FTAI did not differ significantly based on treatment in either biological type. Higher rates of estrous cyclicity among Bos taurus heifers resulted in higher FTAI pregnancy rates among Bos taurus (51%) compared to Bos indicus-influenced heifers (39%). However, pregnancy rates of respective RTS did not differ based on biological type. In summary, long-term CIDR-based protocols provide a simple, effective method of estrus synchronization in Bos indicus-influenced and Bos taurus beef heifers. [ABSTRACT FROM AUTHOR]

Two long-term estrus synchronization protocols were evaluated among Bos indicus-influenced and Bos taurus beef heifers on the basis of estrous response and pregnancy rate resulting from fixedtime artificial insemination (FTAI). Estrus was synchronized for 1139 heifers in three locations, and heifers were assigned to one of two treatments within each location based on reproductive tract score (RTS; 1-5 scale). Heifers assigned to the 14-d CIDRPG protocol received a controlled internal drug release (CIDR) insert (1.38 g progesterone) on Day 0 with removal on Day 14, administration of prostaglandin F2α (PG; 25 mg im) on Day 30, and administration of gonadotropin-releasing hormone (GnRH; 100 μg im) concurrent with FTAI 66 h after PG. Heifers assigned to the 9-d CIDR-PG protocol were administered PG concurrent with CIDR insertion on Day 5, PG concurrent with CIDR removal on Day 14, PG on Day 30, and GnRH concurrent with FTAI 66 h after PG. Estrus detection aids were applied at CIDR removal and PG to evaluate estrous response. Mean RTS differed (P < 0.0001) based on biological type, with higher rates of estrous cyclicity (RTS 4 and 5) among Bos taurus heifers (72%) than Bos indicus-influenced heifers (27%). The proportion of heifers expressing estrus following CIDR removal was greater (P = 0.01) among heifers assigned to the 14-d CIDR-PG (88%) compared to the 9-d CIDR-PG protocol (83%). Estrous response following CIDR removal was higher (P < 0.0001) among Bos taurus (95%) compared to Bos indicus-influenced (75%) heifers. Rate of estrous response prior to FTAI did not differ based on treatment but was higher (P < 0.0001) among Bos taurus heifers (60%) than Bos indicus-influenced heifers (45%). However, biological type did not affect estrous response when RTS was included in the model, as RTS affected (P < 0.0001) the rate of estrous response at CIDR removal and prior to FTAI. Heifers that expressed estrus prior to AI achieved higher (P < 0.0001) AI pregnancy rates than heifers failing to express estrus. Pregnancy rates to FTAI did not differ significantly based on treatment in either biological type. Higher rates of estrous cyclicity among Bos taurus heifers resulted in higher FTAI pregnancy rates among Bos taurus (51%) compared to Bos indicus-influenced heifers (39%). However, pregnancy rates of respective RTS did not differ based on biological type. In summary, long-term CIDR-based protocols provide a simple, effective method of estrus synchronization in Bos indicus-influenced and Bos taurus beef heifers. [ABSTRACT FROM AUTHOR]

We tested the hypothesis that the uterus of virgin heifers and pregnant cows possessed a resident microbiome by 16S rRNA gene sequencing of the virgin and pregnant bovine uterus. The endometrium of 10 virgin heifers in estrus and the amniotic fluid, placentome, intercotyledonary placenta, cervical lumen, and external cervix surface (control) of 5 pregnant cows were sampled using aseptic techniques. The DNA was extracted, the V4 hypervariable region of the 16S rRNA gene was amplified, and amplicons were sequenced using Illumina MiSeq technology (Illumina Inc., San Diego, CA). Operational taxonomic units (OTU) were generated from the sequences using Qiime v1.8 software, and taxonomy was assigned using the Greengenes database. The effect of tissue on the microbial composition within the pregnant uterus was tested using univariate (mixed model) and multivariate (permutational multivariate ANOVA) procedures. Amplicons of 16S rRNA gene were generated in all samples, supporting the contention that the uterus of virgin heifers and pregnant cows contained a microbiome. On average, 53, 199, 380, 382, 525, and 13,589 reads annotated as 16, 35, 43, 63, 48, and 176 OTU in the placentome, virgin endometrium, amniotic fluid, cervical lumen, intercotyledonary placenta, and external surface of the cervix, respectively, were generated. The 3 most abundant phyla in the uterus of the virgin heifers and pregnant cows were Firmicutes, Bacteroidetes, and Proteobacteria, and they accounted for approximately 40, 35, and 10% of the sequences, respectively. Phyla abundance was similar between the tissues of the pregnant uterus. Principal component analysis, one-way PERMANOVA analysis of the Bray- Curtis similarity index, and mixed model analysis of the Shannon diversity index and Chao1 index demonstrated that the microbiome of the control tissue (external surface of the cervix) was significantly different from that of the amniotic fluid, intercotyledonary placenta, and placentome tissues. Interestingly, many bacterial species associated with postpartum uterine disease (i.e., Trueperella spp., Acinetobacter spp., Fusobacteria spp., Proteus spp., Prevotella spp., and Peptostreptococcus spp.) were also present in the uterus of virgin heifers and of pregnant cows. The presence of 16S rRNA gene sequence reads in the samples from the current study suggests that the uterine microbiome is established by the time a female reaches reproductive maturity, and that pregnancies are established and maintained in the presence of a uterine microbiome. [ABSTRACT FROM AUTHOR]

Chemical pregnancy testing is an alternative to traditional methods of pregnancy diagnosis (either manual palpation or ultrasound) in postpartum dairy cows and heifers. The objective was to validate a chemical pregnancy test that confers the advantages of using whole blood, rapid incubation times, and visual readout. Blood and milk samples were collected from Holstein dairy cows [n = 320; 162 ± 62 (mean ± SD) d in milk] on a confinement farm in northeast Missouri at 28 d after artificial insemination (AI). The samples were assayed for pregnancy-associated glycoproteins (PAG) by using a rapid visual test as well as traditional plasma- and milk-based tests. Transrectal ultrasonography diagnosis for pregnancy at 35 to 38 d after AI was the reference (gold) standard for all PAG tests. One hundred fifty-nine cows were diagnosed as pregnant by the reference standard (pregnancies per AI = 49.7%). The tests were ELISA and either optical density (OD; measured with a microtiter plate reader; plasma, milk, and rapid visual tests) or visual readout (rapid visual test) were used to diagnose pregnancy. When OD was used, the percentage of pregnant cows classified correctly (sensitivity) for the plasma, milk, and rapid visual tests were 97 ± 1, 96 ± 2, and 95 ± 1% (±SE), respectively. The sensitivity of the rapid visual test when assessed visually was 98 ± 1%. The specificity (proportion of nonpregnant cows classified correctly) for the plasma, milk, and rapid visual was 94 ± 2%, 94 ± 2%, and 93 ± 2% when an OD was used. When read visually, the specificity of the rapid visual test was lesser (85 ± 3%) because some cows with faint visual signals yielded false positive diagnosis. The overall accuracy (proportion of pregnant and nonpregnant cows diagnosed correctly) was similar for all tests (plasma, milk, rapid visual OD, and rapid visual; 96 ± 1, 95 ± 1, 94 ± 1, and 92 ± 2%, respectively). In a second experiment, lactating Holstein cows (n = 291) from 4 commercial confinement dairy farms in western Kentucky were tested 25 to 95 d after AI using the rapid visual test. The OD of the rapid visual test followed the known profile for PAG in circulation during the first trimester of pregnancy. The conclusion is that the rapid visual test has equal sensitivity and accuracy as existing PAG tests. A slightly lower specificity was found when the rapid visual test was read visually. [ABSTRACT FROM AUTHOR]

Timed artificial insemination (AI) programs have increased reproductive efficiency in dairy herds. A low timed AI pregnancy per AI is partially explained by cows that fail to respond optimally to the series of treatments that are designed to synchronize ovulation for AI. We hypothesized that testing cows for plasma progesterone concentrations during a timed AI protocol could be used as an early diagnostic test for nonpregnancy. Lactating Holstein cows (n = 160) in 2 confinement- style dairies were used. Cows were treated with Presynch Ovsynch 56 for timed AI. Concentrations of progesterone in plasma were measured at -3, 0, 7, and 25 d relative to timed AI. Progesterone data were analyzed and receiver operating characteristic curves were generated by using logistic regression. The area under the receiver operating curves for a progesterone test for nonpregnancy on d -3 (PGF2α), 0 (AI), 7, and 25 d relative to timed AI were 0.68, 0.52, 0.55, and 0.89, respectively. The cutpoints and sensitivity (respectively) for the progesterone test were 0.51 ng/mL (lower = nonpregnant) and 28.2% for the day of PGF2α, 0.43 ng/ mL (greater = nonpregnant) and 17.9% for the day of AI, 1.82 ng/mL (lower = nonpregnant) and 23.1% for 7 d after AI, and 2.67 ng/mL (lower = nonpregnant) and 76.0% for 25 d after AI. The false positive rate was less than 5% for all tests. Analysis of a second data set from a published study gave approximately the same cutpoints and sensitivity. When both studies were combined, approximately 20% of nonpregnant cows could be identified with a single test that was done before or shortly after AI with a false positive rate of less than 5%. When 2 and 3 tests were applied sequentially, the sensitivity for identifying nonpregnant cows increased from 38.4 to 50.5%. The pregnancy per AI for those cows that met the established progesterone criteria was approximately 3 to 4 times greater than those that failed to meet the criteria. The conclusions were that cows destined to be nonpregnant after timed AI can be identified before or shortly after AI. Testing for nonpregnancy before or shortly after AI may have utility with respect to eliminating a nonproductive AI (cows identified before AI) or shortening the time to reinsemination (cows identified by 1 wk after AI). [ABSTRACT FROM AUTHOR]

The ruminant trophoblast produces pregnancyassociated glycoproteins (PAG) that can be detected in the blood of pregnant animals. The objective was to determine the accuracy of a rapid ELISA PAGbased test for the purpose of pregnancy detection in cattle. Blood was sampled from dairy cattle (539 Holstein cows, 173 Holstein heifers, 73 Guernsey cows, 22 Guernsey heifers, and 12 Jersey heifers) and crossbred beef cattle (145 cows and 46 heifers) that were =25 d after insemination (range = 25 to 45 d for dairy and 29 to 56 d for beef). Cattle were examined by ultrasonography for detection of pregnancy within 2 d of blood collection. Whole blood or plasma was incubated in a polystyrene tube coated with a monoclonal PAG antibody for 15 min. The tubes were then washed and subjected to sequential incubations with a biotinylated polyclonal PAG antibody (15 min, followed by wash), a horseradish peroxidase-streptavidin solution (15 min, followed by wash), and a peroxidase substrate. Tubes were visually assessed for color after 15 min (clear solution = PAG negative, not pregnant; blue solution = PAG positive, pregnant). Total assay time was approximately 90 min. The ultrasound examination was used as the standard for pregnancy diagnosis. The sensitivity (99.8 ± 0.2%), specificity (91.7 ± 1.4%), and negative predictive value (99.7 ± 0.3%) for the PAG test used in dairy cattle were similar for different breeds and for cows and heifers. The positive predictive value for the test was greater in dairy heifers than in dairy cows (96.5 ± 1.4% vs. 90.5 ± 1.7%, respectively). In beef cattle, the sensitivity (100%), specificity (92.3 ± 3.0%), positive predictive value (95.0 ± 2.0%), and negative predictive value (100%) for the PAG test were similar for cows and heifers. The accuracy of the test was not different for dairy and beef cattle. In conclusion, the rapid ELISA pregnancy test based on PAG was highly sensitive and specific for pregnancy detection in dairy and beef cattle. [ABSTRACT FROM AUTHOR]

The objective was to compare pregnancy per AI (P/ AI) with conventional (CON) or sex-sorted (SS) semen from a single sire within a fixed-time AI (FTAI) program designed for dairy heifers. Holstein heifers (n = 240) were assigned to treatment (CON or SS) according to body weight and reproductive tract score. All heifers underwent FTAI by using the "Show-Me-Synch" protocol [controlled internal drug release (CIDR) insert from d 0 to 14 followed by PGF2α (25 mg i.m.) 16 d after insert removal (d 30) with GnRH (100 µg i.m.) and FTAI at 66 h after PGF2α]. A single professional technician performed the FTAI. Heifers were fitted with heat detection patches at PGF2α to characterize estrous response. Estrous response did not differ between CON (63/120; 53%) and SS (70/120; 58%) treatments. The CON heifers, however, achieved greater FTAI P/AI (82/120; 68%) compared with SS (45/120; 38%) heifers. The P/AI did not differ for CON heifers that exhibited or failed to exhibit estrus before FTAI [44/63 (70%) vs. 38/57(67%), respectively]. For SS heifers, however, those that exhibited estrus had greater P/AI compared with those that failed to exhibit estrus [32/70 (46%) vs. 13/50 (26%)]. Pregnancy per AI resulting from FTAI was greater for heifers that were inseminated with CON semen compared with those that received SS semen. The expression of estrus before FTAI did not affect P/ AI when CON semen was used, whereas the P/AI with SS semen was greater for heifers detected in estrus. Further studies are required to develop strategies for using sex-sorted semen when inseminating heifers at predetermined fixed times on the basis of expression of estrus before FTAI. [ABSTRACT FROM AUTHOR]

There are limited data available regarding pathogens causing intramammary infections (IMI) in Jersey cows. The objectives of this study were to characterize the prevalence of IMI caused by different microorganisms in lactating Jersey cattle and evaluate the associations among microbes and somatic cell count (SCC) and persistence of IMI. This prospective, observational, longitudinal study included lactating Jersey cows (n = 753) from 4 farms within a 415 km radius of Columbia, Missouri. Quarter foremilk samples were aseptically collected monthly for 3 consecutive months. Microorganisms were identified using aerobic milk culture and MALDI-TOF mass spectrometry. A commercial laboratory measured SCC using flow cytometry. Milk culture results were used to classify single microorganism infections as persistent (same microorganism species identified at first sampling and one other sampling) or nonpersistent infection. Mixed models were built to evaluate the associations between IMI status and SCC natural logarithm (lnSCC), as well as persistence and lnSCC. Overall, staphylococci were the most commonly isolated microorganisms among the 7,370 quarter-level milk samples collected. Median prevalence (using all 3 samplings) of specific microbes varied among farms; however, Staphylococcus chromogenes was a common species found at all farms. The most common microbial species that persisted were Staph. chromogenes, Staphylococcus aureus, Staphylococcus simulans, and Streptococcus uberis. Streptococcus dysgalactiae and Staph. aureus were the IMI associated with the most inflammation based on lnSCC. The small number of herds included in this study with the large variation in herd type limits the generalizability of the data. However, results of this study seem to be similar to those of previous studies in other breeds, suggesting management factors are more important than breed-specific differences when evaluating causes of IMI and associated subclinical mastitis., (The Authors. Published by Elsevier Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).)

The postpartum uterus involutes to its pre-pregnant and fully functional state within approximately 60 d after calving. Uterine glands are essential for fertility but little is known about their regeneration postpartum. Likewise, the effect of uterine disease (metritis) on gland regeneration is unknown. We hypothesized that uterine glands would be regenerated early postpartum and that metritis would be associated with slower gland regeneration to affect their numbers later postpartum during the breeding period. Postpartum dairy cows were diagnosed as healthy (n = 17 and 9 for experiment [Exp.] 1 and 2) or metritis (n = 17 and 10 for Exp. 1 and 2, respectively) at 7 to 10 d postpartum. Cows were slaughtered at approximately 1 mo (Exp. 1) or approximately 80 or 165 d (Exp. 2) postpartum for the collection of the uterus. Uterine tissue was sectioned and the number of glandular cross-sections per unit area was counted and cross-sectional area measured. Cellular proliferation within the luminal epithelium (LE) and glandular epithelium (GE) was quantified by MKI67 (marker of cellular proliferation) immunohistochemistry. In early postpartum cows (Exp. 1), the greatest amount of MKI67 staining was found in the deep endometrium (cells closest to the myometrium). Cows with purulent material in the uterine lumen at d 30 slaughter (Exp. 1) had fewer endometrial glands per unit area in the deep and middle endometrium when compared with nonpurulent cows. The MKI67 staining was less in the deep endometrial GE and LE for purulent compared with nonpurulent cows. Estrus cyclicity was associated with a greater number of gland cross-sections in the deep and middle endometrium. Later postpartum (80 and 165 d; Exp. 2), there was greater glandular development compared with Exp. 1 and a tendency for a lesser number of gland cross-sections per unit area in diseased cows without an effect on MKI67 staining in the GE or LE. We conclude that uterine disease slows the development of uterine glands early postpartum (by 1 mo) through a mechanism that involves cellular proliferation within the GE. The impact of the early postpartum disease on glandular development later postpartum (Exp. 2) appeared to be less. Additional time, therefore, may allow recovery of the GE in later postpartum cows., (© 2023.)

An experiment was conducted to compare the 7 & 7 Synch and 7-day CO-Synch + controlled internal drug release (CIDR®) treatment regimens before fixed-time artificial insemination (FTAI) of beef cows with conventional or sex-sorted semen. Cows (n = 1538) were blocked based on age and days postpartum (DPP) and randomly assigned to treatment regimen and semen type. Cows assigned to the 7-day CO-Synch + CIDR treatment regimen (n = 769) were administered gonadotropin-releasing hormone (GnRH) and an intravaginal progesterone-releasing insert (CIDR) on Day - 10, and administration of prostaglandin F 2α (PG) coincident with CIDR removal on Day - 3. Cows assigned to 7 & 7 Synch (n = 769) were administered PG and a CIDR device on Day - 17, GnRH on Day - 10, and PG coincident with CIDR removal on Day - 3. Cows were administered GnRH coincident with FTAI, which was performed 66 h after CIDR removal with conventional (20 × 10 6 cells) or sex-sorted (4 × 10 6 cells) semen. Expression of estrus was affected by treatment regimen (P = 0.01) and by treatment regimen × DPP (P = 0.0004), as a result of imposing the 7 & 7 Synch regimen; therefore, a greater percentage of cows expressed estrus (82% compared with 64%), particularly among cows with greater DPP. Pregnancy percentages resulting from FTAI were less (P < 0.0001) when using sex-sorted semen but greater among cows treated with 7 & 7 Synch (conventional semen: 72%; sex-sorted semen: 52%) compared with 7-day CO-Synch + CIDR (conventional semen: 61%; sex-sorted semen: 44%)., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Estrus is an important behavior that can potentially be subjected to genomic selection. Circulating estradiol concentrations at estrus may be a useful phenotype if the absolute concentrations of estradiol are associated with overt phenotypes for estrus (activity, rump touches, or both; e.g., mounts, chinrests) that can be easily observed. The objective was to measure plasma estradiol concentrations at estrus and associate these measurements with the increase in activity (steps per hour) and rump touches received at estrus. We also tested the effect of lactation on the estrus traits that we measured. Cows (n = 11 lactating and n = 9 nonlactating) were treated with PGF 2α to synchronize estrus. A jugular vein was cannulated to collect blood every 2 h for plasma estradiol measurement. Plasma LH was measured during the periestrual period to determine the time of the LH surge. Cows were fitted with an accelerometer to measure activity (steps per hour) and a capacitive touch sensing device to measure the number of rump touches and total touch time. Plasma estradiol concentrations were poorly correlated with overt signs of estrus during the period leading up to maximum estrus activity. After peak estrus activity (when cows were going out of estrus and plasma estradiol concentrations were decreasing), a stronger correlation was detected between overt signs of estrus and plasma estradiol concentrations. Effective selection for improved estrus expression based on plasma estradiol concentrations will depend on whether the cow is coming into or going out of estrus at the time of blood sampling. An association existed between lactation and fewer number of hours in estrus when estrus was defined by an increase in activity (steps per hour). Lactating cows had a shorter interval from the onset of estrus to the LH surge, and the shorter interval to the LH surge may have reduced the period of elevated estradiol during estrus in the lactating cows. Understanding mechanisms that control the sensitivity of the cow to estradiol and making appropriate selection decisions based on these mechanisms will likely increase overt signs of estrus in dairy cows., (Copyright © 2021 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Estrus traits have economic value in dairy production systems and could be incorporated into genetic selection indices. In an effort to further understand selection responses, 2 studies were performed to estimate the intra- and interclass correlation coefficients for estrus traits. Holstein-Friesian cows (n = 1,197; study 1) across 5 pasture-based grazing dairy herds were fitted with a capacitive touch sensing (CTS) device on the rump (FlashMate, Farmshed Labs Limited, Hamilton, New Zealand). The daily number of rump touches were subjected to a peak detection program to objectively identify periods of increased rump touches above baseline (indicative of estrus). The number of times touched and the sum of the touch duration were used to compare farms and estimate the intraclass correlation (repeatability). For study 2, postpartum Holstein (n = 85) and Guernsey (n = 5) cows in a confinement-style dairy were used. Cows were fitted with an IceQube accelerometer (IceRobotics Ltd., Edinburgh, United Kingdom) to measure steps taken per hour and a CTS device was applied to both rumps. The interclass correlation for the number of rump touches and number of steps taken during estrus was calculated. Data collected from 5 herds (study 1) demonstrated a 2- to 3-fold difference between herds in the number of rump touches and total touch time during estrus. The intraclass correlation (repeatability; estimates of maximum heritability) for rump touches during estrus was 0.22. For study 2, the number of steps and the number of rump touches during estrus increased in a synchronous manner. The intraclass correlation (repeatability) for number of steps during estrus was 0.26. The interclass correlation (r) for the number of rump touches and the number of steps was 0.46 (R 2 = 0.21). Based on the R 2 , at least 20% of the variation in the number of steps during estrus was explained by the number of touches to the rump of the cow. Selecting cows for the number of steps taken during estrus could increase the number of rump touches (mounts, chin rests, and so on, received from other cows) if a genetic correlation exists for the phenotypic correlation that we observed., (Copyright © 2021 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Within seasonal dairy systems, cows that calve late in the calving season are less likely to become pregnant and maintain a yearly calving interval. Very few studies have examined effective strategies for reproductive management of these late-calving cows. The objectives were to evaluate the reproductive performance of early- and late-calving dairy cows that were either inseminated after observed estrus (control) or enrolled in a timed AI and resynchronization protocol [progesterone (P4) Ovsynch Resynch)]. Early-calving cows calved during the first week of the calving season, whereas late-calving cows calved after 6 wk but were at least 10 d in milk at study commencement. Three dairy herds participated in the study with 391 cows total. Within each calving group, cows were randomly assigned to P4 Ovsynch Resynch or control (no treatment) in a 2 × 2 experimental design. Artificial insemination continued for 6 wk after mating start date (MSD) and was followed by 6 wk of natural service. The interval from MSD to AI was shorter (11.7 vs. 14.7 d) and the 3-wk pregnancy rate (49.5 vs. 21.2%) and the 6-wk pregnancy rate (60.8 vs. 42.4%) were greater in the early-calving compared with the late-calving control cows. By design, synchronized cows received timed AI on MSD and were not included in the statistical analysis of submission rate and interval from MSD to AI. The proportion of cows that received a second AI was not increased by the progesterone-based resynchronization strategy but was greater in early-calving compared with late-calving cows. The 12-wk pregnancy rate was greater (64.5 vs. 45.0%) in the early-calving synchronized cows compared with the late-calving synchronized cows. The interval from MSD to pregnancy was 6 and 12.6 d shorter for synchronized compared with control cows in the early- and late-calving groups, respectively. The results demonstrated reduced reproductive performance of late-calving cows compared with early-calving cows. Nonetheless, a major improvement to reproductive performance was achieved by targeting late-calving cows with a synchronization program, even when cows were only 20 to 50 DIM at first AI. Resynchronization of estrus with a progesterone device only, however, was not sufficient to increase the proportion of nonpregnant cows that received a second AI., (© 2021.)

An experiment was designed to evaluate treatments to promote ovarian follicular maturity in advance of administration of exogenous gonadotropin-releasing hormone (GnRH; 100 μg gonadorelin) for control of the bovine estrous cycle. We hypothesized prostaglandin F 2α (PGF 2α ; 500 μg cloprostenol) followed by an intravaginal progesterone-releasing insert (CIDR; 1.38 g progesterone) would induce greater follicle size and serum estradiol at the time of GnRH administration. Postpartum cows (n = 194) in two locations were assigned to one of five treatments based on age, days postpartum, and body condition score. Cows in Treatment 1 were treated with the standard 7-d CO-Synch + CIDR protocol: administration of GnRH and CIDR insertion on Day -10, and administration of PGF 2α and CIDR removal on Day -3. Treatments 2-5 were designed in a 2 × 2 factorial arrangement, with Treatment 1 included as an additional reference. On Day -17, cows in Treatments 2-5 received a CIDR insert, either with (Treatments 2 and 3) or without (Treatments 4 and 5) administration of PGF 2α at CIDR insertion. On Day -10, all cows were administered GnRH, and CIDR inserts were either removed (Treatments 2 and 4) or remained in place until Day -3 (Treatments 3 and 5). Treatment with PGF 2α and CIDR in advance of GnRH (Treatments 2 and 3) resulted in increased diameter of the largest ovarian follicle (P < 0.001) and increased serum concentrations of estradiol (P < 0.0005) on Day -10. In addition, variation among cows in CL status (no CL vs. a single CL vs. multiple CL) on Day -3 tended to be decreased (P = 0.08), with cows more likely to have a single CL rather than no CL or multiple CL. Lastly, the proportion of cows expressing estrus prior to fixed-time artificial insemination tended (P = 0.08) to be improved. Results support the hypothesis that administration of PGF 2α and treatment with a CIDR for 7 days prior to GnRH promotes follicular maturity in advance of GnRH administration and may provide an approach by which to enhance response of postpartum beef cows to GnRH-based estrus synchronization programs., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Uterine disease early postpartum reduces fertility during the breeding period. One potential mechanism involves the reduced functional capacity of the uterus to support pregnancy. A second potential mechanism involves damage to ovarian follicles associated with systemic inflammation. We categorized lactating Holstein cows into healthy (n = 63) and diseased (n = 39) uterus groups based on the percentage of polymorphonuclear neutrophils in the uterine lumen during the second and third month postpartum and evaluated the functionality of their ovaries and their capacity to establish and maintain pregnancy. Cows were enrolled in a timed artificial insemination protocol (Presynch Ovsynch) so that the first artificial insemination was approximately 75 d postpartum. Ovarian follicles and corpora lutea were counted and measured using transrectal ultrasound, ovulatory responses were assessed, and luteal phase progesterone concentrations were measured. Pregnancy was detected on d 18, 20, 22, 25, 32, and 45 through chemical (d 18 to 25) or ultrasonographic methods (d 32 and 45). The percentage of cows ovulating during the Presynch period; the number, diameter, and ovulatory capacity of follicles during the Ovsynch period; and plasma progesterone concentrations following ovulation were similar for healthy and diseased cows. The initial period of pregnancy establishment (d 18 to 22) appeared to be unaffected by disease because a similar percentage of healthy and diseased cows were pregnant during this period. Embryonic loss occurred in both healthy and diseased cows after d 22. Based on a relatively small number of pregnancies (n = 30 healthy and n = 17 diseased), the cumulative embryonic loss after d 22 was greater in diseased compared with healthy cows. In short, uterine disease as defined in this study did not affect cyclicity, ovarian follicular growth, or plasma progesterone concentrations. Percentages of healthy and diseased cows that were pregnant were similar from d 18 to 22 after artificial insemination. Greater embryonic loss was observed after d 22 in diseased compared with healthy cows, but this observation was based on a small number of pregnancies and should be studied further in larger trials with greater statistical power., (Copyright © 2020 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

This experiment was designed to evaluate breeding strategies involving natural service or fixed-time artificial insemination (FTAI) in Bos indicus-influenced beef heifers (n = 1456) when there were field-type management conditions. Body weights and reproductive tract scores (RTS; Scale 1-5) were obtained for heifers before assignment to one of five treatments: 1) Non-synchronized control exposed for natural service (NS), n = 299; 2) melengestrol acetate + natural service (MGA + NS; 0.5 mg/heifer/d), n = 295; 3) 14-d controlled internal drug release insert + natural service (CIDR + NS), n = 289; 4) 14-d MGA-prostaglandin F 2α (PG) + FTAI, n = 295; or 5) 14-d CIDR-PG + FTAI, n = 278. Fertile bulls were placed in pastures with heifers of the three NS treatment groups for a 65-day period which began 10 days after progestin treatments (MGA or CIDR) ended. Heifers in FTAI treatment groups were administered PG (25 mg, IM) 16 days after CIDR removal or 19 days following MGA withdrawal, respectively, and FTAI was performed at 66 (CIDR-PG) or 72 h (MGA-PG) after PG. Gonadotropin-releasing hormone (GnRH; 100 μg, i.m.) was administered at FTAI. Pregnancy status was determined at the end of a 65-day breeding period. Pregnancy rates on Days 21 and 65 of the breeding period differed among treatment groups based on pre-treatment pubertal status (P ≤ 0.02) and body weight (P ≤ 0.05) but did not differ by group. These data highlight the need for continued research efforts to improve reproductive management of Bos indicus-influenced females., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Less than optimal circulating progesterone as well as glucose, insulin, and IGF1 concentrations in lactating cows may contribute to embryonic loss if placental development is dependent on concentrations of these hormones. There was comparison of fetal growth in lactating dairy cows with a contemporary group of nulliparous heifers (negative control for lactation). There was also assessment of the association between conceptus development and circulating hormone and metabolite concentrations and the response to an intravenous glucose administration. The embryo and amniotic vesicle were measured every 2-3 days during a 2-week period (days 33-45 of pregnancy). Blood samples were collected at the time of ultrasonography and analyzed for glucose, insulin, IGF1, and progesterone. There was also an intravenous glucose administration. Lactating cows had lesser blood concentrations of glucose, progesterone, and IGF1 during pregnancy. With respect to glucose administration, cows had lesser insulin and glucose than heifers at time 0 but heifers released three-fold more insulin than cows in response to glucose infusion. Cows had slightly larger fetuses when compared with heifers. When included in the model for embryo or amniotic vesicle length or area, concentrations of circulating glucose, insulin, IGF1, or progesterone did not explain a large amount of variation in values for these variables (P > 0.10). The conclusion was that cows differed from heifers for fetal growth but concentrations of circulating metabolites were not associated with size of the fetus. There was no evidence for an association between the hormonal or metabolic milieu and conceptus development., Competing Interests: Declaration of Competing Interest The authors have no conflict of interest., (Copyright © 2020. Published by Elsevier B.V.)

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., (Copyright © 2019 Elsevier Inc. All rights reserved.)

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., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Aims: To compare the effect of two partial mixed ration diets containing either sulfate or chloride-based anionic salts, fed to grazing prepartum dairy cows, on concentrations of Ca, Mg, P and beta-hydroxybutyrate (BHB) in plasma, disease incidence and milk yield during the early postpartum period., Methods: The study was conducted on a seasonal-calving grazing dairy farm located in Benton (MO, USA). In August 2016, two groups of 200 cows were randomly assigned at 30 days before expected parturition to receive either a sulfate or chloride-based anionic diet, to achieve a dietary cation-anion difference (DCAD) of -25 mEq/kg DM. Cows were fed partial mixed rations to provide 50% of their DM intake, with 50% provided by grazing fescue pasture. Urine samples were collected from 20 cows from each group once a week for 5 weeks until calving for pH assessment. At parturition, 42 cows per group were selected at random and blood samples collected on Days 1, 2, 3 and 7 postpartum. The study continued until 100 cows per group calved. Health events and cumulative milk yield until 30 days postpartum were recorded. Concentrations of Ca, P, and Mg in plasma at Days 1, 2, 3, and 7, and BHB in plasma at Day 7 postpartum were assessed., Results: Mean urine pH was lower in cows in the chloride than sulfate group (p≤0.06) on four of five sampling occasions. Mean concentrations of Ca in plasma on Day 1 were 2.00 (95% CI=1.94-2.05) and 1.91 (95% CI=1.88-1.97) mmol/L for the chloride and sulfate groups, respectively (p=0.15), and on Day 3 were 2.03 (95% CI=1.97-2.08) and 1.90 (95% CI=1.84-1.96) mmol/L, respectively (p=0.038). Concentrations of Mg, P and BHB in plasma and incidence of diseases postpartum were similar in both groups (p>0.05). There were no cases of clinical hypocalcaemia in either group., Conclusions and Clinical Relevance: Prepartum cows fed a partial mixed ration with a negative DCAD containing chloride-based anionic salts and free access to a fescue pasture had lower prepartum urine pH, and higher concentrations of total Ca in plasma during the first week postpartum, than cows receiving a partial mixed ration containing sulfate-based anionic salts.

Fatty liver is a common condition affecting dairy cattle during the periparturient period, characterized by a pathological accumulation of triglycerides (TG) in the hepatocytes. The objective of this study was to evaluate the diagnostic potential of fine needle aspiration cytology in fresh liver specimens using liver TG concentrations as a gold standard. Fifty-seven liver samples from Holstein cows were collected during processing at a slaughterhouse. Tissue and fine needle aspirate samples were obtained from the parietal upper portion of the caudate lobe. Two samples of liver tissue were collected with a 16 gauge × 15 cm biopsy needle for histological and TG concentration assessment. A third sample was collected for cytology using an 18 gauge × 5.08 cm needle. The contents of the needle were transferred to a glass slide, spread, and air-dried. Liver samples were assayed by colorimetry/fluorimetry to determine TG concentrations. Concentrations of TG <2% were considered normal. Histological and cytological evaluations were conducted by 2 different pathologists blind to the visual classification. Sensitivity (Se) and specificity (Sp) were calculated. Cytology had a Se and Sp of 73 and 85%, respectively. Histopathology had a Se and Sp of 45.9 and 100%, respectively. The likelihood of having higher scores for histopathology and cytology increased as a function of liver TG content (mg/g)., (Copyright © 2018 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Although cowside testing strategies for diagnosing hyperketonemia (HYK) are available, many are labor intensive and costly, and some lack sufficient accuracy. Predicting milk ketone bodies by Fourier transform infrared spectrometry during routine milk sampling may offer a more practical monitoring strategy. The objectives of this study were to (1) develop linear and logistic regression models using all available test-day milk and performance variables for predicting HYK and (2) compare prediction methods (Fourier transform infrared milk ketone bodies, linear regression models, and logistic regression models) to determine which is the most predictive of HYK. Given the data available, a secondary objective was to evaluate differences in test-day milk and performance variables (continuous measurements) between Holsteins and Jerseys and between cows with or without HYK within breed. Blood samples were collected on the same day as milk sampling from 658 Holstein and 468 Jersey cows between 5 and 20 d in milk (DIM). Diagnosis of HYK was at a serum β-hydroxybutyrate (BHB) concentration ≥1.2 mmol/L. Concentrations of milk BHB and acetone were predicted by Fourier transform infrared spectrometry (Foss Analytical, Hillerød, Denmark). Thresholds of milk BHB and acetone were tested for diagnostic accuracy, and logistic models were built from continuous variables to predict HYK in primiparous and multiparous cows within breed. Linear models were constructed from continuous variables for primiparous and multiparous cows within breed that were 5 to 11 DIM or 12 to 20 DIM. Milk ketone body thresholds diagnosed HYK with 64.0 to 92.9% accuracy in Holsteins and 59.1 to 86.6% accuracy in Jerseys. Logistic models predicted HYK with 82.6 to 97.3% accuracy. Internally cross-validated multiple linear regression models diagnosed HYK of Holstein cows with 97.8% accuracy for primiparous and 83.3% accuracy for multiparous cows. Accuracy of Jersey models was 81.3% in primiparous and 83.4% in multiparous cows. These results suggest that predicting serum BHB from continuous test-day milk and performance variables could serve as a valuable diagnostic tool for monitoring HYK in Holstein and Jersey herds., (Copyright © 2018 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

An experiment was designed to evaluate endocrine parameters, ovarian dynamics, and pregnancy rates to fixed-time artificial insemination (FTAI) following the 9-d CIDR-PG protocol in comparison to the 14-d CIDR-PG protocol. While both are long-term protocols using CIDR treatment for presynchronization, the 9-d CIDR-PG protocol differs from the 14-d CIDR-PG protocol in that prostaglandin F 2α (PG) is administered at CIDR insertion and removal to facilitate a decreased length of progestin treatment and potentially enhance response to the presynchronization treatment. Estrus was synchronized for 393 mature beef cows across five locations. Treatments were represented in each location, and cows within each location were randomly assigned to one of the two protocols based on age, days postpartum (DPP), and body condition score (BCS). Cows assigned to the 14-d CIDR-PG treatment received a CIDR insert (1.38 g progesterone) on Day 0 with removal of CIDR on Day 14, and 25 mg PG 16 d after CIDR removal on Day 30. Cows assigned the 9-d CIDR-PG treatment received 25 mg PG and a CIDR insert (1.38 g progesterone) on Day 5; 25 mg PG and removal of CIDR on Day 14; and 25 mg PG 16 d after CIDR removal on Day 30. In both treatments, cows received FTAI on Day 33, 72 h after PG. All cows were administered 100 μg gonadotropin-releasing hormone (GnRH) concurrent with insemination. For a subset of animals in each treatment, ovarian ultrasound was performed and blood samples were collected for determination of serum estradiol concentrations at CIDR removal, PG administration, and FTAI. Protocols were compared on the basis of estrous response and pregnancy rate resulting from FTAI. Serum estradiol concentrations, follicle size, and estrous response did not differ based on treatment. However, cows assigned to the 9-d CIDR-PG protocol tended to achieve greater FTAI pregnancy rates than cows assigned to the 14-d CIDR-PG protocol (62% versus 52%; P = 0.07). Across treatments, greater pregnancy rates tended (P = 0.10) to be achieved by cows that expressed estrus prior to FTAI (69% for 9-d CIDR-PG, 58% for 14-d CIDR-PG) than by cows that failed to express estrus (55% for 9-d CIDR-PG, 47% for 14-d CIDR-PG). In summary, the 9-d CIDR-PG protocol is an effective protocol for synchronization of estrus among mature beef cows, and pregnancy rates to FTAI tended to be improved through use of the 9-d CIDR-PG compared to the 14-d CIDR-PG protocol., (Copyright © 2017 Elsevier Inc. All rights reserved.)

This experiment was designed to compare pregnancy rates in postpartum beef cows following split-time (STAI) or fixed-time (FTAI) artificial insemination. Estrus was synchronized for 671 cows at seven locations following administration of the 7-d CO-Synch + CIDR protocol (100 μg GnRH + CIDR insert [1.38 g progesterone] on d 0; 25 mg prostaglandin F 2α [PG] at CIDR removal on d 7). Cows were assigned to treatments that were balanced across locations based on age, body condition score, and days postpartum at the time treatments were initiated. All cows in treatment 1 (n = 333; FTAI) were inseminated at 66 h after PG and GnRH was administered concurrent with insemination regardless of estrus expression. For cows in treatment 2 (n = 338; STAI), inseminations were performed at 66 or 90 h after PG, and estrous status was recorded at these times. Cows in the STAI treatment that exhibited estrus by 66 h were inseminated at that time and did not receive GnRH, whereas AI was delayed 24 h until 90 h after PG for cows that failed to exhibit estrus by 66 h. Gonadotropin-releasing hormone (100 μg) was administered concurrent with AI at 90 h only to cows failing to exhibit estrus. Estrus expression that occurred during the 24 h delay period among cows assigned to the STAI treatment increased the total proportion of cows that expressed estrus prior to insemination (1 = 60%; 2 = 86%; P < 0.001). Pregnancy rates for cows inseminated at 66 h that exhibited estrus did not differ between treatments (1 = 58%; 2 = 58%; P = 0.93); however, pregnancy rates among non-estrous cows at 66 h were improved (1 = 35%; 2 = 51%; P = 0.01) among cows assigned to the STAI treatment when insemination was postponed by 24 h. Consequently, total AI pregnancy rate tended to be higher for cows that received STAI (1 = 49%; 2 = 56%; P = 0.06). In summary, following administration of the 7-d CO-Synch + CIDR protocol, total estrous response increased and pregnancy rates resulting from AI tended to be higher among cows assigned to STAI versus FTAI treatments., (Copyright © 2017. Published by Elsevier Inc.)

Two long-term, CIDR-based estrus synchronization protocols were evaluated among Bos indicus-influenced and Bos taurus beef heifers. Treatments were evaluated on the basis of estrous response and pregnancy rate resulting from fixed-time artificial insemination (FTAI), and these outcomes were analyzed retrospectively relative to reproductive tract score (RTS; Scale 1-5) at treatment initiation. Estrus was synchronized for 1139 heifers in three locations, and heifers were assigned to one of two treatments within each location based on RTS. Heifers assigned to the 14-d CIDR-PG protocol received a controlled internal drug release (CIDR) insert (1.38 g progesterone) on Day 0, CIDR removal on Day 14, administration of prostaglandin F 2α (PG; 25 mg im) on Day 30, and administration of gonadotropin-releasing hormone (GnRH; 100 μg im) concurrent with FTAI on Day 33, 66 h after PG. Heifers assigned to the 9-d CIDR-PG protocol received administration of PG concurrent with CIDR insertion on Day 5, administration of PG concurrent with CIDR removal on Day 14, administration of PG on Day 30, and administration of GnRH concurrent with FTAI on Day 33, 66 h after PG. Estrus detection aids were applied at CIDR removal on Day 14 and at PG on Day 30 to evaluate estrous response rate. Mean RTS differed (P < 0.0001) based on biological type due to higher rates of estrous cyclicity (RTS 4 and 5) among Bos taurus heifers (72%; 416/574) than among Bos indicus-influenced heifers (27%; 150/565). The proportion of heifers expressing estrus following CIDR removal was greater (P = 0.01) among heifers assigned to the 14-d CIDR-PG treatment (88%; 492/559) compared to the 9-d CIDR-PG treatment (83%; 480/580). Estrous response following CIDR removal was also higher (P < 0.0001) among Bos taurus (95%; 547/574) compared to Bos indicus-influenced (75%; 425/565) heifers. Rate of estrous response prior to FTAI did not differ significantly based on treatment but was higher (P < 0.0001) among Bos taurus heifers (60%; 344/574) than among Bos indicus-influenced heifers (45%; 253/565). However, the effect of biological type on estrous response was not significant when RTS was included in the model, as RTS significantly (P < 0.0001) affected the rate of estrous response both at CIDR removal and prior to FTAI. Across treatments and biological types, heifers that expressed estrus prior to AI achieved higher (P < 0.0001) AI pregnancy rates than heifers failing to express estrus. Pregnancy rates to FTAI did not differ significantly based on treatment in either biological type. Higher rates of estrous cyclicity among Bos taurus heifers resulted in higher FTAI pregnancy rates among Bos taurus (51%; 290/574) compared to Bos indicus-influenced heifers (39%; 218/565). However, pregnancy rates of respective RTS did not differ based on biological type. In summary, long-term CIDR-based protocols provide a simple, effective method of estrus synchronization in Bos indicus-influenced and Bos taurus beef heifers. Moreover, these results highlight the importance of management practices that result in high rates of estrous cyclicity prior to protocol initiation, particularly among later maturing breeds and biological types., (Copyright © 2017 Elsevier Inc. All rights reserved.)

This experiment was designed to evaluate split-time artificial insemination (AI) in beef heifers following administration of the 14-day controlled internal drug release (CIDR)-prostaglandin F 2α (PG) protocol and to compare pregnancy rates among nonestrous heifers based on administration of GnRH at AI. Estrus was synchronized for 1138 heifers across six locations. Heifers received a CIDR insert (1.38 g progesterone) on Day 0 with removal on Day 14. Estrus detection aids (Estrotect) were applied at PG (25 mg), 16 days after CIDR removal on Day 30. Heifers were assigned to balanced treatments based on reproductive tract score and weight, and treatments were represented within each location. Split-time AI was performed at 66 and 90 hours after PG, and estrus was recorded at these times. Heifers in both treatments that exhibited estrus by 66 hours were inseminated and did not receive GnRH, whereas AI was delayed 24 hours until 90 hours after PG for heifers that failed to exhibit estrus by 66 hours. For heifers in treatment 1 that were inseminated at 90 hours, GnRH (100 μg) was administered concurrent with AI at 90 hours. Heifers in treatment 2 that were inseminated at 90 hours did not receive GnRH. Estrous response did not differ between treatments at 66 hours after PG (treatment 1 = 70%; treatment 2 = 71%; P = 0.58) or during the 24-hour delay period (treatment 1 = 59%; treatment 2 = 52%; P = 0.21). There was no effect of treatment on pregnancy rates resulting from AI for heifers inseminated at 66 hours (treatment 1 = 58%; treatment 2 = 62%; P = 0.86) or 90 hours (treatment 1 = 44%; treatment 2 = 39%; P = 0.47) after PG; and there was no difference between treatments when considering total AI pregnancy rate (treatment 1 = 54%; treatment 2 = 56%; P = 0.60). Ovulation was confirmed via ultrasonography for a subset of heifers that failed to exhibit estrus prior to 90 hours after PG. For heifers that failed to exhibit estrus by 90 hours, success of ovulation did not differ between treatments (treatment 1 = 52%; treatment 2 = 50%; P = 0.64) nor did AI pregnancy rate (treatment 1 = 24%; treatment 2 = 15%; P = 0.97). In summary, when split-time AI was used in conjunction with the 14-day CIDR-PG protocol in heifers, comparable pregnancy rates were achieved without administering GnRH., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Two experiments evaluated controlled internal drug release (CIDR)-based protocols to synchronize estrus in primiparous 2-year-old beef cows. In each experiment, treatments were balanced according to body condition score and days postpartum. Experiment 1 compared the 14-day CIDR-PG (14-d) and 7-day CO-Synch + CIDR (7-d) protocols on the basis of estrous response, pregnancy rates after fixed-time artificial insemination (FTAI), and final pregnancy rate. Cows assigned to 14-d (n = 355) received a CIDR insert on Day 0 with removal on Day 14. Cows assigned to 7-d (n = 349) received gonadotropin releasing hormone (GnRH) and a CIDR insert on Day 23. On Day 30, CIDRs were removed from 7-d cows, and PGF 2α was administered to all cows in each treatment. On Day 33, GnRH was administered concurrent with FTAI at 66 and 72 hours after PGF 2α for 7-d and 14-d treated cows, respectively. Estrous response before FTAI was higher for 7-d compared with 14-d cows (74% vs. 43%, respectively; P < 0.0001); however, pregnancy rates resulting from FTAI were similar (14-d 63%; 7-d 64%; P = 0.52). Ovarian follicular dynamics and serum estradiol-17β concentrations were evaluated among a subset of cows assigned to each protocol. Dominant follicle diameter was smaller at PGF 2α (P = 0.04) and FTAI (P = 0.002) among 14-d cows compared with 7-d cows; however, estradiol-17β at PGF 2α (P = 0.06) and FTAI (P = 0.001) was greater for 14-d versus 7-d treated cows. Experiment 2 compared estrous response and pregnancy rates in 2-year-old beef cows after FTAI- or split-time artificial insemination (STAI) following synchronization of estrus with the 14-day protocol. Cows assigned to FTAI (n = 266) were inseminated at a fixed time concurrent with GnRH at 72 hours after PGF 2α regardless of estrus expression, whereas cows assigned to STAI (n = 257) were inseminated based on estrus expression as determined by activation of an estrus detection aid. Cows assigned to STAI that exhibited estrus by 72 hours were inseminated; however, AI was delayed until 24 hours after GnRH (96 hours after PGF 2α ) for nonestrous cows. Total estrous response was increased for STAI- versus FTAI-treated cows (STAI 64%; FTAI 42%; P < 0.0001); pregnancy rates resulting from AI were similar (STAI 55%; FTAI 56%; P = 0.60). In summary, the 14-day CIDR-PG and 7-day CO-Synch + CIDR protocols can be used effectively to synchronize estrus before FTAI in primiparous 2-year-old beef cows. Although expression of estrus was increased using STAI in conjunction with the 14-day protocol, this approach did not increase pregnancy rates compared with FTAI., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Lymphocytic foci (also known as lymphoid aggregates or tertiary lymphoid structures) form within the bovine endometrium after antigenic challenge. Their presence in the pregnant uterus provides evidence for a chronic inflammatory condition perhaps arising from an early postpartum uterine infection. The chronic inflammation that includes the foci could explain greater embryonic loss in dairy cows with early postpartum uterine disease. The objectives were to characterize the size and location of the foci in the pregnant uterus, determine their composition using immunohistochemistry, and associate their presence with the development of the pregnancy and embryonic loss. Pregnant cows (n = 43) were slaughtered on days 28, 35, or 42 of pregnancy. Uterine tissue was collected and processed for histologic and immunohistochemical analysis. The number of small (<100 micron diameter), intermediate (100-250 micron diameter), and large (>250 micron diameter) foci was counted. The number of cows averaging 0, 0.1 to 1, 1.1 to 2, and more than 2 foci per section (small, intermediate, and large; combined) was 7 (16%), 14 (33%), 11 (26%), and 11 (26%), respectively. The average number of small and intermediate foci found in the histologic sections was greater in cows with evidence of uterine infection postpartum (P < 0.05). Lymphocytic foci were distributed within the caruncle and the intercaruncular tissue and comprised a core of CD3-positive cells (T cells) surrounding CD79-positive cells (B cells). The number of lymphocytic foci was correlated with a total inflammation score (on the basis of the total number of inflammatory cells in the endometrium; r(2) = 0.49; P < 0.001) and a fibrosis score (based on the extent of fibrosis in the endometrium; r(2) = 0.33; P < 0.001). Cows with a high foci count (averaging more than 0.5 foci per section) had lesser (P < 0.01) placental weight on Day 42 of pregnancy. There was no effect of foci count on placental weight on Day 28 or 35. Two cows with embryonic loss were in the highest quartile for foci count. In conclusion, cows with chronic inflammation as evidenced by a large number of lymphocytic foci had reduced placental weight during pregnancy. The number of foci in pregnant cows was associated with early postpartum uterine disease. Whether the foci themselves are inhibitory to pregnancy development or are associated with other bacteriological, morphological, or biochemical changes to the uterus that lead to infertility will need to be investigated., (Copyright © 2016 Elsevier Inc. All rights reserved.)