Effect of Genetic and Environmental Factors on Twin Pregnancy in Primiparous Dairy Cows.

Twin pregnancies are highly undesirable in dairy cattle; they compromise the health and wellbeing of a cow and dramatically impair the farm economy. Recently, a genomic prediction for twin pregnancies has been developed. The objective of this study was to assess environmental and management risk factors affecting the incidence of twin pregnancies in high-producing dairy cows in their first lactation, with a special emphasis placed on the genomic prediction values of twin pregnancy. Our study population of primiparous cows proved valuable in identifying factors other than genomic predictive values that influence twin pregnancy rates. The odds ratio for twin pregnancies was 0.85 (p < 0.0001) for each unit of a prediction value increase, 3.5 (p = 0.023) for cows becoming pregnant during the negative photoperiod, and 0.33 (p = 0.016) for cows producing ≥42 kg of milk at AI, compared with the remaining cows who produced <42 kg of milk. As a general conclusion, the practical implication of our findings is that genomic prediction values can identify the risk of twin pregnancy at a herd level. Given the cumulative effect of genomic selection, selecting animals with a reduced genetic risk of twin pregnancies can contribute to reducing the incidence of twin pregnancies in dairy herds.

Genomic Prediction for Abortion in Lactating Holstein Dairy Cows.

Abortion in dairy cattle causes great economic losses due to reduced animal health, increase in culling rates, reduction in calf production, and milk yield, among others. Although the etiology of abortions can be of various origins, previous research has shown a genetic component. The objectives of this study were to (1) describe the development of the genomic prediction for cow abortions in lactating Holstein dairy cattle based on producer-recorded data and ssGBLUP methodology and (2) evaluate the efficacy of genomic predictions for cow abortions in commercial herds of US Holstein cows using data from herds that do not contribute phenotypic information to the evaluation. We hypothesized that cows with greater genomic predictions for cow abortions (Z_Abort STA) would have a reduced incidence of abortion. Phenotypic data on abortions, pedigree, and genotypes were collected directly from commercial dairy producers upon obtaining their permission. Abortion was defined as the loss of a confirmed pregnancy after 42 and prior to 260 days of gestation, treated as a binary outcome (0, 1), and analyzed using a threshold model. Data from a different subset of animals were used to test the efficacy of the prediction. The additive genetic variance for the cow abortion trait (Z_Abort) was 0.1235 and heritability was 0.0773. For all animals with genotypes (n = 1,662,251), mean reliability was 42%, and genomic predicted transmitting abilities (gPTAs) ranged from −8.8 to 12.4. Z_Abort had a positive correlation with cow and calf health traits and reproductive traits, and a negative correlation with production traits. Z_Abort effectively identified cows with a greater or lesser risk of abortion (16.6% vs. 11.0% for the worst and best genomics groups, respectively; p < 0.0001). The inclusion of cow abortion genomic predictions in a multi-trait selection index would allow dairy producers and consultants to reduce the incidence of abortion and to select high-producing, healthier, and more profitable cows.

Effects of feeding rumen-protected methionine pre- and postpartum in multiparous Holstein cows: Lactation performance and plasma amino acid concentrations.

Objectives were to evaluate the effect of feeding rumen-protected methionine (RPM) in pre- and postpartum total mix ration (TMR) on lactation performance and plasma AA concentrations in dairy cows. A total of 470 multiparous Holstein cows [235 cows at University of Wisconsin (UW) and 235 cows at Cornell University (CU)] were enrolled approximately 4 wk before parturition, housed in close-up dry cow and replicated lactation pens. Pens were randomly assigned to treatment diets (pre- and postpartum, respectively): UW control (CON) diet = 2.30 and 2.09% of Met as percentage of metabolizable protein (MP) and RPM diet = 2.83 and 2.58% of Met as MP; CU CON = 2.22 and 2.19% of Met as percentage of MP, and CU RPM = 2.85 and 2.65% of Met as percentage of MP. Treatments were evaluated until 112 ± 3 d in milk (DIM). Milk yield was recorded daily. Milk samples were collected at wk 1 and 2 of lactation, and then every other week, and analyzed for milk composition. For lactation pens, dry matter intake (DMI) was recorded daily. Body weight and body condition score were determined from 4 ± 3 DIM and parturition until 39 ± 3 and 49 DIM, respectively. Plasma AA concentrations were evaluated within 3 h after feeding during the periparturient period [d -7 (±4), 0, 7 (±1), 14 (±1), and 21 (±1); n = 225]. In addition, plasma AA concentrations were evaluated (every 3 h for 24 h) after feeding in cows at 76 ± 8 DIM (n = 16) and within 3 h after feeding in cows at 80 ± 3 DIM (n = 72). The RPM treatment had no effect on DMI (27.9 vs. 28.0 kg/d) or milk yield (48.7 vs. 49.2 kg/d) for RPM and CON, respectively. Cows fed the RPM treatment had increased milk protein concentration (3.07 vs. 2.95%) and yield (1.48 vs. 1.43 kg/d), and milk fat concentration (3.87 vs. 3.77%), although milk fat yield did not differ. Plasma Met concentrations tended to be greater for cows fed RPM at 7 d before parturition (25.9 vs. 22.9 µM), did not differ at parturition (22.0 vs. 20.4 µM), and were increased on d 7 (31.0 vs. 21.2 µM) and remained greater with consistent concentrations until d 21 postpartum (d 14: 30.5 vs. 19.0 µM; d 21: 31.0 vs. 17.8 µM). However, feeding RPM decreased Leu, Val, Asn, and Ser (d 7, 14, and 21) and Tyr (d 14). At a later stage in lactation, plasma Met was increased for RPM cows (34.4 vs. 16.7 µM) consistently throughout the day, with no changes in other AA. Substantial variation was detected for plasma Met concentration (range: RPM = 8.9-63.3 µM; CON = 7.8-28.8 µM) among cows [coefficient of variation (CV) > 28%] and within cow during the day (CV: 10.5-27.1%). In conclusion, feeding RPM increased plasma Met concentration and improved lactation performance via increased milk protein production.

Embryo Mortality Around the Period of Maintenance of the Corpus Luteum Causes Alterations to the Ovarian Function of Lactating Dairy Cows.

Objectives were to identify cows with embryo mortality (EM) around the period of corpus luteum maintenance by interferon tau (IFNT) and to characterize ovarian function in cows that underwent EM. Lactating Holstein cows received artificial insemination (AI) (Day = 0) with semen or extender only. From Day 14 to 42 transrectal ultrasonography was performed daily to monitor ovarian dynamics and uterine contents whereas blood was collected every 48 h to determine ISG15 and MX2 mRNA abundance in blood mononuclear cells (Day 14 to 22 only) and determination of hormone concentrations. Cows were classified in the following reproductive status groups: cyclic (inseminated with extender; n = 15), pregnant (embryo present on Day 42; n = 23), no embryo (n = 23), and EM (n = 14). EM was defined as the presence of an embryo based on interferon-stimulated genes (ISG) mRNA abundance and concentrations of pregnancy-specific protein B (PSPB) above specific cutoff points but no embryo visualized by ultrasonography. Within the EM group, early EM (up to Day 22) was when ISG fold changes were above specific cutoff points from Day 18 to 22 and PSPB below 0.7 ng/ml on and after Day 24, whereas late EM (after Day 22) was when PSPB was above 0.7 ng/ml on or after Day 24 regardless of ISG expression. This experiment provided evidence that the combination of ISG expression patterns and PSPB concentrations is a reasonable method to determine EM around the period of corpus luteum maintenance by IFNT because cows with evidence of EM had patterns of ISG expression more similar to pregnant than cyclic cows or cows with no embryo. Within the EM group, only cows with late EM had delayed luteal regression and longer interovulatory intervals. No major alterations in follicular function were observed after the onset of luteolysis. Our results suggest that embryo development needs to continue beyond 22 days after AI to effectively prevent luteolysis and extend the luteal phase.