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Genomic evaluation for abortions and twinning in dairy cattle.

N. Vukasinovic




Genomic evaluation for abortions and twinning in dairy cattle.
N. Vukasinovic*, D. Gonzalez-Pena, J. Brooker, C. Przybyla, S. DeNise. Zoetis Kalamazoo, MI.

Abortions and twinning are undesirable reproductive outcomes in dairy herds. Both traits are believed to be largely caused by environmental factors. However, studies have shown that there is a substantial genetic component to these conditions. The objective of this study was to develop genetic and genomic evaluation for abortions and twinning in Holstein cattle using single-step genomic BLUP (gBLUP) methodology. Production, reproduction, and pedigree data recorded on farms using herd management software were available for this study. Abortions (ABRT) were defined as a recorded abortion event between 42 and 260 d after the successful breeding. Twinning (TWIN) was defined as a pregnancy resulting in birth or abortion of twin calves (alive or dead). The traits were analyzed using the univariate threshold animal model with repeated observations. The model included the fixed effect of parity (1—5) and the random effects of animal, herd x year x season of calving, and permanent environment. In addition, the model for ABRT included the fixed effect of the breed composition of the embryo (purebred vs. crossbred), the random effect of service sire, and the covariates of milk yield and days open. The data consisted of 3,848,620 and 5,338,162 records with an overall incidence of 11.0% and 3.0% for ABRT and TWIN, respectively. Genotypes were available on 978,368 animals. The estimated heritabilities were 0.077 and 0.089 for ABRT and TWIN, respectively. Predicted transmitting abilities (PTA) were expressed in percent points as deviations from the average estimated probability of a disorder in the base population, which was defined as all animals with phenotypes born in 2015. The PTA ranged from −8.72 to 12.92 and from −6.98 to 20.39 for ABRT and TWIN, respectively, with higher values representing higher risk of having a disorder. The reliabilities of PTA for young genotyped animals without own phenotypes were on average 0.36 and 0.39 for ABRT and TWIN, respectively. Genetic and genomic selection of animals less prone to abortions and twinning could be a useful tool for improving reproductive performance in dairy herds.

Keywords: abortion, twinning, genomic evaluation.