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G. A. Franco, R. F. G. Peres, C. F. G. Martins, J. L. M. Vasconcelos, K. G. Pohler, 081 Sire Effect on Pregnancy Associated Glycoprotein (PAG) Concentrations in Nelore Beef Cows, Journal of Animal Science, Volume 95, Issue suppl_1, December 2016, Page 40, https://doi.org/10.2527/ssasas2017.081
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Abstract
Understanding the causes of embryonic mortality (EM) is fundamental to developing management strategies that decrease economic loss in cattle. Though late EM (after d 28 of gestation) represents a smaller proportion of reproductive failure compared to early gestation EM (∼10% vs. ∼35%), economic consequences are reported to be disproportionately greater due to delayed conception date which limits cow productivity. Placental insufficiency is considered to be a major cause of late EM and bovine pregnancy-associated glycoproteins (PAG) have been used as a marker of placental function. Although the functional role of PAG is unclear, it has been shown that many factors affect PAG concentrations including pregnancy stage, breed, parity, sire, and fetal sex. Limited data have been reported on sire effects on PAG concentration, however, based on the influence sire has on placental development, we were interested in this potential relationship. The objectives of this study were to determine how breed and fertility of sire influences PAG concentration at d 30. Postpartum Nelore beef cows (n = 1228) were artificially inseminated at a fixed time (d 0) after synchronization of ovulation. A subset of cows (n = 492) were inseminated with commercially available Angus or Nelore semen, and another subset (n = 736) were inseminated with 6 Angus bulls of unknown fertility. Pregnancy diagnosis by ultrasound was performed and serum samples were collected on Day 30. Serum concentrations of PAG were quantified using an in house PAG ELISA with antibodies raised against PAGs expressed early in gestation. Overall pregnancy rate was 53.75% (range 36.52% to 67.92%). Late EM was 6.21% (range from 1.53% to 11.69%). Serum concentration of PAG were significantly higher in cows gestating a pregnancy sired Angus compared to Nelore bulls (Nelore 9.67 ± 0.48 ng/ml vs. Angus 11.87 ± 0.52 ng/ml; P = 0.0023). Late EM occurred in 41 cows that had a viable embryo on Day 30 of gestation but failed to maintain pregnancy until d 100. Three sires in this experiment accounted for more than 70% of the late embryonic mortality and had lower PAG compared to other 3 bulls (8.5 ± 0.35 ng/ml vs. 9.48 ± 0.36 ng/ml; P = 0.0562). These data indicate that pregnancies from bulls with high embryonic loss had lower PAG concentration on d 30, suggesting PAG may serve as a novel marker for bull fertility.
