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ARS Home » Plains Area » Miles City, Montana » Livestock and Range Research Laboratory » Research » Publications at this Location » Publication #361156
Research Project: Alleviating Rate Limiting Factors that Compromise Beef Production Efficiency

Location: Livestock and Range Research Laboratory

Title: Pregnancy Associated Glycoproteins (PAGs) and late embryonic mortality in high vs sub fertility heifers

Author
item REESE, SYDNEY - Texas A&M University
item Geary, Thomas
item FRANCO, GESSICA - Texas A&M University
item MORAES, JOAO - University Of Missouri
item SPENCER, THOMAS - University Of Missouri
item POHLER, KY - Texas A&M University

Submitted to: Theriogenology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/29/2019
Publication Date: 9/1/2019
Publication URL: https://handle.nal.usda.gov/10113/6699706
Citation: Reese, S.T., Geary, T.W., Franco, G.A., Moraes, J.G., Spencer, T.E., Pohler, K.G. 2019. Pregnancy Associated Glycoproteins (PAGs) and late embryonic mortality in high vs sub fertility heifers. Theriogenology. 135:7-12. https://doi.org/10.1016/j.theriogenology.2019.05.026.
DOI: https://doi.org/10.1016/j.theriogenology.2019.05.026

Interpretive Summary: Pregnancy losses in cattle can be high. Bovine pregnancy associated glycoproteins (PAG) are produced by embryos and enter the cow’s blood. Levels of PAG in the blood are predictive of embryo health. Our goal was to determine if fertility status is associated with PAG level and if it is repeatable within cows. We expected PAG levels would be higher in high fertility compared to low fertility cows but not repeatable between pregnancies. Cow fertility was based on pregnancy success following repeated embryo transfer. Pregnancy was determined using ultrasound for comparison of PAG level. Level of PAG in the blood was not different between high and low fertility cows. Level of PAG was not repeatable between pregnancies. However, high fertility cows had less pregnancy loss.

Technical Abstract: Reproductive inefficiency and infertility are a major financial burden to domestic livestock. Variables associated with these reproductive losses during early gestation include contributions from the oocyte, uterus, sperm, embryo and placenta. Bovine pregnancy associated glycoproteins (PAG) are produced by the binucleate cells of the ruminant placenta and can be used to diagnose pregnancy. Increased circulating concentrations of PAG early in gestation have been correlated with pregnancy success and predictive of impending embryonic mortality in both beef and dairy cattle. The objectives of the current study were to determine whether: 1) heifer fertility status is associated with circulating concentrations of PAG and pregnancy loss; and 2) PAG concentrations within the same animal are repeatable across multiple pregnancies. We hypothesized maternal PAG concentrations would be increased in high fertility compared to subfertile heifers but not repeatable across subsequent pregnancies in the same heifer. Serial embryo transfer (ET; n = 4 rounds) was used to classify predominately Angus heifers (n = 95) as highly fertile (HF; 100% pregnancy success) or subfertile (SF; 25%-33% pregnancy success) based on day 28 ultrasound diagnosis. Blood samples were collected at both day 28 and 44 for quantification of circulating PAG concentrations by an in house PAG ELISA with antibodies raised against early secreted PAGs. Pregnancy was terminated at day 44 of gestation and heifers were allowed 30 days recovery before synchronization for the next ET. Only heifers that were diagnosed pregnant by ultrasound were used in this study (HF: n = 30, SF: n = 53). Serum concentrations of PAG were not different between HF (5.90 ' 0.27 ng/mL) and SF (5.56 ' 0.31 ng/mL; P = 0.16) heifers at day 28 of gestation nor was there a difference at day 44 of gestation (P = 0.32). Subfertile heifers had increased pregnancy loss between days 28 and 44 of gestation. Based on odds ratio analysis SF heifers had a 2.09 times chance to undergo pregnancy loss between day 28 to 44 compared to HF (P < 0.05). There was no correlation (P > 0.05) in maternal circulating concentrations of PAG between pregnancies on day 28 or 44 of gestation in samples obtained from HF heifers. In summary, circulating concentrations of PAG are not different between HF and SF heifers; however, HF classified heifers have decreased pregnancy loss between day 28 and 44 of gestation.