PSVIII-23 Late-Breaking: Effect of reproductive tract size and position scores and estrus on reproductive performance in beef cows.

摘要

The primary objective of this study was to identify if reproductive tract size-position score (SPS) and estrus expression prior to artificial insemination (AI) influences concentration of pregnancy-associated glycoproteins (PAGs) and pregnancy success. Angus females (n = 1397) were FTAI’d to Angus sires at d 0 after estrus synchronization using a 7-day CO-Synch CIDR protocol. Reproductive tract SPS were assigned on d 0 as SPS1 as small and compact resting within the pelvic cavity; SPS2 as intermediate, resting partially outside the pelvic cavity; and SPS3 as larger and resting outside the pelvic cavity. Estrotect patches received scores on d 0 of 1 (< 25% activation), 2 (< 50% activation), 3 (< 75% activation), or 4 (>75% activation) where patch scores of 1 and 2 signified no estrus expression, whereas scores of 3 and 4 indicated estrus expression. Pregnancy diagnosis was performed by ultrasound on d 30 after FTAI and serum samples were also collected on d 30 of gestation for quantification of PAGs. SPS3 females were more likely to exhibit estrus compared to both SPS1 (P = 0.0107) and SPS2 (P = 0.0291) females (48.98% vs 35.42% and 37.98%, respectively). Circulating PAG concentrations were significantly higher among females that exhibited increased estrus intensity compared to females that exhibited no estrus activity (P = 0.0023). Reproductive tract SPS by PAGs was not significant when parity was included as a covariate in the model (P > 0.05). Pregnancy loss did not correlate with reproductive tract SPS or estrus expression (P > 0.05); however, females that exhibited estrus at TAI did have a significantly higher pregnancy rate at d 30 of gestation (P < 0.0001) and AI calving rate (P = 0.0280) compared to females that did not show estrus. In summary, estrus is associated with increased pregnancy rates and SPS3 females exhibited estrus more frequently.