Conception rates after artificial insemination as affected by heparin binding protein-B5 in frozen semen

Abstract

An experiment was conducted to determine the effect of heparin binding proteins (HBP-B5) on fertilizing capacity of frozen-thawed bovine semen. Frozen semen was obtained from Brahman (n=8) and Brangus (n=6) bulls and evaluated for the presence of HBP-B5 (21, 24, and 31 kDa forms) on the sperm membranes. Bulls were classified into one of three fertility groups, High (H), Medium (M), or Low (L), according to their BBP-B5 profile. Non-lactating, multiparous Angus or Hereford cows (n--108) were assigned for mating with semen from a Brahman sire in the H, M, or L BBP-B5 classification. Lactating, multiparous Angus cows (n=178) were assigned for mating with semen from Brangus sires in the H, M, or L BBP-B5 classification. Cows were observed twice daily for estrus during the 45-d Al breeding season. Pregnancy was determined by palpation per rectum 60 d after the end of the breeding period. Main effects of HBP-B5 classification on pregnancy rate were determined by chi square analysis. Effects of treatment on services per conception were determined by GLM procedures. Pregnancy rates for non-lactating cows inseminated with semen from L, M, or H BBP-B5 sires (P>.10) were 86, 79, and 90%, respectively. Non-lactating cows mated to H HBP-B5 sires required fewer (P<.05) services per conception (1.23 + .09) than cows mated to M HBP-B5 sires (1.52+ .20). Services per conception in non-lactating cows mated to L HBP-B5 sires (1.33+ .07) did not differ from either H or M HBP-B5 sires. Pregnancy rates for lactating cows mated to L, M, or H HBP-B5 sires (P>.10) were 76, 73, and 72%, respectively. Services per conception in lactating cows did not differ among L, M, or H HBP-B5 sires (1.51 + .07, 1.56 +.10, and 1.52 + .07, respectively). Probabilities to become pregnant were not significantly increased due to bull fertility as projected by HBP-B5 profile. Increased cow body condition improved probabilities of becoming pregnant in lactating cows and in all cows after all services were given (P<.05). Probabilities of increasing pregnancy were enhanced in all groups if pregnancy was established after one service as compared to two services (P<. I 0). These data indicate that evaluation of HBP-B5 profiles in frozen bovine semen was related to fertility after Al in non-lactating cows. Pregnancy probabilities also increase as cow body condition increases in lactating and all cows, and also increase in cows that conceive after one service.