Title: The effects of selecting for the myostatin F94L polymorphism on reproductive traits in pubertal heifers Authors
|Tait Jr, Richard|
Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: March 6, 2013
Publication Date: July 8, 2013
Citation: Forbes, E.D., Swanson, O.L., McNeel, A.K., Tait, Jr., R.G., Smith, T.P.L., Bennett, G.L., Hoagland, T.A., Zinn, S.A., Lents, C.A., Perry, G.A., Cushman, R.A. 2013. The effects of selecting for the myostatin F94L polymorphism on reproductive traits in pubertal heifers. Journal of Animal Science. 91 (E-Supplement 2):287 (Abstract #W181). Technical Abstract: The myostatin F94L polymorphism influences carcass traits in steers; however, the influence of this polymorphism on female reproductive performance should be characterized as part of using it for marker assisted selection. Results from USMARC indicate that heifers that are homozygous for the L allele (L) reach puberty later than heifers that are homozygous for the F allele (F, wild-type), but no one has investigated the influence of this polymorphism on reproductive function in pubertal heifers. We hypothesized that reproductive function would be decreased in heifers that were L. Homozygous heifers that were pubertal (n = 5/genotype) were synchronized with two shots of PFG2alpha given 11 d apart and observed every 4 h for behavioral estrus with the aid of estrus detection patches. Heifers were slaughtered on d 4 after estrus, and the uterus, ovaries, and anterior pituitary were collected, measured, and weighed. A representative piece of one ovary was fixed for histological evaluation, and a sample of subcutaneous adipose was collected and frozen to measure relative levels of chemerin mRNA, a marker of adiposity. Follicular fluid was aspirated from all small follicles (1-5 mm), pooled within heifer, and frozen. Data were analyzed using a MIXED model with genotype as a fixed effect. Heifers that were F had lighter birth weights than heifers that were L (P = 0.04), but there was no difference in weaning weight, slaughter weight, or chemerin mRNA levels in the adipose. Heifers that were L exhibited behavioral estrus 14 h sooner after PGF2alpha than heifers that were F (P = 0.06). There was no difference in reproductive organ measurements or numbers of follicles in the ovaries between genotypes. Follicular fluid estradiol concentrations tended to be greater in L heifers than F heifers (P = 0.10). Reproductive tract development is not altered in heifers homozygous for the L allele, although they reach puberty later. A shorter time from PGF2alpha to estrus indicates that timing of insemination in timed-AI protocols may need to be altered for L heifers. USDA is an equal opportunity provider and employer.