|SUMMERS, ADAM - University Of Nebraska|
|Cushman, Robert - Bob|
|CUPP, ANDREA - University Of Nebraska|
Submitted to: Western Section of Animal Science Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 5/1/2012
Publication Date: 7/1/2012
Citation: Summers, A.F., Cushman, R.A., Cupp, A.S. 2012. Heifers with low antral follicle counts have low birth weights and produce progeny with low birth weights. Proceedings, Western Section, American Society of Animal Science. 63:217-220.
Technical Abstract: Research has demonstrated that heifers with increased numbers of ovarian antral follicle count (AFC) have improved hormonal profiles and improved fertility. Interestingly, heifers with low AFC had lower birth weights, suggesting that genes influencing growth and development also influence the development of the reproductive tract and establishment of the ovarian reserve. To determine the relationship of AFC to heifer BW, reproductive tract characteristics, and first calf performance, composite (MARC III x Red Angus) heifers (n = 362) were used over a 3 yr period. In yr 1 heifers grazed winter range or corn residue and were offered no supplement or 0.45- 0.90 kg/d (31% CP, DM Basis) during development. In yr 2 and 3 heifers grazed winter range and were fed a dried distillers grain-based (DDG) or corn gluten feed-based supplement offered at 0.59% and 0.78% BW, respectively, throughout development. Supplements were formulated to be isocaloric but differed in undegradable protein. All heifers in yr 2 and 3 were fed ad libitum meadow hay while grazing dormant pasture. Prior to breeding, heifers were transrectally ultrasounded to determine AFC and classified as high (>/= 26 follicles; HIGH) moderate (16 to 25; MOD) or low (= 15; LOW). There was no diet x AFC classification interaction. HIGH heifers have greater (P = 0.05) birth, weaning, and adjusted 205-d weaning BW compared with LOW. Pre-breeding BW, total AFC, and proportion of mature BW at breeding were greater (P < 0.01) for HIGH compared with LOW heifers. Overall pregnancy rate was similar (P = 0.36) among AFC classifications. Progeny birth BW was greater (P = 0.03) for calves born to HIGH compared with LOW heifers. Taken together these data indicate a relationship between AFC and BW through the first breeding season and progeny calf BW. The low birth BW in heifers with low AFC and in their progeny continues to support a possible link between genes that influence growth and development and establishment of the ovarian reserve.