ARS | Publication request: Effects of protein supplementation during heifer development on reproductive characteristics and success in beef heifers

Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: March 5, 2011
Publication Date: July 1, 2011
Citation: Summers, A.F., Cushman, R.A., Weber, S.P., Spangler, M.L., Cupp, A.S. 2011. Effects of protein supplementation during heifer development on reproductive characteristics and success in beef heifers [abstract]. Journal of Animal Science. 89 (E-Supplement 1):91 (Abstract #M241).

Technical Abstract: A 2-yr study was conducted to determine the effects of feeding different protein supplements during heifer development on reproductive traits and performance. Our hypothesis was that protein supplementation would enhance reproductive performance in heifers with below average reproductive characteristics. Heifers from two herds at the University of Nebraska Animal Development and Research Center were used with heifers (Angus and Angus x Simmental hybrids) from the teaching herd (n = 56) being fed a modified dried distillers grain (MOD) supplement at 1.36 kg/d from weaning (mid September) through May. Heifers (MARC III x Red Angus) from the physiology herd (n = 173) were randomly assigned to groups and fed dried distillers grain-based (DDG) or corn gluten feed-based supplement (CFG) offered at 0.59% and 0.78% BW, respectively, from mid-November through May. Supplements were formulated to be isocaloric but differed in undegradable protein. All heifers were fed ad libitum meadow hay through winter while grazing dormant pasture. Prior to breeding, heifers were transrectally ultrasounded to determine antral follicle count (AFC), uterine horn diameter (UHD), ovarian size, presence of a CL, and to determine reproductive tract score (RTS). Heifers developed on MOD diet were 23 d older (P < 0.01) and had greater (P < 0.01) ovarian area, total AFC, and percent of CL present compared to other groups. However; MOD heifers had lower (P < 0.01) UHD compared to other groups. There was no difference (P = 0.19) in proportions of heifers bred to A.I.; however, overall pregnancy rates were lower (P < 0.01) for MOD compared to other groups. There was a positive effect of small follicle counts on RTS [RTS = 3.9 + 0.01(small follicles); P < 0.01, r2 = 0.04] and AFC [AFC = 4.9 + 0.8(small follicles); P < 0.01, r2 = 0.86]. Although MOD and DDG diets were similar, results from these groups varied, suggesting that age led to some variation in response to these supplements. We also conclude that RTS and AFC are influenced by small follicle counts. USDA is an equal opportunity provider and employer.