Submitted to: Journal of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: November 21, 2006
Publication Date: February 7, 2007
Citation: Riley, D.G., Chase, C.C., Coleman, S.W., Olson, T.A. 2007. Heterosis for reproductive traits in young F1, Romosinuano, Brahman, and Angus cows[abstract]. Journal of Animal Science.85(2):Paper No.11. Technical Abstract: The objective of this research was to estimate heterosis for reproductive performance of young cows that were produced by matings of Romosinuano (R), Brahman (B), and Angus (A) bulls and cows. Cows (n = 659) were spring-born in 2002 to 2005. After weaning, they were placed with bulls until confirmed pregnant. After their first calving, cows were exposed to bulls each spring for 90-d breeding seasons. All F1 cows were with bulls of the other (third) breed. Purebreds were with bulls of the other two breeds (one-half with each). Cows that calved and those that later weaned a calf were given values of 1; otherwise 0. Calf crop born and weaned (separate analyses within cow ages), and age in days at first calving were evaluated. Fixed effects included breed of cow's sire and dam and their interaction, year, source of A sire (within herd or outside). Sire within sire breed and cow within sire were random effects. Three-yr-old cows sired by outside A bulls had a higher calf crop born (0.17 +/- 0.09) than cows sired by Brooksville A bulls (P = 0.05), otherwise, source of A sire was not important. Means for age at first calving ranged from 394 +/- 16 (A-sired heifers out of B dams) to 621 +/- 17 d (B purebreds) and heterosis estimates were -47 (9%), -80 (14%), and -102 (18%) d for RA, RB, and BA, respectively (P < 0.004). Heterosis for calf crop born ranged from 7 to 26% (higher than purebred averages) for all pairs of breeds as 2-yr-olds, and from 13 to 43% for 3-yr-olds. Brahman-Angus heterosis was 0.17 +/- 0.07 (21%) as 4-yr-olds and RB heterosis was 0.25 +/- 0.08 (32%) as 5-yr-olds (P < 0.009). Heterosis estimates for calf crop weaned were large, and ranged from 16% (2-yr-old RB) to 77% (3-yr-old BA) of purebred averages. For age at first calving, and calf crop born and weaned, though not always significantly different, BA heterosis estimates were largest, RB estimates were intermediate, and RA estimates were lower. Heterosis may be most influential on reproductive performance of 3-yr-old cows. Romosinuano crosses displayed substantial heterosis for these traits.