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Title: Post-weaning growth of tropically adapted purebred and crossbred calves when finished in a temperate climate

item Coleman, Samuel
item Phillips, William
item Riley, David
item Chase, Chadwick - Chad

Submitted to: American Society of Animal Science Southern Section Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 1/15/2009
Publication Date: 7/31/2009
Citation: Coleman, S.W., Phillips, W.A., Riley, D.G., Chase, C.C. 2009. Post-weaning growth of tropically adapted purebred and crossbred calves when finished in a temperate climate. American Society of Animal Science Southern Section Meeting. 87, E-Suppl. 3:2.

Interpretive Summary:

Technical Abstract: Typically the adaptation of beef cows that is required for the subtropics has been accomplished by using percentage Brahman breeding. Compromised fertility and carcass quality have increased interest in tropically adapted Bos taurus breed types. Tropically adapted cattle have a reputation for poor gains and efficiency when finished in temperate environments. The objective of this study was to evaluate three breeds [A=Angus (control); B=Brahman; and R=Romosinuano] and all possible crosses during different segments of post-weaning growth. Calves (n = 435) born over three years were weaned in late Sept,, backgrounded for at least 21 d (BKG), shipped 2025 km to El Reno, OK in Oct., fed a preconditioning diet for 28 d (RCV), grazed wheat from Nov. to May (WHT), and finished (FIN) on a conventional feedlot diet, and serially slaughtered after approximately 95, 125 and 150 days on feed. Average daily gains (ADG) during each segment were tested using a mixed model that included calf age at weaning, year, breed, winter treatment (control or supplement with reduced grazing of wheat; for wheat and feedlot) and interactions. Sire within sirebreed was random. Year and breed effects were significant (P < 0.05) in all phases and gains were positive for each phase. Heterosis was exhibited (P < 0.05) for all F1 combinations in all phases except for B-R during the finishing phase. Maternal and direct effects were inconsistent among breeds across segments and often cancelled each other. From weaning to harvest, calves from A and B sires gained 0.83 kg/d while R calves gained 0.75 kg/d (P < 0.05). Breed of dam effects on steer gains were all different (A = 0.88; R= 0.81; and B = 0.71). Steers with 100% tropical adaptation tended to gain at a slower rate than calves with temperate adaptation. Whether the cause is climate related or the effect of differing growth curves cannot be ascertained at this time.