Heterosis and direct effects for Charolais-sired calf weight and growth, cow weight and weight change, and ratios of cow and calf weights and weight changes across warm season lactation in Romosinuano, Angus, and F1 cows in A

Authors: RILEY, DAVID - West Texas A & M University; Burke, Joan; Chase, Chadwick - Chad; Coleman, Samuel

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/12/2015
Publication Date: 1/8/2016
Citation: Riley, D., Burke, J.M., Chase, C.C., Coleman, S.W. 2016. Heterosis and direct effects for Charolais-sired calf weight and growth, cow weight and weight change, and ratios of cow and calf weights and weight changes across warm season lactation in Romosinuano, Angus, and F1 cows in A. Journal of Animal Science. 94(1):1-12. 10.2527/jas.2015-9484.
DOI: https://doi.org/10.2527/jas.2015-9484

Interpretive Summary: ow-calf production in the southeastern U.S. is impaired by the environmental stressors heat stress and the dominant forage, tall fescue which leads to fescue toxicosis, which costs the beef industry up to a billion dollars annually. Use of a tropically adapted Bos taurus beef breed, Romosinuano, that is more thermo-tolerant may allow for a tolerance to fescue toxins and improve production parameters on Arkansas pastures. Scientists from Texas A&M, USDA, ARS Booneville, AR, El Reno, OK and Clay Center, NE determined that the Romosinuano breed may offer some resistance to endophyte toxins, but the Angus breed has better production on endophyte-free tall fescue pastures. These results provide information on potential genetics for cow-calf production on endophyte-infected tall fescue, information that is important to producers, extension agents, and scientists.

Technical Abstract: The use of Brahman in cow-calf production in the southeastern U.S. offers some adaptation to the harsh characteristics of endophyte-infected tall fescue. Other breeds, such as the Criollo breed Romosinuano, may provide similar adaptative characteristics. The objectives were to evaluate Romosinuano as straightbred and crossbred (F1) cows with Angus for weights and gains of their Charolais-sired calves, their own weights, weight change across lactation intervals, and the ratios of calf weight:cow weight and cow weight change:calf weight gain across a 7 mo lactation period in Arkansas. Cows (n = 91) were bred to Charolais bulls after their second parity. Calves (n = 214) were born from 2006 to 2009. Cows and calves were weighed in early (approximately April, June), mid (July), and late lactation (August, weaning in October). Animal was a random effect in analyses of calf data; sire was random in analyses of cow records and ratios. Fixed effects investigated included calf age in days as a linear covariate, calf sex, cow age-year combinations, sire breed of cow, dam breed of cow, and interactions. Subsequently, the effect of forage type (endophyte-free vs. endophyte-infected tall fescue) grazed was assessed. Heterosis and breed direct and maternal effects were estimated both with and without modeled forage type. Cows sired by Angus bulls from outside the research herd had calves that were heavier and had greater interval weight gains (P < 0.05) at all times of record than Angus bulls from the FL research herd. Estimates of heterosis for calf weight and gain ranged from 9.3 ± 4.3 to15.4 ± 5.7 kg from mid-lactation through weaning (P < 0.05); estimates of heterosis for gain were similar. Romosinuano direct effects (of the cow) were –6.8 ± 3.0 and –8.9 ± 4.2 kg for weights recorded in April and June. Calf weights and weight gains from birth to each time were greater (P < 0.05) for calves of cows grazing endophyte-free tall fescue than for those grazing endophyte-infected tall fescue for all except weights in July. Cows sired by outside Angus bulls were heavier (P < 0.05) in early lactation than FL Angus bulls, but not in August or at weaning. Cow weight change in intervals from April to each time of record were negative for Angus cows (there was no source of Angus sire difference for cow weight change, P > 0.37), and lower (P < 0.05) than cows in the other groups. Cows grazing endophyte-free tall fescue were heavier (P < 0.05) at all times of record, but had more weight loss in late lactation (August, weaning) than cows grazing endophyte-infected tall fescue. In summary, the Romosinuano breed may offer some resistance to endophyte toxins, but the Angus breed has better production on endophyte-free tall fescue pastures.