Genetic parameters, heterosis, and breed effects for body condition score and mature cow weight in beef cattle

Authors: RIBEIRO, ANDRE MAURIC - University Of Nebraska; SANGLARD, LETICIA - University Of Nebraska; Snelling, Warren; Thallman, Richard - Mark; Kuehn, Larry; SPANGLER, MATTHEW - University Of Nebraska

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/12/2022
Publication Date: 1/19/2022
Citation: Ribeiro, A.F., Sanglard, L.P., Snelling, W.M., Thallman, R.M., Kuehn, L.A., Spangler, M.L. 2022. Genetic parameters, heterosis, and breed effects for body condition score and mature cow weight in beef cattle. Journal of Animal Science. 100(2). Article skac017. https://doi.org/10.1093/jas/skac017.
DOI: https://doi.org/10.1093/jas/skac017

Interpretive Summary: Body condition score, a measure of fat deposition, and mature weight are both important indicators of mature cow efficiency. Often mature weight is adjusted for body condition score; however, this adjustment may lead to lost information and decreased genetic variance if the traits are genetically correlated and both traits are heritable. Understanding genetic relationships between both traits could improve our ability to provide selection tools to improve efficiency in the beef cattle industry. Therefore, our objective was to estimate genetic parameters, heterosis and breed effects for both traits using data from the crossbred U.S. Meat Animal Research Center Germplasm Evaluation program. Cows evaluated were daughters or granddaughters of repetitive industry bulls from 16 different beef cattle breeds. Results indicated that both traits were heritable and could be included in selection programs. While the genetic relationship between both traits was positive, selection in one trait could still be achieved without changing the other. Breed effects reported will help producers evaluate the suitability of several different beef cattle breeds, especially in environments where feed resources are a limiting factor.

Technical Abstract: Understanding the genetic relationship between mature cow weight (MWT) and body condition score (BCS) is useful to implement selection programs focused on cow efficiency. The objectives of this study were to estimate genetic parameters, heterosis, and breed effects for MWT and BCS. In total, 25,035 and 24,522 overlapping records were available for MWT and BCS on 6,138 and 6,131 cows, respectively, from the Germplasm Evaluation program, a crossbred beef population at the U.S. Meat Animal Research Center. Pedigree was available for 48,013 individuals. Univariate animal models were used to estimate heritabilities for each trait by parity. Bivariate animal models were used to estimate genetic correlations between parities within a trait and between traits within parities. Bivariate repeatability animal models were used to estimate genetic correlations between traits across parities. Estimates of heritability for different parities ranged from 0.43 ± 0.05 to 0.55 ± 0.07 for MWT and from 0.12 ± 0.03 to 0.25 ± 0.04 for BCS and were lower with the repeatability model at 0.40 ± 0.02 and 0.11 ± 0.01 for MWT and BCS, respectively. Estimates of repeatability were high for MWT (0.67 ± 0.005) and low for BCS (0.22 ± 0.006). Estimates of genetic correlation for MWT and BCS between parities were, in general, high, especially between consecutive parities. Estimates of genetic correlation between MWT and BCS were positive and moderate, ranging from 0.32 ± 0.09 to 0.68 ± 0.14. The direct heterosis estimates were 21.56 ± 3.53 kg (P = 0.001) for MWT and 0.095 ± 0.034 (P <= 0.001) for BCS. Ordered by decreasing MWT, the breeds ranked Brahman, Charolais, Angus, Simmental, Salers, Hereford, Santa Gertrudis, Chiangus, Brangus, Red Angus, Shorthorn, Maine-Anjou, Gelbvieh, Beefmaster, Limousin, and Braunvieh. Ordered by decreasing BCS, the breeds ranked Brahman, Red Angus, Charolais, Angus, Hereford, Brangus, Beefmaster, Chiangus, Salers, Simmental, Maine-Anjou, Limousin, Santa Gertrudis, Shorthorn, Gelbvieh, and Braunvieh. Estimates of breed differences for MWT were also adjusted for BCS (AMWT), and in general, AMWT depicted smaller differences between breeds with some degree of re-ranking (r = 0.59). These results suggest that MWT and BCS are at least moderately genetically correlated and that they would respond favorably to selection. Estimates of breed differences and heterotic effects could be used to parameterize multibreed genetic evaluations for indicators of cow maintenance energy requirements.