|RETALLICK, KELLI - KANSAS STATE UNIVERSITY|
|BORMANN, JENNIFER - KANSAS STATE UNIVERSITY|
|WEABER, ROBERT - KANSAS STATE UNIVERSITY|
|MACNEIL, MICHAEL - DELTA G|
|BRADFORD, HEATHER - KANSAS STATE UNIVERSITY|
|MOSER, DANIEL - KANSAS STATE UNIVERSITY|
|Thallman, Richard - Mark|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/29/2017
Publication Date: 4/13/2017
Publication URL: http://handle.nal.usda.gov/10113/5700711
Citation: Retallick, K.J., Bormann, J.M., Weaber, R.L., MacNeil, M.D., Bradford, H.C., Freetly, H.C., Hales Paxton, K.E., Moser, D., Snelling, W.M., Thallman, R.M., Kuehn, L.A. 2017. Genetic variance and covariance and breed differences for feed intake and average daily gain to improve feed efficiency in growing cattle. Journal of Animal Science. 95:1444-1450.. https://doi.org/10.2527/jas.2016.1260.
Interpretive Summary: Feed costs represent more than two-thirds of the cost of beef production in the United States. Thus, high profit margins are attainable through selection programs that increase gain and decrease feed intake. This project utilized a crossbred data set of 18 popular beef cattle breeds to estimate genetic potential for decreased intake and increased gain. Estimated relationships indicated a high potential for selection for increasing feed efficiency on both high concentrate (finishing steers) and high roughage (developing heifers) rations. Breed effects for intake and gain as well as indices of both traits were estimated. These effects can be used to select breeds with increased efficiency on either concentrate or roughage rations.
Technical Abstract: Feed costs are a major economic expense in finishing and developing cattle; however, collection of feed intake data is costly. Examining relationships among measures of growth and intake, including breed differences, could facilitate selection for efficient cattle. Objectives of this study were to estimate genetic parameters for growth and intake traits and compare indices for feed efficiency to accelerate selection response. On-test ADFI and on-test ADG (TESTADG) and postweaning ADG (PWADG) records for 5,606 finishing steers and growing heifers were collected at the U.S. Meat Animal Research Center in Clay Center, NE. On-test ADFI and ADG data were recorded over testing periods that ranged from 62 to 148 d. Individual quadratic regressions were fitted for BW on time, and TESTADG was predicted from the resulting equations. We included PWADG in the model to improve estimates of growth and intake parameters; PWADG was derived by dividing gain from weaning weight to yearling weight by the number of days between the weights. Genetic parameters were estimated using multiple-trait REML animal models with TESTADG, ADFI, and PWADG for both sexes as dependent variables. Fixed contemporary groups were cohorts of calves simultaneously tested, and covariates included age on test, age of dam, direct and maternal heterosis, and breed composition. Genetic correlations (± standard errors) between steer TESTADG and ADFI, PWADG and ADFI, and TESTADG and PWADG were 0.33 ± 0.10, 0.59 ± 0.06, and 0.50 ± 0.09, respectively; and corresponding estimates for heifers were 0.66 ± 0.073, 0.77 ± 0.05, and 0.88 ± 0.05, respectively. Indices combining EBV for ADFI with EBV for ADG were developed and evaluated. Greater improvement in feed efficiency can be expected using an unrestricted index versus a restricted index. Heterosis significantly affected each trait contributing to greater ADFI and TESTADG. Breed additive effects were estimated for ADFI, TESTADG, and the efficiency indices.