|Thallman, Richard - Mark|
|RETALLICK, KELLI - Kansas State University|
|BORMANN, JENNIFER - Kansas State University|
|WEABER, ROBERT - Kansas State University|
|MOSER, DANIEL - Kansas State University|
|MACNEIL, MICHAEL - University Of The Free State|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/17/2018
Publication Date: 4/4/2018
Citation: Thallman, R.M., Kuehn, L.A., Snelling, W.M., Retallick, K.J., Bormann, J.M., Freetly, H.C., Hales, K.E., Bennett, G.L., Weaber, R.L., Moser, D.W., MacNeil, M.D. 2018. Reducing the period of data collection for intake and gain to improve response to selection for feed efficiency in beef cattle. Journal of Animal Science. 96:854–866. https://doi.org/10.1093/jas/skx077.
Interpretive Summary: Feed efficiency is one of the most economically important traits in beef production and is sufficiently heritable to respond to genetic selection. However, selection for feed efficiency requires measuring the amount of feed consumed by individual animals. Currently, this is done in both research and industry settings in special facilities with electronic equipment designed specifically for this purpose. The high cost of measuring feed intake is due primarily to facility and labor costs and severely limits the number of animals measured both in research projects and by cattle breeders. It has been proposed that the cost per animal could be reduced by shortening the period of time the animals are in the facility. Previous research has shown that the feeding period could be considerably shorter without significantly reducing the accuracy of measuring feed intake, but that the shorter period is not sufficient to obtain an accurate measurement of the animals’ weight gain that coincides with the feed intake. Therefore, it has been further proposed to use feed intake measured over a short period along with weight gain over a much longer period together in an index to estimate feed efficiency. This paper used individual feed intake and weight gain data on 6,331 beef cattle to retrospectively evaluate this proposal. The analysis confirmed that feed intake measured over a shorter period is nearly as accurate as when measured over a longer time. However, the analysis included weight gains over both the same period as the feed intake was recorded and over a much longer time period. The best predictions resulted from using both the short and long measures of weight gain together with feed intake to predict feed efficiency. It is recommended to include gain over the period coinciding with intake recording and gain over a much longer period of time simultaneously in a genetic evaluation and to use all three traits in a selection index for feed efficiency.
Technical Abstract: Shortening the period of recording individual feed intake may improve selection response for feed efficiency by increasing the number of cattle that can be recorded given facilities of fixed capacity. Individual DMI and ADG records of 3,462 steers and 2,869 heifers over the entire intake recording period (range 62 to 154 d; mean 83 d; DMI83 and ADG83, respectively), DMI and ADG for the first 42 d of the recording period (DMI42 and ADG42, respectively), and postweaning ADG based on the difference between weaning and yearling weights (PADG) were analyzed. Genetic correlations among DMI42 and DMI83, ADG42 and ADG83, ADG42 and PADG, and ADG83 and PADG were 0.995, 0.962, 0.852, and 0.822, respectively. Four objective functions [feed:gain ratio in steers (FGS) and heifers (FGH); residual gain (RG); and residual feed intake (RFI)] based on DMI83 and ADG83 were considered. Indices using DMI42 and ADG42 (I42); DMI42 and PADG (IPW); and DMI42, ADG42, and PADG (IALL) were developed. Accuracy of the 5 EBV, 4 objectives, and 12 objective × index combinations were computed for all 12,033 animals in the pedigree. Accuracies of indices (IA) were summarized for animals with accuracies for objectives (OA) of 0.25, 0.5, 0.75, and 1. For the RG objective and animals with OA of 0.75, indices I42, IPW, and IALL had IA of 0.63, 0.55, and 0.67, respectively. Differences in IA increased with increased emphasis on ADG83 in the objective. Differences in IA between I42 and IPW usually increased with OA. Relative efficiency (RE) of selection on 42-d tests compared with 83 d was computed based on differences in IA and selection intensities of 5%, 25%, 50%, and 75% under the 83-d scenario, assuming 65% more animals could be tested for 42 d. For 25% selected for the RG objective, and animals with OA of 0.75, indices I42, IPW, and IALL had RE of 1.02, 0.90, and 1.10, respectively. As % selected, OA, and emphasis on DMI increased, RE increased. Relative efficiency varied considerably according to assumptions. One-half of the scenarios considered had RE > 1.15 with a maximum of 2.02 and 77% RE > 1.0. A shorter period of recording DMI can improve selection response for feed efficiency. Selection for the efficiency objectives would not affect PADG. It will be most effective if ADG over the period coinciding with intake recording and ADG over a much longer period of time are simultaneously included in a multiple-trait genetic evaluation with DMI and used in a selection index for efficiency.