Impact of Direct and Indirect Selection Criteria for Feed Efficiency on Profitability of Japanese Black Cattle Selection Strategies

¹ Animal Breeding and Genetics Group, Department of Animal Sciences, Egerton University, P. O. Box 536, 20115 Egerton, Kenya
² Laboratory of Animal Husbandry Resources, Division of Applied Biosciences, Graduate School of Agriculture, Kyoto University, 606 8502 Kyoto, Japan

^* To whom correspondence should be addressed. E-mail: a.kahi{at}incip.org.

	Abstract

The objective of this study was to determine the impact of use of residual feed intake (RFI) and the blood concentration of insulin-like growth factor I (IGF) as selection criteria for feed efficiency on profitability of Japanese Black cattle selection strategies with restricted test capacity. A breeding objective that integrated the cow-calf and feedlot segments was considered. Selection strategies were defined that differed in whether information on IGF and RFI during performance testing (RFIpt) was used to make selection decisions, and in the number of animals measured for IGF. In all strategies, sires were selected from the proportion chosen during the first selection stage (performance testing), modeling a two-stage selection process. The impact on genetic gain and profitability of variations in test capacity, of the genetic correlations of IGF with marbling score (MS) and RFIpt, and non-zero economic values for, and, hence, inclusion of RFI of the cow (RFIc) and feedlot animals (RFIf) in the breeding objective, was examined. Additional genetic gain and profitability was generated when information on IGF concentration and RFIpt in the performance tested young bulls was included in the selection criteria. Profit per cow was optimal when measurement of IGF and RFIpt were incorporated together in the selection index. Increasing test capacity resulted in an increase in genetic gain in all strategies and profit per cow was optimal in all strategies when 900 places were available for performance testing. Profit per cow was more sensitive to changes in the genetic correlation between IGF and MS than between IGF and RFIpt, especially when more animals were measured for IGF, or else the favorable relationship between IGF and MS had no significant effect on profit per cow. Additional genetic gain and profitability were generated in each strategy when RFIc and RFIf were included in the breeding objective with non-zero economic values. These results may be used to provide guidance to Japanese Black cattle breeders, and, in the absence of more breed-specific information, may also have application in other Japanese beef breeds.

Key Words: breeding program design, carcass traits, insulin-like growth factor I, Japanese Black cattle, residual feed intake, selection strategies