|LOPEZ-VILLALOBOS, N - Massey University|
|NORTHCUTT, S - American Angus Association|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/6/2011
Publication Date: 7/15/2011
Citation: Macneil, M.D., Lopez-Villalobos, N., Northcutt, S.L. 2011. A prototype national cattle evaluation for feed intake and efficiency of Angus cattle. Journal of Animal Science 89(12):3917-3923.
Interpretive Summary: Feed intake is a biologically important and economically relevant trait in beef production. In the past efficiency of beef production has been genetically improved through selection for increased growth. However, that selection has had adverse consequences for cow size and carcass weight. This has resulted in cows that required more feed to sustain reproductive success and over-weight carcasses at harvest. A new system for genetic evaluation of feed intake and efficiency was developed in this research. This system makes use of feed intake measurements from bull-test stations, experiment stations, and individual breeders to derive genetic predictions for animals with measured feed intake and their relatives. It also uses information from related traits to increase the accuracy of that genetic prediction. The genetic prediction for feed intake is combined with genetic predictions for weaning weight, postweaning growth, and subcutaneous fat depth to provide genetic predictions for efficiency. This result is being applied in the national cattle evaluation for the Angus breed. It is particularly useful to seedstock producers in reducing the cost of beef production.
Technical Abstract: Recent development of technologies for measuring individual feed intake has made possible the collection of data suitable for breed-wide genetic evaluation. Goals of this research were to estimate genetic parameters for components of feed efficiency and develop a prototype system for conducting a genetic evaluation of Angus cattle for feed intake. Weaning weight (WWT), postweaning gain (PGN), subcutaneous fat depth (SQF) and feed intake data were accumulated by the American Angus Association from a variety of cooperators and augmented with data collected for routine genetic evaluation of Angus cattle. The feed intake data were standardized (SFI, mean 0 and variance 1) within contemporary groups. Numbers of animals with observed phenotypes were 18,169, 7,107, and 4976, and 4,215 for WWT, PGN, SQF, and SFI, respectively. The 4-generation pedigree for animals with records contained 45,120 individuals. (Co)variance components were estimated with ASREML, fitting a 4-trait animal model with fixed contemporary groups for weaning weight (WWT), postweaning gain (PGN), subcutaneous fat depth (SQF) and standardized feed intake (SFI). Heritability estimates were 0.33±0.03. 0.31±0.04, 0.26±0.04 and 0.42±0.05 for direct effects on WWT, PGN, SQF, and SFI, respectively. Genetic correlations of WWT and PGN with SFI were 0.40±0.07 and 0.55±0.10, respectively, and indicate their value as indicator traits in predicting EPD for feed intake. The genetic correlation of SQF and SFI was not different from ). For all animals with a recorded feed intake phenotype, accuracy of their EPD for feed intake range from 0.16 to 0.64 with a mean of 0.26. However, 9.075 animals had an accuracy that was equal to or exceeded 0.2 for their feed intake EPD. Post-analysis calculation of measures of efficiency EPD was pursued. This work demonstrates the feasibility of conducting a national cattle evaluation for feed intake using indicator traits to reduce opportunity for selection bias, increase accuracy of the evaluation for a substantial number of animals and ultimately facilitate calculation of selection indexes.