Genetic change results from selection on an economic breeding objective in beef cattle1

Abstract

The objective of this study was to evaluate and quantify the genetic progress achieved in a New Zealand Angus nucleus herd through long-term selection for an economically based, multi-trait breeding objective. A 4-trait breeding objective was implemented in 1976 and selected on through 1993 with traits consisting of slaughter weight and dressing percentage of harvest progeny and cull cows, and the number of calves weaned in the lifetime of each cow. These traits were related to gross income with none related to costs of production. To overcome this, economic weights were adjusted down for increased feed requirements of faster growing (and generally larger) animals. Performance and pedigree information was recorded on 16,189 animals from 1976 through 1993 and included weaning, yearling, and mature cow weights along with the lifetime number of calves weaned by each cow. These traits were used in the phenotypic selection indexes developed to predict the defined breeding objective. Individual performance was adjusted by least squares for major environmental fixed effects and deviated from contemporaneous means. Genetic and residual (co)variances were re-estimated for each of the traits using REML techniques and used to calculate EBV for each trait. These EBV were in turn used to calculate annual genetic changes. The average annual genetic changes for weaning weight direct and maternal breeding value were 0.43 +/- 0.05 and 0.03 +/- 0.22 kg/yr, respectively. Corresponding annual genetic changes for postweaning BW gain, yearling weight, harvest weight, and mature BW were 0.29 +/- 0.03, 0.72 +/- 0.06, 1.7 +/- 0.13, and 0.13 +/- 0.09 kg, respectively. The annual change in number of calves weaned per cow lifetime was 0.006 +/- 0.001 calves/cow and the change in dressing percentage was estimated to be -0.035 +/- 0.003 %/yr. At the end of the program, 3.21 generations of selection had occurred with a mean accumulated selection differential of 3.87 SD. Change in objective traits due to selection was similar to or exceeded change predicted at the onset of the program with the exception of mature BW and dressing percentage. Genetic change in mature BW was not different from zero, whereas the predicted change was 29.3 kg. The overall genetic trend in the breeding objective exceeded that predicted at the onset of the program. Results of this study showed that selection on indexes developed to predict an economically based, multi-trait breeding objective will produce genetic change.

Economic selection index development for Beefmaster cattle II: General-purpose breeding objective1

“…Most currently available indices are designed to be used by multiple breeders for specific market-ing end points. These typically use industry economic averages to determine economic weights, and there is considerable evidence that index selection by this method is successful (MacNeil, 2003;Enns and Nicoll, 2008). Currently, Beefmaster Breeders United (BBu) reports 10 EBV but provides no tools that facilitate multiple-trait selection.…”

Economic selection index development for Beefmaster cattle II: General-purpose breeding objective

“…These typically use industry economic averages to determine economic weights, and there is considerable evidence that index selection by this method is successful (MacNeil, 2003;Enns and Nicoll, 2008). Currently, Beefmaster Breeders United (BBu) reports 10 EBV but provides no tools that facilitate multiple-trait selection.…”

Application of aggregate genotype in beef cattle breeding

“…Newman et al, 1992;Amer et al, 1998;Mwansa et al, 2002;Fernàndez-Perea & Alenda Jimènez, 2004;Crews et al, 2006). However, very few of the published indices were implemented in practical breeding schemes, as pointed out by Enns and Nicoll (2008). In recent years, TMI's are implemented in several countries in broad breeding goals for beef cattle, e.g.…”