Genetic parameters for carcass traits estimated from Angus field records

Abstract

The American Angus Association has sponsored a carcass evaluation since 1974. The carcass data collected as a part of this program are used by the association to conduct a biannual sire evaluation for carcass merit. This paper presents age-adjustment factors and genetic parameter estimates for carcass traits to be used in the Angus carcass genetic evaluation program. Because of the large range in slaughter ages, age classes were defined as all those animals slaughtered at an age of < or = 480 d and those with a slaughter age > 480 d. Linear and quadratic partial regressions on slaughter age for hot carcass weight (HCW), USDA marbling score (MS), 12th rib longissimus muscle area (LMA), and 12th-rib fat thickness (FT) were estimated within sex and age class. Quadratic age regressions were not significant, nor was the linear age regression coefficient for FT in steers in the > 480-d age class. Heritability estimates for age-constant HCW, MS, LMA, and FT were .31, .26, .32, and .26, respectively. The estimated genetic correlation (rg) between HCW and LMA was .47. The estimated rg between HCW and FT was .38 and between MS and FT was -.13. The linear genetic trends for CWT and LMA were significantly positive at .414 kg/yr and .075 cm2/yr, respectively. The genetic trends for FT and MS were very small but significantly negative at -.004 cm/yr and -.003 units/yr, respectively.

Genetic parameters among growth and carcass traits of Canadian Charolais cattle

“…Koots et al (1994b) reported a mean genetic correlation of 0.38 between HCW and FAT, which was similar in sign but larger in magnitude than in the present study. Similarly, positive and small to moderate genetic correlations between HCW and FAT have been reported with Angus field data (0.38, Wilson et al 1992) and experimental crossbred data (0.13, Crews and Kemp 1999). Although the point estimate for the correlation between direct genetic effects of HCW with MAR was negative (-0.21 ± 0.09), this correlation would not be considered antagonistic because the method for assigning MAR to carcasses resulted in carcasses with higher degrees of marbling receiving lower marbling scores.…”

“…Heritability estimates generally compared favorably with those summarized by Koots et al (1994a), where weighted average heritabilities were equal to or greater than those of the present study with the exception of HCW, which was higher here than in that summary (0.23). The moderate heritability for HCW in the present study compares more favorably to the estimate of 0.31 reported by Wilson et al (1992) using Angus field data, but was lower than the estimates of 0.48 and 0.61 by Benyshek (1981) and Meyer et al (2004), respectively, using Hereford field data. Experimental data from the Meat Animal Research Center in Nebraska yielded HCW heritability estimates of greater than 0.44 in three studies (MacNeil et al 1984;Splan et al 1998Splan et al , 2002.…”

“…The heritability estimate for REA (0.43 ± 0.04) was very similar to the weighted average estimate of 0.42 reported by Koots et al (1994a) as well as estimates reported elsewhere [0.40, Benyshek (1981), 0.38, Johnston et al (1992], but was lower than estimates of 0.58 to 0.61 reported by Splan et al (1998Splan et al ( , 2002 and of 0.68 reported by Meyer et al (2004). The moderate heritability estimate of 0.34 ± 0.04 for MAR was higher than comparable field data estimates ranging from 0.23 to 0.26 (Johnston et al 1992;Wilson et al 1992;Woodward et al 1992) in Angus, Charolais and Simmental, but was similar to the estimate of 0.36 reported by Meyer et al (2004) using Hereford field data in Australia. Higher heritability estimates have been reported from Hereford field data (Benyshek 1981) and experimental crossbred populations (Splan et al 1998;Splan et al 2002).…”

“…This comparison suggests that choice of end point adjustment has an effect on sign and magnitude of genetic correlations among carcass traits. The genetic correlation of -0.06 between HCW and MAR reported by Wilson et al (1992) using Angus field data was near zero. The genetic correlation of HCW with PLY (-0.05 ± 0.08) was essentially zero, a result similar to that reported by Crews and Kemp (1999), indicating that selection for PLY could be implemented independent of carcass weight.…”

“…The heritability for FAT reported here (0.38 ± 0.04) was in the lower portion of the range reported in recent studies, where estimates ranged from 0.35 (Crews and Kemp 1999) to 0.66 (Splan et al 1998). The estimate of 0.26 in Angus by Wilson et al (1992) was lower than other published estimates, as was the estimate of 0.20 reported by Meyer et al (2004). The heritability estimate for REA (0.43 ± 0.04) was very similar to the weighted average estimate of 0.42 reported by Koots et al (1994a) as well as estimates reported elsewhere [0.40, Benyshek (1981), 0.38, Johnston et al (1992], but was lower than estimates of 0.58 to 0.61 reported by Splan et al (1998Splan et al ( , 2002 and of 0.68 reported by Meyer et al (2004).…”