Comparison of different models to estimate genetic parameters for carcass traits in a commercial broiler line

Abstract

ABSTRACT. The effect of genetic and non-genetic factors for carcass, breast meat and leg weights, and yields of a commercial broiler line were investigated using the restricted maximum likelihood method, considering four different animal models, including or excluding maternal genetic effect with covariance between direct and maternal genetic effects, and maternal permanent environmental effect. The likelihood ratio test was used to determine the most adequate model for each trait. For carcass, breast, and leg weight, and for carcass and breast yield, maternal genetic and permanent environmental effects as well as the covariance between direct and maternal genetic effects were significant. The estimates of direct and maternal heritability were 0.17 and 0.04 for carcass weight, 0.26 and 0.06 for breast weight, 0.22 and 0.02 for leg weight, 0.32 and 0.02 for carcass yield, and 0.52 and 0.04 for breast yield, respectively. For leg yield, maternal permanent environmental effect was important, in addition to direct genetic effects. For that trait, direct heritability and maternal permanent environmental 909 ©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 9 (2): 908-918 (2010) Genetic parameters for carcass traits in broiler line variance as a proportion of the phenotypic variance were 0.43 and 0.02, respectively. The results indicate that ignoring maternal effects in the models, even though they were of small magnitude (0.02 to 0.06), tended to overestimate direct genetic variance and heritability for all traits.

Genetic basis of leg health and its relationship with body weight in purebred turkey lines

“…This is likely due to the fact that in the present study the age of the birds at the time of measuring the traits was 17 to 18 wk, compared to an age of 5 to 6 wk in chickens. However, while this percentage may seem low, studies comparing models including and excluding maternal effects have shown that omission of the maternal effects may result in an overestimation of the direct heritability (e.g., Koerhuis and Thompson, 1997; Clément et al, 2001; Grosso et al, 2010). To evaluate the effect of the permanent environmental effect of the dam, all 4 models also were run without this effect, which resulted in increased heritabilities for the leg health traits in the range of 0.01 to 0.06.…”

Estimates of (co)variance components for production and reproduction traits with different models in Fars native fowls

“…It is noted that if a negative dependence exists between direct and maternal genetic effects, the dam either gives her offspring a plus set of genes for the direct additive effect and a poor maternal effect, or vice versa (Szwaczkowski, 2003). Moreover, some authors have suggested that negative estimates of medium to high magnitude for r am can be related to the size of the data set, its structure, and the magnitude of the direct and maternal additive genetic variances (Grosso et al, 2010;Heydarpour et al, 2008).…”

Twenty-five years of selection for improved leg health in purebred broiler lines and underlying genetic parameters

“…Studies comparing models with and without maternal effects show that the direct heritability may be overestimated if significant maternal environmental effects are not fitted (e.g., Koerhuis and Thompson, 1997;Clément et al, 2001;Grosso et al, 2010). To evaluate the effect of not fitting this effect, line B was analyzed using a model without PEm.…”