Genetic variations in locally adapted turkeys. 3. Influence of direct and maternal genetic effects on growth and growth-related traits

This study was conducted to determine direct and maternal genetic effects, direct and maternal heritabilities as well as phenotypic variances and correlations on growth and some growth-related traits on locally adapted ecotypes of turkeys in southeastern Nigeria. Three parental lines with black (B), bronze (Br), or white (W) plumage colored genotypes were compared. Traits considered were body weight at 4, 8, and 12 weeks-old (BW4, BW8, BW12, respectively), breast width at 4, 8 and 12 weeks-old (BrWt4, BrWt8, BrWt12, respectively), and shank lengthsat 4, 8 and 12 weeks old (SL4, SL8, SL12, respectively). Data were analyzed using restricted maximum likelihood under an animal model. The direct genetic variance ranged from 0.02 to 21.2 and the maternal genetic variance from 0.02 to 567, while the phenotypic variance ranged from 1.57 to 1226. Direct heritability estimates had values from 0.01 (BW8, BW12, SL4) to 0.20 (BrWt4). Maternal heritability estimates ranged from 0.01 (SL8) to 0.74 (BrWt4) and the estimates of maternal environmental variance as a proportion of phenotypic variance varied from 0.005 (BW4) to 0.63 (SL8). The correlations between direct and maternal additive genetic effects (ram) were all high with some being negative, e.g., -0.98, -0.96, -0.96, -0.95, -0.98 for BW4, BrWt4, BrWt12, SL4 and SL8, respectively while these were positive for the other traits: 0.87, 0.89, 0.76 and 0.99 for BW8, BW12, BrWt8, and SL12, respectively.