SILVA, Ana Mary.; ALENCAR, Maurício Mello de.; FREITAS, Alfredo Ribeiro de.; BARBOSA, Rogério Taveira.; BARBOSA, Pedro Franklin.; OLIVEIRA, Márcia Cristina de Sena.; CORRÊA, Luciano de Almeida.; NOVAES, Antonio Pereira de.; TULLIO, Rymer Ramiz.
Resumo:
The objective of this study was to estimate heritabilities of and genetic correlations among male body weight (BW12)
and scrotal circumference (SC12) at 12 months of age, and female body weights at first (BWFC) and second (BWSC) calvings, age at
first (AFC) and second (ASC) calvings, adult weight (AW), and mature weight (A) and maturation rate (k) obtained by the use of the
Von Bertalanffy model. The restricted maximum likelihood method with an animal model that included the fixed effects of contemporary
group and the random effects of animals, was used to estimate the variance and covariance components. The heritability estimates were
equal to: 0.37 (BW12), 0.30 (SC12), 0.38 (A), 0.35 (k), 0.12 (AFC), 0.33 (BWFC), 0.04 (ASC), 0.39 (BWSC), and 0.38 (AW). The genetic
correlations among BW12 and the female traits were: 0.19 (parameter A), 0.62 (parameter k), -0.58 (AFC), 0.69 (BWFC), -0.56 (ASC),
0.61 (BWSC), and 0.60 (AW). The genetic correlations among SC12 and the female traits were: -0.24 (A), 0.27 (k), -0.47 (AFC), 0.09
(BWFC), -0.67 (ASC), 0.07 (BWSC), and -0.17 (AW). These results indicate that male body weight and scrotal circumference and female
weights (BWFC, BWSC and AW) and growth curve parameters A and k have enough additive genetic variation to respond to mass
selection. Selection to increase male body weight at 12 months of age should result on favorable correlated changes in AFC, ASC and
parameter k of females, but with increases in female body weights (BWFC, BWSC and AW). Selection to increase SC12 should result
on desirable correlated responses in AFC, ASC and k, without any considerable change in female adult body weights.