TALHARI, Fernando Molinari.; ALENCAR, Maurício Mello de.; MASCIOLI, Arthur dos Santos.; SILVA, Ana Mary da.; BARBOSA, Pedro Franklin.
Résumé:
The objective of this study was to estimate the genetic correlations of female body weights at weaning (BWW), 12
(W12) and 18 (W18) months of age with age at first calving (AFC), body weight at first calving (WFC), adult body weight (ABW), and
the parameters for mature weight (A) and maturation rate (k) obtained using the Von Bertalanffy model, in a Canchim herd. The restricted
maximum likelihood method, with two-trait analyses, was used with models that included the fixed effects of contemporary group and
the random additive direct effect. For BWW the model also included the covariate age of cow at calving (linear and quadratic effects)
and the additive maternal and the permanent environmental random effects, and for ABW the model included also the fixed effect of age
of cow. The means of the heritability estimates were equal to: 0.37 (BWW), 0.31 (W12), 0.35 (W18), 0.39 (A), 0.29 (k), 0.13 (AFC),
0.39 (WFC), and 0.42 (ABW). The genetic correlations between BWW and the other traits were: 0.46 (A), 0.02 (k), -0.12 (AFC), 0.66
(WFC) and 0.42 (ABW). With W12 they were equal to 0.39 (A), 0.31 (k), -0.32 (AFC), 0.77 (WFC) and 0.66 (ABW), while with W18
they were equal to 0.21 (A), 0.42 (k), -0.29 (AFC), 0.65 (WFC) and 0.60 (ABW) These results indicate that selection to increase BWW,
W12, W18, WFC, ABW, and parameters A and k should result in direct genetic responses, and that selection to increase female body
weights from weaning to 18 months of age should result in favorable responses in AFC and parameter k, but in unfavorable correlated
responses in WFC and ABW.
