Heterosis upon weights in Canchim and Aberdeen Angus calves and in their reciprocal crosses

Abstract

The study was conducted to estimate heterosis upon birth weight (PNT), weaning weight (P210), yearling weight (P365) and daily weight gain from birth to weaning (G210) and from weaning to one year of age (G365) in the first, second, third and fourth generations of a rotational crossbreeding system between Canchim (C) and Aberdeen Angus (A). Data from 1,147 calves born from 1981 to 1998 were analyzed by least squares procedures fitting a linear model that included the linear and the quadratic effects of age of the dam of the calf plus the fixed effects of sex, genetic group, month and year of birth of calf. Estimates of heterosis and of other genetic differences were obtained by linear contrasts of appropriate means and tested by the t test. The contrast C-A was positive and significant (P < 0.001) for all five traits. The contrast F₁CA-F₁AC was negative and highly significant (P < 0.001) for P210 and for G210 and significant (P < 0.05) for P365. The F₁ generation exhibited heterosis of 4.8% for P210 and of 4.9% for G210. Maternal heterosis was 3.7%, 5.8%, 6.3% and 20.4%, respectively, for P210, G210, P365 and G365. The heterosis estimated for the mean of the third and fourth generations of the rotational crossbreeding system between C and A was 4.6% for P210, 5.3% for G210 and 3.5% for P365.