Desempenho ponderal de machos Charolês, Nelore e suas cruzas F1

Abstract

The objective of the present study was to evaluate in Charolais and Nellore calves and their crossbred F1 the genetic (crossbreed system, genetic group and heterotic and racial additive effects) and environmental effects influence on weight at birth, adjusted weight for 205, 365, 550 and 730 days of age, and daily average gain of weight from birth to 205, from 205 to 365, from 365 to 550, and from 550 to 730 days of age. Four hundred fifty eight males bovines, all belonging to the same herd, born among the year of 1985 and 1995, from the continuous rotary crossbreed between Charolais and Nellore races were used. The animals were distributed per crossbreed system, defined (Charolais and Nellore) and crossbreed (½ Charolais ½Nellore and ½Nellore ½Charolais). The environmental effects analyzed were cow age at calving (3 to 12 years) and calves birth month (September to December). The data were submitted to variance analysis, f test and t Student test at 5% of significance. The heterotic and racial additive effects were obtained by contrast. Charolais calves presented higher performance in pre- weaning than Nellore, being the individual racial additive genetic effect positive. The maternal racial additive genetic effect influenced just weight at birth (5.26 kg). The heterosis was significant for weaning weight (11.0 kg) and weight gain from birth to weaning (0.052 kg/day). The crossbreed exceeded Nellore in all characteristics and was similar to Charolais for weaning weight. The weight at birth increased with the increasing in cow age at calving, while for the others characteristics of pre- weaning, the influence of genotype x environmental interaction was more evident for defined than crossbreed. The birth month influenced the weight at birth and the gain weight from birth to weaning, with maximum values for born in the months of October (34 kg) and December (0.572 kg/day), respectively. Charolais bovines are superior to Nellore race for performance characteristics in post- weaning, being the individual racial additive genetics effects positives and influence the weight and weight gain from 205 to 365 and from 550 to 730 days of age. Crossbred steers are superior in relation to defined for evaluated weights in post weaning besides of better performance in weight gain from 205 to 365 and from 365 to 550 days of age. The genotype x environmental interaction influenced the weights at year, at yearling and the daily average weight gain from yearling to two years old. The birth month influenced weight at year, and the daily average weight gains from weaning to one year old and from one year old to yearling, with maximum weights for the ones that were born in October, September and December, respectively.