F. P. Lima.
Estudo de alguns fatores de variação do peso à desmama dos bezerros de raças zebuínas de corte.
Para a determinação das influências do sexo, época do ano, ordem das parições e ano sobre o peso â desmama, 693 bezerros foram observados durante 6 anos, desde o nascimento até 210 dias de idade, sendo 171 da raça Gir, 300 da Nelore e 222 da Guzerá. Os resultados da análise estatística mostraram que na raça Gír todos os fatores considerados determinaram diferenças significativas nos pesos à desmama, sem exceção. Na raça Nelore apenas não revelou significância a ordem de parições e, na raça Guzerá, além dessa última, também o ano deixou de manifestar influência do ponto de vista estatistico. Os coeficientes de variação encontrados foram 11.05% para o Gir, 11.60% rara o Nobre e 13,21% para o Guzera, Ainda que parciais e preliminares, os resultados deste trabalho1 devido ao número reduzido de dados e de anos em que se basearam, sugerem com muita evidência que todos os fatores estudados ao importantes no estabelecimento de programas de seleção de bezerros zebuínos das raças de corte em estudo.
Effects of sex and environmental factors on weaning weights of Zebu calves.
In this paper the author reports observations which were carried out during 6 years (1964-1969) in the “Estação Experimental de Zootecnia”, at Sertãozinho, SP, about some factors affecting the weaning weights of zebu calves from Gir, Nelore and Guzera breeds. In this study, the weaning weights of 693 calves at 210 days, were classified according to the following factors: sex, weaning season, calving order of cows, and year. A brief report is presented about climate and soil of the region, management of the animals, control of the records and statistical procedures for adjustment of data. Statistical analysis showed that in Gir breed every factors determined significative differences in adjusted weaning weights, but in relation to Nelore breed there was no significance for calving order, and to Guzera, in adition to this factor, the year also did not have influence. Male calves were significantly heavier than female calves in ali breeds. In relation to the weaning season (February -March, April-May, and June-July) the observed differences were highly significant for all the breeds, an further-more, lighter calves were weaning in June-July. These results also showed that Nelore calves have the worst response to the unfavorable conditions of weaning season, which apparently could justify some previous accepted observations about the low milk production efficiency of Nelore cows. On the contrary, Guzera calves presented the smallest range variation among the adjusted weaning weights considering the first and the third season. The adjusted weaning weights of Gir and Guzera calves were consistently lower for the first calving than for the following, but only in Gir breed was observed a significative difference. The overall picture is showing a general tendency to increase adjusted weaning weights as the calving sequence in going up until the fourth or fifth one, and afterwards a decreasing effect was observed. For Nelore calves, however, this situation did not become so clear. Considering the year factor, significative differences were found only in Gir and Nelore breeds. During 1964 all the breeds had lighter weaning weights, apparently associated with a low rain fall that must have damaged growth and regrowth of the pastures that year. Guzera calves good responses seem to indicate that this breed is better adapted to unfavorable conditions of environment. The conclusions drawn in this work should be considered as partial and preliminary results due to the limited number of records and years of observation in which they were, obtained. Although, they strongly suggest that every studied factors are important to the establishment of selection programs of beef zebu cattle.