Effect of weaning weight on the post-growth rate of Morada Nova lambs raised in extensive production system in the State of Ceará (Brazil)

Abstract

The study aimed to evaluate the effect of weight at weaning on post-growth rate of lambs as an attempt to estimate optimal weaning weight for Morada Nova breed white lambs, kept under extensive system. A total of 31 male and female, 19 born in April and May, 2001, and 12 born in February and March, 2002, aging 60 or 90 days, were evaluated. The treatments (T) consisted of: T1= 9 to 10.4 kg at weaning; T2 = 10.5 to 12.4 kg at weaning, and T3 = equal or superior to 12.5 kg at weaning. Post-weaning growth rate was evaluated by weighting animals consecutively, every fifteen days, for a period of 180 days after weaning. Data, including age and weight at weaning, gender and year of birth, were analysed with the aid of General Linear Models (GLM) and Tukey tests for comparison of means. The results showed that lambs weaned at weight varying from 9 to 10.4 kg presented lower body weight than those whose weight at weaning varied from 10.5 to 12.4 kg or above 12.5 kg. These two last groups did not differ one from the other. Animal gender affected (P<0.05) post-weaning growth significantly, with males presenting higher weight than females (20.7 kg and 17.6 kg, respectively). Although animals born in the year 2002 weighted higher than those born in 2001, no significant difference was found between them. The results led to the conclusion that minimal body weight at weaning for Morada Nova breed white lambs kept under extensive system should be equal or superior to 10.5 kg.