Growth and mature weight of Mehraban Iranian fat-tailed sheep

The growth curves of 1239 Mehraban Iranian fat-tailed sheep were fitted using Brody's model. A is the asymptotic weight in the equation W-t = A X (1 - Be--kt), where W is the weight at time t and B and k are constants. Least-squares analyses were run on the estimates of mature weight, rate of maturing and weight from birth to 48 months. Year, sex and type of birth significantly affected all growth curve parameters. Lambing year, age of dam at lambing, sex and type of birth significantly affected the pre-weaning growth period (90 days) while the major source of variation in post-weaning growth were sex and type of birth. None of the first-order interactions included in the analysis were significant. Males were heavier at mature weight (81.04 +/- 2.39 kg vs 62.95 +/- 1.88) than females but they matured more slowly. Twins were lighter at mature weight (60.82 +/- 2.07 kg vs 81.04 +/- 2.18) than singles. It was concluded that to improve the growth rate, attempts must be made to improve the management with special attention to nutrition conditions.