GROWTH AND MATURE WEIGHT OF MEHRABAN IRANIAN FAT-TAILED SHEEP

The growth curves of 1239 Mehraban Iranian fat-tailed sheep were fitte d 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 co nstants. Least-squares analyses were run on the estimates of mature we ight, rate of maturing and weight from birth to 48 months. Year, sex a nd type of birth significantly affected all growth curve parameters. L ambing year, age of dam at lambing, sex and type of birth significantl y affected the pre-weaning growth period (90 days) while the major sou rce of variation in post-weaning growth were sex and type of birth. No ne of the first-order interactions included in the analysis were signi ficant. Males were heavier at mature weight (81.04 +/- 2.39 kg vs 62.9 5 +/- 1.88) than females but they matured more slowly. Twins were ligh ter at mature weight (60.82 +/- 2.07 kg vs 81.04 +/- 2.18) than single s. It was concluded that to improve the growth rate, attempts must be made to improve the management with special attention to nutrition con ditions.