Environmental effects on growth traits and fleece weights in Baluchi sheep

Data from 20249 Baluchi lambs, recorded from 1966 to 1989 in the Abbasabad Sheep Breeding Station located in the north-east of Iran (Mashhad), were us ed to investigate the influences of environmental factors, multiplicative a nd additive adjustment factors for lamb weights at birth (BW), weaning (WW) , six month (W6) and 12 months (YW) of age, preweaning (WG) and postweaning (PWG) gains, lamb fleece weight (LFW) and ewe fleece weight before first m ating (FW1). Significant effects of flock, year, sex, birth-rearing type an d parity of ewe were observed for lamb weight dr different ages and weight gains. Male lambs were heavier than females and the difference between them increased with age of lamb. The ratio of single lamb weight (S-S) to twin birth and single rearing (Tw-S) and twin birth and twin rearing (Tw-Tw) dec reased with advancing age of lamb. Lambs born at parity 4-6 were heavier th an lambs of younger or older ea es. Weight gain declined in all subclasses from weaning to 12 months of age. The effects of flock and year were signif icant for lamb and ewe fleece weights. In addition the effect of sex was si gnificant for LFW. Based on a test of heterogeneity of variance among class levels of fixed effects, multiplicative adjustment of sex, type of birth a nd parity of ewe for BW, and the effects of sex and parity of ewe for lamb weight at other ages were recommended. For LFW the effect of sex should be considered for multiplicative adjustment. Due to homogeneous variances, the additive adjustment for effect of birth-rearing type should be considered for WW, W6 and YW.