| Popis: |
Summary Data from 20 249 Baluchi lambs, recorded from 1966 to 1989 in the Abbasabad Sheep Breeding Station located in the north-east of Iran (Mashhad), were used to investigate the influences of environmental factors, multiplicative and 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 mating (FW1). Significant effects of flock, year, sex, birth-rearing type and parity of ewe were observed for lamb weight at 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) decreased with advancing age of lamb. Lambs born at parity 4–6 were heavier than lambs of younger or older ewes. Weight gain declined in all subclasses from weaning to 12 months of age. The effects of flock and year were significant for lamb and ewe fleece weights. In addition the effect of sex was significant for LFW. Based on a test of heterogeneity of variance among class levels of fixed effects, multiplicative adjustment of sex, type of birth and 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. |
