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SUMMARY The present study investigated environmental factors affecting birth (BW), weaning (WW) and yearling body weights (YW) and estimated the heritabilities and genetic correlations of these traits in a Barki sheep flock maintained in the north western coast of Egypt. Body weight data of 1046 animals (542 females and 504 males) progenies of 163 sires and 557 dams obtained from 1963 to 2005 were used. Data were analyzed using a model composed of location, year of birth within location, sex of lamb and age of dam. Moreover, heritabilities as well as genetic and phenotypic correlations were estimated using multiple traits animal model. Barki males had significantly heavier body weights than females at birth (3.64 kg vs 3.46 kg), weaning (19.56 kg vs 18.44 kg) and at 12-month of age (32.05 kg and 30.02 kg). Year of birth within location showed highly significant effects on the studied body weights. Furthermore, age of dam revealed highly significant effect on birth weight, where older dams tend to produce heavier lambs than those of younger ones. These results clearly indicate that corrections for the studied environmental effects are necessary to increase accuracy of direct selection for BW, WW and YW. Heritability for weaning weight was found to be higher (0.41) than BW (0.32) and YW (0.30). Therefore, selection based on WW would probably be more effective compared with BW or YW. Hence, heavier body weights at weaning are worth to be considered in the Barki sheep flock if the improvement of mutton production is the objective.

GENETIC AND PHENOTYPIC PARAMETERS OF BIRTH, WEANING AND YEARLING BODY WEIGHTS OF BARKI SHEEP RAISED IN THE NORTH WESTERN COAST OF EGYPT