Evaluation of performance and estimation of genetic parameters for milk yield and reproductive traits in Awassi and Asaf sheep breeds and crosses in the Palestinian territory.

This study aimed to estimate genetic parameters, including heritability and repeatability, for milk yield and prolificacy in sheep. It included 3682 records from 1837 ewes across various breeds: Awassi, Assaf, and Awassi x Assaf crosses, two Awassi lines: Improved Awassi, AFEC Awassi. The study measured total milk yield (TMY), yield up to 120 days (TMY120), and yield up to 150 days (TMY150), alongside reproductive traits: litter size (LS), number of lambs born alive (NLBA), and lambing interval (LI). The analysis utilized a mixed model and the REML procedure to estimate genetic parameters. Results indicated that litter size (LS) had no significant impact on milk traits, whereas breed, location, ewe parity, and lambing season showed significant effects. Lactation length also significantly influenced TMY. For reproductive traits, treatment was significant for NLBA, with location associated with breed, parity, and season affecting all traits. Heritability estimates for TMY ranged from 0.00 in Awassi x Assaf crosses to 0.11 in Awassi, and for TMY120 and TMY150, from 0.00 in Awassi x Assaf crosses to 0.16 in Awassi. Estimates for LS and NLBA varied similarly. The heritability for LI was 0.03 in Awassi and zero in other breeds and crosses. The findings suggest that in the northern West Bank regions of Nablus and Jenin, Assaf or Awassi x Assaf breeds are preferable. The study underscores the importance of comprehensive performance and pedigree recording for effective sheep farm management.