Genetic and Environmental Influences on Awassi Lamb Weights with Implications for Breeding and Management in Jordan

Awassi sheep demonstrate a robust capacity to thrive in arid climates, underscoring the feasibility of sheep farming in challenging environments. However, productivity constraints necessitate the application of selective breeding techniques and improved management practices. This study, conducted at the Al-Fjaj Station in Jordan, analyzed 2,263 weight records from Awassi sheep reared under a semi-intensive system to assess the environmental and genetic determinants of lamb weight and to estimate heritability and breeding values. Analysis of variance indicated that factors such as birth type, sex, parity, and ewe age at lambing significantly influenced lamb weight. Notably, single-born lambs were heavier at birth, males consistently exhibited greater weights than females, and lambs from younger ewes were initially lighter but demonstrated compensatory growth over time. Although strong positive correlations were observed among weaning, six-month, and yearling weights, birth weight had a relatively minor influence on subsequent weight development. The findings further revealed that individual rams exerted a significant effect on lamb weights, with heritability estimates indicating a moderate genetic contribution. These results suggest that selection based on a single weight trait may confer benefits across other traits and that the observed decline in breeding values with age supports the application of index selection. In conclusion, the strategic selection of rams with superior breeding values, in conjunction with rigorous monitoring of weight measures, is critical for advancing genetic progress and ensuring sustainable lamb production in arid regions.