Estimate of Genetic Parameters for Pre-Weaning Growth Traits and Kleiber Ratio in Palestinian Sheep Breeds

Data on 1440 Awassi (AW), 2114 Assaf (AF), 261 Crossbred (XB), and 439 Improved Awassi (IA) lamb genotypes from 689 AW, 1009 AF, 105 XB, and 195 IA dams, and 152 sires, obtained from three geographical districts in the West Bank and collected between 2010 and 2015, were analyzed to estimate (co)variance components and genetic parameters for pre-weaning growth traits, including birth weight (BW), weaning weight (WW), pre-weaning average daily gain (PADG), and Kleiber ratio (KR). Explanatory statistical analyses employed the least squares method of the following factors: lamb genotype, mating type (natural mating or artificial insemination), lamb sex, and birth type, on lamb pre-weaning growth traits. The estimation of genetic parameters was performed by an animal model in Restricted Maximum Likelihood (REML) The heritability estimates for lamb traits showed that AF lambs had the highest heritability for KR 0.62, while IA lambs had a relatively high heritability for PADG 0.42. In terms of genetic correlations, the correlation between birth weight and PADG was strongest in AW 0.80, and IA lambs had a negative genetic correlation between BW and WW −0.28. For maternal genetic correlations, AF lambs exhibited a high maternal correlation between BW and WW 0.78, and AW lambs had a strong maternal correlation between PADG and KR 0.57. Phenotypic correlations were particularly strong in XB lambs between BW and KR 0.79. It was concluded that IA lambs had higher BW, and AF lambs excelled in WW and PADG. These results indicated the potential for genetic improvement in feed efficiency among AF lambs, whereas AW lambs exhibited a stronger environmental influence on growth traits.