Genetic analysis of reproductive characteristics in Iran-Black sheep

Abstract

This study was conducted to estimate genetic parameters and trends for reproduction traits using data collected at the breeding station of Iran-Black sheep during 1980 to 2004. The traits included in the analyses were litter size at birth (LSB) and weaning (LSW) and litter mean weight per lamb born (LMWLB) and weaned (LMWLW) as basic traits, and total litter weight at birth (TLWB) and weaning (TLWW) as composite traits. Direct heritability estimates for LSB, TLWB, LMWLB, LSW, TLWW and LMWLW were 0.11, 0.07, 0.33, 0.08, 0.09 and 0.11, respectively. The permanent environmental effects had significant impact on all traits and ranged from 0.05 to 0.16. Effect of service sire was highly significant (p < 0.01) for all traits except LMWLW. Estimates of genetic correlations ranged from -0.76 (LSB-LMWLB) to 0.98 (LSB-LSW). Phenotypic and environmental correlations were generally lower than those of genetic correlations. Environmental correlations ranged from -0.55 (LSW-LMWLW) to 0.99 (LSB-LSW). Also, the estimated correlation for the effect of service sire ranged from -0.77 (LMWLB-TLWW) to 0.96 (LSB-LSW and LSB-TLWW). The results suggest that selection based on TLWB could be more effective than the other traits to enhance reproductive performance in Iran-Black ewes.

Estimation of Repeatability and the Most Probable Producing Ability (MPPA) Based on Birth Weight and Weaning Weight for Ranking of Sapudi Sheep

“…Genetic and environmental factors influence birth weight characteristics of Sapudi lambs; permanent factors constitute 10.8%, while temporary environmental factors constitute 89.2%. The repeatability value of birth weight obtained from the results of this study is almost the same (low category) when compared to that reported in lambs, namely 0.118 (Piwczyński et al, 2011), 0.13 (Ozturk et al, 2018), and 0, 19 (Yafarivard et al, 2015 but lower than the Iranian lamb of 0.27 including the medium category (Baneh et al, 2019).…”