ESTIMATION OF GENETIC AND PHENOTYPIC TRENDS FOR IMPROVING BODY WEIGHT TRAITS IN SOHAGI SHEEP

Document Type : Original Article

Authors

1 Department of Sustainable Development, Environmental Studies and Research Institute (ESRI), University of Sadat City, Menofyia, Egypt

2 Animal Production Department, Faculty of Agriculture, Sohag University, Egypt

Abstract

The objective of this study was to estimate the genetic and phenotypic trends of birth weight (BW), weaning weight (WW) and yearling weight (YW) in a Sohagi sheep flock at Sohag University's experimental farm from 2001 to 2021.  Data from 1284 lambs, which the progeny of 44 sires and 488 dams, were used to assess the impact of various environmental factors on these traits.  The averages of BW, WW and YW were found to be 2.98±0.01 kg, 15.05±0.07 kg and 32.61±0.17 kg, respectively. The heritability (h²), animal breeding values (BVs), and genetic and phenotypic correlations were estimated.  Genetic and phenotypic trends were assessed by regressing breeding values and phenotypic values on year of birth. Genetic correlations among BW, WW, and YW were found to be higher than phenotypic correlations.  Throughout the study period the breeding values ranged from -0.047 kg to 0.0834 kg for BW, -0.2487 kg to 0.9820 kg for WW, and -0.5529 kg to 1.7732 kg for YW. Genetic and phenotypic trends have changed significantly over time. Positive and significant genetic trends were observed for BW at 0.006 kg/year, WW at 0.038 kg/year and YW at 0.080 kg/year, indicating genetic improvement.  However, negative phenotypic trends were noted for BW at -0.009 kg/year, WW at -0.073 kg/year and YW at -0.095 kg/year. These declines likely result from the more significant negative environmental trends which may reflect challenges such as disease, inadequate nutrition, and harsh climatic conditions

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