Abstract
Aim:The aim of this study was to estimate the heritability, genetic and phenotypic correlations, and the genetic trends for pre-weaning growth traits including the birth weight (BWT), weaning weight (WWT), pre-weaning daily gain (PWDG), and weaning age (WA) in Awassi lambs.Materials and Methods:A total of 5131 Awassi lambs from two Jordanian sheep breeding stations were used. A multitrait animal model and restricted maximum likelihood methods were used to estimate the covariances between the studied traits.Results:The mean±standard deviation of BWT, WWT, PWDG, and WA was 4.48±0.8 kg, 17.13±0.7 kg, 0.2±0.07 g, and 65.5±0.7 days, respectively. Heritability estimates were 0.30±0.04 for BWT, 0.19±0.04 for WWT and PWDG, and 0.2±0.04 for WA. Positive genetic correlations were obtained between BWT and other traits, while negative correlations were obtained between WWT, PWDG, and WA (−0.50±0.12) and between WWT and WA (−0.67±0.14). The positive phenotypic correlation was obtained between WA and PWDG (0.63±0.01). The highest additive genetic variance was obtained for WA (34.58), while the lowest was estimated for PWDG (6.22E-04). The highest phenotypic variance was obtained for WA (175.5), while the lowest value obtained was for BWT (0.54). Maternal additive variance ranged between 0.13 and 0.03. The genetic trends were around zero for all studied traits.Conclusion:Selection should be conducted using animals with high estimated breeding values through controlled breeding.
Highlights
Genetic selection is one of the most important methods that has been used to maximize the expected genetic gain of livestock through crossbreeding programs and breed selection using specific gene markers or genomic selection methods [1]
Awassi breed is considered as an important genetic resource that plays a significant role in sheep industry in more than 30 countries in the Middle East as well as worldwide [2]
It has been reported that sex, genetic group, and season of birth have a significant effect on the traits such as birth weight (BWT), weaning age (WA), and weaning weight (WWT) [1,2,3]
Summary
Genetic selection is one of the most important methods that has been used to maximize the expected genetic gain of livestock through crossbreeding programs and breed selection using specific gene markers or genomic selection methods [1]. Awassi sheep is the most common breed of sheep in Jordan. Awassi breed is considered as an important genetic resource that plays a significant role in sheep industry in more than 30 countries in the Middle East as well as worldwide [2]. It has been reported that sex, genetic group, and season of birth have a significant effect on the traits such as birth weight (BWT), weaning age (WA), and weaning weight (WWT) [1,2,3]. The Creative Commons Public Domain Dedication waiver (http:// creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated
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