Estimation of the associations between GH and DGAT1 genes and growth traits by using decision tree in Awassi sheep.

GH and DGAT1 are candidate genes associated with growth traits in sheep breeds. This study aims to determine the association between growth traits and GH and DGAT1 gene polymorphism using three statistical methods in Awassi sheep. The polymorphism was detected by the PCR-RFLP method. Three genotypes (AA, AB and BB) were observed for GH gene locus with allele and genotype frequency 0.70(A) and 0.30(B); 0.60(AA), 0.20(AB) and 0.20(BB). Three genotypes (CC, CT and TT) were found for DGAT1 gene locus with allele and genotype frequency 0.58(C) and 0.42(T); 0.47(CC), 0.23(CT) and 0.30(TT). The genes were in agreement with Hardy-Weinberg equilibrium (p > 0.05). CHAID, CRT and GLM were used to identify the association between growth traits and gene polymorphism. The results showed an association between GH locus and body weight and tail length. Also, found an association between DGAT1 locus and tail length. The three methods showed similar results in determining the association between genes and growth traits. Thus, the CHAID and CRT methods can evaluate the association between genes and growth traits.

Estimate of the Association of IGF-I and IGFALS Genes with Growth Traits in Hamdani Sheep

Abstract IGF-I and IGFALS play a vital stimulator role in skeletal growth, cell differentiation, metabolism, and other physiological processes. A total of 65 (male and female) animals were used in the study. Animals were measured for growth traits at birth weight, weaning weight, and weights at 6 months. The average daily gain (ADG) was calculated from birth to weaning (ADG1) and from birth to 6th month (ADG2). PCR-RFLP analysis was used to detect IGF-I polymorphism at the 5' regulatory region and IGFALS at Exon 1. Three genotypes (AA, AB and BB) were observed for IGF-I/BfoI locus with allele and genotype frequency 0.79(A) and 0.21(B); 0.71(AA), 0.15(AB) and 0.14(BB). Also, three genotypes (AA, AB and BB) were found for IGFALS/HinfI site with allele and genotype frequency as 0.22(A) and 0.78(B); 0.11(AA), 0.23(AB) and 0.66(BB). The genes were in agreement with Hardy-Weinberg equilibrium (p>0.05). Association analysis suggested that IGF-I and IGFALS significantly affected the growth traits (P<0.05). In terms of birth weight, The AA genotypes of IGF-I were higher than AB and BB. The AB genotype in terms of IGF-I had higher ADG2 compared with other genotypes. The AA genotype of the IGFALS gene was higher in terms of birth weight than other genotypes. In addition, the BB genotype was higher ADG1 than AA and BB. It is suggested that polymorphism of the IGF-I and IGFALS genes may be a potential molecular marker for growth traits in Hamdani sheep.