TRANSFORMING GROWTH FACTOR-Β (TGF-β3) GENE VARIATIONS IN DUAL PURPOSE CHICKEN STRAINS AND ITS ASSOCIATION WITH GROWTH TRAITS

Abstract

Studies on TGF-β3 genes suggests that they are crucial for maintaining healthy tissues and development and are located on chicken chromosome 5 which are close to genes that might influence body weight and feed conversion ratio (FCR) in chickens. TGF-β3 gene polymorphs in dual purpose chicken were investigated to understand their association with various chicken growth and morphological traits in three chicken populations. Methods: 450 chickens of 150 per strains were used, comprising of Noiler® (150), FUNAAB Alpha® (FA - 150), and Sasso® (150), reared from day old to 20 weeks of age. Growth and morphological traits such as body weight (BW), height at withers (HW), body length (BL), breast girth (BG), and wing length (WL) were measured from 4 weeks to 20 weeks of age at 4 weekly intervals. Genomic DNA was extracted for polymerase chain reaction (PCR) with primers of TGFβ3 gene. PCR amplicons were sequenced and genotyped using genotype by sequence method, with two SNP primers as two SNP genotypes were identified. The identified SNPs were on exon 3 at positions 7941745 and 7941722 of the TGFβ3 gene which were named 7941745A>C and 7941722A>T respectively. Chi square results demonstrated that the population used was under Hardy-Weinberg equilibrium (HWE) for the two SNP genotypes, with 7941745A>C and 7941722A>T having a dominant allele A. Marker trait association results revealed that 7941745A>C was not significantly associated (P>0.05) with breast girth, body length and wing length, however, there was a significant association (P<0.05) with body weight and height at withers, with strains Sasso and FA showing more association than Noiler. 7941722A>T had no significant association with all the growth traits except body weight (P<0.05) with strains Sasso and FA showing more association. Marker-trait association results suggest that AA and CC genotypes for SNPs 7941745A>C gene could be used as a genetic marker when improving body weight and size of the chicken strains under selection, whereas genotype AA and AT could be used in improving bodyweight only amongst the chicken strains studied. This research, therefore, suggests that the TGF-β3 gene could be a candidate gene that significantly influences the body weight and height at withers of chicken, hence might be used as potential genetic markers in dual purpose chicken breeding.