Crossbreeding analyses and polymorphic associations of gallinacin genes with growth traits in chickens

A simple crossbreeding experiment between Fayoumi (F) and Rhode Island Red (R) and their F1 of ½R½F and ½F½R crosses was conducted. A total number of 480 chicks produced from four genetic groups was used to estimate direct additive genetic effects (GI), maternal effects (GM) and direct heterosis (HI) for growth traits by using generalized least squares procedure. The studied traits were body weights at hatch, 2, 4, 6, 8 and 10 weeks of age and daily gains during the intervals of 0-2, 2-4, 4-6, 6-8 and 8-10 weeks of age. Candidate gallinacin genes of GAL 2, GAL 3, GAL 4 and GAL 5 were genotyped using PCR-RFLP, associating the SNP with body weights and gains. Direct additive effects were mostly significantly (P≤0.01) in favour of R breed by 7.4 to 57.9 g for body weights and by 0.8 to 1.8 g for daily gains. The estimates of maternal effect were mostly significantly (P˂0.01) in favour of R breed and ranging from 0.8 to 25.1 g for body weights and 0.5 to 2.3 g for daily gains. All the estimates for direct heterosis were positive and significant (P˂0.01) and ranged from 0.15 to 35.2 g for body weights and 0.3 to 1.5 g for daily gains. The GAL 2 gene was one homozygous genotype in the four genetic groups, while in GAL 3, GAL 4 and GAL 5 genes only one homozygous genotype in Fayoumi breed was observed. The genotypes of Gal 3 gene had significant associations with most body weights and gains (p<0.05) in R, ½R½F and ½F½R genetic groups. The genotypes of GAL 4 and GAL 5 genes were associated significantly with most body weights and daily gains during the intervals of 0-2 and 2-4 weeks of age in½R½F and ½F½R genetic groups. In practice, the molecular associations obtained for GAL 3, GAL 4 and GAL 5 genes could be used in marker assisted selection programs to improve growth traits in chickens.