PHENOTYPIC AND MOLECULAR CHARACTERIZATION OF SOME-CHICKEN GENOTYPES FOR GROWTH AND EGG PRODUCTION

Abstract

The importance of indigenous chicken production in meeting daily household income and protein needs cannot be overemphasized. Therefore, this study was designed to evaluate five poultry species [four indigenous: Normal feather (NF), Naked neck (NN), Frizzle feather (FF) Fulani ecotype (FE) and one exotic meat-type chickens: Hubbard Broiler (HB)] for growth, haemato-biochemical, egg quality characteristics and gene expression profile. It was conducted at the Federal University of Technology, Akure (FUTA) Teaching and Research Farm, Poultry Unit for a period of 8 weeks. Data on growth performance, haematology and eggs’ nutrient compositional studies were collected using standard methods. Also, total RNAs from the selected tissue samples were isolated and quantified using the manufacturer’s protocols. Analytical results of the morphometric traits indicated that genotypes and genotypes*sex interaction were important sources of variation and exerted significant (p<0.05) influence on linear traits such as breast girth (BRG), drumstick length (DSL) and shoulder-to-tail length (STL). Among the genotypes, Fulani ecotype had the heaviest body weight and longest linear body traits compare to the other genotypes used in this study. The best and highest relationship existed between BWT-BRG (r=0.96) in Fulani chicken. The correlation coefficients in normal feather were generally low compared with the others genotypes. However, most of the phenotypic correlations were significant, positive and strong, generally greater than 0.40. Breast girth had the highest mean value contribution to body weight at the ages studied among the genotypes but mostly observed in FE and NN chickens. On the basis of R2, the allometry growth function produced the best fit from the BRG among the genotypes at week 8 of age. The results of haematological indices by genotypes, genotypes*sex interactions were not significantly different (p>0.05). The values of serum biochemical constituents showed no significant difference (p>0.05) in the sex of the chickens. High density lipoproteins were statistically different (p<0.05) between the genotypes of the chickens. The external egg quality parameters except egg weight and shell colour were significantly different (p<0.05) among the chicken genotypes. Internal egg characteristics (yolk weight, yolk width, albumen weight and Haugh’s unit) were significantly influenced (p<0.05) by the chicken genotype. Most of the internal and external egg quality investigated revealed that Hubbard genotype was superior to the indigenous species especially in egg weight. Proximate compositions of the chicken eggs revealed a significant difference (p<0.05) in their nutrient composition based on genotype. There was no significant difference (p>0.05) in the amino acid profile of the albumen, yolk and whole egg of the chicken eggs. The mRNA expression levels of the studied genes (growth hormone, pituitary specific transcription and insulin-like growth factor-1) among the 5-chicken genotypes and their sexes were significant (p<0.05) on the growth traits but were observed similar between the sexes of Hubbard chickens. The results also indicated that sex was a determining factor in the mRNA expressions of the studied genes and live weights at week 8 of age in chickens. The three growth genes showed significant (p<0.05) pleiotropic effects and were well expressed in the selected tissues (hypothalamus, liver and breast muscle) especially the breast muscle of the Fulani ecotype and naked neck chickens. The expressions of the genes were significantly (p<0.05) higher in the males than the females. It could be concluded that the selection of these genes would contribute greatly to the rapid growth of chickens which would generally affect economic traits of indigenous chickens. Selection should be made in favour of breast muscle in Fulani ecotype and naked neck chickens so as to improve muscular accretion leading to weight gain and their subsequent incorporation as meat producing indigenous chickens. Further molecular researches on some other traits of economic importance should be carried out. Lastly, this study showed that genomic selection and breeding to improve the growth rate and egg production of indigenous chicken genotypes were feasible. The gene expression profiling showed that the differentially-regulated genes were keys to poultry breeding programmes. The differential mRNA expression profiles of those genes among the genotypes gave the right understanding for future selection and breeding for a better growth and egg producing animal especially in Nigeria that can cope with the challenging climate due to the current trend of global warming.