Influence of Chicken Growth Hormone Gene on the Linear Morphometry and Production Performance of Three Chicken Genotypes in Nigeria
Okafor, L. O.
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Recently, there is a trend on the development and improvement of the locally adapted chickens within their environments. This would enable them to withstand the climatic conditions and endemic poultry diseases. The research was conducted in order to characterize the chicken growth hormone (cGH) gene and associate its relationship with linear morphometry and production performances in three genotypes of Nigerian chicken namely: the Funaab Alpha, the Shika Brown and the Local chicken. The study was carried out at the Poultry unit of the Teaching and Research Farms, Federal University of Technology Owerri, Imo-state and Molecular Genetics Laboratory of the Department of Animal Science, University of Port-Harcourt, River-state. The objectives were: 1. To determine the growth, laying performance and egg quality characteristics of the three genotypes. 2. Determine the linear morphometry of the genotypes and to establish the relationships between the linear morphometry, growth, egg quality and laying performance of the chickens. 3. Characterize the cGH gene status of the three genotypes and to establish its relationship with the linear morphometry and production performance of the chickens. A total of two hundred and seventy chickens (ninety per genotype) were used on a three replicate pens of thirty birds each. The birds were sourced at day old, brooded and raised to egg production on deep litter during which data were collected on growth performance index, linear body measurements, egg quality characteristics and laying performance, and genomic analysis for chicken growth hormone gene. Data collected were subjected to analysis of variance of General Linear Model procedure (SAS, 2004). Correlation and Regression were done using Pearson‟s moment correlation of SAS (2004), while significant means were separated using Duncan‟s new multiple range test (Duncan, 1955). Significant differences (P<0.05) were obtained on growth performance index (body weight, weight gain, feed intake and feed conversion ratio) with the Funaab Alpha as the best performed genotype, then the Shika Brown and the local chicken respectively. This suggested that Funaab Alpha is good in meat production. On egg laying and quality characteristics, significant differences (P<0.05) were obtained in most of the traits studied. Shika Brown had the best performance in most traits (egg length and width, egg weight, shell thickness, albumen height, width and length, yolk height and width, shell colour; albumen, yolk and egg shape indices and Haugh unit), then the Funaab Alpha and local breed followed respectively. This finding is suggesting Shika Brown a better breed for egg production while Funaab Alpha could qualify better as dual purpose breed. Significant difference (P<0.05) was also obtained in the linear body measurements. Funaab Alpha had the most performance, then Shika Brown and the Local chicken followed respectively. Highly significant (P<0.01) and positive correlation were obtained between the body weight and linear morphometry, egg weight, egg length, egg width, albumen height, albumen width, albumen length, shell colour, yolk height, yolk width, yolk index, albumen index and shape index; between the shell thickness and egg width, Haugh unit and albumen index, yolk height and yolk width, albumen index. Significant (P<0.05) and positive correlations were found to exist between shell thickness and egg weight, yolk height and Haugh unit, yolk index and albumen index, Non-significant (P>0.05) and positive correlations were also found to exist between the shell colour and shell thickness, yolk index, egg shape index; shell thickness and egg length, albumen width, yolk height, yolk width, shape index; egg weight and Haugh unit, yolk index, egg shape index. Highly significant (P<0.01) and negative correlation were found to exist between shell thickness and body weight, linear morphometry, egg length and shape index, Haugh unit, albumen length and yolk index, shape index, yolk width and yolk index. Significant (P<0.05) and negative correlation exist between albumen width and yolk index, while non-significant (P>0.05) and negative correlation exist between albumen index and shape index, yolk height and shape index, albumen length and Haugh unit, albumen width and shape index, shell thickness and albumen height, albumen length, Haugh unit, yolk index, albumen index. Multiple linear regression of the body weight on linear morphometry in the three genotypes were highly significant (P<0.01) with coefficient of determination of 0.92, 0.88 and 0.36 for Funaab Alpha, Shika Brown and local chicken respectively. This result suggests that evaluation of linear measurements in Funaab Alpha and Shika Brown would appear to be a useful criterion to improve body weight. Two base pair substitution mutation (GT and CA) were found on locus 5 chromosome for the Funaab Alpha and locus 6 chromosome for the Shika Brown and local chicken respectively. Local genotype had highest number (6) of haplotypes while Funaab Alpha and Shika Brown had haplotypes number of 4 each. This suggested that local chicken had more allelic variation than the other two genotypes. On the other hand, Funaab Alpha had heterozygosity of 0.48 more than the Shika Brown and local chicken with heterozygosity of 0.44 each, indicating higher genetic variability. Meanwhile, negative theta value (-0.0843) obtained in F statistics indicated heterozygote excess (outbreeding) which means that the chickens were outbred. Genetic distances and identities revealed that Funaab Alpha and Shika Brown were most related (0.07) with closest identity (0.93) than any other group in this study. Association of cGH gene with linear body measurements and production performances revealed non-significant (P>0.05) differences in most traits between the mutant and the normal genotypes.