GENETIC, PHENOTYPIC AND ENVIRONMENTAL CORRELATIONS AND HERITABILTY ESTIMATES OF THE REPRODUCTIVE TRAITS OF THE NIGERIAN HEAVY LOCAL CHICKEN ECOTYPE HENS

Abstract Correlation is the statistical association between two random variables or bivariate data, while, heritability is a measure of the relative contribution of genes to the phenotypic value of a trait. The objective of this study was to investigate the genetic, phenotypic and environmental correlations and heritability estimates of the reproductive traits of the Nigerian heavy local chicken ecotype hens. A total of 145 and 150 point of lay pullets of the Nigerian heavy local chicken ecotype (NHLCE) from generation (G) 7 and G8 populations, respectively, were used for the study. The term generation G7 and G8 was used to describe birds that have been subjected to continuous selection by index for up to seventh and eighth generations. At 16th week of age, the point of lay hens were selected and placed in the battery cages to be monitored for short term egg production. The short term egg production lasted for 16 weeks (112 days). During these period of egg production, the hens were fed with formulated breeder’s diet (layers mash) and clean drinking water served ad libitum. Routine management practices and medication were provided as at when due. Data on the following reproductive traits were collected. Such traits included Age at first egg (AGEFE), First egg weight (FEGGWT), Egg weight at 112 days egg production (EGGWT@112DEP), Body weight at first (BWFE), Average egg weight (AEW), Total egg number (TEN) and Body weight at 112 days egg production (BWT@112DEP). Data collected were subjected to genetic, phenotypic and environmental correlation analysis and heritability estimation. The results indicated that genetic correlations analysis between pairs of some selected reproductive traits were positive across generations G7 and G8. In generation G7, genetic correlation between BWFE and AEW recorded high coefficient of 0.694, while, generation G8 recorded moderate coefficient of 0.398. The heritability estimates ranged from low 0.12 on FEGGWT to high 0.40 on AGEFE in generation G7, whereas, in G8, it ranged from low 0.10 on TEN to moderate 0.39 on AEW. Heritability estimates across populations indicated that whole population recorded higher heritability estimate compared to selected population and control population. It was therefore, concluded that body weight at first egg is positively correlated to average egg weight. Age at first egg has moderate to high heritability estimate 0.37 to 0.45 across generations G7 and G8. Also, the whole population recorded moderate to high heritability estimate 0.21 to 0.53, whereas, the selected and control populations recorded low to moderate heritability estimates (0.15 to 0.33) across the reproductive traits of the Nigerian heavy local chicken ecotype.