POLYMORPHISM OF PIT-1 GENE, MORPHOMETRIC TRAITS AND THERMOPHYSIOLOGICAL INDICES IN TWO CHICKEN GENOTYPES IN SMALLHOLDER FLOCK IN NASARAWA STATE

Pituitary specific transcription factor 1 (Pit-1) is a transcription factor involved in controlling immune system of the body through mechanism of growth hormone cascade in birds. This study aimed at assessing phenotypic and genetic diversity of Pit-1 gene in chickens kept by rural farmers in Nasarawa State, Nigeria. A total of 180 birds, six (6) weeks of age (growers) of both sexes comprising equal number of indigenous normal feathered and Noiler chickens reared by smallholder farmers with similar management system in the three Senatorial zones of Nasarawa State, Nigeria were randomly sampled. Body weight (BW), six primary biometric traits [body length (BL), breast circumference (BC), thigh circumference (TC), foot length (FL), total leg length (TLL) and wing length (WL)] and four morphological indices [massiveness (MAS), stockiness (STK), long-leggedness (LL) and condition index (Cl)] were measured or determined on each bird on a four weekly basis for six (6) months. At the same time, rectal temperature (RT), pulse rate (PR) and respiratory rate (RR) of birds were taken according to standard methods. One (lml) of blood sample was also obtained from each bird for genomic analysis. The general linear model (GLM) was used to test the fixed effects of Strain (Bi), Sex (Sj) and Location (Lk) as well as their interactions on body traits. Sequence alignments, translations and comparisons were carried out and Phylogenetic trees constructed using the appropriate options of MEGA 6. Noiler birds recorded higher (P<0.05) morphometric traits than their indigenous counterparts. Noiler birds were also superior (P<0.05) to their indigenous counterparts for morphological indices except for stockiness. Male birds recorded higher (P<0.05) body parameters and morphological indices than their female counterparts. The results of location effect were also significant (P<0.05). Heat tolerance traits and stress index for strain effect were not significant, except for pulse rate that appeared higher in the Noiler birds. The female birds also appeared more thermally stressed (P<0.05). For location effect, birds in Nasarawa South were thermally stressed which implies thermal discomfort. There were significant effects (P<0.05) of strainsex, strainlocation, sex * location interactions on most body parameters, morphological indices and heat tolerance traits of birds. The body weights of both Noiler male and female chicken were heavier and from the quadratic functions were predicted at an optimality age of 25.833 and 27.25 weeks. Nonsynonymous substitutions exceeded those of synonymous substitutions (dN /dS> 1) in Nigerian indigenous chickens, implying positive selection while those of Noiler indicated purifying selection (dN/dS<l). The Neighbour-Joining and UPGMA trees showed that the sequences of Pit 1 gene of Nigerian indigenous chicken clustered closely with those of the Noiler chicken. The between-genotype variations obtained in this study would provide basis for the conservation and genetic improvement of the two sampled chicken genotypes in Nigeria.