Comparative Growth Performance of Kuroiler and Nigerian Indigenous Naked Neck Chickens Kept in a Tropical Environment

Chicken production is an essential venture for steady household income generation, poverty alleviation and provision of quality nutritional aids. This study was conducted to compare growth performance of Kuroiler and Nigerian indigenous naked neck chickens reared in the tropics. A total of 538 birds comprising 345 indigenous Nigerian naked neck and 193 Kuroiler chickens genotypes were sampled. Body weight and linear body measurements were observed at 2, 4, 6, 8 and 10th week. Data obtained were subjected to 2-way analysis of variance using GLM procedure of SAS. There exist signicant variations in chicken genotype with growth performance. Kuroiler birds signicantly showed heavier mean body weight (p<0.05) at various critical growth stages observed than the Nigerian indigenous naked neck chickens reared under same conditions. The inuence of genotype and sex on mean body weight and breast girth measures of chickens remain insignicant throughout early growth stages. However, at 6th, 8th and 10th week of age, Kuroiler breeds demonstrated superior growth rate and performance response compared to Nigerian indigenous naked neck fowls. Both chicken breeds exhibited differential growth patterns and sexual dimorphism in favour of male populations. Introduction and crossing of Kuroiler strains with Nigerian indigenous naked neck birds might result in better performance and adaptability.


Introduction
Chicken constitute a unique and vital component of the global animal genetic resources. Chicken production has become a globally accepted practice appraised for regular household income generation, rural poverty alleviation and provision of quality nutritional aids for human needs, sustenance and industrial uses. The current demand for available animal-based protein sources will double progressively in the coming years due to rising human population. Poultry products especially chicken derivatives are common and the most affordable animal protein sources in developed and developing regions worldwide. Chickens are recognized as valuable component of global genetic resources (Ogbu, 2021), and the most widely distributed avian specie in the Nigerian poultry production industry with a total According to Lawrence and Fowler, (2002) growth describes an increase in the number of cells or body size per unit time. Growth in chicken is a complex trait believed to be in uenced by genetic and nongenetic factors as: genotype, sex, breeds, nutrition, adaptability and management pro le. Indigenous fowls unlike the exotic breed exhibits sigmoid growth (Ismail, 1997). This growth pattern is also associated with Nigerian indigenous naked neck chickens.
The naked neck chickens represent a breed of birds naturally devoid of feather coverage on the neck and vent region. Naked neck trait results from an autosomal gene in chicken (Warren, 1933) and controlled by an incompletely dominant allele located near the middle of chromosome 3 (Duodo, 2013). Indigenous Nigeria naked neck chickens are possess robust adaptability and can thrive e ciently in the tropics and hot humid zones. They are distributed in rural areas, reared by the majority of the rural poor (Ogbu, 2021).
Keeping naked neck birds under warm and hot humid areas support the attainment of bird's growth potential, body weight and egg production (Galal and Fathi, 2001). The growth rate and production level of Nigerian indigenous chickens are quite slow relative to exotic strains under similar conditions. An insight into understanding the genetic variation of these useful breeds becomes imperative to identify populations with superior merit. This study therefore focus on comparative evaluation of growth

Results And Discussion
Effect of genotype on chicken growth trait Table 1  Wk=week, KLR=Kuroiler, NKN=Nigerian indigenous Naked neck, BG=Breast girth, BWT=body weight, N=Number of observations, g=grams and Cm= Centimeter.
Effect of sex on chicken growth trait Table 2 presents the effect of sex on chicken growth parameters. Sex did not have signi cant effect on chicken growth traits at 2 nd and 4 th week. However, at 6 th , 8 th and 10 th week of age, the males were generally superior (p<0.05) to females of both Kuroiler and Nigerian indigenous naked neck chickens in mean body weight and average breast girth measures subjected to same management pro le.
Table2. Effect of sex on chicken growth trait abc Mean with different superscripts on the same column are signi cantly different (p<0.05).
Wk=week, =male, =female, BG=breast girth, BWT=body weight, N=Number of observations, g=grams and Cm= Centimeter. Table 3 show the effect of genotype and sex interaction on chicken growth parameters. Sex and chicken genotype combination showed no signi cance on early birds growth traits. When compared with respect to genotype and sex interactions, Kuroiler sexes differ signi cantly in breast size and body weight from  Wk=week, KLR=Kuroiler, NKN = Nigerian indigenous Naked neck, =male, =female, BG=Breast girth, BWT=body weight and N= number of observations, g=grams and Cm= Centimeter.

Effect of Sex and Genotype interaction on chicken growth traits
Growth in farm animals re ects a biological increase in an animal's size or mass over its lifetime. Superior growth performance of Kuroiler chicken breeds compared to Nigerian indigenous naked neck fowls observed in this study might be attributed to better genetic potential that exotic breeds have acquired over series of selection and multiple cross breeding have genetically improved their growth rate and production potentials. This reveals that the genetic constitution of Nigerian indigenous naked neck chickens is still intact has not yet undergone full gene mixing with exotic lines (Islam, 2009). The signi cant sex effect to on body weight and linear measurements at 6 th to 10 th week is in agreement with literature (Ajayi and Ejiofor, 2009). Heavier weight of male to female birds in this study is consistent with In conclusion, the chickens exhibited differential growth patterns, attributable to genetic composition and strain differences. Kuroiler revealed superior growth rate and performance relative to Nigerian indigenous naked neck chickens. Introduction of Kuroiler strains and subsequent crossbreeding with Nigerian indigenous naked neck birds might improve their performance and adaptability. Nigerian indigenous naked neck hens  Kuroiler hens.