In Ethiopia, most chicken populations are non-descriptive type. However, they showed a great variation in their production performance which might be due to their widespread distribution and adaptive response to different ecological conditions1-3. In Ethiopia, indigenous chicken is distributed in huge number (95.86%) across different agro-ecological zones4 under a traditional family-based scavenging management system5.
Morphometric traits are the quantitative analyses of the structure, shape and size of an organism. The derivation of live body weight from linear body measurements has been reported to be a practical and easy technique, especially for rural poultry breeders with lack of resources and materials6.
Phenotypic correlation estimates between live body weight and linear body traits could guide the breeder in the choice of body size traits to incorporate into selection index. According to Olawunmi et al.7 characterization of indigenous chickens is a necessary pre-requisite for the development of indigenous breed and rural poultry development.
In addition to body weight, a few conformation traits are known to be good indicators of physical growth and market value of indigenous chickens. Poultry breeders have tried to establish the relationship that exist between body weight and linear body parameters such as beak length, body length, chest circumference, comb length, ear lobe length, shank circumference, shank length, wattle length and wingspan. Relationships between body weight and linear body measurements are important for predicting body weight and can also be applied speedily in selection and breeding programmes8. Attah et al.9, Sowande and Sobola10 and Goe11 used body measurements to predict body weight of different animal species in previous studies. However, there is little information on the prediction of body weight of chickens using linear body measurements12,13. This study was designed to determine the relationship between body weight and linear body measurements and to establish predictive model for estimating body weight using linear body measurements of Ethiopian indigenous chicken.
MATERIALS AND METHODS
Description of the study sites
Sampling methods: The study sites were identified using purposive sampling technique by considering existence of indigenous chicken population, dissemination of exotic chickens and agro-ecology.
Experimental chicken and parameters: A total of 520 adult chickens (130 males and 390 females) were randomly selected from three agro-ecologies (120 from lowland, 200 from midland and 200 from highland).
Live body weight measurement: Body weight of each experimental chicken was measured using spring scale.
Linear body measurements: Linear body measurements of beak length (BeL), body length (BL), body weight (BW), breast circumference (BC), comb length (CL), ear lobe length (ElL), shank circumference (SC), shank length (SL), wattle length (WL) and wingspan (WS) were determined (Table 1).
Data analysis: The data were analyzed using Statistical Analysis System (SAS) and Statistical Package for social science (SPSS). The correlation between live body weight and linear body measurements was determined using Pearson’s product moment correlation coefficient (r). Linear regression analysis of the linear body parameters was also performed using the following simple and multiple linear regression models:
Simple regression model:
Multiple regression models:
Y = B+β1X1+β2X2+ … +βkXk
: Dependent variable (body weight)
: Independent variables (BeL, BoL, CC, CL, ELL, SC, SL, WL, WS)
: The intercept
: The slopes
Mean values for body weight and linear body measurements of cocks and hens are presented in Table 2 a and b. There was significant (p<0.05) difference in all linear body measurements and body weight for cocks and hens.
Agro-ecology effect: Agro-ecology had significant effect (p<0.05) on body length, live body weight, Breast circumference, shank circumference, shank length and wingspan. However, had no significant effect (p>0.05) on beak length, comb length, ear lobe length and wattle length.
Sex effect: Sex had a significant effect (p<0.05) on all linear body measurement and body weight of chickens. Male chickens were higher than the female chicken for all linear body measurements and live body weight.
Sex by agro-ecology: Sex by agro-ecology interaction had no significant effect (p>0.05) on all the linear body measurements and body weight of indigenous chicken.
Correlation between linear body measurements and body weight: Live body weight had significant and positive correlation with all linear body measurements (Table 3). The strong, positive and significant correlations of live body weight with considerable traits can enable us in predicting the values of one trait based on the other trait.