Evaluation of growth curve traits and associated genetic parameters in Harnali sheep

Abstract

• Five non-linear models were used for fitting the growth curve data of Harnali male and female sheep. • Brody model was considered as most appropriate model on the basis of goodness of fit criteria. • Female lambs had high maturation rate but lower mature weights than male lambs. • The genetic variability among the growth curve traits was low in magnitude. The aims of the present study were to compare growth curve traits using various growth models and to estimate associated genetic parameters under most appropriate growth model using data records of weights at birth, 3, 6, 9 and 12 months of age pertained to 96 male and 196 female Harnali sheep for the period of year 2014–2018. Five growth models viz., Brody, Gompertz, logistic, Bertalanffy, negative exponential, were fitted and compared using goodness of fit criteria. Out of all models, Brody model was found to be most suitable model as it showed highest values of adjusted R 2 and lowest values of root means square error (RMSE), Akaike’s information criterion (AIC) and Bayesian information criterion (BIC). The estimates of growth curve traits viz., asymptotic weight (A), value for inflexion point (B) and rate of maturation (k) under Brody model were 36.35, 0.89 and 0.15 for male; 22.57, 0.84 and 0.27 for female; and 26.64, 0.86 and 0.22 for overall lambs, respectively. The least-square modelling showed that year of birth, sex and weight of ewe at lambing had significant (P < 0.05) influence on estimated growth traits. The female lambs showed high maturing rate but lower mature weights than male lambs. The estimates of heritability for A, B and k were 0.13, 0.15 and 0.15 respectively. The genetic correlation of k with A and B was positive. The low genetic variability among the growth curve parameters indicated that environmental variations must be controlled through appropriate measure in order to achieve desired growth and to set selection programs.