Nigerian Fulani ecotype chickens - II – Estimation of growth curve parameters

In the study, growth curves of Nigerian Fulani ecotype chickens (NFEC) were modelled  under two production systems with four non-linear growth functions with a view to  establishing growth descriptors for NFEC. Two hundred, day-old chicks of NFEC were  obtained from an established population of NFEC. The chickens were separated randomly to  intensive and pastured poultry production systems at 12 weeks of age. Data on body weight  were taken weekly over a period of 20 weeks. Four non-linear growth functions including  Gompertz, Logistic, Bertalanffy and Richard's models were fitted using the NLIN procedure  of SAS while the best fit model was selected using the goodness-of-fit tests. For all the models, parameter (A), the asymptotic weight, ranged between 1800g and 2417g for male  and 1208g and 1550g for female chickens respectively. Parameter (B), the scaling parameter  ranged from 0.77 and 19.79. Parameter K, which is the maturity index, ranged between 0.16 and 3.97 for both sexes. The R values ranged between 0.9689 and 0.9987 for all the models  fitted. Gompertz and Bertalanffy models emerged as the best fit functions. Age and body  weight at inflection of NFEC were also predicted by the study. Growth curve parameters of  NFEC in the pastured poultry system were not significantly different from those in the  intensive system. The growth curve parameters estimated indicates that NFEC growth  performance can be improved through effective breeding strategies and improved  management practices.