Modelling Growth Curves in a Nondescript Italian Chicken Breed: an Opportunity to Improve Genetic and Feeding Strategies

Growth, known as the relation between liveweight and age, is explained mathematically by functions that have parameters with biological meaning. These parameters are used to describe growth pattern over time and to estimate the expected weight of animals at specific ages. Animal growth generally follows a sigmoidal pattern and several nonlinear functions have been used to describe it. This study was carried out to estimate the parameters of logistic, Gompertz and Richards growth curve models in a nondescript chicken breed population from southern Italy to determine the goodness of fit. Male and female birds were weighed weekly starting from two to twenty-four weeks of age. Based on our dataset, chickens showed a slow-growth pattern. All the growth functions evaluated were easily fitted to the observed data by nonlinear regression; our findings showed that Gompertz model fitted liveweight data very well both for male and female birds being the best model for studying the growth of our animals. Nevertheless, the four-parameter Richards function provided also a good fit of the data. Success in studying the growth characteristics of our nondescript chicken breed will contribute to define appropriate feeding regimens and to develop selection programme.