AvinespModel: predicting poultry growth, energy and amino acid requirements.

In Brazil, modelling isstill rarely used as there are no local models that can be applied as tools to optimize poultry or pig production. Aiming at filling this gap and stimulating interest in modelling in Brazil, the Nutrition and Modelling research group of Universidade Estadual Paulista (UNESP)-Jaboticabal developed the AvinespModel. The objective of this chapter is to present the theoretical background of the AvinespModel, to describe its structure, to demonstrate how it was evaluated, and to discuss its implications and future perspectives. The model estimates ad libitum feed intake, live weight, body composition and nutritional requirements of broilers and layer replacement pullets. It also estimates the response of an average chicken to a given feed and environment. Diet composition and chicken genotype are considered model inputs. Actual protein and lipid body mass are used as body state variables. The effective energy (EE) system, as proposed by Emmans (1994), is applied. Euler's integration method was applied to solve equations with one-day integration steps (dt). Rates are expressed on a daily basis, energy in megajoules and mass in grammes. In the model, feed intake and nutritional requirements of an animal are estimated as a function of its growth rate and body composition. The Gompertz (1825) equation is used in this model to describe protein deposition in the body and feathers based on biologically meaningful parameters. In order to estimate the desired lipid deposition, its ratio to protein deposition potential is established in the model. All the parameters required to describe specific genetic strains were obtained from studies conducted at the Poultry Science Laboratory of the Faculty of Agriculture and Veterinary Sciences (FCAV) at UNESP-Jaboticabal. The principle used to estimate feed intake in the model assumes that the bird attempts to eat sufficient to meet its growth potential (desired feed intake), considering its digestive capacity limitations and the environment. Estimates obtained with Avinesp for growth and responses to nutrient intake, health challenge and environmental temperature were consistent with the findings in the literature. Avinesp simulates the effects of different nutritional, feeding, health and environmental scenarios. Therefore, the proposed model, in addition to estimating nutritional requirements, may also be used as a tool to aid decision making by farmers and companies.