Simulating responses of flocks of broiler chickens, muscovy ducklings and laying hens to varying dietary concentrations of amino acids or crude protein

Abstract

Simulating responses of flocks of broiler chickens, muscovy ducklings and laying hens to varying dietary concentrations of amino acids or crude protein.

Four models were developed to assess nutritional requirements and performance responses of broiler chicken flocks, muscovy duckling flocks and layers flocks to varying dietary concentrations of amino acids or proteins. The models were based on individual estimations of requirements expressed as amino acid or protein concentration of the diets (g/kg). Requirement distributions were very close to normal. All nutritional responses of flocks were curvilinear. The models allow to assess the effects of genetic characteristics of individuals (growth rate, fatness, energy efficiency) on nutritional requirements. Lastly, these models led to an economical approach of nutritional requirements. In growing birds, growth rate has a very limited effect on amino acid requirement expressed as dietary concentration. On the contrary, body lipids and efficiency of energy utilisation for maintenance have a pronounced effect on these requirements ; lean or efficient birds require diets concentrated in these nutrients. In laying hen, egg mass is the main factor explaining amino acid requirements. Body weight and efficiency of energy requirements for maintenance also have significant, but less pronounced effects.