Modelling responses of broiler chickens to dietary balanced protein

Protein is an important nutrient for growing broiler chickens, as it affects broiler performance, feed cost as well as nitrogen excretion. The objective of this dissertation was to develop a growth model for broiler chickens that could be easily used by practical nutritionists. The model should facilitate the selection of feeding strategies (in terms of dietary protein and energy)<span class=GramE>that results</span>in the desired body composition of broilers while minimizing costs.</span><p class=MsoNormal><span lang=EN-GB>Two important theories that are generally used in animal growth models were validated for broiler chickens. It was confirmed that, where protein is limiting, protein deposition rate will not increase with additional energy intake. The second theory, stating that the fat-free body composition is independent from nutrition, is not a valid assumption for broiler growth models.</span><p class=MsoNormal><span lang=EN-GB>It was demonstrated that broiler responses to dietary balanced protein level (DBP) depend on previous protein nutrition. These results suggest that DBP levels in grower and finisher diets should not be optimised independently, but simultaneously.</span><p class=MsoNormal><span lang=EN-GB>A model was developed that predicts broiler responses (growth rate, feed conversion ratio, carcass yield and breast meat yield) to DBP level. The model makes it possible to construct tailor-made dose-response curves without actual experimentation.</span><p class=MsoNormal><span lang=EN-GB>Based on the predictions by this new model and data on feed and meat prices, the economic aspects of DBP level in broiler diets were evaluated. It was shown that formulating diets for maximum profit instead of maximum broiler performance may strongly increase profitability of a broiler production enterprise. Model simulations revealed as well that DBP level for maximum profitability depend on how the broilers are marketed; as whole birds, carcass or cut up