EVALUATION OF THE PROTEIN TO ENERGY RATIO CONCEPT IN BROILER AND TURKEY NUTRITION

The main objective of feed formulation should be to maximize profits, the difference between returns (growth response) and costs [feed intake (FI)]. For broilers and growing turkeys it is necessary to predict the BW and feed intake responses in order to estimate which protein and energy levels maximize profits for the producer. Data from the literature were collected to evaluate whether growth and FI responses can be better predicted from the dietary protein to energy ratio than protein and energy levels. The Ordinary Least Squares method was applied to estimate the coefficients (B(n)) of each model. The best model was selected through the J-test. The protein to energy ratio model was not selected in any case by the J-test. The model based on the protein and energy levels was selected by the J-test to predict the BW response in eight out of nine cases and to predict FI in six out of nine cases. A nested selection was performed to find models for each data set that only include coefficients that are significantly different from zero. The nested selection showed that BW and FI responses can be predicted successfully from protein and energy levels with coefficients of determination between .79 and .97 for broiler chickens and between .45 and .65 for turkeys. Nutritionists should consider the use of models, like the protein and energy levels model, that explain and predict BW and Fl responses. Future modeling research should consider important factors in broiler production, like age, sex, and temperature.