The nutrition of meat-type ducks. 2. The effects of variation in the energy and protein contents of diets on biological performance and carcass characteristics

Abstract

In three experiments, ducklings aged 2 or 3 weeks were grown to 8 weeks of age on diets containing from 12 to 25 % crude protein, and from 11 .6 to 15.2 MJ metabolizable energy (ME)/kg 'as fed'. Generally the highest growth rates and best feed conversions were observed on diets with the highest energy content. A dietary protein content of about 12% was adequate for maximum growth, best feed conversion, and the highest protein efficiency ratio. Where comparison could be made, males grew faster than females. ME contents of the diet determined by total collection of excreta or its estimation using Cr2O3 were in good agreement. ME values for the diets declined as ducklings aged, as did nitrogen balance. Carcass protein decreased and carcass fat increased as the energy (kJ) to protein (%) ratio increased. Dressing percentage tended to increase with increasing dietary energy. Females had higher dressing percentages than males. It would appear that, for best growth rate and feed conversion, a low protein of 12-13 % and a high energy diet of about 14.0 MJ ME/kg, corresponding to an energy to protein ratio of about 1000, are adequate for ducks grown from 2 to 8 weeks. For maximum carcass lean, and minimum fat content, a low energy (kJ) to protein (%) ratio of about 600 is desirable. This corresponds to dietary concentrations of about 15 MJ/ME kg of diet and 24% crude protein.