Determination of the Minimum Crude Protein Requirements of Broiler Starters and Finishers in the Tropics

Abstract

THREE experiments were conducted with broiler chicks to determine the minimum crude protein levels in the diets of broiler starters and finishers reared in a tropical environment. The first two trials covered both the starter and finisher periods of 12 weeks while the third experiment covered only the finishing period. The calculated dietary crude protein levels used in the first trial were 14,16 18, 20, 22 and 24%; in the second trial, 20, 22, 24 and 26% and in the third trial, 14, 16, 18 and 20% on air dry basis. Results showed the 24% crude protein (trial 1) and 26% crude protein (trial 2) diets promoted highly significantly better live weight gains than all the other rations during the starter period while during the finishing period, there were no significant differences in the liveweight gains on the diets containing 18, 20, 22, 24 and 24% although growth was always better on the higher protein diets. Diets containing 14, 16 and 18% crude protein were grossly inadequate for the broiler starters while during the finishing period, if all the birds were on adequate broiler starter diets before being put on finisher diets, all those diets promoted growth almost equally well, there being no significant differences among growth rates. The feed/gain ratios followed the same trends as obtained for growth rates, the ratios becoming significantly better for higher protein diets. Mortality was highest for the lowest protein diets and lowest for the highest protein diets, while the percent nitrogen retained tended to be better, though not significantly so, for the higher protein diets. On the basis of these studies, it is recommended that the diets of broiler starter chicks in the tropics should not contain less than 24% crude protein, while those of the finishers should not contain less than 18% crude protein on air dry basis for optimal results.