The replacement of some of the soybean meal by the first‐limiting amino acids in practical broiler diets

Abstract

1. Four trials were carried out with broilers from 5 to 9 weeks of age in order to determine the effect of reducing dietary protein concentration, with and without special supplementations of methionine and lysine, on the amount of carcass fat. 2. In all trials fat deposition increased progressively as the protein concentrations of well‐balanced standard finisher diets were lowered by replacing soybean meal with sorghum grains (milo). 3. The increased degree of fatness was the result of graded increases in food consumption, and consequent decreases in food utilisation, caused by inadequate dietary protein. 4. In three out of four trials the above negative trends could be partly or completely reversed by special supplementations with methionine and lysine in amounts to restore the dietary concentration of these first‐limiting amino acids to those of the control diets. 5. It appears that broilers overeat in a compensatory attempt to obtain the limiting amino acids required for optimal growth rate, as long as the deficiency is not severe enough to cause an amino acid imbalance. Notes Contribution from the Agricultural Research Organisation, The Volcani Center, Bet Dagan, Israel. 1974 Series, No. 284—E.