Abstract
Poultry rations utilizing maize as the main ingredient are commonly deficient in tryptophan. White Leghorn pullets producing about 85% of eggs were fed maize-soybean meal type diets containing graded leves of tryptophan: 0.066% (60% of the requirement), 0.097% (88%), 0.128% (116%), 0.221% (201%) and 0.721% (655%) in Groups 1, 2, 3, 4 and 5, respectively. Minerals, vitamins and amino acids other than tryptophan were added to the diets to meet the requirements. Group 6 was fed the commercial laying diet as a control. As a result, no significant difference in egg production was found among the groups in the first 5-day period, but thereafter Groups 1 and 2 showed reduced egg production. Egg weight of Groups 1 to 3 was decreased with the lapse of time, whereas that of Groups 4 to 6 was increased. Reflecting these results, the daily egg production on a weight basis decreased from the initial to the final stage, the difference between both stages being largest in Group 1 followed by Groups 2, 3, 5 and 4. Feed consumption was also decreased by the deficiency in tryptophan in the order to the extent of deficiency. The birds of Groups 1 to 4 lost their body weight, whereas those of Groups 5 and 6 did not. These results demonstrate the rapid ill-effect of tryptophan deficiency on the egg production and the absence of any ill-effect of tryptophan excess. It is suggested that the tryptophan requirement of laying pullets is more than 0.11% of the diet; should preferably be 0.17% as recommended by MORRIS and WETHLI.
The author thanks Mr. K. ASAKURA and Ms. M. KOMIYA for their technical assistance.
