Amino Acid Supplementation of Low Protein Layer Diets

Experiments were conducted at the South Dakota State University Poultry Research Center to study the effects of amino acid supplementation of low protein diets on performance of laying type hens. Hans, housed in 8-inch cages, were fed at 24 weeks of age typical 16% protein corn-soy diets diluted with glucose to 10.8% protein and supplemented with 0.15% DL-methionine, 0.19% L-lysine and 0.04% DL-tryptophan. After about 20 weeks of depletion, supplements of 0.05 and 0.1% DL-threonine and DL-valine and 0.1% DL-isoleucine alone and in all combinations were fed for a further period of 16 weeks using a factorial design. Individual supplements of threonine and valine did not show any improvement in egg production, feed consumption, feed conversion or egg quality. Isoleucine at the 0.1% level showed a highly significant improvement (P<.01) in egg production. Both low and high levels of threonine and valine when supplemented in equal proportions showed improved egg production, but it was not superior to that observed with isoleucine supplementation alone. Egg size and egg quality were not influenced by the above dietary supplementations. Based on the above performance, hens in a second study were fed the above basal diet further supplemented with 0.1% DL-isoleucine. They satisfactorily maintained egg production comparable to that of hens receiving 0.1% DL-isoleucine Supplementation in Experiment 1. Supplemental effects or single and combined 0.05 and 0.1% levels of threonine and valine with 0.25 or 0.5% glycine supplements were studied for a 16-week period, following 16-week depletion period. Neither the low nor high level of glycine showed any improvement in egg production or feed efficiency. The combined low levels of glycine and valine were somewhat effective in improving egg production and feed efficiency. However, hens on the combined high levels of glycine and threonine laid at a 10% higher rate more efficiently than hens on the basal diet. Plasma levels or free amino acids somewhat reflected the effects or dietary supplementation upon egg production and indicated that 0.1% threonine effectively supplemented the basal diet. The excess dietary glycine probably caused more effective utilization of threonine for increased egg protein synthesis. Hens fed the 10.8% protein diet supplemented with amino acids produced eggs with less essential amino acids in the albumen than hens fed a 16% protein diet. This indicates that further work is needed on the low protein diet to produce eggs with more optimum amino acid levels.