Studies on lysine nutrition of chicks

Effects of lysine deficiency on the incorporation of 14C-amino acids injected to chicks

Abstract

In our previous reports the effects of graded levels of lysine deficiency on energy utilization were studied. It has been indicated that chicks fed slightly lysine deficient diets had greater gain in tissue fat but a lower gain in protein. Quite severe lysine deficiency produced lowered efficiency of conversion of dietary metabolizable energy to tissue energy gain.
In this experiment, 14C-chlorella protein hydrolysate was injected intraperitoneally to chicks fed the diet containing 0.76, 0.91 and 1.06 percent lysine to study protein and energy metabolism under lysine deficient conditions. Six hours after the injection the radioactivity of excreta and expired 14CO2 were measured. Subsequently, the chicks were decapitated and the radioactivity of various body components were measured.
The results are following:
1. The incorporation of 14C into the carcass protein and the acid soluble fraction was lower with severely deficient lysine level. On the other hand, the incorporation of 14C into the protein in liver increased with severe lysine deficiency.
2. The expired 14CO2 of chicks fed the severely lysine deficient diet was significantly increased compared to that of the slightly eficient and the optimum fed chicks.
3. The incorporation of 14C into tissue fat was stimulated in chicks fed the slightly deficient diet and this higher incorporation was partly counterbalanced by the lower incorporation into the carcass protein.