The influence of dietary methionine, protein, and energy levels on glutamic-oxalacetate and glutamic-pyruvate transaminases of chicken.

The variations were tested in dietary methionine, protein, and caloric density on the glutamic-oxalacetate transaminase (GOT) and glutamic-pyruvate transaminase (GTP). The GOT was not affected by the protein and methionine levels either in the plasma or liver. Plasma GTP tended to increase (P less than 0.01) between 0.28% and 0.44% methionine levels in experiment I and between 0.26% and 0.50% in experiment 2. In the liver, the GTP activity was similar in both experiments. The interaction between methionine + cystine and protein was significant in their effect on the GTP activity. This enzyme decreased in the plasma with increasing methionine + cystine level, while it increased with increasing protein level. The GTP activity was negatively correlated (r = -0.52) with the energy level in the liver. From the trends of the GTP activity, the minimum and optimum methionine levels in broiler diets can be derived.