[The effect of dietary lysine excess and deficiency on metabolism in Japanese quail]

We conducted three experiments with Japanese quail to study the influence of deficient and excessive contents of lysine in the feed in relation to certain zootechnical parameters, protein value, to the active of liver xanthine dehydrogenase, content of free plasma lysine under the conditions of the maximum saturation of blood pool, and to the changes in 14C-labelled lysine degradation. The zootechnical parameters and protein value were optimum at the content of 5.22 g Lys per 16 g nitrogen in the feed, the activity of liver xanthine dehydrogenase was maximum. In a separate experiment the maximum saturation of blood pool determined with respect to a lysine supply in the feed reached the highest value at 6.88 g Lys per 16 g nitrogen and it decreased later on although the lysine supply increased. We assume the existence of a regulating mechanism that does not allow exceeding certain lysine concentrations in the blood plasma. Lysine degradation measured by the value of 14CO2 expired from 14C-labelled lysine was higher both with lysine deficient and excessive content, than with the lysine content in the feed approaching the required value.