Tryptophan metabolism in pigs: relation to synthesis and function of serotonin.

Contrary to blood serotonin the level of free and total tryptophan is distinctly influenced by feed intensity and composition. Piglets show a considerably higher plasma free tryptophan and blood serotonin content than adult pigs, just as boars possess a significantly higher blood level of tryptophan and serotonin than sows. A pronounced individual variation of blood serotonin and a much less variable content among littermate pigs provide evidence that blood serotonin is genetically controlled. Tryptophan is readily absorbed and distributed in a characteristic manner among investigated organs and tissues. A genetical control of blood serotonin and its possible relation with type of reaction exhibited by ergometer exercised pigs support the influence of tryptophan and serotonin on the ability of pigs to withstand controlled environmental conditions such as physical exercise.