The Use of Tryptophan in Shelter Dogs to Treat Stress-related Anxiety Disorders

Fifty-three sheltered dogs exhibiting high anxiety levels were studied for a period of six weeks in order to evaluate clinical responses to treatment with tryptophan. The effect of the diet on the behavior and fecal cortisol levels were assessed weekly throughout the study. The animals were randomly separated into two groups (Tip-1 and Trp-2) according to the amounts of administered tryptophan. Each group received the diet orally during the first week considering as a standard diet control; the Tip- 1 group received 0.6% of tryptophan and the Trp-2 group received 1.2%. Differences were found between the treatment groups. These differences were only significant (P<0.05) in regards to the social behavior during the final week. The results indicated that the dogs spent less time engaged in abnormal behaviors (P<0.05 and P<0.001) than in other behaviors. Likewise, significant differences in cortisol levels (P<0.05) were detected between the first and the sixth week. Cortisol values were lower, although not significantly (P>0.05) between the fifth and first week of treatment. No correlation was found between cortisol levels and the increase of behaviors studied.