"Effect of Dietary Protein Content and Tryptophan Supplementation on Dominance Aggression, Territorial Aggression, and Hyperactivity in Dogs"
The prospective crossover study dealt with 11 dogs diagnosed with dominance aggression, 11 dogs with territorial aggression, and 11 dogs with hyperactivity (diagnosis made by a behaviorist on basis of history and clinical findings).
Note: In the descriptions of criteria for these dogs, there is no mention of exercise or mental stimulation in their daily routine. I think this crucial.
They placed each of the dogs on 4 diets, fed 1 week each in random order with a transition period of not less than 3 days between each diet. Minimal total duration was 40 days for each dog.
Two diets had low protein (LP) content (approx 18%), and two diets had high protein (HP) (approx 30%). Two of those diets, 1 HP and 1 LP, were supplemented with tryptophan (trp).
Based on the week of feeding, the dogs' owners were asked to score their dogs daily for dominance aggression, territorial aggression, fearfulness, hyperactivity and excitability.
Not taking into consideration what is defined as dominance or territorial aggression, fearfulness, hyperactivity or excitability, and not taking into consideration an outlet, physically and/or mentally of the dogs involved in the study - the results showed that dogs fed the HP diet without Trp supplementation had the highest (least manageable) dominance score for all above issues. Dogs fed the LP without Trp diet had the highest territorial score. Hyperactivity and excitability were not significantly altered by either diet.
As Trp is a known "natural serotonin solution", I believe the use of it during the protein study should remain seperate from results of just feeding the non-supplemented food. Obviously, if Trp is used as a mood regulator, and said to help children with ADD, it logistically will help calm and or regulate certain behaviors in dogs at appropriate dosages.
The above study was funded by Hills.