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  6. Effect of Dietary Protein Content and Tryptophan Supplementation on Dominance Aggression, Territorial Aggression, and Hyperactivity in Dogs

Effect of Dietary Protein Content and Tryptophan Supplementation on Dominance Aggression, Territorial Aggression, and Hyperactivity in Dogs

Jean S. DeNapoli, Nicholas H. Dodman, Louis Shuster, William M. Rand,  Kathy L. Gross, 2000


L-tryptophan is a biosynthetic precursor for the neurotransmitter serotonin. It has been hypothesized that decreased concentrations of this amino acid would lead to reduced formation of serotonin and possibly more aggressive responses to stimuli in dogs. Three groups of dogs with dominance aggression, territorial aggression, and hyperactivity respectively were fed diets differing in protein and tryptophan levels. It was found that, for dogs with dominance aggression, adding tryptophan to a high-protein diet or changing to a low-protein diet may reduce aggression. For dogs with territorial aggression, a low-protein diet with added tryptophan may be helpful in reducing aggression. The behavior of hyperactive dogs was not influenced by dietary protein content or addition of tryptophan.

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  1. I find the information about tryptophan interesting, but I find the conclusions about protein very flawed when you look at the diet in the study. The high protein diets used, compared to the low protein diets also have a very low fat content compared to the low protein diets. Therefore the study can just as well be interpreted as “low fat diets contribute to aggression”. It is ultimately an uncontrolled study.
    Anyone reading this study may also find the study on fats and aggression interesting that was conducted 7 years later: https://www.dogtraining.world/knowledge-base/aggressive-dogs-characterized-low-omega-3-polyunsaturated-fatty-acid-status/

  2. Very interesting article. Supposedly even in people, tryptophan has a mild sedation effect. I’ve been told that is why people feel so drowsy after eating turkey on T-day. Supposedly, turkey has a high level of tryptophan. So I wasn’t surprised that it had an effect on dogs. So I did a little research and I looked at Athena’s calming chews. Each chew has 17 mg of tryptophan. Her dose for her weight is four chews, so her intake would be 68mg. I don’t give her the “calming” chews as a supplement daily mainly because they tend to be expensive. Usually, I save them when I take her to the veterinarian. It is hard to quantify the effectiveness of that one dose. Also, the chews have other ingredients such as hemp, chamomile, valerian root, and passion flower. So as a little experiment, I will go to the health food store and get pure tryptophan and give Athena 68mg daily and see if that has an effect on her behavior. I will monitor her behavior and use a daily journal to report my findings. I will track her behavior in general and try to quantify it in the following ways including 1) her reactions to other dogs when I am driving. 2) her reaction to other dogs walking by. 3) her reaction to the UPS driver and the mailman and 4) her reaction to other dogs in various settings and 4) her performance in her scent work practice and competitions. The last being is very important to me because she is very, very good. I want her to be able to walk around the competition grounds without being known as a dangerous dog. All of this will hopefully help with the behavior problems and make it easier to implement the work I am doing for her aggression. I’ll take any other suggestions. Let me know.