Also called · growling · nipping · turning aggressive · aggressive behaviour
What it looks like
- Growls or shows teeth at family members
- Overreacts to strangers and other dogs
- Gets wound up by small triggers
Why it happens
Study 1 — severe aggression fell on low and moderate protein
Dogs with dominance-type and territorial aggression and a tendency to hyperactivity were fed low (17%), moderate (25%) and high (32%) protein diets for two weeks each. In dogs with fear-related territorial aggression, severe aggression decreased on the low and moderate protein diets. (Dodman et al., JAVMA 208:376-379, 1996)
Study 2 — adding tryptophan split the outcome
Four diets compared high (30%) and low (18%) protein with and without added tryptophan. In dogs showing aggression toward their owners, the high-protein diet without tryptophan significantly increased aggression, while in territorial aggression, the low-protein diet with tryptophan significantly reduced it. No effect was found on fear-based aggression, hyperactivity or excitability. (DeNapoli et al., JAVMA 217:504-508, 2000)
Why low protein plus tryptophan
Tryptophan is the precursor of serotonin, the neurotransmitter involved in emotional balance. When brain serotonin falls, animals become anxious or aggressive. But tryptophan makes up less than 1% of most proteins and has to compete with the other large neutral amino acids — abundant in high-protein diets — to cross the blood-brain barrier. Lowering protein and adding tryptophan improves its odds in that competition, so more reaches the brain.
Not giving too much protein is the safer side
Dogs are reported to prefer a diet at 30% protein and to eat more when it is lower. But since high protein is implicated in aggression, it is better not to overdo protein where problem behaviour is a concern.
Nutrition before birth matters too
Protein and calorie deficiency has a large effect on the behaviour of young animals. Offspring of undernourished mothers showed physical abnormalities together with a markedly nervous, irritable disposition, and puppies fed a corn-based protein-deficient diet are also reported to become nervous.
What to do
Rule out pain and disease first
Pain can raise anxiety and aggression and bring problem behaviour to the surface or worsen it. Medical investigation comes before behaviour work.
Check the protein level of the food
Start by finding out whether the current food is high-protein. No food is marketed specifically for treating aggression, but the view is that a renal therapeutic diet may serve as a substitute given its low protein.
Keep behaviour modification at the centre
Dietary change is a support, nothing more. Run it alongside counselling from a behaviour specialist.
Create an outlet
An environment where natural behaviour cannot be expressed produces boredom and frustration, and is a predisposing factor for every problem behaviour. Fill it with walks, play and scent work.
Watch out for
The low-protein and tryptophan approach is described as something to try as an adjunct to behaviour modification, and no more. It is not a problem that food alone fixes.
Amino acid imbalance causes loss of appetite. Adding tryptophan needs care.
The concept of "dominance aggression" is now largely rejected, so reading it as "a dog highly aggressive toward its owner" is the sounder interpretation. Training aimed at establishing rank has weak support.
See a vet if
Has bitten a person
Attacks suddenly with no warning
Personality changed abruptly — rule out pain and neurological disease
Common questions
What the studies found was a significant reduction in particular types of aggression, and the effect size was not dramatic. Treat it as a support to behaviour modification.
Adding it on your own is not advised, as an amino acid imbalance can cause loss of appetite. Talk to your vet.
Related behaviors
Was this useful?
General behaviour and nutrition information. It does not replace diagnosis or prescription. Similar behaviour does not always have the same cause, and the cause is not necessarily diet or environment — have a vet rule out illness first, and consult a behaviour specialist where needed.