While no specific foods have been linked to aggression in dogs, some studies show that overall dietary protein levels can have a statistically significant effect on some types of canine aggression. Other research suggests that dry dog food ingredients like food colorants, soy protein and sugar can influence behavior. Additionally, supplements like tryptophan may lower aggression.
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Types of Dog Aggression
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Dog aggression is complex and often poorly understood. Very often what looks like aggression is fear or stress. A fear-aggressive dog will threaten and can bite if she feels cornered. A territorial-aggressive dog may act much the same way, but because he feels compelled to meet a challenge or protect territory, not out of fear.
A dog who chases and even kills other small animals, including smaller dogs, is often operating out of prey drive: the instinctual urge to bring down prey for food. This is not considered classic dog-aggression, where the dog will challenge and fight other dogs to prove dominance. Many dogs can be unsafe around dogs and other animals, yet loving and gentle with people.
Very dominant dogs will challenge their owners or anyone else just because they can. These dogs often make excellent pets and superior working or sport dogs, but need firm, consistent and experienced owners.
Canine personalities are in part predetermined by genetics; hardwired if you will. However, it is most often the behavioral cues, training and care they receive from their owners that determine how they direct and control their aggression. Dietary choices may be part of the care that influences dog aggression.
Protein Levels and Aggression
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According to research by Dr. Nicholas Dodman at Tufts College of Veterinary Medicine in 2000, fear-aggressive behavior was significantly reduced in dogs fed a low (17%) protein diet when compared to medium (25%) and high (32%) protein diets. The same study concluded that dietary protein had no effect on dominant-aggressive dogs.
This study confirmed numerous earlier studies linking high protein levels with different types of aggression. The speculation is that high protein levels in the food provide an over-abundance of amino acids, essentially crowding out the amino acid tryptophan. Tryptophan is essential for seratonin production, which has a calming and stabilizing effect on canine behavior.
Tryptophan Supplements
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Other research compared dogs supplemented with tryptophan to dogs receiving no additional tryptophan in the diet. Even when given to dogs receiving a high-protein diet, dogs with dominant and territorial aggression showed statistically significant lower levels of aggression.
In a Tufts study of tryptophan supplementation, the dogs were given the supplement with food orally twice a day, at one mg per pound of the dog's weight. There may be some side effects, including vomiting and diarrhea, from tryptophan. Consult a veterinarian before giving it to your dog.
Other Ingredients
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Other ingredients in dog food are suspected of causing aggressive behavior, but have not been extensively studied. Some experts suspect soy protein (a common dry pet food ingredient) containing plant estrogens may upset hormonal balances, thus causing hyperactivity and aggression. Some research has focused on the long-term effects of synthetic food colorants and preservatives on the physical and mental well-being of dogs. Feeding a high-quality dog food with few additives and natural preservatives alleviates some of these concerns.
Expert Insight
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While food and diet may certainly affect canine behavior, including aggression, merely changing the diet is only part of the solution. Enlist the help of a qualified trainer or behaviorist if you are concerned about your dog's aggression.
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