Food allergies have been recognized in animals for many years. In normal animals, the gastrointestinal (GI) tract differentiates between nutrients and potentially harmful substances, such as bacteria. Antigens that bypass the intestinal mucosal barrier can be eliminated in the lymph nodes and liver. Because foods are potential antigens, oral tolerance (recognition) develops in animals soon after weaning to allow absorption of small peptides, amino acids, and other nutrients. An allergic reaction to food suggests a defect in oral tolerance.
Understanding Food Allergies in Dogs
The Cardinal Sign: Pruritus
The cardinal sign of food allergy in both dogs and cats is pruritus. The pruritus is nonseasonal and continuously present.
Skin and Gastrointestinal Manifestations
Dogs can exhibit various primary and secondary skin lesions, including papules, erythema, excoriations, pustules, epidermal collarettes, hyperpigmentation, and seborrhea. GI disorders occur in some animals with immunologic food allergy, and the signs tend to be nonspecific and intermittent or chronic. Acute GI signs are more likely associated with nonimmunologic food intolerance (diet-responsive enteropathies).
Diagnosing Food Allergies: The Food Trial
A diagnosis of food allergy requires a food trial, which is a 2-step process. First, the animal is introduced to an elimination diet. Commercial laboratories may offer serum testing. Typically, IgE or IgG antibodies directed against foods are measured. Both false-positive and false-negative results are common. Practitioners using serum testing for environmental allergens (atopy) should avoid ordering food allergy panels because clients become convinced that their pets cannot tolerate foods listed as “allergens.” This will limit food options (false positives) or lead to inappropriate choices for a food trial (false negatives).
The Role of Novel Proteins
Novel proteins are rare or unique animal proteins that are less common than the chicken or beef found in many dog food formulations. Introducing novel protein dog foods into your dog’s diet can provide the unique amino acids and other nutrients that would otherwise be missing from eating solely chicken- or beef-based foods. Also, some proteins are known as “heating” or “cooling” proteins and can have a significant effect on a dog’s internal body temperature to prevent overheating.
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What are Novel Protein Diets?
Novel protein diets include ingredients, such as rabbit, venison, fish, duck, or kangaroo, on the theory that other commercial pet foods rarely use these ingredients, so previous exposure in patients is not likely. Unfortunately, more and more OTC retail products are becoming available with these ingredients. Most novel protein veterinary diets are formulated for adult maintenance, not growth or reproduction.
Veterinary vs. Over-the-Counter Options
A number of pet foods can only be distributed by veterinarians who dispense the food in the context of a veterinarian-client-patient relationship. Many pet food companies have introduced products that contain unusual or novel ingredients. However, retail foods are not specifically formulated as medical diets to be used in the diagnosis and treatment of disease. The ingredient lists may contain protein sources not advertised on the front of the label, so a careful evaluation is necessary. Veterinary novel protein and hydrolyzed diets are preferable to OTC commercial foods.
Exploring Different Novel Protein Sources
Bison
Bison has one of the highest protein contents of all meats, making it an ideal choice for high protein dog food. But it is still considered a “lean protein” because it is relatively low in saturated fat.
Venison
Meat that comes from deer is known as venison, and it’s a naturally low-fat, low-cholesterol protein that also provides a number of other important nutrients. Venison dog foods can be great for weight loss and can also help boost energy levels.
Lamb
Lamb is perhaps the most common among novel proteins because it is featured in many popular dog food formulations. But that doesn’t mean the health benefits of lamb dog food should be overlooked. Lamb has a higher iron content compared to chicken and can be a great alternative to beef and chicken for dogs with allergies.
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Wild Boar
Wild boar protein is an excellent novel protein because in addition to providing a number of essential vitamins and nutrients, it is also a hypoallergenic protein.
Pork
Pork protein is relatively easy for dogs to digest and contains more calories per pound compared to many other types of animal protein. This can make pork dog food a good choice for dogs that are underweight or who have digestive issues. However, pork also contains a higher fat content than some other proteins.
Duck
Duck protein is generally lean, easy to digest and contains a wealth of nutrients and amino acids that contribute to strong muscle growth. Duck protein is known as a “cooling protein” that may benefit dogs that are more prone to overheating, especially during summer months.
Quail
Quail eggs have been called a “superfood” for humans, and quail protein offers much of the same nutritional value for dogs. Quail dog food formulations are rich in calcium, zinc and essential vitamins, but are generally lower in calories-per-pound compared to other proteins. This is why quail can be a healthy ingredient for dogs on a weight loss diet.
Turkey
Turkey contains a variety of amino acids as well as magnesium, phosphorous and zinc, all of which can contribute to a healthy coat and strong bone development. Turkey dog food offers lean protein and can be a good novel protein alternative to chicken-based dog food formulations.
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Trout
Trout can be a welcome addition to a high-protein dog food diet because it is packed with protein while remaining relatively low in fat.
Menhaden Fish
Many people haven’t heard of menhaden fish because it isn’t likely to be on the menu at your local seafood restaurant.
Whitefish
Whitefish offers lean protein that can assist in weight loss while also providing a number of other health benefits. Whitefish dog food is high in B vitamins, omega-3 and omega-6 fatty acids, taurine and selenium which is an antioxidant that can also promote a strong immune system.
Other Considerations for Food Trials
Client Compliance is Key
The main challenge of performing a food trial is client compliance. No matter which foods are chosen, the trial will fail if owners feed treats, snacks, rawhides, pig ears, human foods, and flavored supplements or if pets have access to scraps, garbage, outdoor feeding, etc. The medical records should be reviewed to make sure flavored medications have not been dispensed.
Home-Prepared Options
Dogs and cats can be fed ingredients intended for human consumption. A wider variety of foods can be used, and are not limited to those sold by pet food companies. Typically, one protein source (eg, meat, fish, beans, tofu) is combined with one carbohydrate source (eg, rice, potato, oatmeal).
Hydrolyzed Diets as an Alternative
Hydrolyzed diets are not designed to be novel. Instead, they are formulated to provide small peptides instead of intact proteins and large polypeptides. Hydrolyzed protein sources include soy, chicken, and chicken liver; these sources are added to carbohydrates, such as rice, potato, or starch from corn or potatoes.
Addressing the Term "Hypoallergenic"
The term hypoallergenic is actually incorrect, as all foods are antigenic in that they are foreign proteins.
Monitoring and Management
Expected Response Time
Animals with immunologic food allergies and food-responsive enteropathies will usually respond positively to food trials within 4 to 12 weeks.
Challenge Testing
A challenge test should be performed once the animal is free of significant clinical signs. Most animals will relapse or develop clinical signs within 1 to 2 weeks (sometimes just a day or two) when fed small amounts of the allergenic food.
Prognosis
The prognosis is excellent for food-allergic animals, as long as the allergenic foods or ingredients are identified and avoided.
Optimizing a High-Protein Diet
Variety is Beneficial
The best high-protein diet has a variety of meats and protein sources because of all the nutrients and amino acids dogs get from rotating them. That’s why Full Circle Feeding is the best approach for feeding your dog a high-protein diet.
Hydration is Crucial
With higher protein levels, more moisture intake and hydration is needed to support digestion. So, it’s good practice to mix in wet foods with dry kibble when introducing other proteins.
Freshness Matters
Buying smaller bags will help maintain the food’s freshness while allowing you to rotate your pet’s food more often.