By Dr. I Elizabeth Borgmann.

In the previous article we addressed what little information could be gleaned from a pet food label. I want to discuss the purpose of various ingredients in the pet food diets and perhaps bust some myths.

But first you must understand what the basic nutrient categories are and what your pet might need.

Both dogs and cats are classified as carnivores, but based on dentition, gastro intestinal length and amino acid requirements, cats are true carnivores and dogs are omnivores. That means you can make a vegetarian diet for dogs but will never be able to make a similar diet for cats.

What is important in proteins is the amino acids (the protein building blocks). Dogs can make some of the amino acids from precursors but cats cannot. They need meat sources for those particular few amino acids. Cats need added arginine, taurine, methionine and cystine.

The body only needs so much protein for growth and rebuilding and the rest will be used for calories. Adult cats need about twice the proteins that adult dogs do and young growing animals need more protein than adult pets. An adult cat needs about 12 mice per day to meet their nutrient requirements.

The body does not care about the source of the proteins. It doesn’t matter if it comes from chicken, beef, lamb or plants as long as it gets what it needs. In other words, the source doesn’t matter (as long as your pet does not have allergies).

Can you have too much protein? Foods can have anywhere from 15 to 60 per cent protein. To start with, excess protein is not needed. More is not better. Excess protein is turned into calories. If a pet has kidney disease, the body can’t keep up with the protein break down and it is too much of a strain on the kidneys.

The right level of protein for the life stage is important. This is one of the problems with diets that state they are good for all life stages. As well, as a pet ages, a better, more ‘perfect’ protein level (based on amino acids ratios) is needed.

Carbohydrates are used for energy only. Again, the source does not matter. It can be wheat, corn, or rice. Of all the life stages, the greatest need for energy occurs 3 to 5 weeks post whelping.

Excessive energy can have a negative effect on bone development in growing dogs. Some research into diets designed to augment cancer treatment suggest a high protein and high fat diet is best because cancer cells use carbohydrates as a source of food.

Fats are very important in the diet. They absorb and transport fat soluble vitamins, and provide essential fatty acids (EFA’s). Two EFA’s are linoleic and linolenic fatty acids. EFA’s are just that – essential – for the skin, coat, brain and retina.

Fat needs to be present in diets, but growing large breed dogs need less fat. Some older pets need more fat for calories and to improve the absorption of vitamins. What fat level an older pet needs depends on its body condition score.

Anti-oxidants must be present in diets as well. Vitamins are also essential. Fat soluble vitamins include A,D,E and K. Water soluble vitamins are the B complex vitamins and Vitamin C. Cats need additional niacin (preformed vitamin A) found only in animal tissue. Dogs can make this from tryptophan. Cats need four times the amount of B vitamins. An excess of fat soluble vitamins can be toxic.

Macro minerals include calcium, phosphorus, potassium, sodium and magnesium. Micro minerals include iron, zinc, copper, manganese, iodine, cobalt and selenium. Many, if not most, pet foods have too much calcium and most home cooked diets have too little. Phosphorus tends to be too high in both home and pet foods.

Pet foods tend to be high in sodium chloride (salt). Minerals interact. You need a balance. For example, more than 1500 mg of iron is toxic. And more than 4% calcium adversely affects the absorption of magnesium.

Growing large breed dogs need less calcium than smaller puppies. There is good reasoning behind regular and large breed puppy diets. Breeding animals need 2 to 5 times the amount of calcium compared to pets on a maintenance diet.
The most important mineral issue for pets is calcium and phosphorus.

Twenty five percent of young dogs have kidney issues. Too much phosphorus (home cooked diets) and too much calcium/phosphorus (commercial diets) can have a detrimental effect on the kidneys.

Because you do not see kidney disease until 75 per cent of kidney function is lost it is important to use quality foods that have adequate but not excessive calcium phosphorus ratios.

There is debate about the importance of the different levels of sodium and chloride. If hypertension or kidney disease is present, excess sodium chloride is detrimental. Pets with heart disease should have a diet lower in sodium chloride.

Mineral levels are also important for cats and preventing lower urinary tract issues. The urinary pH (acidity) must be controlled and there should not be an excess of magnesium or phosphorus. Science is now getting to a point that it almost knows what is needed and in what balance but research continues.

Fibre is another component of diets. There are different types of fibre and different uses of fibre. There is fibre to help with hairballs. And fibres to help with gastro intestinal motility. There are fibres to help maintain a healthy bacterial population in the bowels. There is fibre to form kibbles to help reduce dental tartar.

Additional components may be added to a diet for specific purposes. Older dogs and breeds predisposed to hip dysplasia or arthritis may be on diets with supplemental glucosamine and Omega 3 fatty acids. Are those levels at preventive or therapeutic levels? Pets with behavioural problems may have added Omega 3 fatty acids.

More confused than ever? No, it is not easy to choose a pet food.
This is where your veterinarian plays a role. They need to look at life style, age, breed and breed related disease predisposition, reproductive state, weight, physical exam findings and laboratory findings to help you choose an optimum diet.

The diets in the store are for healthy puppies and kittens, adults and senior pets with no underlying health issues. And even there, some foods are better than others.

Dr. Borgmann has been practicing in the Fraser Valley for over 8 years and can be reached at the Whatcom Road Veterinary Clinic