Variety is the spice of life, and that's not just true for people. Dogs and cats enjoy a change in the routine too. Nowhere is this more relevant than in our diets. The major pet food companies want pet owners to believe that it's best to feed the exact same food throughout a pet's life. That kind of loyalty is fantastic for the corporate bottom line. It's not, however, fantastic for us. In fact, it can be detrimental to our health.

All mammals do best when they eat from a broad spectrum of foods, getting different vitamins and minerals from each. Our bodies usually function at optimum levels with periodic changes in diet. Many people do not realize that allergies often build up gradually because of excess exposure to one food. Of course, some allergies are immediate, but many are not. In other words, it is very common for a dog or cat who has been fed one protein all of his or her life to develop an allergy to it.

Most pet nutritionists recommend rotating food on a regular basis. Once every few months is a comfortable guideline for many pet owners. If, however, a dog or cat is not sensitive to change, it's perfectly okay to rotate the diet frequently. In my case, for instance, all of the dogs in my house switch proteins several times monthly. We've lived this way since we were puppies, so we're not very sensitive to change.

Some animals, however, are a little more sensitive, so it's always a good idea to transition a bit slowly. Mix food for about five days before switching completely. A good formula is 75% old food and 25% new for two days; 50% and 50% for one day; and 25% old and 75% new for two days. Some animals will not require this, but it's wise to err on the conservative side just in case there are digestive issues.

The return for a little effort will be a healthier and happier pet who will not become bored with his or her diet. In addition, you will be able to take advantage of all of the advances in the pet food industry. Feeding one food over the course of a pet's lifetime means that your dog or cat will never benefit from the great new options that are constantly on the market. The very best food today will most assuredly not be the very best food 10 years from now.

Rotating food does not necessarily mean changing brands, of course. Most pet food companies offer several different proteins within their lines. The most common are chicken, lamb and beef. Today, however, many proteins are widely available in pet food, including buffalo, salmon, duck, rabbit, pork, venison and others. If you want to offer something new to your dog or cat and it is not in your current brand's line, you should feel completely comfortable buying a different company's food. The most important thing is to make sure that whatever food you feed is free of by-products, digest, BHA, BHT, ethoxyquin, generic fat sources and sugar. It's also a good idea to avoid corn and wheat in maintenance diets, as they are rarely seen on the ingredient panels of healthy foods.

Of course, there are some animals who must adhere to a strict diet because of existing allergies or sensitivities. Animals with these issues do have to be more cautious. I certainly do not want to suggest something that will make life unpleasant for pets or their people! If, however, your dog or cat does not react poorly to dietary change, there's no time like the present to make mealtime a bit more exciting. Your best friend will thank you for it. Bone appétit!

Albert, a Jack Russell Terrier, is Chairman of the Board of Wylie Wagg, a shop for dogs, cats, and their people, in Middleburg, Fairfax and Falls Church.