Our choices for our pet reflect our great concern for their health and welfare and the best way that people feel they can control their pet’s health is through the food that they choose.
People spend hours on-line, reviewing the information on pet foods, and reading other people’s reviews and opinions on certain foods. The science itself is confusing and scary, and all too often people fall back on what looks good to them, or what seems to be a normal and logical situation.
Happily, marketing departments understand the human psyche better than most shoppers themselves, and have positioned any given food to appeal to people’s sensitivities and desires.
Currently, “grain free” is the hot trend, with “grain free” pet diets popping up daily. A higher protein, lower grain content diet is certainly is more appropriate in the cat, as Drs. Zoran and Buffington pointed out in the September 2011 (Volume 239, no.5) issue of the Journal of the AVMA, but is it appropriate in the dog? As a marketing trend, it appears to be following on the coattails of the feline recommendation, and also echos the current fad for “gluten free” which is popping up on labels for things that never had any gluten in them in the first place, like honey and wine, and fruit. For people with celiac disease, this is certainly an improvement, but the vast majority of us don’t have celiac disease, and in dogs, even fewer have celiac disease. (The Irish Setter gets the unfortunate distinction as the breed most likely to develop celiac disease.)
Can dogs digest grains? Is it truly appropriate to feed our housepets like a wild animal? The March 2013 issue of Nature answers this question, although, to be fair, the authors of the study really weren’t looking at the question from a “feeding pet dogs” perspective. They were more interested in the anthropological aspects of two species deciding to co-exist as one’s lifestyle changed, and then developing parallel genetic changes that reflected a changing dietary environment, which is, admittedly, very interesting.
A study done by Dr. Erik Axelsson and his colleagues looked at the genetic code of the wolf and the genetic code of the dog mostly just to identify differences. Why is it that the dog was domesticable, but not really the wolf? A sub-problem was how do you get a sort of “generic” dog genome, when there are so many different breeds and you don’t want to introduce a breed-specific type of bias into the overall question. This sub-problem was solved by pooling the samples of 60 different breeds of dogs, so that individual variation, created by selective breeding, was not a factor in the study, and this pooled sample became a “virtual mutt.”
When the samples were run and matched up, there were several areas of difference between the representative dog genome and the wolf genome. Several genes related to behavior, but 3 important genes show changes that correlate with gain-of-function to create proteins that break down complex sugars and starches and transport this sugar molecule across intestinal cell walls. The gene that causes the enzyme amylase to be produced has an increased number of copies. In fact, there is a 7 fold increase in the number of copies of this gene in the dog, compared with the wolf. This is called ‘gene amplification” and this situation has been seen in human populations where the ancestors have consumed diets rich in starch. So the same molecular mechanism has happened in both people and dogs—different species—exposed to the same diets—an example of parallel evolution!
Domestication of the dog was an important step in the evolution of humankind, and the thinking is that early ancestors of modern dogs probably scavenged around waste dumps near human settlements about 11,000 to 13,000 years ago. This correlates with the development of agricultural societies as humans transitioned from the Paleolithic to the Neolithic era. As humans decided to stay in one place, and grow their food, there was a concurrent increase in the ability to digest starches.
But pet owners will tell us that the switch to grain-free seemed to help their dogs have fewer allergies, less scratching, and less visits to the vet! What’s up with this? If dogs CAN digest starches and sugars in the same way that most humans can, then what is responsible for the improvement? Well, many foods become contaminated with a version of the house dust mite and in some patients, these can be highly allergenic. It may also be that there is an underlying sensitivity to a component in the previous food that is absent in the new food, irrespective of the grain present or absent. And it may be completely unrelated—there may be a decrease in the flea burden in the yard or neighborhood due to a change in some local micro environment—or a change in flea control measures that were also instituted concurrently.
