Adventures in Pet Food

Debbie Phillips-Donaldson, editor-in-chief of Petfood Industry, shares her insights and opinions on all things pet food, addressing market trends as well as news and developments in pet nutrition, food safety and other hot topics for the industry.
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Pet food proteins: Rotation diets, cross reactions and more

Some pet food companies, along with pet owners and retailers, advocate and follow a “rotation diet” philosophy that believes it’s healthier for a pet to eat a variety of pet foods, preferably in a regular rotation, versus eating the same diet day in and day out. Does any research exist to proof that?

The short answer is no, but a discussion about the concept with Kelly Swanson, Ph.D., a professor researching comparative nutrition and nutrigenomics at the University of Illinois Urbana-Champaign, provided a few intriguing highlights and potential areas for study.

Gut immune system learns what is safe

Answering questions about novel proteins as part of the Ask the Pet Food Pro series of Zoom chats on June 23, Swanson was asked specifically whether his experience in nutrigenomics has shown that offering a variety of proteins and ingredients is beneficial, versus a repetitive diet. That discussion came right after one about the role of proteins in allergenicity and hypoallergenic diets for pets, and Swanson started by referencing that, after saying he and his team have not tested the concept of a variety of proteins versus the same diet.

“I think it’s in the area of allergy. And especially I think there is always that thought that, for a young growing puppy and a kitten, should you expose them to many proteins?” he responded. “It’s almost like, you know, the first couple days, first few weeks of life, our gut has to develop a tolerance. So the gut, the gut immune system, kind of has to learn what is safe, what is a potential pathogen or a problem. And so that tolerance and education, if you will, of the gut and the gut immune system occurs.

“Some people will say, I should feed just one protein for life, or another say, just give them everything else, and I’m not sure, I think the jury’s still probably out on that,” he continued. “There are so many complicating factors, and I’m not sure there’s enough biological variability and just exposures. I’m not sure if there is really one right answer to that.”

Yet, if evidence of an allergy does arise in a pet, he added, then a single protein may be called for.

Does cross reactivity among proteins happen?

The questions related to allergenicity in pets and its possible relation to protein in pet food were also thought-provoking. For example: “In pet prescription hypoallergenic diets fed to dogs and cats with food allergies, has much been looked at as far as cross reactivity between proteins?”

“I guess we know that occurs,” Swanson responded. At least in people, he said; for instance, if someone is allergic to peanuts, they might be allergic to other nuts. Another example in humans: “If you’re allergic to beef, any dairy products, they’re still coming from the cow, so they might also trigger that immune response.”

Swanson said he believed there is data that this type of situation has occurred, but he doesn’t know if there is data saying that if you’re allergic to a particular protein, you’re also likely to be allergic to another protein. “A lot of it comes down to the origin of that protein and the similarity of those proteins really, and what initiated that immune response. And if it’s similar enough, the immune system is probably going to react to a very similar protein in the same way.”

Yet there could be one exception to this situation, he added. “If you have hydrolyzed proteins, where you can reduce the size of those proteins under, typically, that level is 10,000 daltons. Some will argue maybe it’s a little bit lower than that in some of the diets, but if you get to a different level, these proteins can kind of fly underneath the radar of the immune system. And so you maybe could bypass some of those issues with cross reactivity, but then you’d be having to hydrolyze those proteins.” He added that commercial pet foods with hydrolyzed proteins are available.

Stirring up more questions

Swanson also agreed that finding the answers to many of these pressing pet nutrition questions hinges on further research being needed. “Yeah, that never ends,” he said. “It always seems that as we think we know more, we stir up more and more questions. And then we have other questions to answer.”

Such is the nature of science, particularly when it comes to an area like companion animal nutrition that often needs more of it.

Note: Swanson will be presenting and leading a panel discussion on research into fresh and human-grade pet food at Petfood Forum 2021 on September 24.

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