Photo by Riis Williams
Louie, a Chihuahua-dachshund mix (chiweenie), eats many different foods. "I think there's a lot to be said for rotation feeding," his owner, who works at a pet food store, reasons, " — hitting the right thing from time to time and not the wrong thing all the time."
For all of his life, 10-year-old Louie has been something of a smorgasbord diner. The chiweenie eats a variety of brands of kibble, with and without grain. He's dabbled in raw foods. And when he can get away with it, he makes off with a share of his owner's breakfast.
That owner, Abbey Bellefeuille, got into a habit of rotating foods while trying to halt recurrent ear infections in her Australian shepherd, Luna. Bellefeuille suspected Luna's ears reflected a food allergy. Louie got to try different foods along with Luna.
Both tolerated the change just fine, neither showing the stomach upset that can happen in some pets when switching food brands or formulations. Both dogs seem to enjoy the change and are healthy, Bellefeuille said, so she stuck with the practice. (Luna's ear infections cleared up with age.)
These days, Bellefeuille has another reason to keep changing it up: a parade of pet food recalls and advisories that involve big and small pet-food makers alike.
The past 18 months have seen more than 40 dog- or cat-food recall notices in the United States alone. Many are run-of-the-mill recalls involving batches of food contaminated with Salmonella bacteria or foreign objects like rubber. Others are more attention-getting, such as an episode in early 2018 of dog foods tainted with pentobarbital, a euthanasia drug. And in late 2018 and early 2019, multiple dog food brands — from obscure names to the well-established Hill's label — were found to have excessive, potentially deadly, levels of vitamin D.
One of the biggest pet-food worries today is a mystery that hasn't resulted in a recall. It's rattled nerves precisely because of the uncertainty, plus the potential for grave implications: a suspected association between some grain-free formulations and a serious heart disease called dilated cardiomyopathy (DCM).
The situation is drawing marked attention from dog owners. When the FDA, in an investigation update on June 27, identified 16 pet-food brands most often named in cases of diet-associated DCM in dogs, Facebook users shared a list posted by the VIN News Service 22,000 times.
"With all these things hitting the news headlines, like grain-free and dilated cardiomyopathy," Bellefeuille said, contemplating her rotation-feeding habit, "I know I'm hitting the right answer some of the time and I'm not hitting the wrong answer all of the time."
A pet store chain in California, Pet Food Express, actively recommends rotating:
"We have long recommended this as a best practice both to provide a wider variety of nutrients and to prevent excessive exposure to the same ingredients ..." it says on a blog post about the DCM and grain-free foods issue. "Unless your pet has a grain sensitivity, there is no particular advantage to a grain-free diet and no reason you couldn’t switch between grain-containing and grain-free diets. Of course, watch your pet closely and discontinue feeding any food that creates problems or that they won’t eat."
Some veterinarians agree, comparing a varied diet to diversifying an investment portfolio to limit financial losses.
"My argument is, if there is a problem with one of the foods, it may not become a problem [for your pet] because you're diluting it out," said Dr. Joe Bartges, a professor of medicine and nutrition at the University of Georgia College of Veterinary Medicine. Bartges also is a nutrition consultant at the Veterinary Information Network, an online community for the profession and parent of the VIN News Service.
"I am a huge believer in variety," he told VIN News. "Our cats, we feed six to eight types of canned and dry food. We make food. We give them treats."
The cats, now age 2, have been in the household since they were kittens, Bartges said. "We started early giving them a variety and they never have stomach upset. ... They look good, their coats are good, and when you pick them up, [you can tell that] they are so muscular."
Bartges didn't always advocate variety in pet diets. "I was trained in the '80s," he said, when the prevailing wisdom was, "pet food companies are good, everything is good, there's not a problem."
Over time, he said, "What I learned is that business is business. Although they're doing their best, there are problems with business. Just like with spinach, with car manufacturers, with electricity. It's like the stock market. That's why diversification is so good."
Dr. Paul Pion, president and co-founder of VIN, advocates "mixing it up" for the same reason. Thirty-two years ago, Pion and colleagues made a blockbuster discovery that a lack of the amino acid taurine in their diets led cats to develop DCM. Giving them taurine supplements reversed their heart condition, curing the fatal disease.
The taurine finding in cats doesn't necessarily translate to the contemporary issue in dogs because cats obtain taurine almost exclusively from their food. Dogs are able to synthesize taurine from two other amino acids, cysteine and methionine. And while taurine deficiency has been associated as the cause of DCM in a few breeds of dogs, it is not the major cause of DCM in dogs as it was in cats.
To this day, no one knows taurine's precise role in heart health. The universe of unknowns in pet nutrition is why Pion supports periodically switching foods — that, and the fact that in repeated instances, whether with taurine deficiency in cats or the current trouble involving grain-free dog foods, the animals usually affected are those that ate a specific diet exclusively for a long time.
"Given the pet-food induced problems we've seen over the past few decades from manufacturers with the best of intents, plus what we don't know about nutrition, is it wise to feed one food to our pets exclusively?" he said. "Even when we are doing the best we can with what we know, we are at risk because of what we don't know."
Rotating not standard advice
Although a rotation diet has some strong proponents, it is far from standard veterinary advice, and some veterinary nutritionists are dubious of the practice. Common wisdom says to choose one "complete and balanced" diet, and if the pet likes it and does well (its stool is firm, its coat is glossy, it's not lethargic, fat, skinny or itchy), stick with it.
Pet-food marketing promotes the idea that one food can do it all for a dog or cat. "All life stages" formulas are said to be suited to all breeds, ages and sizes.
The history of commercial pet foods extends more than 150 years. The Pet Food Institute, a trade group for U.S. pet food makers, credits a businessman named James Spratt with introducing the first commercially prepared pet food in England around 1860.
"After seeing dogs being fed leftover biscuits from a ship, Spratt formulated the first dog biscuit: a mix of wheat meals, vegetables, beetroot and beef blood. Spratt’s business venture was a success, meeting a new market demand and selling to English country gentlemen for sporting dogs," according to a PFI webpage on the history of pet food.
The article goes on: "A British public company took over Spratt’s formula and production began at a U.S. operation in about 1890. Additional companies began to develop their own recipes for biscuits and dry kibble, using the current nutritional knowledge of the time period. Canned dog food, 'Ken-L Ration,' was introduced in 1922. Its main ingredient was horse meat, which was considered an acceptable ingredient source at the time. Our understanding of and relationship with horses has since evolved, and as they have become pets, there is no longer a market for horse meat."
Purina (now Nestlé Purina), maker of diets for dogs and cats, opened a research facility in 1926 to develop formulations for companion animals that would provide "complete and balanced" nutrition, according to Dr. Kurt Venator, the company's chief veterinary officer.
"They key is to make sure that it's all based and rooted in a foundation of science," Venator said, noting that as scientific knowledge evolves, so does the understanding of an adequate diet for an animal at different stages of life.
The concept that an animal can live on largely the same food for a lifetime was supported by a Purina study published in the Journal of the American Veterinary Medical Association in 2002. The thrust of the research was the effect of diet restriction on a dog's lifespan and age-related changes: It found that dogs fed less lived longer. The study also incidentally demonstrated that basically the same diet served the animals' lifetime nutritional needs.
"All dogs were fed the same 100 percent nutritionally complete and balanced diets (puppy, then adult) for the entire period of the study, from eight weeks of age until death — only the quantity of food was different," Purina reported in a press release.
For the consumer, there's a certain comfort, not to mention convenience, in selecting the same familiar bag of food every time.
Bellefeuille, owner of the dogs Louie and Luna, is a sales associate at an independent pet store near Seattle. At work, she talks about pet food often with pet owners. "A lot of people like the convenience of knowing what works for their dog and what they trust for their dog and going back to it," she observed. "... Some people are nervous to switch."
Despite scientific evidence that essentially the same food can sustain a dog for life, it would be an overstatement to say that a single formulation can do it all for every dog or cat. "No diet is ideal for all pets at all times," Dr. Cecilia Villaverde, a veterinary nutrition consultant in Ireland and a VIN consultant, said by email.
Even pets who are healthy all their lives may do better with different formulations at different ages. Venator noted that Purina introduced puppy chow in 1963 after determining that puppies need more protein than adults. Today, formulations designed for senior dogs are common, as well. Venator said Purina recommends not one single diet for a lifetime but rather, diets based on "life stage" — puppy, adult and senior.
In an interview by email, another VIN nutrition consultant, Dr. Lisa Weeth, who has a private consultancy in Los Angeles, observed: "Technically, dogs (and all animals for that matter) require nutrients, not ingredients, so it is theoretically possible to find a single diet that will meet the nutrient needs of a given dog. But the reality is that for that same dog, its nutritional needs will vary over its lifetime, depending on the life stage (puppy vs. adult vs. senior vs. geriatric) and with concurrent disease. Some caregivers may luck out and have a healthy, robust dog that does well on the first all-life-stages diet that they happened to buy, [but] the majority of dogs will require some diet adjustments over time."
How about routinely rotating foods?
Weeth is neither for nor against it, although she has some concerns. "We don't have any evidence that diet rotation is better than sticking with one formula that is working (assuming [the animal is a] healthy, non-reproductive adult), but we also don't have any evidence that it is wrong, as long as the transitions are made slowly to allow for gastrointestinal adaptation to the new food," she said, noting that "fat and fiber and digestibility changes can cause diarrhea if owners switch too quickly."
However, Weeth cautioned, if the pet "develops a sensitivity or allergy to a particular diet and the owners are changing to a new diet brand and ingredient deck every few months, it will be harder to figure out the sensitivity."
She tells owners who wish to rotate brands to "stick to a more narrow ingredient exposure list, like poultries and red meats, but no fish or exotic meats and grains, so if we need them [to rule out possible allergies or sensitivities], we have some ingredient options."
Villaverde likewise approaches the idea of rotating diets cautiously. Generally speaking, she has no objection as long as each of the diets being used are complete and balanced and suited for the particular pet. However, in certain situations, she said, it is not a good option. One example is "animals that have a medical condition or very narrow nutrition needs that do really well with one specific diet."
She has personal experience with this situation: "My own cat with megacolon, he does well with one specific therapeutic diet and blocks with other diets," Villaverde offered. "I live in constant fear of him going off the food!"
Dr. Jennifer Larsen, a professor of clinical nutrition at the University of California, Davis, Department of Veterinary Medicine, and a VIN consultant, doubts that rotating diets is beneficial.
"I think this strategy to avoid possible formulation errors (like vitamin D toxicity) or contamination seems a bit haphazard," she said by email. "You cannot predict when or even if this will happen so cannot guess when to change — it seems like a poor way to try to increase food safety. It also makes it hard to identify what the cause of any potential problem is, depending on how frequently foods are rotated or mixed (for example, diarrhea develops but you cannot tell which diet or characteristic or ingredient might be to blame, if any)."
She mused: "If the issue were more of a marginal or overt deficiency or toxicity, then I suppose you could minimize the negative outcome but again, you'd never know if that were the case. It's a bit of wishful thinking rather than a sound nutritional practice."
Still, Larsen said, "If rotation is well tolerated by the pet, I don't see a specific downside; just lack of specific benefit, I think."
Dr. Scott Campbell, a veterinary nutritionist in Australia and VIN consultant, is in favor of rotating diets, provided the diets are complete and balanced, and preferably developed by reputable companies.
How does he judge "reputable"? Campbell looks for manufacturers whose diets have been tested in feeding trials (rather than merely substantiating nutrient content, an option allowed under guidelines of the Association of American Feed Control Officials); whose formulations have been on the market for years; that provide contact information; and that has nutritionists on staff.
"Beyond that, I like the idea of rotation," Campbell said, " — and sustainability and low cost and whole, fresh ingredients, etc."
VIN News Service commentaries are opinion pieces presenting insights, personal experiences and/or perspectives on topical issues by members of the veterinary community. To submit a commentary for consideration, email firstname.lastname@example.org.