Before you change the diet…

Prior to deciding to change a patient from one diet to another, you should understand a few things

Naughty Girl is a healthy six-month old terrier puppy who is being fed a complete and balanced commercial growth food. She lives with Bad Boy, a four-year old beagle-spaniel cross who is fed an adult maintenance dog food.

Bad Boy is brought to your clinic for a two-day history of vomiting and acting sluggish (or punky). Your physical exam reveals some pain on abdominal palpation and a lab test for canine pancreas-specific lipase is ‘abnormal,’ suggesting an elevated lipase level. Your suspicion of pancreatitis is high and, after rehydrating the dog with fluids, you send him home on a fat-restricted therapeutic diet.

Is a diet change warranted in this situation?

Nutrition textbooks and veterinary nutritionists refer to dietary fat as a ‘nutrient of concern’ or ‘key nutritional factor’ when talking about nutritional management for patients with pancreatitis. However, before automatically switching a patient’s diet, conduct a thorough nutritional assessment to get the whole picture of what’s happening in the home environment.

Performing a nutritional assessment involves collecting information about the patient, the diet, and feeding management (Baldwin, et. al. 2010). This is not a process requiring extra time or work—a nutritional assessment begins with routine information collected about the type of food going into the animal’s bowl at mealtime, the source of water, the number and types of treats, as well as supplements and medications given on a daily or weekly basis. A member of your health-care team can get these details in the exam room or by having the owner complete a diet history form in the reception area. A third approach would be to have clients complete an online diet history form (available on your website) prior to arriving for their scheduled appointment.

Table 1: Nutrients of concern for different GI conditions.

The nutritional assessment continues when you perform a thorough physical exam and record the animal’s body weight, muscle condition, and body condition score in the medical chart. Questions about feeding management and the home environment (such as when and where the animal is fed, other animals in the home, number of food and water bowls, number of litter boxes, etc.) provide useful pieces of information that may shed light on some aspect of the animal’s medical condition or are equally important for short- or long-term recommendations.

In the case of Bad Boy, a nutritional assessment would include a few key questions about when, where, and how often both dogs are fed (together or separate? multiple meals each day or food available at all times?). Questioning the owner(s) would reveal that when Naughty Girl doesn’t finish all her food, Bad Boy gets to her bowl and gobbles up whatever is left. Comparing the fat and protein content of the puppy product to the adult maintenance diet (based on grams per 100 calories rather than percentages) would reveal the puppy food is higher in fat and protein, suggesting a possible etiology for pancreatitis. The adult dog food is appropriate from the standpoint it meets the nutritional requirements for Bad Boy, and so it doesn’t actually need to be changed. However, the feeding management in the home requires some adjustment to prevent Bad Boy from eating the higher-fat, higher-protein puppy food. The purpose of taking a thorough diet history is that you may learn the food in the bowl is not the problem, which means an immediate change in food type may not be indicated.

Gastrointestinal (GI) diseases are complicated because organ functions are complicated. Across North America, the commercial foods fed to dogs and cats are equally complex—more than 30 nutrients are needed to make a complete and balanced pet food, and each product can have a dozen or more ingredients to meet the required nutrients. Nutritional management of GI diseases requires thinking about the nutrients of concern for an animal (Table 1) and sometimes the ingredients, too. Integrated functions of the liver, gallbladder, pancreas, and small and large intestines need to be understood in terms of how different nutrients (proteins, fat, complex carbohydrates, minerals, and vitamins) are digested, absorbed, metabolized, stored, and excreted from the body.

Few controlled prospective clinical studies are available to consider as evidence for nutritional management of GI diseases; of those published, the focus has been on the role of dietary protein, fat, or fibre. A recent review summarized the potential benefits of nutrient modifications for some enteropathies (Rudinsky, et. al. 2018). The authors concluded more than one dietary trial may be warranted in dogs or cats who fail to respond the first time a food is changed.

A little bit of math goes a long way

Before deciding to change a patient from one diet to another, you should understand how many calories (and how much protein and fat) are being consumed from the current diet. Equally important, you also should understand how those same nutrient intakes will change when the animal’s food is switched. This process begins by calculating the patient’s resting energy requirement (RER) using the equation: 70 x (Body Weightkg 0.75) = calories per day. Next, estimate daily energy requirement (DER) by multiplying the RER value by a ‘fudge factor’ ranging between 1.1 and 1.6 (Hand, Thatcher, Remillard, Roudebush, 2010). For healthy animals in good body condition, a conservative value of 1.2 is a reasonable place to start. To estimate the patient’s minimum dietary protein needs, use the following rules of thumb: 2.2 g per kilogram body weight per day for dogs, and 4.5 to 5 g per kilogram body weight per day for cats (Laflamme and Hannah, 2013). Once you have calculated these values, compare the number of calories and protein consumed in the current diet with what would be consumed from the new diet.

When using veterinary therapeutic diets, specific information about the grams of protein or fat per 100 calories can be found in the published product guides or online at the manufacturer’s website. For over-the-counter dog and cat foods, an easy three-step process is available to estimate the protein or fat concentration on a calorie basis (Shmalberg, 2013). The two pieces of information needed from the pet food label or the company website are the per cent crude protein or crude fat, and the Kcals per kg.

Anytime you’re considering a diet change, you or someone on your health-care team should coach the owner(s) on how to transition their pet to the new diet. To maximize acceptance and minimize GI upset, a gradual transition over 10 days should be followed. On day one to three, the pet should be fed 25 per cent of a new food with 75 per cent of the current food. On day four to six, feed 50 per cent new and 50 per cent current food. On day seven to 10, feed 75 per cent new and 25 per cent current food. After day 10, the pet should have transitioned completely to the new diet. Offering the new and current foods side-by-side in separate bowls will allow the pet to make a choice and may improve the acceptance rate.

Monitoring during the transition period (and afterward) is an important step in determining whether a diet switch is successful or not. Daily or weekly record-keeping at home can be done by owners using a computer spreadsheet or paper and pen, and can include appetite, energy or activity level, fecal score (a ‘poop diary’), and an ‘itchy-scratchy diary.’ Weekly or monthly monitoring at your clinic might include body weight and body condition score checks. The process of monitoring can help foster a sense of teamwork with your client, keeping them engaged and you informed of the animal’s progress on a new diet.


  1. 2010 AAHA Nutritional Assessment Guidelines for Dogs and Cats, C. Baldwin, J. Bartges, T. Buffington, et. al., AAHA, Accessed Dec. 1, 2018.
  2. Beyond the Guaranteed Analysis, J. Shmalberg, Today’s Veterinary Practice, 43-45, 2013.
  3. Nutritional Management of Chronic Enteropathies in Dogs and Cats, A. Rudinsky, J. Rowe, V. Parker, JAVMA 253(5); 570-578, 2018
  4. Discrepancy Between Use of Lean Body Mass or Nitrogen Balance to Determine Protein Requirements of Adult Cats DP Laflamme, SS Hannah, J Feline Med Surg. 15;691-697, 2013:
  5. Applied Veterinary Clinical Nutrition, Andrea Fascetti and S. Delaney, 2012, Wiley Blackwell
  6. Canine and Feline Nutrition, A Resource for Companion Animal Professions, 3rd edition
  7. Case, Daristotle, Hayek and Raasch 2011, Mosby Elsevier, Maryland Heights, MO.
  8. Small Animal Clinical Nutrition, 5th edition Hand, Thatcher, Remillard and Roudebush 2010, Mark Morris Institute, Topeka, KS.

Sarah K. Abood, DVM, PhD, is assistant professor, department of clinical studies, at the University of Guelph’s Ontario Veterinary College (OVC). Her focus is teaching nutrition in the curriculum and running the clinical nutrition service. Dr. Abood can be reached at

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