Introduction
Nutrition is part of every patient visit. The veterinary technician weighs the patient, scores body and muscle condition, takes the diet history, reads the food label with the owner and turns the veterinarian's plan into a number of calories and a measured amount of food. Those small daily tasks prevent obesity, catch weight loss early and keep sick patients eating.
This guide covers the six nutrient classes, the extra needs of cats, life stage feeding, the parts of a pet food label, the resting and maintenance energy formulas, the WSAVA nutritional assessment, therapeutic diets and a basic weight loss plan.
Key facts
- The six nutrient classes are water, protein, fat, carbohydrates, vitamins and minerals. Only protein, fat and carbohydrate provide energy.2
- Unlike dogs, cats need dietary taurine, arachidonic acid and preformed vitamin A, and they need more arginine, niacin and pyridoxine.2
- Resting energy requirement (RER) = 70 x (body weight in kg)0.75 kcal/day. The linear formula, 30 x kg + 70, is for animals over 2 kg.2
- Typical maintenance multipliers: neutered adult dog 1.6 x RER, neutered adult cat 1.2 x RER, puppy under 4 months 3 x RER.2
- WSAVA recommends a nutritional screening on every patient as the fifth vital sign.5
- On the 9-point scale, the goal for most pets is a body condition score (BCS) of 4 to 5 of 9.5
- The AAFCO nutritional adequacy statement tells you the species and life stage a food is complete and balanced for.4
- Treats should make up no more than about 10% of daily calories.56
How the VTNE tests this
- Assess and record nutritional status as part of initial and ongoing patient evaluation (Domain 5 Task B; K31 nutrition).1
- Calculate RER and MER from body weight, then convert calories to a volume of food.
- Identify the nutrient a cat must receive in its diet, or the deficiency that a given diet causes.
- Interpret parts of a pet food label: the nutritional adequacy statement, guaranteed analysis and product name rules.
- Choose the client-education point or diet type for a scenario, such as an overweight dog or a cat with kidney disease.
Core concepts
The six nutrient classes
Water is the most important nutrient. A lack of water can kill an animal in a matter of days, so clean water should always be available.2 Most mammals need about 44 to 66 mL/kg of water a day in a thermoneutral environment. Canned foods hold 60% to more than 87% moisture and dry foods 3% to 11%, so pets on canned food drink less.2
Protein supplies essential amino acids, which the body cannot make in enough amounts and must get from food. Dogs need 10 essential amino acids: arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. Cats need taurine as well.2 Fat carries the fat-soluble vitamins A, D, E and K and supplies essential fatty acids. All mammals need linoleic acid, an omega-6 fatty acid found in vegetable oils.2
Energy is measured in kilocalories (kcal), also written Calories with a capital C. One kcal is 1,000 calories.2
Why cats are different
Cats are strict carnivores. Their metabolism expects a meat diet, and several nutrients that dogs make or convert must come ready-made in a cat's food.
| Nutrient | Why the cat needs it in the diet | Effect of deficiency |
|---|---|---|
| Taurine | Essential amino acid for cats; plant proteins contain none | Dilated cardiomyopathy and central retinal degeneration |
| Arginine | Needed in higher amounts; supplies the urea cycle that clears ammonia | Hyperammonemia, seen with hepatic lipidosis in anorectic cats |
| Arachidonic acid | Cats cannot readily convert linoleic acid to it; found in animal fat, not vegetable oil | Essential fatty acid deficiency |
| Vitamin A (preformed) | Cats lack the gut enzyme that cleaves beta-carotene | Ocular changes such as night blindness |
| Niacin, pyridoxine (B6) | Higher requirement than dogs | B-vitamin deficiency signs |
Source: Merck Veterinary Manual, Nutritional Requirements of Small Animals2; Washabau and Day, Liver9.
Cats also run continuous gluconeogenesis, making glucose from amino acids, and cannot turn it down during fasting.2 This is one reason a cat that stops eating needs attention quickly. A cat diet must contain animal protein or added synthetic taurine, because plant proteins contain no taurine.2
Life stage feeding
AAFCO, the Association of American Feed Control Officials, recognizes the life stages gestation/lactation, growth, maintenance and all life stages.4 Growth, pregnancy and lactation raise nutrient needs well above maintenance.3
- Puppies. Feed three times a day from weaning to 6 months, then twice a day to 12 months. Large and giant breed puppies should eat a growth diet labelled for growth of large size dogs (32 kg or more as an adult). A slow growth rate is better than a fast one. Weigh weekly and adjust the amount so the puppy gains a small amount each week.3
- Kittens. Usually move to an adult diet between 8 and 12 months.3
- Adults. Most dogs become obese if fed free choice. Portion control, such as two measured meals a day, is the best way to prevent obesity in most dogs.3
- Pregnant bitch. Maintenance amounts for the first two thirds of gestation, then at least 20% to 30% more in the last third. Lactating bitches may need 2 to 4 times maintenance.3
- Pregnant queen. Gains weight steadily from early pregnancy and needs more calories almost at once. Lactating queens need 2 to 3 times normal intake.3
- Seniors. Older cats digest fat and protein less well and often struggle to keep weight on. Older dogs may need more protein, not less.3
Energy: RER and MER
RER is the energy a healthy, fed animal uses at rest in a thermoneutral environment, including recovery from activity and feeding. Maintenance energy requirement (MER) is RER multiplied by a factor for the patient's life stage and neuter status (Table 2).2
- Exponential formula, any weight: RER = 70 x (BW in kg)0.75
- Linear formula, animals over 2 kg only: RER = 30 x (BW in kg) + 70
| Patient | MER (kcal/day) |
|---|---|
| Adult dog, intact | 1.8 x RER |
| Adult dog, neutered | 1.6 x RER |
| Adult dog, obesity prone | 1.4 x RER |
| Puppy, under 4 months | 3 x RER |
| Puppy, over 4 months | 2 x RER |
| Adult cat, intact | 1.4 x RER |
| Adult cat, neutered | 1.2 x RER |
| Adult cat, obesity prone | 1 x RER |
| Kitten | 2.5 x RER (or free choice) |
Source: Merck Veterinary Manual, Nutritional Requirements of Small Animals, table Daily Maintenance Energy Requirements for Dogs and Cats.2
Every formula is a starting point. Two animals of the same weight can differ by as much as 30% in the calories they need. Adjust the amount using body weight and BCS at rechecks.2
Reading a pet food label
AAFCO model regulations require these label elements: product and brand name, the species the food is for, net quantity, guaranteed analysis, ingredient statement, nutritional adequacy statement, feeding directions, and the name and address of the manufacturer or distributor.4 A picture of a dog or cat alone does not name the species.4
| Element | What it shows |
|---|---|
| Product name | Name rules set the minimum amount of the named ingredient (see below) |
| Guaranteed analysis | Minimum crude protein and crude fat, maximum crude fiber and moisture, as fed |
| Ingredient statement | All ingredients in descending order of predominance by weight |
| Nutritional adequacy statement | Species and life stage; whether met by formulation or by an AAFCO feeding trial |
| Feeding directions | Amount of food per body weight per day; a starting guide only |
| Calorie content | kcal per kg as fed and kcal per familiar unit, such as per cup or per can |
| Guarantor | Name and address of the manufacturer or distributor |
Source: AAFCO, Reading Labels.4
Product name rules:4
- 95% rule ("Beef Dog Food"): the named ingredient is at least 95% of the product, not counting added water, and at least 70% counting water.
- 25% rule ("Chicken Dinner", "Entree", "Platter"): at least 25% not counting water, and at least 10% of the total.
- "With" rule ("Dog Food with Chicken"): at least 3% of the named ingredient.
- Flavor rule ("Chicken Flavor"): only enough of an ingredient to give a detectable flavor.
The nutritional adequacy statement is the most important part of the label.4 "Formulated to meet the AAFCO Nutrient Profiles" means the recipe meets the profile on paper. "Animal feeding tests using AAFCO procedures substantiate" means the food passed a feeding trial. "Intermittent or supplemental feeding only" means the food is not complete and balanced. Treats labelled "snack" or "treat" do not need a statement.4
Procedure or technique
Nutritional screening and diet history
- Weigh the patient on the same scale each visit and record the weight in kg.
- Score body condition on the practice's chosen scale and record the denominator, for example 6/9. WSAVA uses a 9-point scale.5
- Score muscle condition by looking at and palpating the temporal bones, scapulae, lumbar vertebrae and pelvic bones.5
- Take the diet history: brand and exact product, amount and how it is measured, treats, table food, supplements, who feeds the pet and other pets in the home.
- Check for screening risk factors (see the flowchart). Flag any for the veterinarian, who decides whether an extended evaluation is needed.5
- Calculate the daily calories the veterinarian orders, then convert to cups or cans using the label's calorie content.
- Explain the plan to the owner and book a recheck weigh-in.
Weight loss plan: the technician's part
Obesity is linked with osteoarthritis, kidney disease, skin disease, insulin resistance and neoplasia in dogs, and with skin problems, diabetes mellitus, neoplasia and urolithiasis in cats.6 On the 9-point scale each point above 5 is roughly 10% excess weight, so a BCS of 8/9 is about 30% over ideal.7
- The veterinarian sets an ideal (target) body weight.
- Calculate RER at the ideal weight, not the current weight.6
- One published approach feeds 60% to 70% of that value. Many clinicians restrict cats more cautiously, near 70%, because of the risk of hepatic lipidosis.6 The veterinarian sets the final number.
- Prefer a therapeutic weight loss diet. Cutting back a normal maintenance food also cuts every other nutrient.2
- Build a treat allowance of about 10% of daily calories into the plan.6
- Schedule monthly weigh-ins and adjust calories to the trend.6
Therapeutic diets
Therapeutic diets, also called veterinary medical foods, change certain nutrients to help manage a disease. Some limit nutrients below normal levels, so they carry an "intermittent or supplemental" statement and may say "use only as directed by your veterinarian".4 Renal diets are low in phosphorus with modest amounts of high-quality protein. Dogs and cats with chronic kidney disease (CKD) fed renal diets live longer, and these diets are recommended from CKD stage 2.8 The technician's job is to dispense the right diet, explain why it matters and make the change gradual.
Flowchart
Species differences
- Dog. Can use plant beta-carotene for vitamin A and convert linoleic acid to arachidonic acid. Most adults gain weight on free-choice feeding, so measure meals.23
- Cat. Needs taurine, arachidonic acid and preformed vitamin A in the diet, and more arginine. Needs some animal protein, because plant proteins contain no taurine, unless synthetic taurine is added.2 Lower MER multipliers than the dog (1.2 x RER neutered).
- Cat under calorie restriction. Prolonged fasting risks hepatic lipidosis, so weight loss plans for cats are more conservative.6
- Bitch and queen in pregnancy. The bitch needs extra food only in the last third of gestation; the queen needs more almost from the start.3
Calculation
Worked example 1: daily food for a healthy neutered dog. A 10 kg neutered adult dog eats a dry food with 350 kcal per cup. How many cups a day?
- RER = 70 x (10 kg)0.75 = 70 x 5.62 = 394 kcal/day
- MER = 1.6 x 394 kcal/day = 630 kcal/day
- Cups = 630 kcal/day / (350 kcal/cup) = 1.8 cups/day. The kcal units cancel and leave cups/day.
Check with the linear formula: 30 x 10 + 70 = 370 kcal/day. The two formulas give close but not identical answers; use the one your clinic and the question name.
Worked example 2: weight loss starting point. A dog weighs 40 kg and the veterinarian sets an ideal weight of 32 kg.
- RER at ideal weight = 70 x (32 kg)0.75 = 70 x 13.45 = 942 kcal/day
- Treat allowance at 10% = 0.10 x 942 kcal/day = 94 kcal/day; the meal portion supplies the other 848 kcal/day.
Using current weight (40 kg) would give 70 x 15.91 = 1,114 kcal/day and slow or stop the weight loss.
Safety, legal and client education
- A cat diet with no animal protein or added taurine leaves the cat short of taurine. Vegetable oils supply no arachidonic acid, and plant beta-carotene cannot meet a cat's vitamin A need.2
- An all-meat or hamburger and rice diet can cause calcium deficiency and nutritional secondary hyperparathyroidism. Feeding only liver can cause vitamin A toxicity.2
- Raw eggs contain avidin, which destroys biotin. Raw fish contains thiaminase, which destroys thiamine.2
- Adding calcium, phosphorus or vitamin D to a complete and balanced growth diet is rarely needed and may be harmful.3
- Owners may think a BCS 4 to 5 pet looks too thin. Show them the ribs and waist you are feeling.5
- Teach owners to measure food with a measuring cup or kitchen scale, and to count treats and table food as calories.
- Recommending a therapeutic diet and setting calorie targets are veterinary decisions. The technician calculates, dispenses and educates under the veterinarian's direction.
Common mistakes and exam traps
- Calculating weight loss calories from current weight instead of ideal weight.
- Using the linear RER formula on a patient of 2 kg or less. Use the exponential formula for small patients.
- Confusing the label rules: "Beef Dinner" (25%) contains far more beef than "with beef" (3%), and "beef flavor" may contain only a flavoring amount.
- Reading guaranteed analysis values as exact amounts. They are minimums (protein, fat) and maximums (fiber, moisture).
- Thinking taurine is the only cat-specific need. Arginine, arachidonic acid and preformed vitamin A are tested too.
- Forgetting the denominator: a BCS written as "6" could mean 6/9 or an obese 6/6. Record it as 6/9.5
Quick review
- Six nutrient classes; water is the most important; only protein, fat and carbohydrate supply energy.
- Cats need dietary taurine, arachidonic acid and preformed vitamin A, plus more arginine.
- Taurine deficiency: dilated cardiomyopathy and central retinal degeneration.
- Arginine shortfall in anorectic cats: hyperammonemia.
- RER = 70 x BW(kg)0.75; linear 30 x BW + 70 only over 2 kg.
- MER: neutered dog 1.6, intact dog 1.8, neutered cat 1.2, young puppy 3 x RER.
- WSAVA: screen every patient; risk factors trigger an extended evaluation.
- Ideal BCS for most pets is 4 to 5 of 9; each point above 5 is about 10% overweight.
- Label: adequacy statement gives species, life stage and how adequacy was shown.
- Name rules: 95%, 25% (dinner), 3% (with), flavor.
- Weight loss: RER at ideal weight, treats 10% or less, monthly weigh-ins.
- Renal diets: low phosphorus, modest high-quality protein.