Nutritional Assessment and Requirements
What the exam expects
Nutritional assessment is a structured process, not a single lab value. Know the ABCD framework: Animal (signalment, life stage, activity, reproductive status), Body condition (BCS 1-9 or 1-5, muscle condition score), Clinical signs and history (diet log, appetite, vomiting, diarrhea, weight trend), and Diet (what, how much, how often, supplements, treats).
Resting energy requirement (RER) is derived from metabolic body weight: RER = 70 x (BW kg)^0.75. Maintenance energy requirement (MER) is a multiple of RER that varies with life stage and neuter status; illness factors are applied cautiously because overfeeding is a common error. Water requirement is roughly 1 mL/kcal of energy consumed, or about 50-60 mL/kg/day in dogs and cats.
Traps to watch for
- Ideal vs current weight: energy calculations in obese patients should target ideal weight, not current weight.
- Life-stage multipliers: growing puppies and kittens, gestation/lactation, and working dogs need higher factors; neutered indoor adults sit near the low end.
- Essential nutrients: cats are obligate carnivores and require preformed taurine, arginine, arachidonic acid, vitamin A, and niacin; dogs do not. Taurine deficiency links to dilated cardiomyopathy and feline central retinal degeneration.
- Muscle condition score is independent of BCS; a thin-appearing cat can still be sarcopenic.
Worked example
A 20 kg neutered adult dog: RER = 70 x 20^0.75 = 70 x 9.46 = 662 kcal/day. Using a maintenance factor of 1.6, MER = 662 x 1.6 = ~1060 kcal/day. If the diet is 3500 kcal/kg, that is 1060 / 3500 = 0.30 kg/day. Divide by meals to get per-meal amounts.