Nutritional assessment is considered one of the five vital assessments by the World Small Animal Veterinary Association (do for every pet, every time they come in):
1. Temperature
2. Pulse
3. Respiration
4. Pain assessment
5. Nutritional assessment
Nutritional assessment is critical in patients recovering from major or minor trauma or interventions, including general anaesthetic, operations, burns, or starvation.
Starvation in an otherwise unstressed patient leads to a decrease in metabolic rate to conserve lean muscle mass and preferentially use fat for energy
Starvation in a patient experiencing major trauma or disease can significantly raise the metabolic rate and requirement, and lean muscle mass is lost alongside fat. This increase can last for upwards of 30-70 days, even with minor trauma.
Why isn’t my patient eating? Consider all of these:
● Pain
● Nausea and other GI disturbances (even in absence of vomiting, some individuals have high vomiting threshold)
● Dietary factors - preferences for flavour, texture, aroma
● Environmental stress - does the patient feel safe enough to eat?
● Cognitive disorders - head trauma, cognitive dysfunction, encephalopathy ● Iatrogenic food aversion - see below for tips to avoid
● Medication effects
● Dehydration/electrolyte imbalance
Systemic Effects of Negative Energy Balance - can impact healing and recovery:
● GI - increased transit time, decreased absorption, bacterial translocation, villous atrophy
● Renal - increased calcium & phosphorus excretion, decreased acid excretion, decreased GFR
● Immune - decreased: humoural response, barrier function, inflammatory response & leukocyte activity
● Cardiovascular - arrhythmias, reduced heart muscle weight
● Respiratory - reduced: response to hypoxia, lung elasticity, tidal volume, secretion production; altered permeability
● Musculoskeletal - decreased muscle strength, mass
Goals of Recovery Nutrition Plans
1. Meet nutritional needs (kcals and nutrients)
2. Support reduced recovery times and increased chances for survival
3. Immune function support
4. Support response to drug therapy
Does my patient need nutritional support? How to assess the risk:
Low Risk:
● Food intake <80% RER for <2-3 days
● Expected course of illness <3 days
Moderate Risk:
● Food intake <80% RER for 3-5 days
● Presence of weight loss
● Hypoalbuminaemia
● Expected course of illness 2-3 days
High Risk
● Food intake <80% RER for >3 days
● Severe vomiting/diarrhoea
● Body condition score <4/9
● Muscle mass score <2/3
● Expected course of illness >3 days
Adapted from Perea, SC. Parenteral Nutrition. In: Fascetti AJ, Delaney SJ, eds. Applied Veterinary Clinical Nutrition. Chichester, UK: John Wiley & Sons, Inc., 2012:355; with permission.
Nutritional Support Plans
Choosing a Diet:
Nutrients to Consider:
Protein - sufficient to spare use of muscle; high digestibility
Fat - provides caloric density to reduce necessary food volume; adds palatability ○ Omega 3 Fatty Acids - helps modulate inflammation
Arginine - immune and wound healing support, counteracts catabolism ○ Glutamine - provides energy source for enterocytes, helpful after starvation ○ Taurine - immune support; combats oxidative damage
Antioxidants - combat oxidative damage from free radicals
Zinc - acts as cofactor for antioxidants; tissue repair; albumin synthesis ○ B-vitamins - lost as water-soluble nutrients from vomiting/diarrhoea
Electrolytes - replace losses from illness
How Much to Feed:
Resting Energy Requirement calculation based on Body Weight:
RER = 70 kcal x (BW0.75)
● Start by targeting RER within first 3 days, but needs may exceed 2xRER in some recovery cases or where weight gain is needed.
● To avoid refeeding syndrome in severely malnourished patients, gradually increase feed over first few days (e.g. 33% of RER on Day 1, 66% on Day 2 and 100% on Day 3). ● Do not attempt to reach normal body weight during hospitalisation - short term weight fluctuations are mostly water weight. Establishing normal body weight will happen over time once discharged.
Assisted Feeding:
Preferred routes of feeding: voluntary intake > enteral nutrition > parenteral nutrition
Consider assisted feeding early and proactively (e.g., at time of general anaesthesia) - if pet is at risk of not eating 80% of RER for >3 days, the need for nutritional support is imminent.
Strategies to encourage voluntary intake and avoid food aversion:
Do not force or syringe feed - will not meet caloric need, creates food aversions
Keep environment calm, peaceful, move slowly. Consider all sounds (music, alarms), smells (cleaning products, pheromones), visuals (other pets, etc).
Offer food and give pet a chance to eat in peace; but do not leave food in cage overly long, especially with a nauseated or painful pet. Offer, then remove.
Smorgasbords can be overwhelming. Offer 1-2 options at a time.
What tube to use:
Consider functionality of upper GI tract/entire GI tract, length of time likely to need ● Consider nutrient/kcal density of food and need for dilution with water in smaller tubes, which increases volume
Hill’s Prescription Diet stews can all be blenderised to fit into a 10-French of larger tube without need for dilution
Feed smaller meals 4-6 times daily to avoid gastric distension
Nasal tubes: difficult to achieve caloric needs in most pets due to small size; generally less comfortable. Choose for short term use when unable to anaesthetise to place larger tube.
Resource: WSAVA Feeding Guide for Hospitalised Dogs and Cats, 2020
How long to leave tube in
Pet should be eating some food voluntarily 5-7 days
Pet should be eating >75% RER for at least 2 days
©Hill’s Pet Nutrition, 2024
Hillary Pearce, DVM, MRCVS
Hill's Pet Nutrition, Ltd. | Associate Manager, Professional and Veterinary Affairs, United Kingdom and Republic of Ireland