Enteral Nutrition and Energy Requirements in Animals

Clinical Safety Note: Regardless of the method used, verifying proper tube placement is a critical step to ensure patient safety and prevent aspiration. This is most commonly achieved using radiographs to confirm the tube's position within the GI tract.

Calculating Resting Energy Requirement (RER)

Before feeding begins, the clinician must determine the patient's nutritional needs. The baseline for this is the Resting Energy Requirement (RER), which represents the number of kilocalories (kcal) required per day to maintain basic physiological functions while the animal is at rest.

The formula to calculate RER is:

$RER = (30 \times \text{body weight in kg}) + 70$

Worked Example: Calculating Food Volume

Once the RER is established, you must determine how much of a specific liquid diet is required. This is done by dividing the total RER by the caloric density of the food (expressed in $\text{kcal/ml}$).

Scenario: A 3kg feline patient requires feeding with Hills A/D, which has a caloric density of $1.3 \text{ kcal/ml}$.

1. Calculate RER: $\begin{aligned} RER &= (30 \times 3 \text{ kg}) + 70 \\ RER &= 90 + 70 \\ RER &= 160 \text{ kcal/day} \end{aligned}$

2. Calculate Daily Food Volume: $\begin{aligned} \text{Food per day} &= \frac{160 \text{ kcal/day}}{1.3 \text{ kcal/ml}} \\ \text{Food per day} &\approx 123 \text{ ml/day} \end{aligned}$

Water Requirements

Hydration is just as critical as caloric intake, especially in patients recovering from vomiting or diarrhea, which can lead to severe dehydration and electrolyte imbalances. Water requirements are calculated based on the RER, but the multiplier differs between species to account for their specific physiological needs.

• Dogs: $\text{RER} \times 1.6 = \text{mls of water needed}$
• Cats: $\text{RER} \times 1.2 = \text{mls of water needed}$

Exam Tip: Always remember that water requirements are species-specific. While both use RER as a baseline, dogs require a higher multiplier ($1.6$) compared to cats ($1.2$).