Creating a nutritionally balanced diet requires a combination of locally available vegetables, wild browse, and other food items. The majority of the daily provision by weight should consist of vegetables. A highly effective target for managed gibbon diets is to provide 30 to 40% leafy vegetables (for example bok choy, napa cabbage, or water spinach), 20 to 30% non-leafy/non-root vegetables (such as cucumbers, green bean stems and stalks), and up to 20% root vegetables (such as carrots, potatos, or sweet potatoes). Whenever possible, unless individual circumstances dictate otherwise, vegetables should be fed raw. At least 10% of the diet should be browse: leaves, twigs, shoots of wild plants naturally consumed by gibbons.
In terms of nutrient composition, the overall diet should aim for roughly 15% crude protein. While wild gibbons opportunistically consume insects or bird eggs, it is not necessary to feed captive gibbons animal-based proteins like hard-boiled eggs or chicken. Instead, protein should be sourced from pulses (like lentils, beans or peas) and seeds. These energy-dense items should total less than 10% of the overall diet. Dietary fats should be limited to 4-6%. Excessive fat, particularly from oils or peanut butter, can cause diarrhea and long-term these can also lead to obesity. If a diverse mix of native browse, leafy greens, and pulses is provided, vitamin and mineral supplements are rarely necessary, though they may be prescribed by veterinary staff for individuals recovering from severe historical malnutrition.
Now that we understand what components the diet should have, we need to also determine, how much to feed. For this, we need to calculate our animal’s energy requirement.