Now that we have an understanding of what components the diet should include, and in what proportion, and how much energy a gibbon needs, we can formulate the actual diet. To illustrate the process, we will break this down into smaller steps.
Step 1: Establish the total food weight target
To satisfy a primate’s physical hunger and fiber needs without overfeeding calories, we need to calculate the daily fresh matter intake. This is the target weight of the diet as we feed it: a standard baseline is to provide 10% to 15% of the animal’s body weight in total fresh food per day.
- Total daily food weight target: For a healthy, active 10 kg siamang, eating 15% of their body weight in fresh food, means 1,500 grams (1.5 kg) of total fresh food per day.
- This diet must, in the same time, fulfill the animal’s energy need, as well as macronutrient (protein, fat and carbohydrate) requirements. Typically it is not difficult to achieve enough carbohydrates are consumed, but it can be challenging to find the right balance of fats, protein and fibre in the diet.
Step 2: Build the foundation of the diet
As we discussed previously, the majority of the diet should consist of raw vegetables. We divide this into the three categories: leafy green vegetables (group A), root vegetables (group C) and other vegetables (group B).
- Group A – Leafy green vegetables (35% of total weight): 525 grams
- Examples: Raw bok choy, napa cabbage, or water spinach.
- Group B – Non-leafy/Non-root vegetables (25% of total weight): 375 grams
- Examples: Raw cucumbers, green bean stems, and various plant stalks.
- Group C – Root vegetables (15% of total weight): 225 grams
- Examples: Raw carrots, or sweet potatoes.
Step 3: Ensure enough protein is provided
To hit the target of roughly 15% crude protein without resorting to animal products, we introduce cooked pulses and seeds. These are normally kept under 10% of the overall physical weight to prevent excessive calorie density.
- Pulses and seeds (10%): 150 grams
- Examples: Cooked lentils, chickpeas, split peas, or pumpkin seeds.
- Be careful, as seeds and nuts are high in fats, and therefore, in energy. A good balance in our case could be about 120g pulses (lentils beans or peas) and only about 30g of seeds (eg. pumpkin seeds). An alternative approach could be to include some avocado in the diet, which contains large amount of fats as well. However, as avocado contains more water than seeds, you’d need about 100g avocado to replace 30g of seeds.
- Note: Nutritional targets (like 15% protein) are normally calculated on a “Dry Matter” basis, meaning all water is mathematically removed to evaluate the concentrated nutrients. Because the fresh vegetables in Step 2 can be up to 90% water, their dry weight is very low. On the other hand dry pulses, seeds and nuts are low in water, meaning their dry matter is high. Therefore, even small portions of these can provide the concentrated proteins (and quite a bit of energy) necessary for our diet.
Step 4: Add wild browse
The final weight percentage is dedicated entirely to wild browse, leaves, and branches. While browse provides some micro-nutrients, its primary purpose is behavioral enrichment and the provision of fibre, keeping the siamang active and mimicking wild foraging times.
- Wild browse (10% of total weight): 150 grams
- Examples: Fresh, non-toxic local tree leaves, twigs, and bark.
- Note: Because leaves are extremely light, even just 150 grams of fresh browse will look like a quite big pile compared to 100 grams of root vegetables.
Step 5: Verify the energy content and nutrient requirements
Once the physical weight items are prepared, staff should do a quick check against the calorie target and nutrient requirements:
- Calorie check: The combined energy value of this 1,500 gram diet is approximately 730 to 750 kcal/day. This falls into the upper range required for an active 10 kg siamang in a large enclosure. About 2/3 of all energy in this diet comes from root vegetables, pulses and seeds.
- Fats kept low (4-6%): The natural fats found within the vegetables, combined with about 30 grams of seeds, yield roughly 6% fat on a Dry Matter basis, staying at the higher end of the recommended limits. Most of the fats in this diet come from seeds. Vegetables, browse and pulses are all very low in fats.
- Protein kept moderate (about 15%): This diet yields roughly 16% Crude Protein (on a Dry Matter basis), achieving the required amount. Protein is relatively evenly distributed within this diet, as both vegetables, pulses, browse and seeds contain some.
- Consider micronutrients: For most animals this diet will provide the necessary vitamins and minerals. However, some animals might require additional micronutrients, due to historical malnutrition, or due to temporary circumstances (eg. animals kept completely indoors will need additional vitamin D provision in their diet). A veterinarian should decide if supplementation is required.
Step 6: Design a daily feeding routine
Now that we have our full day diet plan, we just need to divide the whole amount with the number of feeds. In most cases it would be ideal to provide at least 3 feeds per day, to mimic the slow and steady foraging of wild gibbons. This would mean to split the diet into three portions. It is not necessary that at every meal every component is provided, though it’s generally recommended to give browse as frequently as possible. In many instances it helps to provide only one type of food at a meal, especially when animals are picky eaters and selectively leave some of their diet.