Nutrition

Healthy and varied nutrition is important for all organisms. When compiling a diet for an animal in captivity, it is best to investigate what the natural diet of this species consists of. Many water turtles eat animal food when they are young. Many species also add plant-based foods to their menu as they age, and some species almost only eat plants as adult animals.

Turtles are cold-blooded animals and therefore do not use the energy they gain from their food to keep their bodies at a stable temperature. As a result, they need less nutrition than warm-blooded animals. Pets such as dogs and cats must be fed several times daily. If the same were to be done in turtles, the animals would quickly get too fat.

Very young animals up to six months old should be fed as much feed daily as they can eat within minutes. Some older animals can be fed the same amount every other day. For adult water turtles, feeding 3 times a week is sufficient. Give the animals as much as they can eat in a few minutes. Turtle species that are not very active, like musk turtles, should be fed more moderately. Feed per feeding amount of food that would fit in the head of the animal.

Water turtles can only swallow food in the water. Therefore, the food should be offered in the water and not placed on the land part. Turtle species that live mainly on land, such as Terrapene and Cuora can also eat on dry land.

Most water turtles are carnivore or omnivorous. Species such as the DiamondBack Turtle (Malaclemys terrapin) only eat animals and are therefore carnivores. Red earded sliders and yellow bellied sliders (Trachemys ssp.) are examples of omnivorous species. They eat both animals and plants Young animals of these species eat almost exclusively animal food in order to be able to grow and develop quickly. When they reach adulthood, plants make up a larger part of the diet. 

Macronutriënts:

Macronutriënts are nutrients that make up the bulk of nutrition, these are proteins, fats and carbohydrates.

Proteins consist of amino acids and are used for growth and recovery. Proteins from the diet that a turtle absorbs are broken down into amino acids in the gastrointestinal system. These are then used to produce new proteins and enzymes for the turtle.

Carbohydrates are simple sugars (e.g. granulated sugar) and multiple sugars (e.g. starch). Sugars are mainly used as a source of energy and to a lesser extent as a building material.

Fats are energy-rich connects consisting of glycerol and fatty acids. Fats are used to store energy when sufficient food is available and converted back into energy in periods of scarcity. Fat is also important to absorb vitamins and as a building material.

Micronutriënts:

Micronutrients are nutrients that make up only a small part of nutrition.

• Vitamins are compounds that occur in small amounts in food and of which vitamin D can also be produced by animals themselves. They play an important role in all kinds of bodily functions. For example, vitamin D is needed to absorb calcium from food and vitamin C is an important part of enzymes and hormones.
• Minerals are substances that occur in small amounts in food and are used for building and recovery, such as calcium, phosphorus, sodium etc. These substances are the building blocks for, for example, the skeleton and shell. They also play an important role in fluid management and muscle and nerve functions.
• Trace elements are minerals that are needed in very small quantities such as iodine and iron. These substances are needed in the endocrine system, as part of enzymes (iron in red blood cell hemoglobin) etc.

Calcium : Phosphate ratio: 

Calcium and phosphate are both needed for a healthy skeleton. These two substances should be present in the turtle's body in a correct ratio. When a turtle receives too much phosphate in relation to the amount of calcium, its body will correct this by extracting calcium from the blood and ultimately also from the skeleton. This finally leads to metabolic bone disease. Conversely, too much calcium and/or too little phosphate also leads to health problems. An ideal ratio between calcium and phosphate is 2:1.

In addition to calcium-rich prey, water turtles can also be provided with extra calcium in the form of sepia. This is the internal shell of squid and sea cats. The whole shell or pieces of shell can be put in the water so that the animals can eat it if they need it.

For species that live and eat mainly on land, such as Terrapene and Glyptemys, calcium powder can also be sprinkled over the feed. Be carefull with calcium powder that have added vitamins.  Depending on the amounts of vitamins and the frequency of use of the powder, an overdose could occur. An overdose of vitamin can damage the health of the animal. Therefore it is better to opt for a calcium powder without vitamins and if desired a separate powder with only vitamins and follow the recommended dosage.

Insects as prey item:

Many aquatic turtle species eat insects and insect larvae. Insects are a good source of protein and unsaturated fatty acids. However, most insects that are typically fed to aquatic turtles are high in phosphate, which gives them a poor calcium : phosphate ratio. This can be somewhat reduced by feeding the insects with calcium rich food. Insect larvae such as mealworms and wax moth larvae also contain a lot of fat and can best be fed to aquatic turtles in moderation. Hermetia larvae are larvae of the black soldier fly and may be a better food choice than mealworms. They are nutritionally comparable but have a much better calcium : phosphate ratio. Cockroaches contain a lot of protein. They can easily be made even more nutritious by gutloading them as cockroaches will eat almost anything.

Invertabrates as prey items:

Animals such as worms, woodlice and snails are excellent food for aquatic turtles and are eagerly eaten. They contain a lot of protein, little fat and have a favorable calcium : phosphate ratio due to their high calcium content.

Worms and woodlice are easy to catch from your own garden and, moreover, they move a lot, which makes them very attractive for young animals that still have to get used to food.
Snails can be given with shell and all. The shell is a good source of calcium and also gives the turtles something to do to get to their meal. While snails are a great food you have to be carefull, they may have eaten slug pellets or carry parasites. Only collect them in places where no poison is sprinkled and freeze them before feeding (defrost again before giving them to the turtles of course) to kill parasites.
Freshwater shrimp and small freshwater crayfish are also suitable food for aquatic turtles. Because of their shell they contained a lot of calcium and almost all turtles like to eat them. 

Vertebrate prey items:

Small prey such as nest mice and fish are also suitable as food for turtles. Muscle meat from larger animals such as beef, pork and poultry can also be given, but it is better to opt for whole animals. In addition to proteins and fats, these also contain almost all necessary vitamins, minerals and ballast materials.

Fish, especially very small fish, are also suitable for feeding. One point to note is that many fish species contain thiaminase. This is an enzyme that breaks down vitamin B. If the diet is too one-sided, the animal runs the risk of a vitamin B deficiency. This manifests in neurological damage. Therefore, feed your animals a varied diet to avoid shortages.

Seafood:

Seafood such as mussels, cockles, squid, shrimp and krill can be fed to aquatic turtles. Don't give them too often. Marine animals do not occur in the natural habitat of most aquatic turtles, with the exception of Malaclemys terrapin.

Commercial pellets:

Commercial turtle food is available in many brands, sizes and compositions. Avoid dried fish and shrimp. These can be given as a treat, but add little nutritional value to the diet of aquatic turtles. Choose good quality sticks and granules.

Aquatic turtles can also be fed cat food. They contain a lot of proteins, vitamins and minerals. Depending on the brand, they contain 10 -25% fat and should not be fed too much. Due to their high protein and fat content, they strongly pollute the water.

Lundi pellets for waterfowl are also suitable as feed. Not all species of aquatic turtles like to eat them. They are high in protein, vitamins and minerals and low in fat. These granules have the disadvantage that they sink quickly and fall apart in the water.

Koi pellets are suitable for feeding to aquatic turtles. They are available in a wide variety of size, composition, color and buoyancy. The advantage of koi pellets is that they contain little fat, proteins, vitamins and minerals and are easy to eat. Red granules in particular have a strong attraction to turtles.

Avoid dried fish and shrimp that are sold in pet stores as food for turtles. These are only suitable as a treat and not as food.

Plants:

Aquatic plants such as duckweed, waterweed, cabomba and lily pad can be offered as vegetable food. Vegetables such as endive, spinach and bean sprouts are also eaten well. Lettuce can also be given, but contains mainly water and few nutrients.

Species that eat fruits in their natural habitat can be fed with the following fruits: blueberries, blackberries, raspberries, strawberry, apple, plum, pumpkin and cherries. Banana can occasionally be given as a treat.

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