For tortoise, terrapin and turtle care and conservation
Dietary supplementation of tortoises is important as they have specific dietary requirements for minerals and vitamins. Sadly it is unknown exactly how much is required for these for different species, different ages of tortoises and the requirements for breeding females. The amount of supplementation required also depends on the diet being eaten by the tortoise (which is different to the diet being offered of course). Thus it is only possible to provide some general guidelines on which sort of supplementation to use and how often to provide it.
The calcium level required in a tortoise’s diet is generally accepted as being 1% of the dry matter and a calcium: phosphorous ratio of 2:1 in the total diet is recommended. However, at certain life stages there are increased demands on calcium. For example, to lay a single egg can require an extra 500mg of calcium to be added to the diet. Thus reproductively active females have a higher requirement and some authors recommend providing them with a 10:1 ratio in the diet. These females may also be anorexic and thus avoid ingesting calcium just at the point when they need it.
This is why we can see problems with reproductive disease or nutritional related problems in breeding females when the males on the same diet show no clinical signs.
When selecting a supplement it is important to choose one with a high calcium to phosphorous ratio, such as Nutrobal® which has a ratio of 46:1. Other products are available on the market, which contain calcium carbonate. These can be used to provide extra calcium without increasing phosphorous levels. Products such as Nutrobal® do contain other vitamins and minerals and are fine to be used for juveniles and reproductively active females. High calcium content foods should be selected and calcium carbonate can also be used to balance out the diet. Cuttlefish is commonly used for tortoises but should not be relied upon as a calcium source. Ultraviolet light is also important to enable the tortoise to produce vitamin D and relying on dietary sources is not advised until research proves this to be suitable for basking chelonians.
Providing multivitamin supplementation is also advised and there are products that contain water soluble vitamins, such as vitamin A. Vitamin A deficiency is still commonly seen most notably in aquatic species such as Red Eared Terrapins. Older animals may benefit from lower calcium levels and products such as Arkvits® can be used. It is important to read the label on all supplements and to use them in moderation.