Promotie: Vitamin D and mineral metabolism in the hindgut fermenting Pachyderms

Elephants, rhinoceroses and tapirs (pachyderms) in zoos have problems with their mineral balance, including calcium deficiency (Asian elephant), phosphate deficiency (black rhinoceros), and iron overload disorder (rhinoceroses and tapir species). An imbalance in these minerals can lead to serious health problems such as stagnation during birth, impaired bone growth and even death. 
An obvious explanation for the emergence of mineral imbalances are differences in captive living conditions compared to the wild environment. The natural habitat of pachyderms is much closer to the equator, thereby exposing the animals to higher temperatures and more UV light. Both are necessary for adequate vitamin D production. Vitamin D plays an important role in mineral balance, especially that of calcium and phosphate. Additionally, the food provided in zoos differs from that in the wild, because the plants they normally eat are not available in Europe.
The studies showed that Asian and African elephants and Malayan tapirs in captivity seem to produce little to no vitamin D in the skin, in contrast to the Indian and black rhinos. However, black rhinos don't seem to be able to produce enough in winter. In African elephants and Malayan tapirs, no problems with calcium or phosphate were identified, suggesting that the role of vitamin D in the balance of these minerals is less significant, as is also the case in horses.
In addition to the higher availability of iron due to a different diet, the iron surplus in the black rhino may also be due to dysregulations in the body of this species, which also can lead to a shortage of phosphate. 
Aforementioned results are useful to formulate a more targeted advice to adjust living conditions for these animals in zoological collections, thereby helping to improve their health and welfare.