Disorders of calcium metabolism have been reported in captive primates on many occasions. Dietary supplementation and outdoor access (exposure to natural UVB radiation) are two techniques commonly employed to provide adequate vitamin D levels to prevent these disorders. However, whether outdoor access in northern Europe provides sufficient UVB for primates which originate from regions much closer to the equator has not been proven. The natural habitat of New World primates is a range in Central and South America that lies between latitudes 20° north and 20° south. Lemurs naturally inhabit Madagascar and the Comoro Islands, which lie between 11° and 26° south. The UK zoo in which the current study was carried out lies on latitude 51° north.
In order to determine whether outdoor access was beneficial to New World primate and lemur species at the UK zoo in terms of UVB exposure, serum levels of 25-hydroxy-vitamin D3 and environmental UVB levels were measured in summer and winter. All of the primates received vitamin D3 supplementation in their diet, and these dietary levels remained constant throughout the year.
Environmental UVB levels at the zoo were shown to be substantially lower than those that occur in the native habitats of the primates. UVB levels at the zoo were also shown to be substantially lower in winter compared to summer. In the majority of New World species sampled, mean vitamin D3 levels were found to be low compared to previously published values and did not vary significantly between summer and winter. In contrast, the mean lemur vitamin D3 levels were generally found to be high compared to previously published values and did vary significantly between summer and winter, summer levels being greater than winter values.
Possible reasons for the difference observed between the New World primates and lemurs in terms of variation of vitamin D3 levels between summer and winter include the lemurs’ sunning behaviour allowing them to make better use of the UVB levels available, or an innate New World primate requirement for higher levels of UVB than lemurs in order to produce vitamin D3.
This study shows that simply providing outdoor access in northern Europe (and therefore other regions of similar latitude) cannot be relied upon to supply UVB levels sufficient to prevent vitamin D deficiency in New World primate species.
The authors wish to thank the veterinary staff and primate keepers at Bristol Zoo Gardens, Adrian Sayers, Frances Baines, Christoph Schwitzer, Kate Robson Brown and Pinmoore Animal Laboratory Services for their help with this project. Rowena Killick’s residency is sponsored by Bristol Zoo Gardens and the RCVS Trust.