By Mark A. Mitchell DVM, MS, PhD, DECZM (Herpetology)

Rabbits are popular pets, with 3.2 million in U.S. households, according to a 2012 AVMA survey. Veterinarians should be prepared to help educate their clients about best practices for rabbit husbandry.

Rabbits’ lighting needs have not been explored in depth. Rabbits evolved to be crepuscular (active at dawn-dusk) to diurnal (daytime); therefore, they spend a fair amount of their day exposed to natural sunlight, which provides three important spectrums of light:

ultraviolet light, associated with the photobiochemical synthesis of vitamin D in some vertebrates;

visible light, which allows vertebrates to see in a certain range of colors; and

infrared light, associated with the heat provided by the sun.

The importance of ultraviolet radiation for captive animals is only now being investigated, primarily in reptiles. Because rabbits, much like diurnal reptiles, can synthesize vitamin D when exposed to natural ultraviolet B radiation, we recently studied the impact of artificial ultraviolet B radiation on the vitamin D levels of captive rabbits. We found vitamin D levels significantly higher in rabbits exposed to artificial ultraviolet B radiation than in their cohorts not exposed to ultraviolet B radiation.1

Given the importance of vitamin D as an essential hormone that regulates many biological functions, a further study was completed by Dr. Megan Watson to evaluate the long-term (6 months) effects of exposing rabbits to ultraviolet B radiation. The findings reinforced the pilot study and showed that rabbits exposed to ultraviolet B radiation maintained significantly higher vitamin D levels over the course of the study. No side effects were found to be associated with regular exposure to ultraviolet B radiation. The research suggests that pet rabbits housed indoors would benefit from exposure to ultraviolet B radiation.

It should be noted that housing indoor rabbits near windows will not provide exposure to ultraviolet B radiation because glass removes these short ultraviolet B wavelengths. However, commercial ultraviolet B light bulbs are available at many pet retailers. Current recommendations are that the lights should be placed within 9 inches of the animal’s cage and changed every 9 months, as the ultraviolet B radiation decays over time in these bulbs.

Studies in chinchillas and guinea pigs found similar results, suggesting that these animals may also benefit from exposure to ultraviolet B radiation. We are planning further research into the role of lighting in the long-term health of pet rodents.

1 Emerson JA, Whittington JK, Allender MC, Mitchell MA. Effects of ultraviolet radiation produced from artificial lights on serum 25-hydroxyvitamin D concentration in captive domestic rabbits (Oryctolagus cuniculi). Am J Vet Res. April 2014, Vol. 75, No. 4 , 380-384.

This article appeared in rvetILLINOIS, Vol. 1, Issue 6.