Vitamin D is an important hormone and is essential to many different processes within the body, including calcium homeostasis (through active intestinal and renal absorption of calcium), regulation of parathyroid hormone concentrations, and stimulating osteoclast maturation in the bones.1 In vertebrates, 2 primary methods are used to obtain vitamin D: via ingestion of prey or plant matter containing vitamin D or via photochemical synthesis from exposure to UVB radiation (wavelength, 290 to 315 nm).1 Although various vertebrates, including humans, are known to have the capacity to acquire vitamin D through their diet, dogs and cats are the only species known to use this method as their sole source of acquiring vitamin D.2 The production of vitamin D through exposure to UVB radiation is a multistage process.1 Because UVB exposure is an important catalyst to vitamin D synthesis in many vertebrates, including rabbits,3 it may be essential that they are provided exposure to UVB radiation. Under natural conditions or for animals housed outdoors, this occurs with exposure to sunlight; however, for animals housed indoors, this may not occur because glass or acrylic windows form an effective barrier to UVB radiation.4 It is possible that captive indoor pet rabbits rely on exposure to UVB radiation to generate vitamin D and may be deficient if not provided UVB exposure.
In domestic rabbits, calcium metabolism is somewhat independent of vitamin D because rabbits are known to passively absorb calcium from the intestine and maintain a total serum calcium concentration that is 30% to 50% higher than that reported for other mammals.5 Rabbits’ efficiency with calcium absorption is thought to be related to the increased calcium demand required for the lifelong growth of their teeth.5 Acquired dental disease is a common finding in pet rabbits5–7 and can present a major health risk to the rabbits and financial burden to the owners. It has been proposed that hypovitaminosis D may play a role in the development of nutritional osteodystrophy of the skull and acquired dental disease in pet rabbits.6–9 Given these concerns, it is important to investigate the physiologic relationship between husbandry and vitamin D for captive indoor rabbits. More specifically, because there are currently no recommendations to provide captive indoor rabbits exposure to UVB radiation, there is a need to evaluate whether serum vitamin D concentrations in these animals are influenced by the provision of UVB light.
The purpose of the study reported here was to determine the effects of UVB radiation produced by artificial lights on serum 25-hydroxyvitamin D concentrations in domestic rabbits (Oryctolagus cuniculi). Because exposure to UVB radiation has been shown to increase plasma 25-hydroxyvitamin D concentration in reptiles,10–13 we were interested to determine whether such treatment could have a similar effect on captive indoor rabbits. The biological hypothesis tested was that captive juvenile rabbits exposed to UVB produced by commercial fluorescent light bulbs would have significantly higher serum 25-hydroxyvitamin D concentrations than captive juvenile rabbits that were not exposed to the supplemental UVB.
Sailfin Pet Shop, Champaign, Ill.
72 × 44 × 41.5 cm, Marchioro S.p.A., Isola Vicentina, Italy.
Sunseed Co, Bowling Green, Ohio.
Western Timothy Hay, Oxbow Animal Health, Murdock, Neb.
Wool Formula 17–19, Heinold Feeds, Kouts, Ind.
Butler Animal Health Supply Co, Dublin, Ohio.
Tyco Healthcare Group LP, Mansfield, Mass.
IEC HN-SII Centrifuge, Thermo Electron Corp, Milford, Mass.
CryoTube vials, 1.8 mL, Nunc A/S, Roskilde, Denmark.
Sun-Glow Coil Lantern, 20 W, 5.0 UVB, Fluker Farms, Port Allen, La.
UV meter No. 1400, International Light Inc, Newburyport, Mass.
Diagnostic Center for Population and Animal Health, East Lansing, Mich.
SPSS, version 19.0, SPSS Inc, Chicago, Ill.
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