Captive waterbuck (Kobus ellipsiprymnus) have been found with unexplained high total (tBili) and direct bilirubin (dBili) concentrations compared with wild and domestic ruminant species. We hypothesized that increased bilirubin concentrations in waterbuck are age related and not associated with laboratory or clinical evidence of liver disease.
Retrospective data from clinically healthy (n=46) and diseased (n=26) individuals at the San Diego Zoo Safari Park were compared and subdivided into neonate (<8 dy), juvenile (8 dy to 2 yr), and adult (≥2 yr) groups. Paired t-tests and Chi square analysis showed that diseased waterbuck had significantly lower tBili, dBili, GGT, HCT than healthy waterbuck (p<0.05). No significant association was found between icteric serum and tBili for either population, but the mean tBili for healthy waterbuck (7.60 mg/dL) was significantly higher than reference limits for cattle and other Reduncinae species (p<0.05).1 Healthy juvenile and adult waterbuck had significant positive correlation between clear serum and hyperbilirubinemia (≥3.8 mg/dL), and diseased juveniles had significantly higher mean tBili than diseased neonates (p<0.05).1 Diseased waterbuck overall had a significantly lower mean dBili to tBili ratio than healthy (p<0.05).
Although tBili tended to be higher in adults, significant associations between hyperbilirubinemia, age, and disease status were not seen. Further studies are needed to elucidate the cause of altered tBili concentrations in captive waterbuck, and to verify the presence and type of bilirubin and its association with icterus.
The authors would like to thank the Veterinary Services staff and clerical volunteers from the San Diego Zoo Safari Park, as well as Dr. Marguerite Basso for their help with the collection and compilation of the data.
1. McSherry B.J., J.H. Lumsden, V.E. Valli, J.D. Baird. Hyperbilirubinemia in sick cattle. Can J Comp Med. 1984;48:237–240.