Blood Taurine Dynamics in Captive Lions: Relationship with Feed and Bile Acid Composition

Taurine is an essential nutrient for felines including lions. Various severe symptoms induced by taurine deficiency have been reported for domestic and captive felines. Particularly for captive lions in zoos, little information related to taurine requirements is available. Therefore, this study evaluated the relationship between blood taurine concentration and taurine content in prey feed given at zoos, as well as the composition, types, and conjugation properties of bile acids (BAs) in blood collected repeatedly from four lions housed at three zoos. Blood taurine concentrations in four lions were within the normal range, although individual differences and variations were found. Taurine was abundant in feed supplied at the zoos. A positive correlation between blood taurine concentration and feed amount was observed in lions housed at the same zoo. Approximately 70-80% of the total BA pool was cholic acid, with 50-70% being taurine-conjugated. Individual differences and variations were found. No correlation was found between blood taurine concentration and the compositions of BAs in the blood. Results showed that supply of taurine was sufficient for all lions fed the prey feed. Future studies must be conducted to clarify influences on individual differences, as well as individual variations in blood taurine concentration and blood BA composition.