Metabolic bone disease in lion cubs at the London Zoo in 1889: the original animal model of rickets.

In 1889 Dr. John Bland-Sutton, a prominent London surgeon, was consulted about fatal rickets in over 20 successive litters of lion cubs born at the London Zoo. He evaluated the diet and found the cause of rickets to be nutritional in origin. He recommended that goat meat with crushed bones and cod-liver oil be added to the lean horsemeat diet of the cubs and their mothers. Rickets were reversed, the cubs survived, and subsequent litters thrived. Thirty years later, in classic controlled studies conducted in puppies and young rats, the definitive role of calcium, phosphate and vitamin D in prevention and therapy of rickets was elucidated. Further studies led to identifying the structural features of vitamin D.Although the Bland-Sutton diet provided calcium and phosphate from bones and vitamins A and D from cod-liver oil, some other benefits of this diet were not recognized. Taurine-conjugated bile salts, necessary for intestinal absorption of fat-soluble vitamins, were provided in the oil cold-pressed from cod liver. Unlike canine and rodent species, felines are unable to synthesize taurine, yet conjugate bile acids exclusively with taurine; hence, it must be provided in the diet. The now famous Bland-Sutton "experiment of nature," fatal rickets in lion cubs, was cured by addition of minerals and vitamin D. Taurine-conjugated bile salts undoubtedly permitted absorption of vitamins A and D, thus preventing the occurrence of metabolic bone disease and rickets.