Nutrition of the cat. II. Protein requirements for growth of weanling kittens and young cats maintained on a mixed diet.

Abstract

From time to time during the past century reference has been made to the effects of meat diets on various animal species. The earliest papers refer to lions maintained on carcass meat in the collection of the Zoological Society of London. Crisp (1864) observed enlarged thyroids in lion cubs born at the zoo, and Bland Sutton (1888) described skeletal changes referred to as ‘rickets’ in cubs and young lions. Of an %weekold cub Bland Sutton wrote: ‘instead of playing with its companions it preferred to remain quiet. . . ; when attempting to walk it advanced a few paces, then staggered. . . the hindquarters rolled over. . .convulsions sometimes occurred’. This cub died at 12 weeks: its skull was found to be softened and much thickened. Bland Sutton noticed that cubs of 6 months or more suffered a less severe form of the disease, often surviving a year or two, the only constant sign being a slow progressive paraplegia. Some cubs, to which he gave supplements of bone dust and cod-liver oil, made a good recovery, and were alive and active without any signs of paralysis 2 years later. In spite of this observation, some 25 years later Marine (1914) wrote: ‘In zoological gardens where carnivores are held and bred in captivity and the diet is for the most part beef, goitre, rickets and osteomalacic states are quite common.’ Baumann (1896) observed that dogs fed on flesh diets frequently had enlarged thyroids of low iodine content. Watson (1904) found that fowls fed on raw lean meat and water died, in 3-16 months, with terminal paralytic signs; their thyroids were ten times the normal weight, though histologically normal apart from occasional hyperaemia. The parathyroids were also enlarged, but of normal structure. Watson (1906) reported marked thyroid hyperplasia in suckling rats whose mothers had been fed on meat, compared with the normal thyroids of those whose mothers received a mixed diet. Heitzmann (1873) noticed that rickets developed in cats fed on milk, boiled meat, white bread, boiled potatoes and fat. He was interested in lactic acid as a factor in the aetiology of rickets, but the diet he used was certainly deficient in calcium and probably also in vitamin D. The cats showed swelling and distortion of the long-bone epiphyses after 4-5 weeks on the diet; rickets was confirmed microscopically. After 4-5 months the long bones were soft ‘ . . .elastic, like a fish’, and at post-mortem the * Paper No. 3 : Brit. y. Nutr. (1960), 14, 361.