The development of lesions in vitamin A-deficient adult fowl.

Twenty-five cocks aged 7 months and 43 hens aged 18 months had been fed from hatching diets free from retinol but supplemented with retinoic acid. The retinoic acid supplement was withdrawn from 20 cocks and 23 hens and the birds developed signs of vitamin A deficiency. The deficient birds together with control birds fed retinyl acetate were killed and examined at intervals throughout the 18 days of the experiment. Observations were made on clinical signs; changes in tissues, particularly nasal epithelium, nervous system and bone, and cerebrospinal fluid pressures were recorded. The behaviour of the deficient birds was abnormal by the 3rd day of the experiment, a degree of incoordination was seen after the 6th day, and by the 10th day the weight of the deficient birds was significantly lower than that of the controls. Changes in nasal epithelium and in the periosteum lining the cranial cavity and vertebral canal were seen by the 3rd day of the experiment and after 6 days new spicules of bone were being formed. Compression of central nervous system and nerve fibre degeneration were well established by the 10th day. Dramatic changes in the cerebrospinal fluid pressure were not seen. Only 2 deficient birds had values outside the normal range and these were both recorded at the end of the experiment. These results are discussed and we conclude that the CNS compression is related to the increased deposition of periosteal bone.