Nutrition and skeletal problems in poultry.

Several excellent reviews regarding nutrition and skeletal disorders have appeared in the last 20 yr. This review will cover several areas of vitamin D research, the area of feed deprivation, and bone abnormalities, because there has been considerable interest in these areas during the past 10 yr. Studies indicate that the quantitative requirement for cholecalciferol (D3) for broiler chickens is much greater than previously thought. Ascorbic acid may play a role in stimulating 1-hydroxylation of 25-hydroxycholecalciferol [25-(OH)D3], but the evidence is not clear under exactly what conditions this relationship is important in practical prevention of tibial dyschondroplasia. Studies indicate that dietary supplementation with 1,25-dihydroxycholecalciferol [1,25(OH)2D3] will reduce the incidence of tibial dyschondroplasia in three different strains of broilers bred to develop a high incidence of the disease. But it did not prevent the disease totally in the strains, unless high enough levels of 1,25-(OH)2D3 were fed to reduce growth rate. These studies indicate that these high tibial dyschondroplasia strains have a defect(s) in vitamin D metabolism. Studies continue to elucidate the role of ultraviolet light in preventing leg abnormalities. Only a few studies have been conducted on the efficacy of various vitamin D3 derivatives to prevent tibial dyschondroplasia. Feed deprivation continues to be an intriguing method of preventing tibial dyschondroplasia, and examination of exactly how this prevents the bone abnormality could open avenues for explaining the disease.