Dietary level of fat, calcium, and vitamins A and D3 as contributory factors to rickets in poults.

Two experiments were conducted on dietary predisposition to rickets in poults. The first experiment compared fat type (corn oil or tallow), level of added fat (3.5 or 7%), vitamin D3 (900 or 2,400 IU/kg feed), and total calcium (.6, 1.2, or 3%) inclusion in the diet. Poults fed diets supplemented with corn oil had higher percentage tibia ash than poults fed tallow-supplemented diets. Vitamin D3 included at 2,400 IU/kg feed increased body weights significantly by 2 and 4 weeks of age and lowered plasma alkaline phosphatase (AP) at 2 and 4 weeks compared with diets containing 900 IU/kg feed. Tibia ash was significantly greater with the higher vitamin D3 supplementation at 2 weeks. At 2 weeks of age both low (.6%) and high (3%) levels of dietary calcium increased plasma AP, decreased tibia ash, and decreased body weight compared with diets containing 1.2% calcium. By 4 weeks of age, diets containing 1.2 and 3% calcium had no significant effects on body weight and plasma AP; however, tibia ash was significantly greater with these levels than with the .6% calcium diets. The second experiment compared level of dietary tallow inclusion (2.5 or 7%) and supplementary vitamin A (4,000, 16,000, or 44,000 IU/kg feed). The high tallow diets decreased tibia ash at 3 weeks, and the maximum supplementation of vitamin A significantly depressed body weight. Clinical rickets were first noted at 18 days of age. By 26 days of age the higher level of dietary fat and the highest level of vitamin A caused a significant increase in severity of rickets. The results suggested that rickets can be induced by high dietary levels of tallow and vitamin A.