Increasing dietary cholecalciferol for improved broiler marketability

Two hundred commercial broilers were fed four graded levels of cholecalciferol (200, 400, 600 and 800 icu/kg diet) above recommended levels in a basal diet containing the fixed calcium and phosphorus level. The normal recommended dietary cholecalciferol inclusion level for broilers is 200 icu/kg feed. The experiment was conducted for 8 weeks in a completely randomized design. Higher doses of cholecalciferol produced significant (P<0.05) body weight gain and feed intake. Total feed intake observed (5070 g/bird) and weight gain (2550 g/bird) were at least 19% higher for birds fed 100% dietary cholecalciferol supplementation compared with birds fed at normal recommended dietary inclusion levels. Serum calcium and phosphorus responded positively (P<0.05) to increased levels of dietary cholecalciferol being the highest for 400% dietary cholecalciferol supplementation at 0.90 and 0.77 mmol/L, respectively. Plasma alkaline phosphatase and tibial bone ash was optimum at 400 icu/kg (100% cholecalciferol dietary supplementation) diets, the values being 75 iu/L and 38.6%, respectively. Birds fed the normal recommended dietary cholecalciferol inclusion level (200 icu/kg feed) recorded the lowest values (52 iu/L and 24.3% respectively) for these parameters. Broilers fed the normal dietary cholecalciferol inclusion level showed late signs of tibial dyschondroplasia; this was however not noticeable in birds fed higher doses of vitamin D₃. Histology of liver and kidney did not reveal any significant tissue calcification even at the highest (800 icu/kg diet) dose. It is concluded that higher doses of cholecalciferol in broiler diets may be necessary for optimum performance and reduction of cases of leg abnormalities.