Beta-carotene supplementation of turkey diets varying in fat and retinol

1. The effects of supplementary beta-carotene (BC) at 0, 1.5, 15, 150, 1500 or 15,000 mg/kg diet on performance, incidence of leg problems, tibia ash, and plasma and liver concentration of BC and retinol of poults to 4 weeks of age were studied. 2. Body weight and food intake increased with dietary BC supplementation. Incidence of leg problems was not affected but tibia ash increased with BC supplementation. Plasma and liver BC and liver retinol increased with dietary BC but plasma retinol was not affected. 3. The effects of 0, 1.5, 15 or 150 mg BC/kg in diets containing either 30 or 60 g added fat/kg and either 1.2 or 12.0 mg retinol/kg on the above properties were studied in poults to 4 weeks of age. 4. Performance was not significantly affected by dietary fat. Efficiency of utilisation of food was depressed by the higher concentration of retinol. At 3 weeks of age birds given BC had fewer leg problems and higher tibia ash values than the control birds. Liver BC and retinol and plasma BC concentration increased with dietary BC. By 4 weeks, plasma and liver BC was higher and liver retinol was lower for birds given 1.2 compared with those given 12.0 mg/kg of retinol.