Effect of Different Dietary Levels of Calcium and Non-Phytate Phosphorus, with a Constant Ratio of 2:1, in Starter and Grower Periods on Performance of Broiler Chickens

This experiment was conducted to determine the influence of different concentration of calcium (Ca) and non-phytate phosphorus (NPP), with a constant ratio of 2:1(Ca:NPP), on young broiler chickens. A total of 900 Ross 308 d-old male broiler chickens were randomly allocated to 60 pens (15 birds per pen). Four dietary treatments including high concentration of Ca and NPP (H), moderate concentration of Ca and NPP (M), low concentration of Ca and NPP (L), and very low concentration of Ca and NPP (VL) were given to the birds. The concentration of Ca was 9.6, 7.6, 5.6, and 3.6 g/kg of diet, respectively. In starter period, broiler chickens fed the M diet showed the lowest feed conversion ratio (FCR) in comparison to those received the H, L and VL diets. In grower periods, broiler chickens fed the H diet had the highest average daily feed intake (ADFI); M and L diets showed the highest average daily weight gain (ADG) compared to H and VL diets. In whole period, broiler chickens fed the H and M diets showed the highest ADFI in comparison to those received the L and VL diets and FCR was higher in broiler chickens received H diet in comparison to those fed M, L and VL diets. Decreasing the dietary Ca and NPP level elicited linear reductions in tibia Ca. The count of lactic acid bacteria in the duodenum improved with increasing levels of Ca and NPP. In conclusion, M treatment could support maximal ADG and body weight, while lowest FCR was obtained from birds received L diets. The use of L treatment resulted in comparable Ca and phosphorus content of tibia bone compared to those of M treatment.