Effect of dietary calcium concentrations in phytase-containing diets on growth performance, bone mineralization, litter quality, and footpad dermatitis score in broiler chickens

This experiment was conducted to investigate the effect of dietary Ca concentrations in phytase-containing diets on growth performance, bone mineralization, litter quality, and footpad dermatitis (FPD) score in broiler thickens. A total of 2100 1-d-old Ross 308 broiler chicks was used and allotted to 1 of 5 dietary treatments with 6 replicates consisting of 70 birds in a completely randomized design. Five commercial-type diets were formulated to contain increasing Ca concentrations of 6.0, 7.0, 8.0, 9.0, or 10.0 g/kg. All diets contained 3.5 g/kg nonphytate phosphorus and 1000 FTU/kg phytase. Diets were fed to birds for 21 d. At the end of the experiment, birds were sacrificed for tibia sampling and litter samples were collected. The FPD score was measured visually based on a 6-point scale scoring system. Results indicated that increasing Ca concentrations in phytase-containing diets decreased (linear, P < 0.01) body weight gain, feed intake, and feed efficiency of broiler thickens. The concentrations of ash, Ca, and P in the tibia, and tibia breaking strength were not affected by dietary Ca concentrations. Dietary Ca concentrations had no effect on litter quality including pH and moisture and nitrogen contents. A tendency (linear, P = 0.10) for increased FPD score was observed as dietary Ca concentrations were increased. In conclusion, increasing Ca concentrations from 6.0 to 10.0 g/kg in phytase-containing diets have negative effects on growth performance of broiler chickens during 21 d posthatch, possibly due to decreased FI and subsequent phytase intake. Increasing Ca concentrations in phytase-containing diets have little impact on litter quality but tend to increase FPD incidence in broiler chickens.