Relative bioavailability of phosphorus in high-protein sunflower meal for broiler chickens and effects of dietary phytase supplementation on bone traits, growth performance, and apparent ileal digestibility of nutrients

An experiment was conducted to determine the relative bioavailability (RBV) of P in high-protein sunflower meal (HP-SFM) fed to broiler chickens based on bone traits and to determine the effects of dietary phytase supplementation and increasing levels of HP-SFM as a P source on bone traits, growth performance, and apparent ileal digestibility (AID) of DM and nutrients. In total, 240 broiler chicks were randomly allotted to 1 of 10 experimental diets with 6 replicate cages of 4 birds each and fed experimental diets from day 14 to 21 of age. Diets included a corn-soybean meal-based basal diet (0.35% total P; P-deficient diet), or the basal diet supplemented with 0.05, 0.10, or 0.15% P from either monosodium phosphate (MSP) or HP-SFM. Another 3 diets were formulated by supplementing the HP-SFM-containing diets with 500 phytase unit/kg of phytase. The bone mineral content (BMC), bone area (BA), and bone mineral density (BMD) of femur and tibia and tibia ash content increased (linear, P < 0.01) with increasing dietary P content from MSP. A linear increase in femur and tibia BMC, femur BA, and tibia BMD was also observed (P < 0.01) with increasing level of dietary P from HP-SFM. The RBV of P in HP-SFM based on femur and tibia BMC were 41 and 44%, respectively. Dietary phytase supplementation increased (P < 0.01) most of bone traits of the birds except for femur BMD. In addition, birds fed the diets supplemented with dietary phytase had greater (P < 0.05) BW gain, feed efficiency, and AID of P than those fed the diets without dietary phytase. In conclusion, the estimated RBV of P in HP-SFM to P in MSP were 41 and 44% based on femur and tibia BMC, respectively. Also, dietary phytase supplementation increased AID of P, growth performance, and bone traits of the birds fed P-deficient diets containing increasing inclusion level of HP-SFM as a P source.