Bone phosphorus retention and bone development of broilers at different ages

The present study was carried out to investigate the tibia phosphorus (P) retention and development as well as their correlations and possible mechanisms of broilers at different ages. A total of 320 1-day-old Arbor Acres male broilers were raised in 8 replicate cages of 40 birds per cage, and fed the same corn-soybean diets for 42 d. Plasma and tibia samples of broilers were collected on day 0, 7, 14, 21, 28, 35, or 42. The results showed that the tibia ash P content increased linearly (P = 0.017), and the total P accumulation in tibia ash increased linearly and quadratically (P < 0.001) with age. The traits of bone development including the tibia bone mineral content (BMC), the tibia bone mineral density (BMD), and the tibia ash content increased linearly and quadratically (P < 0.001), while the tibia breaking strength increased linearly (P < 0.001) with age. The tibia bone gal protein (BGP) content decreased linearly (P = 0.011), but neither a linear nor quadratic (P > 0.15) response was observed for the tibia alkaline phosphatase (ALP) with age. The tibia ash P content was positively correlated with the tibia BMD (r = 0.325, P = 0.014), ash (r = 0.325, P = 0.001), and ALP (r = 0.377, P = 0.004). The total P accumulation in tibia ash also was positively correlated with all of the above traits of bone development (r = 0.437 to 0.976, P < 0.001); however, it was negatively correlated with the tibia BGP (r = -0.426, P = 0.0014). Additionally, the tibia ALP was positively correlated with the tibia ash (r = 0.369, P < 0.001), and the tibia BGP was negatively correlated with the tibia BMC (r = -0.453, P < 0.001), breaking strength (r = -0.384, P < 0.001), and ash content (r = -0.361, P < 0.001). The above results indicated that the bone P retention was involved in the bone development of broilers from 1 to 42 d of age possibly via the regulation of the bone ALP and BGP.