Effects Of Different Dietary Phosphorus Levels And Ratio Of Calcium To Phosphorus With Phytase Addition On Metabolism Of Sows And Piglets

The objective of this study was to estimate the influence of different levels and ratio of phosphorus(P) and calcium(Ca) with phytase added on reproductive performance, nutrients digestibility, blood bone metabolism index of sows and piglets and bone of piglets.Seventy-two healthy and pregnancy(2 to 3 fetal, 45 days prior to farrowing) sows(Landrace × Yorkshire) on the same genetic background with close parturition date were randomly divided into nine groups with eight replicates per group. The control group was fed basal diet; Group 2 were fed the basal diet supplemented with phytase; groups 3 to 5 were fed diets with the same Ca level(7.26 g/kg) and phytase supplemented, and inorganic P addition was 75%, 50%, 25%(Ca to total P(TP) ratio was 1.35~1.63)of the control group respectively;Groups 6 to 9 were fed diets with Ca to TP ratio maintained 1.25:1 and phytase supplemented, and inorganic P addition was 75%, 50%, 25% and 0% of the control group respectively. A feeding experiment was conducted until farrowing.The results showed that: 1) In normal P level(5.81 g/kg) groups, supplementation of phytase significantly improved the AD(Apparent digestibility) of feed nutrition and dry defatted bone weight of tibia(P<0.05), and hormonal regulation inhibited bone mobilization of sows(P <0.01). The lower the Ca to TP ratio(1.25:1) and lower inorganic P level, the higher the effect of phytase on nutrient ATTD. 2) Dietary reduction of P level increased the AD of nutrition,bone metabolism index of sows,and reduced serum P significantly(P <0.05) with a linear or quadratic correlation(P <0.05). It increased bone resorption(type I collagen C telopeptide,tartrate resistant acid phosphatase-5b, bone-specific alkaline phosphatase, alkaline phosphatase) and reduced bone mineralization rate(osteocalcin, nursing osteoprotegerin),bone calcium and phosphorus deposition and fat-free weight, the piglets number of born weak significantly(P <0.05) with a linear or quadratic correlation(P <0.05)under the condition of unchanged Ca level or Ca to P ratio. 3) Substitutable inorganic P of phytase is 0.91 and 1.27g/kg which reduced fecal P excretion by 24.70% and 34.48% respectively when under thecondition of unchanged Ca level or Ca to P ratio based on the apparent digestible P. It will be50% of added inorganic P(0.90 g/kg) based on the bone metabolism index of sows and piglets and bone parameters of piglets. Compared with groups Ca level maintained 7.26 g/kg,Groups with Ca to TP ratio controlled 1.25:1 is beter for bone metabolism(P <0.05). In summary:1) Addition of phytase in normal P levels can improve the apparent digestibility of nutrients, reduce bone turnover rate of sows and improve bone formation and dry defatted bone weight of tibia of piglets 2) The lower inorganic P level, the higher the effect of phytase on nutrient AD. Reducing dietary inorganic P level result in a increasement(P <0.05) in absorption and reabsorption of P, bone resorption and bone formation of sows enhanced. In piglrts, bone resorption enhanced but bone formation weakened as dietary inorganic P reduced,that resulted in osteopenia, a reduction of bone mineralization and a increased number of weak piglets. 3) Phytase can reduced 50% of inorganic P added(0.90 g/kg) based on the bone metabolism index of sows and piglets. The ratio of Ca to P maintained 1.25:1 is more superior to improve nutrient digestion and suppress bone resorption of sows.