Effect Of Dietary Phytase Supplementation On Growth Performance In Pigs And Its Mechanism

The effects of lasting phytase supplementation from weaned period to finishing period on growth performance , digestibility of Ca, P and CP , serum index concerning P metabolism and bone development , and the amount of inorganic P for which phytase supplementation can substitute were studied in pigs . This experiment was in a complete randomized design . 72 healthy piglets , homogeneous for weight , parity and age , were divided into four groups with three replicates , each of which including 6 piglets . The four treatment were : 1) corn—soybean meal basal diet(CSBM) (control group), 2)CSBM basal diet plus phytase substituting 50% CaHPO₄ (treatment 1),3) CSBM basal diet plus phytase substituting 75% CaHPO₄ (treatment 2), 4) CSBM basal diet plus phytase substituting 100% CaHPO ₄ (treatment 3). The results were showed as follow : (1) During the weaned and growing periods , there were no significant differences in ADG , ADFI and G:F ratio among treatment 1, treatment 2 and control group (P>0.05);however , ADG.,ADFI and G:F ratio decreased significantly when phytase substituting 100% CaHPO₄ (P<0.05) . (2) In the weaned and growing periods, the digestibility of Ca and P in groups of supplementing phytase were significantly higher than that of control group(P<0.05); the concentration of serum Ca and serum P in treatment 3 was significantly lower than that of control group(P<0.05), while there were no significant differences among treatment 1, treatment 2 and control group (P>0.05) .(3)ln the periods of weaned, growing and finishing, phytase supplementation had no significant effect on serum urea N(SUN) concentration and serum alkalione phosphatase (AKP) activity (p>0.05). (4)The digestibility of phytate P in the stomach significantly increased (P<0.01), and the amount of P excretion decreased as a result of phytase supplementation (weaned and growing period, P<0.01; finishing period, P<0.05).(5)There was no significant difference metacarpal bone ash between groups of phytase substituting 50% or 75% CaHPO₄ and control group , while , the metacarpal bone ash and the metatarsal bone strength in treatment 3 was significantly lower than that of control group ;the metatarsal bone strength in the group of phytase substituting 50% CaHPO₄ was significantly higher than that of Control group (P<0.05) , and there was no significant difference in treatment 2 and control group (P>0.05). (6)In finishing period , the concentration of serum Ca and serum P significantly decreased in treatment 3 compared with that of control group (P<0.05). (7)In the weaned and growing period , supplementing phytase with 750u/kg and 500u/kg respectively could substitute sufficiently 75% CaHPO₄ in control diets ;in the finishing period ,phytase supplementation with 250u/kg for substituting CaHPO4 had no significant effect on the growth performance , the digestibility of CP,Ca and P ,and the concentration of SUN and AKP activity . In a word,in the periods of weaned and growing , phytase supplementation substituting part of CaHPO₄ in corn-soybean based diet of pigs improved Ca,P digestion and utilization . improved bone development, also improved phytate P utilization, and decreased P excretion.