Influence of a novel phytase on Ca and P digestibility in diets fed to sows in late-gestation and lactation

Two experiments were conducted to test the hypothesis that a novel phytase based on Citrobacter braakii increases Ca and P digestibility and influences concentrations of cytokines and bone biomarkers in the serum of gestating and lactating sows. In both experiments, a positive control (PC) diet that met Ca and P requirements was formulated, and a negative control (NC) diet was formulated to be deficient in Ca and P. Two additional diets were formulated by adding 1000 or 2000 phytase units (FYT)/kg of the novel phytase to the NC diet. An additional diet was formulated by adding 1000 FYT/kg of a commercial phytase to the NC diet, and a P -free diet was used to determine basal endogenous loss of P. In experiment 1, 72 gestating sows (day of gestation = 90) were allotted to the six diets and housed individually in metabolism crates. Feces and urine were quantitatively collected for 4 days after 5 day of adaptation. On day 90 and 105 of gestation, blood samples were collected from sows. Results indicated that sows fed diets containing phytase had greater (P < 0.01) P digestibility compared with sows fed diets without phytase, but no difference was observed for P digestibility among the three diets containing phytase. Carboxyterminal cross -linked telopeptide of type I collagen (CTX-I) was greater (P < 0.05) in sows fed the NC diet compared with sows fed the PC diet or diets containing phytase indicating increased bone tissue breakdown in sows fed the NC diet. In experiment 2, 66 lactating sows were allotted to the six diets on day 5 post -farrowing, and feces were collected for 4 days via grab -sampling after 5 days of adaptation. At the start and conclusion of the experiment, blood samples were collected from sows. Results indicated that sows fed diets containing phytase had greater (P < 0.01) digestibility of dry matter, Ca, and P compared with sows fed diets without phytase, but no difference was observed among the three diets containing phytase. Interleukin-1 beta in serum from sows fed 2000 FYT/kg of the novel phytase or the PC diet tended to be less (P < 0.10) compared with that of sows fed the NC diet. Sows fed the NC diet tended to have greater (P < 0.10) CTX-I compared with sows fed the PC diet or the diet containing the commercial phytase. In conclusion, phytase increased P digestibility in both gestating and lactating sows and reduced CTX-I in serum. When 2000 FYT/kg of the novel phytase or 1000 FYT/kg of the commercial phytase were added to the diet, serum concentration of interleukin 6 was also reduced, which may be a result of decreased anti -nutritional effects associated with phytate.