248 Concentration of Net Energy in Corn without or with Microbial Phytase Fed to Group-Housed Pigs

Abstract

Abstract The objective was to test the hypothesis that addition of microbial phytase to corn increases net energy (NE) by group-housed growing pigs. Three diets were formulated. The positive control (PC) diet contained corn as the sole source of energy. The PC diet contained Ca and P at the requirements for pigs (NRC, 2012). The negative control (NC) diet was similar to the PC except that this diet contained 0.08% standardized total tract digestible P and 0.12% total Ca less than the PC diet. The third diet was similar to the NC diet with the exception that this diet contained 1,000 units of phytase per kg diet. Pigs were allowed ad libitum access to feed and water. Pigs (n = 24; initial body weight = 44.99 kg; SD = 2.09) were allotted to the 3 diets using a replicated 6 × 3 incomplete Latin square design with 6 chambers (i.e., 4 pigs/chamber) and 3 periods. Oxygen consumption and CO2 and CH4 production were measured during fed and fasting states and fecal and urine samples were quantitatively collected. The statistical model included diet as the fixed effect and chamber and period as random effects. Result indicated that the apparent total tract digestibility (ATTD) of dry matter and gross energy, energy excretion in feces, urine, and heat, and NE did not differ among the 3 diets (Table 1). However, concentrations of digestible energy (DE) and metabolizable energy (ME) in diets and in corn were less (P < 0.05) in the PC diet compared with the NC diet without phytase, but no difference was observed between the PC diet and the NC diet with phytase or between the 2 NC diets. The ratio between NE and ME was not different among diets, but ME to DE was increased (P < 0.05) by supplementation of phytase to the NC diet. In conclusion, concentrations of DE and ME in corn are less if more feed phosphate and limestone are used in diets. However, concentrations of NE were not affected by supplemental phytase or Ca and P levels, even though ME to NE was increased by supplemental phytase.