Abstract
A total of 2,268 pigs (PIC 337×1050, initially 28.5±2.3 kg) were used in a 55-d growth study. On d 0, pens of pigs were blocked by body weight and randomly allotted to 1 of 6 dietary treatments with 27 pigs per pen and 14 pens per treatment. Treatments were fed in 2 different phases containing 1.05 and 0.89% SID Lys, respectively. The 6 treatments consisted of a control with no phytase and inorganic P from monocalcium P, or 5 diets with 1,500 phytase units (FYT/kg; Ronozyme HiPhos 2,500; DSM Nutritional Products, Inc., Parsippany, NJ) assuming supplier-provided nutrient release values for Ca and P (CaP), Ca, P, and AA (CaPAA), Ca, P, AA, and half of the suggested net energy (CAPAA+halfNE), Ca, P, AA, and full NE (CaPAA+fullNE) and no nutrient release (None). The assumed release values were 0.146% STTD P, 0.102% STTD Ca, 41.8 kcal/kg of NE, and 0.0217, 0.0003, 0.00886, 0.0224, 0.0056, 0.0122, and 0.0163% digestible Lys, Met, Met + Cys, Thr, Trp, Ile, and Val, respectively. All diets within phase were corn-soybean meal-based and contained a STTD Ca:STTD P ratio of 1.60:1. Data were analyzed as a randomized complete block design for a one-way ANOVA using the lmer function from the lme4 package in R. Overall (d 0 to 55), there was no evidence for differences in ADG or ADFI. However, pigs fed the diet containing 1,500 FYT/kg assuming no nutrient release had increased (P< 0.05) G:F compared to pigs fed diets containing 1,500 FYT/kg assuming either CaP or CaPAA+fullNE release, with others intermediate. Based on diet formulation and using supplier recommended phytase release values, all pigs should have had similar performance. However, pigs fed full matrix release values for CaPAA+fullNE had decreased (P< 0.05) G:F, suggesting that full matrix release values, especially energy, may be too aggressive and resulted in diets contributing less nutrients than needed to optimize performance.
130 Assessing current phytase release values for calcium, phosphorus, amino acids and energy in diets for growing pigs
