Assessing phytase release values for calcium, phosphorus, amino acids and energy in diets for nursery and growing pigs

Abstract

Three experiments were conducted to determine the effect of three fermented amino acids (AA) with their respective biomass compared to crystalline AA on the growth performance of swine (n = 315 nursery pigs) and poultry (n = 1,320 or 2,100 broilers for experiment 2 and 3, respectively). Two experiments using a total of 600 nursery pigs were conducted to determine the available P (aP) release of Smizyme TS G5 2,500 phytase. Additionally, two experiments using a total of 3,483 growing-finishing pigs were conducted to determine the effects of feeding 1,500 phytase units of Ronozyme HiPhos phytase when credited with its corresponding nutrient release values. Experiments 1-3 determined that Trp, Thr, or Val with biomass appeared to be equally bioavailable and as suitable for use as crystalline amino acids in swine and poultry diets. In experiments 4 and 5, increasing phytase from 0 to 1,500 FTU/kg in phosphorus deficient diets improved nursery pig performance and bone ash characteristics. Using average daily gain, feed efficiency, and percentage bone ash values, prediction equations were developed, provided a range of aP release values for Smizyme TS G5 2,500 phytase when fed at levels between 150 and 1,500 FTU/kg in diets for 10- to 21-kg pigs. In Experiment 6, growing-finishing pigs fed diets containing high levels of phytase with full nutrient release values (CaPAA+full NE) until market had decreased growth performance and hot carcass weights compared with those not fed any phytase. Removing the phytase at the end of the grower period sufficiently recovered any loss in performance observed. A similar feed efficiency response was observed in experiment 7 with growing pigs, confirming the hypothesis that full nutrient release values attributed to phytase, especially for NE, were too aggressive and resulted in diets contributing less nutrients than needed to optimize performance.