Abstract
Abstract The study determined efficacy of different phytases in diets without inorganic phosphorus (P) in piglets. Piglets (initial body weight 9.7 ± 1.2 kg) were randomly assigned (2 piglets/pen), based on sex and body weight over 6 diets. Positive control (PC) corn-wheat based diet was formulated to meet NRC specification. Negative control (NC) diet was formulated without inorganic P (-0.16% STTD P), with reduced calcium (Ca; -0.15%), net energy (-33 kcal/kg), and standardized ileal digestible amino acids (average -0.02% unit). The NC diets were supplemented with 4 different phytases at 1,500 FTU/kg feed including a novel consensus bacterial 6-phytase variant expressed in Trichoderma reesei (PhyG), a Citrobacter braakii phytase expressed in Aspergillus oryzae (PhyC), a hybrid phytase (Hafnia sp., Yersinia sp. and Buttiauxella sp.) expressed in Aspergillus niger (PhyH) and an Escherichia coli phytase expressed in Pichia pastoris (PhyE). Piglets were fed ad libitum for 42 d. Fecal samples were collected during last 3 d. On d 42, 1 piglet per pen was euthanized and metacarpi collected for bone strength and ash analysis. Data were analysed by one-way ANOVA and treatment mean comparison by Tukey test using JMP 14. Pigs fed NC diets showed reduced (P < 0.05) growth, P digestibility, bone ash and bone strength vs PC and all phytases treatments. Overall feed conversion ratio (FCR) was less (P < 0.05) with PhyG (-22 points) and PhyE (-8 points) vs NC, while PhyC and PhyH showed intermediate FCR between PhyG and PhyE. PhyG improved (P < 0.05) bone strength and P digestibility vs PhyC, PhyE and PC. Based on FCR and bone strength, ranking of the phytases are: PhyG >PhyC >PhyH >PhyE. In conclusion, all phytases improved growth, nutrient digestibility and bone strength vs NC; however, only PhyG fully compensated nutrients and energy reduction, fully recovered performance to the level of PC and resulted in improved bone strength compared with PC.
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