Date of Graduation


Document Type


Degree Name

Master of Science in Animal Science (MS)

Degree Level



Animal Science


Charles Maxwell

Committee Member

Elizabeth Kegley

Second Committee Member

Craig Coon


Nursery Pigs, Phytase


To determine the effects of super-dosing on pigs fed phosphorous and calcium adequate or deficient diets (Experiment 1); the optimum level of corn express phytase (CEP, Experiment 2); and the effects of xylanase/phytase on growth performance (Experiment 3) in pigs fed reduce nutrient diets, weaned pigs were blocked with initial body weight (BW) and allotted to dietary treatments. Treatments were: Positive control (PC), P/Ca adequate diets (NRC 2012); Negative Control (NC), low P (-0.15%) and Ca (-0.12%), +0, 1000, and 4000 FTU/kg of CEP in both PC and NC (Experiment 1); PC, P/Ca adequate diets; NC, decreased P (0.15%) and Ca (0.1%),+ 500, 1000, and 1500 FTU/kg CEP or NC+500 FTU/kg of Hiphos GT (Experiment 2); PC, P/Ca adequate diet (+500 FTU/kg of phytase); NC, reduced ME and AA of feed; NC+15,000 FTU/kg of phytase, +0, 12,000 or 16,000 DXU/kg of xylanase (Experiment 3). Data were analyzed by MIXED procedures of SAS (SAS inst., Cary, NC) with treatments as fixed effect and initial BW as random effect. In Exp. 1, ADG (P < 0.05) and BW (P < 0.05) were linearly increased with increasing level of CEP in pigs fed NC diets, but not in those fed PC diets (CEP x P/Ca-level interaction). CEP supplementation improved percentage bone ash (P < 0.05) quadratically, independent of P/Ca levels. For Exp. 2, increasing CEP increased ADG (P<0.01), G:F (P < 0.05), and BW (P < 0.05) linearly, and added both phytase at 500 FTU/kg (CEP and HiPhos) restored growth performance phenotypes to PC diets. In Exp. 3, adding the combination of 16,000 DXU/kg xylanase and super-dosing phytase restored BW (P > 0.10) similar to the PC when pigs fed reduced ME and AA diets. Pigs fed diets supplement with 16,000 DXU/kg xylanase or super-dosing phytase alone had similar G:F to the PC fed pigs. In addition, pigs fed 16,000 DXU/kg of xylanase diet had similar carcass composition compared to the NC (P > 0.10). These experiments suggest phytase in nutrient deficient diets restores growth performance

similar to pigs fed an adequate diet, and corn expressed phytase is as effective as microbial phytase in pigs.