title: Nutrient utilization and manure P excretion in growing pigs fed corn-barley-soybean based diets supplemented with microbial phytase.
abstract: The effect of high levels of microbial phytase supplementation in diets for growing pigs was studied in a 2-week performance and nutrient digestibility trial involving 28 growing pigs weighing 16.4 +/- 1.06 (mean +/- SD) kg. Seven corn-barley-soybean meal-based diets consisting of a positive control (PC) formulated to meet or exceed NRC nutrient requirements; a negative control (NC) with non-phytate P reduced by 0.1% unit from NRC requirement and fed without or with 500 or 1000 U/kg; a doubled negative control (DNC) with no added inorganic P and fed without or with 2000 or 4000 U/kg. Chromic oxide was added as an indigestible marker and all diets were fed as mash. Pigs fed the PC diet had a higher P digestibility compared with those fed the NC (P < 0.02) and the DNC (P < 0.001) diets. Supplementing the NC diet with pyhtase tended to improve P digestibility (P < 0.10). However, addition of phytase to the DNC diet resulted in linear (P < 0.001) and quadratic (P < 0.03) increases in P digestibility with an overall improvement of 8% and 121% at 4000 phytase U/kg of diet, respectively, compared with the PC and DNC diets. Apparent total tract digestibility of N, OM and DM were higher (P < 0.05) in the PC diet compared with the DNC diet, but not the NC diet (P < 0.10). No effect of phytase addition to NC was observed on Ca, N, DM and OM digestibility. Phytase addition to the DNC diet resulted in a linear increase (P < 0.05) in N, DM and OM digestibility but not Ca. Increasing the levels of phytase supplementation in the NC and the DNC diets linearly decreased fecal P (P < 0.05) content by 45 and 42%, respectively. Adding phytase at 1000 or 4000 U/kg increased P retention (P < 0.05) by 14.3 or 15.6% units, respectively, compared with the PC diet. Urinary P excretion was higher in the group fed the PC diet compared with those fed the NC and DNC diets (P < 0.05). The results of this study show that complete removal of inorganic P from growing pig diets coupled with phytase supplementation improves digestibility and retention of P and N, thus reducing manure P excretion without any negative effect on pig performance.
authors.affiliation: Department of Animal Science, University of Manitoba, Winnipeg Manitoba, Canada.
authors.forename: Adewale
authors.initials: A
authors.lastname: Emiola
authors.forename: Oluwole
authors.initials: O
authors.lastname: Akinremi
authors.forename: Bogdan
authors.initials: B
authors.lastname: Slominski
authors.forename: C Martin
authors.initials: CM
authors.lastname: Nyachoti
mesh_terms: D010832:6-Phytase / Q000008:administration & dosage*; D000821:Animal Feed; D000822:Animal Husbandry; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002118:Calcium / Q000378:metabolism; D019587:Dietary Supplements; D004063:Digestion / Q000187:drug effects / Q000502:physiology; D001467:Hordeum; D008372:Manure; D009584:Nitrogen / Q000378:metabolism; D010758:Phosphorus / Q000378:metabolism*; D013025:Glycine max; D013552:Swine; D003313:Zea mays
chemical_list: D008372:Manure; D010758:Phosphorus; D010832:6-Phytase; D009584:Nitrogen; D002118:Calcium