Phosphorus Fractionation in Manure from Swine Fed Traditional and Low-Phytate Corn Diets

Authors

Brian J. Wienhold, USDA Agricultural Research Service, Soil and Water al. (2000) determined the effect of shaking time and Conservation Research UnitFollow
Phillip S. Miller, University of Nebraska-LincolnFollow

Document Type

Article

Date of this Version

2004

Comments

Published in J. Environ. Qual. 33:389–393 (2004).

Abstract

Traditional corn (Zea mays L.) (TC), the primary grain used in swine (Sus scrofa) diets, stores a majority of its P as phytate, which is largely unavailable for digestion by nonruminant animals. Low- phytate corn (LPC) contains similar amounts of total P but a smaller percentage of P as phytate. When fed to swine, LPC increases P utilization and reduces P content of manure. While differences in P content between manure from animals fed TC and LPC diets have been documented, solubility and lability of manure P have not been compared. Manure P was characterized in manure from swine fed either LPC or TC diets in 2000 and 2001. Total P was lower (20 vs. 34 g kg^-1) and N to P ratio was higher (4.5 vs. 3.3) in LPC manure than in TC manure. Manures were sequentially extracted with deionized water, 0.5 M NaHCO₃, 0.1 M NaOH, and 1.0 M HCl. Extracts were analyzed for inorganic and total P. Most P (approximately 80%) in the extracts was in the inorganic form. Concentration of P in the water-extractable fraction was lower for LPC manure (10.2 g kg^-1 in 2000 and 9.7 g kg^-1 in 2001) than for TC manure (13.6 g kg^-1 in 2000 and 17.0 g kg^-1 in 2001). Percentage of total P in each extract was in the order of: H2O (60%), HCl (22%), NaHCO₃ (12%), NaOH (8%), and residue (<1%). Total P and distribution of P in extracts indicates swine are able to utilize more P contained in LPC feed but the composition of P excreted in LPC manure is similar to TC manure. Solubility, crop availability, and lability of P in LPC manure should be similar to that of TC manure.