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This article in JEQ

  1. Vol. 33 No. 1, p. 389-393
     
    Received: May 28, 2003


    * Corresponding author(s): bwienhold1@unl.edu
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doi:10.2134/jeq2004.3890

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

  1. Brian J. Wienhold *a and
  2. Phillip S. Millerb
  1. a USDA Agricultural Research Service, Soil and Water Conservation Research Unit, University of Nebraska, Lincoln, NE 68583
    b Department of Animal Science, University of Nebraska, Lincoln, NE 68583

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.

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