Manure composition of swine as affected by dietary protein and cellulose concentrations 1 B. J. Kerr,* 2 C. J. Ziemer,* S. L. Trabue,* J. D. Crouse,* and T. B. Parkin† *USDA-ARS, Swine Odor and Manure Management Research Unit, Ames, IA 50011-3310; †USDA-ARS, National Soil Tilth Laboratory, Ames, IA 50011 ABSTRACT: An experiment was conducted to inves- tigate the effects of reducing dietary CP and increasing dietary cellulose concentrations on manure DM, C, N, S, VFA, indole, and phenol concentrations. Twenty-two pigs (105 kg initial BW) were fed diets containing either 14.5 or 12.0% CP, in combination with either 2.5 or 8.7% cellulose. Pigs were fed twice daily over the 56-d study, with feed intake averaging 2.74 kg/d. Feces and urine were collected after each feeding and added to the manure storage containers. Manure storage containers were designed to provide a similar unit area per animal as found in industry (7,393 cm 2 ). Before sampling on d 56, the manure was gently stirred to obtain a represen- tative sample for subsequent analyses. An interaction of dietary CP and cellulose was observed for manure acetic acid concentration, in that decreasing CP lowered acetic acid in pigs fed standard levels of cellulose but increased acetic acid in pigs fed greater levels of cellu- lose (P = 0.03). No other interactions were noted. De- creasing dietary CP reduced manure pH (P = 0.01), NH 4 Key words: cellulose, composition, manure, odor, protein, swine 2006 American Society of Animal Science. All rights reserved. J. Anim. Sci. 2006. 84:1584–1592 INTRODUCTION Swine production has undergone extensive changes during the last 3 decades resulting in larger numbers of swine produced on increasingly smaller areas of land. This has led to increased awareness by the general public and regulatory agencies about issues concerning 1 Mention of a trade name, proprietary product, or specific equip- ment does not constitute a guarantee or warranty by the USDA and does not imply approval to the exclusion of other products that may be suitable. Partial funding through the Defense Advance Research Projects Agency (SCA# 3625-32000-056-02R) and the joint program between ARS and the University of Illinois (Effective Use of Animal Manures in Cropping Systems, Section 224 Crop Risk Management, SCA# 3620-63000-003-01S) has provided valuable assistance in achieving these results. 2 Corresponding author: kerr@nsric.ars.usda.gov Received August 11, 2005. Accepted January 11, 2006. 1584 (P = 0.01), isovaleric acid (P = 0.06), phenol (P = 0.05), and 4-ethyl phenol (P = 0.02) concentrations. Increasing dietary cellulose decreased pH (P = 0.01) and NH 4 (P = 0.07) concentration but increased manure C (P = 0.03), propionic acid (P = 0.01), butyric acid (P = 0.03), and cresol (P = 0.09) concentrations in the manure. Increas- ing dietary cellulose also increased manure DM (P = 0.11), N (P = 0.11), and C (P = 0.02) contents as a percentage of nutrient intake. Neither cellulose nor CP level of the diet affected manure S composition or output as a percentage of S intake. Headspace N 2 O concentra- tion was increased by decreasing dietary CP (P = 0.03) or by increasing dietary cellulose (P = 0.05). Neither dietary CP nor cellulose affected headspace concentra- tion of CH 4 . This study demonstrates that diets dif- fering in CP and cellulose content can significantly im- pact manure composition and concentrations of VFA, phenol, and indole, and headspace concentrations of N 2 O, which may thereby affect the environmental im- pact of livestock production on soil, air, and water. pollution of air, soil, and water from swine production facilities (Hobbs et al., 1997; Mackie et al., 1998; Schiff- man et al., 2005). Because whole-body retention of N, P, and S in swine is only about 50% of total dietary intake (Shurson et al., 1998; Sands et al., 2001; van Kempen et al., 2003), excess nutrients can be released into the environment via excretions from animals. Re- cent air monitoring studies have shown that livestock production facilities have the potential to affect air quality through release of odorous compounds, such as hydrogen sulfide, ammonia, and volatile organic com- pounds into the environment (Schiffman et al., 2001; Zahn et al., 2001a,b). The composition of the manure and potential release of nutrients and volatile emissions into the environ- ment from livestock operations and land-applied ma- nure is partially controlled by dietary inputs (Miller and Varel, 2003). Two approaches to changing dietary composition are controlling dietary CP and fiber content