Manure composition of swine as affected by dietary protein and cellulose concentrations

An experiment was conducted to investigate 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 cm2). Before sampling on d 56, the manure was gently stirred to obtain a representative 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 cellulose (P = 0.03). No other interactions were noted. Decreasing dietary CP reduced manure pH (P = 0.01), NH4 (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 NH4 (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. Increasing 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 N2O concentration was increased by decreasing dietary CP (P = 0.03) or by increasing dietary cellulose (P = 0.05). Neither dietary CP nor cellulose affected headspace concentration of CH4. This study demonstrates that diets differing in CP and cellulose content can significantly impact manure composition and concentrations of VFA, phenol, and indole, and headspace concentrations of N(2)O, which may thereby affect the environmental impact of livestock production on soil, air, and water.