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Foam accumulation in deep-pit manure storages is an increasing concern for swine producers because of the logistical and safety-related problems it creates. To investigate this phenomenon, samples of swine manure were collected over a 13-month period from 58 swine production facilities in Iowa with varying levels of foam accumulation. Samples were tested for a number of physical, chemical, and biological parameters including pH, total and volatile solids, volatile fatty acid concentration, long-chain free fatty acid concentration, biochemical methane potential, methane production rate, surface tension, foaming capacity, and foam stability. Statistical analysis indicated that manure collected from facilities with foam accumulation produced methane at significantly (p < 0.05) faster rates than non-foaming manures (0.148 ±0.004 and 0.049 ±0.003 L CH4 L-1 slurry d-1, respectively) and consequently had significantly (p < 0.05) greater fluxes of biogas moving through the manure. The biochemical methane production assay suggested that manure from foaming pits had less potential to generate methane (123 ±9 mL CH4 g-1 VS) than manure from non-foaming pits (150 ±9 mL CH4 g-1 VS), presumably because more of the methane potential had previously been consumed, as indicated by the higher methane production rates. Short-chain fatty acid concentrations were significantly lower in foaming manures (4200 ±570 mg kg-1) than nonfoaming manures (9470 ±730 mg kg-1). The methane production rate, biochemical methane potential, and short-chain fatty acid assays suggest enhanced anaerobic digestion efficiency from foaming barns as compared to non-foaming barns. Other assays, such as surface tension and foaming capacity, indicated an accumulation of a surfactant at the manure-air interface of the foam, which may be capturing biogas bubbles generated within the manure. Most importantly, the foam layers exhibited a greatly enhanced ability to stabilize bubbles, which appeared to be correlated to the higher solids concentrations that stabilize the bubbles. [ABSTRACT FROM AUTHOR]

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 N2O, which may thereby affect the environmental impact of livestock production on soil, air, and water. [ABSTRACT FROM AUTHOR]