Odorant production and persistence of Escherichia coli in manure slurries from cattle fed zero, twenty, forty, or sixty percent wet distillers grains with solubles1,2

Autor: Mindy J. Spiehs, Calvin L. Ferrell, James E. Wells, Mohammad Koohmaraie, Steven D. Shackelford, Daniel N. Miller, Elaine D. Berry, V. H. Varel
Rok vydání: 2008
Předmět:
Zdroj: Journal of Animal Science. 86:3617-3627
ISSN: 1525-3163
0021-8812
Popis: Corn ethanol production removes starch and concentrates the remaining nutrients, including CP and minerals. When wet distillers grains with solubles (WDGS) are fed to cattle in place of corn, CP and minerals often exceed dietary needs. This may increase N emission, P run-off, and odor production. These vari- ables are evaluated in this study. Crossbred steers (n = 160; 434 ± 8 kg) were assigned in a completely random- ized block design to 9 × 9 m pens with concrete floor (10 animals/pen; 4 pens/treatment). Steers were fed a finishing diet that contained 0, 20, 40, or 60% WDGS on a DM basis, and provided 13.3, 15.5, 20.6, or 24.9% CP, respectively. Two kilograms of manure slurry (14 to 23% DM) were collected from each pen monthly (Aug. 20, Sep. 24, and Oct. 22). Samples were analyzed im- mediately for odorants, DM, pH, NH 3, total alcohol, l- lactate, and concentrations of generic Escherichia coli. After incubation of the samples at 22°C for 2, 4, 7, 10, 15, 21, and 28 d, samples were analyzed for methane production in addition to the above characteristics. Be- fore incubation, NH3, H2S, indole, phenol, isovalerate, isobutyrate, and acetate increased (P < 0.01) with in- creasing amounts of WDGS in the diet. Other odor- ants, including skatole, caproate, valerate, butyrate, and propionate, were greater (P < 0.01) in manure slurries from cattle fed 20 or 40% WDGS, compared to 0% WDGS. The l-lactate was greater (P < 0.01) in slurries from cattle fed 0% WDGS (447 µmol/g of DM) compared with the other treatment slurries (14 to 15 µmol/g of DM). After incubation, l-lactate contributed to lowered slurry pH (6.3, 7.1, 7.6, and 8.2, respectively, for 0, 20, 40, and 60% WDGS), which inhibited mi- crobial fermentation, E. coli persistence, and methane production. Because of the favorable, more neutral pH in the 40 and 60% WDGS slurries, many of the odorant compounds were rapidly converted to methane during a 28-d static incubation. Escherichia coli O157:H7 inocu- lated into subsamples of the manure slurries exhibited behavior similar to that of naturally present generic E. coli, surviving in greater numbers longer (P < 0.05) in 20 and 40% WDGS slurries than in 0% WDGS. These data indicate feeding WDGS can increase odorants in manure slurries and extend the persistence of E. coli.
Databáze: OpenAIRE
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