Ammonia, volatile fatty acids, phenolics, and odor offensiveness in manure from growing pigs fed diets reduced in protein concentration1,2

Abstract

The objective of this study was to investigate whether reducing dietary CP concentration decreases fecal VFA, manure ammonia (NH3) emission and odor, and urinary phenolic metabolites. Six barrows were allotted to one of six dietary treatments in a Latin square design. Treatments consisted of four corn-soybean meal based diets containing 15, 12, 9, and 6% CP, a casein-based diet containing 15% CP, and a protein-free diet (0% protein). Crystalline AA were included in the 12, 9, and 6% CP diets. The casein-based and protein-free diets were used to determine basal endogenous contribution of VFA, phenolics, NH3, and manure odor. Pigs were housed individually in metabolism cages to allow total collection of feces and urine. Feces and urine were collected and pooled within pig and period. Feces and urine were analyzed for VFA and phenolic metabolite concentrations, respectively. Feces and urine were then mixed, stored, and fermented at room temperature for 30 d. For NH3 determination, headspace air was sampled from manure slurries at 24, 48, and 72 h after fermentation. Slurry samples were placed into vials, capped, and randomized before odor panel evaluation. Odor offensiveness was classified on severity: 1 = non-offensive; 2 = mildly offensive; 3 = moderately offensive; 4 = strongly offensive; and 5 = extremely offensive. Reducing dietary CP increased (P < 0.05) fecal VFA concentrations but did not affect phenolic concentrations in urine. Manure NH3 emission was reduced (P < 0.05) as dietary CP concentration decreased from 15 to 0%. The 15% diet had the least offensive manure slurry with odor qualitative ranking of 2.58 (i.e., mild-moderately offensive). Compared with the 15% CP diet, manure from the 9 and 6% CP diets was found to be more offensive (P < 0.05), with qualitative rankings of 2.92 and 3.10, respectively. Odor qualitative rank for the 12% CP, protein-free diet, and casein-based diet did not differ from that of the 15% CP diet. These results indicate that reduction in dietary CP concentrations decreases manure NH3 emission, but it does not diminish manure odor offensiveness and fecal VFA concentrations.

Effects of dietary crude protein level on odour from pig manure

“…According to Canh et al (1998c) fermentable NSP are the most important dietary components determining VFA concentration in the manure. The VFA pool was largely dominated by the short straight -chain VFA such as acetic, propionic and butyric acids which comprised 91% of total VFA in the manure confirming the results of Otto et al (2003) and Le et al (2005a). Branched-chain VFA are only produced from protein metabolism.…”

Impact of dietary protein on microbiota composition and activity in the gastrointestinal tract of piglets in relation to gut health: a review

“…Thereafter, they are detoxified by means of glucuronide and sulfate conjugation in colonic mucosa or liver and excreted via urine, principally as p-cresols (Hughes et al, 2000). A positive correlation between dietary protein intake and urinary phenol excretion has been reported in pigs (Otto et al, 2003).…”

“…The concentration of ammonia in the large intestine depends on the balance between AA deamination and bacterial protein synthesis (Mosenthin et al, 1992;Hughes et al, 2000). Therefore, a reduction of ammonia emission from pig manure seems to be possible by lowering dietary protein (Otto et al, 2003).…”

“…Such a shift of urinary to fecal nitrogen excretion may help to reduce ammonia emission (Mosenthin et al, 1992). Ammonia is one of the major odor components of pig manure contributing to environmental pollution (Otto et al, 2003). The concentration of ammonia in the large intestine depends on the balance between AA deamination and bacterial protein synthesis (Mosenthin et al, 1992;Hughes et al, 2000).…”

Strategies to control odours in livestock facilities: a critical review

“…Feeding pigs with low crude protein diets reduced odour concentration from 30 to 80%, according to Hayes et al (2004) and Le et al (2007). On the other hand, some authors reported that odour concentration and offensiveness increased when low-CP diets supplemented with synthetic amino acids were used (Otto et al, 2003;O'Connell et al, 2006). Finally, other studies could not find differences in odour composition and magnitude when low-CP diets were used (Sutton et al, 1999;Clark et al, 2005;Leek et al, 2007).…”