Adding Post-Extraction Algal Residue (PEAR) to Cattle Finishing Diets Reduces the Quantity of Fecal Volatile Chemicals Often Associated with Feedlot Malodors
Efficiencies of finishing cattle in feedlots have resulted in lower production costs and less expensive beef for consumers. But an increase in the size of feedlots, and resulting waste malodors, along with urban sprawl have brought the public and feedlots closer together and given urgency to finding methods to reduce feedlot malodors. Our objective was to feed post-extraction algal residue (PEAR) to steers to reduce the incidence of fecal malodor chemical compounds. Six steers were fed PEAR (1.25 kg/d, as-fed) along with a 90% concentrate and 10% forage diet, for 35 d before harvest. One wk prior and one wk after the addition of PEAR to the feed, fecal samples were collected from each steer to produce fecal samples with and without PEAR within the same animal. Fecal samples were stored in an enclosed plastic bag immediately after collection (-80°C) until analyses. Each sample was placed in a 760 mL glass jar submerged in a 60°C water bath, and thawed to 25°C. A 75 μm carboxen/polydimethylsiloxane solid phase microextraction (SPME) fiber was then inserted into the jar and collected for 120 min. The SPME was desorbed in a multi-dimensional GC/MS with dual olfactory ports. All eluted chemicals were quantified as total ion counts (TIC) under the curve of each elution peak corresponding to each chemical identified by the MS library. Simple ANOVA was conducted to determine the effect of adding PEAR to the diet of steers on the relative quantity of fecal aroma chemical compounds. The general classification of amine/amide compounds tended (P = 0.071) to be reduced when PEAR was added to the feed. The addition of PEAR reduced the quantity of indole (manure/stench), the butyl ester of acetic acid (acid/burnt aroma), and carbon disulfide (rotten eggs) in fecal samples by 92.5, 80.5, and 97.1%, respectively (P < 0.02). Additionally, the quantity of the volatile chemicals dimethyl disulfide (garlic/burnt rubber), ethyl vinyl sulfide (sulfurous), and butyric acid (vomit) in the feces were reduced (P < 0.05) to undetectable levels with the addition of PEAR in the feed. The addition of PEAR to cattle finishing diets reduced the quantity of volatile chemicals often associated feedlot malodors.
Keywords: Algae, Beef, Odor