Effect of N-(n-butyl) Phosphoric Triamide (NBPT) and Linalool or Pine Oil Extract on Urea Concentration, Odorants, and Coliform Bacteria in Cattle Feedlot Manure

The objectives of this study were to evaluate the influence of a urease inhibitor (NBPT) in combination with plant oils for their ability to maintain urea in feedlot manure, control odor production, and reduce pathogens. Initially, NBPT (40 ppm) and a linalool extract (LE; 4000 ppm) were sprayed once per week (Friday) on three pens (area 15 x 1.2 m behind concrete apron) for four weeks, while another three alternating pens were untreated. Each pen was 30 x 150 m and contained seventy 300 kg animals. After treatment, manure samples from six locations of the experimental area in each pen were collected twice weekly (Monday and Wednesday), analyzed, and results are expressed on a manure dry matter (DM) basis. Following this four-week treatment, NBPT and pine oil extract (POE) were applied for an additional four-week period at the same concentrations as in the first experiment. The NBPT increased (P < 0.01) manure urea concentration (1 to 6 g/kg) in pens treated with either LE or POE. There was a tendency for volatile fatty acid (VFA, odorants) to be reduced (P = 0.09) and L-lactate accumulation to be increased (P< 0.05), with concomitant numerically lower pH values with the POE treatment. Both LE and POE reduced (P < 0.01) butyrate concentrations and reduced (P < 0.01) total coliform bacteria and Eschericheria coli. It is concluded that these treatments applied once per week can conserve urea on the feedlot surface, and reduce odorant concentrations and pathogens in cattle manure; although the environment, especially manure DM, greatly influences these parameters.