PSIV-15 Sustainable nitrogen management: Investigating chemical solutions for feedlot emissions.

Abstract This study investigates the impact of two distinct cattle diets and chemical amendments on nitrogen excretion in a feedlot setting. Two pens (n = 45 hd/pen) of steers were fed diets varying in urea and nitrogen (N) content: (EXS) 0.76% urea and 2.37% N on a dry matter basis (DMB), and (DEF) 0.13% urea and 1.84% N DMB. Steers were housed at Colorado State University’s Climate-Smart Research Facility. On days 0 and 28, feedlot surface material (FSM) samples were collected by dividing the pen into 12 quadrants and collecting a random sample in each quadrant. Samples were dried and analyzed for pH, total carbon (C), total N, and C:N ratio using a Velp 802 Elemental Analyzer. On day 28, FSM from each pen was combined, divided into 18 subsamples (9/pen), and treated with 10 mL of: control (DI water), NaF (10mM NaF), or TA:NaF (5mM:1mM tannic acid: sodium fluoride). Sodium fluoride and tannic acid were selected as a chemical amendment to study their potential for ammonia reduction. After a 16-day incubation period, samples were analyzed. Data was analyzed using JMP (18.1.2) where treatment, diet, and the interaction between treatment and diet were included in a standard least squares model to assess the effects on pH, total N, total C, and C:N ratio. Significance was declared at P < 0.05. While the diet significantly influenced the total C (P < 0.01) and N (P < 0.01) content, chemical amendments did not yield statistically significant effects. Differences in pH (P = 0.24, P=0.69) and C:N (P = 0.52, P = 0.06) were observed between treatments and diets, respectively, though none were statistically significant. No significant interaction between treatment and diet was observed for pH, total N, total C, or the C:N ratio. As the chemical treatments did not significantly alter the N content, they were likely ineffective in mitigating ammonia emissions. The findings suggest that the two-week amendment period may have been insufficient for a clear dosage response, and the chemical concentrations may have been too low to produce the intended effects. Additionally, the uncertainty in FSM sampling time could have impacted results due to potential nitrogen volatilization before collection. Future research should collect fresh fecal samples directly from animals to minimize such variability.