Ammonia, nitrous oxide and methane emissions from excreta of cattle receiving rumen undegradable protein

We hypothesized that supplementation with rumen undegradable protein (RUP) during the rearing phase mitigates nitrous oxide (N2O), methane (CH4), and ammonia (NH3) emissions from excreta of Nellore animals in Urochloa brizantha 'Xaraes' pasture. The treatments applied to soil were urine and dung of animals supplemented without RUP or with RUP in the middle and end of the rearing phase. We assessed N2O and CH4 emissions using a static closed chamber and NH3 emissions using the semi-open static chamber method. No effects were observed for supplement, excreta type, period, or interaction on N2O emissions. The mean emission factor was 0.03% of N in the excreta lost as N2O. Higher NH3 losses were observed for the urine treatments in the end period, regardless of the supplement type. The mean NH3 emission factor for urine was 2.96 and 13.8% for the middle and end periods, respectively, while the mean value for dung was 3.9%. The type of supplement did not affect CH4 emissions, and the mean dung emission factor was 0.12 kg CH4 head(-1) year(-1). In summary, the supplementation of beef cattle in pastures with RUP did not mitigate NH3, N2O, and CH4 emissions from excreta. The excreta emission factors for the GHGs measured, regardless of differences in the type of excreta, type of supplement, and period, were lower than the default value of Intergovernmental Panel on Climate Change revised guidelines. Further studies will be needed to fully understand the mechanisms underlying the effects of RUP on greenhouse gas emissions.