03078naa a2200277 a 450000100080000000500110000800800410001902400540006010000230011424502080013726000090034552021830035465000180253765000160255565000110257165000140258265300230259670000190261970000210263870000200265970000200267970000200269970000170271970000190273677300450275521745022025-04-22       2025    bl uuuu     u00u1 u    #d7 ahttps://doi.org/10.1016/j.livsci.2025.1056942DOI1 aOLIVEIRA, A. F. de  aMethane and nitrous oxide emissions from excreta of different beef cattle breeds fed with different concentratebroughage ratios and finished in feedlots under tropical conditions.h[electronic resource]  c2025  aExcreta from confined beef cattle are sources of greenhouse gas (GHG) emissions; however, little is known about the effects of different concentrate:roughage ratios and cattle breeds on these emissions. This study evaluates methane (CH4) and nitrous oxide (N2O) emissions from the excreta of Nellore or crossbred (Nellore × Angus) beef cattle that are fed diets containing 65 % or 85 % of concentrates under tropical conditions. The excreta were applied to the floor of feedlot pens, and N2O and CH4 emission rates were monitored for 84 days in static chambers. The animals were confined for 106 days to evaluate their intake, weight gain and feed efficiency. In addition to average emission rates, emissions from excreta were estimated based on ratios per kg of dry matter intake (DMI; CH4/DMI and N2O/DMI) and per kg of weight gain (average daily weight gain, ADG; CH4/ADG and N2O/ADG). The data were subjected to variance analysis in a 2 × 2 factorial arrangement, and the means were compared using a Tukey test (P &lt 0.05). Results indicated that CH4 emissions were 2.40 times higher from the excreta of crossbred cattle than in Nellore cattle (P &lt 0.039). N2O emissions were 50.1 % lower from the excreta of animals consuming diets with low concentrate:roughage ratios than in those consuming diets with high concentrate:roughage ratios. The CH4/DMI and CH4/ADG ratios were higher in the excreta of crossbred cattle than in Nellore cattle. The N2O/ADG and N2O/DMI ratios in the excreta of animals fed with high concentrate: roughage ratios were also 18.2 % and 36.1 % higher in crossbred cattle than in Nellore cattle. The N2O/DMI and N2O/ADG ratios in the excreta of crossbred and Nellore cattle were lower when fed with diets containing low compared to high concentrate:roughage ratios. The results suggest that crossbred animals with more concentrate feed diets emit more CH4 and N2O from their excreta. This is the first study to report that Nellore cattle, the predominant breed in Brazil, and diets with lower concentrate:roughage ratios may be associated with a reduced potential for GHG emissions from excreta in confined beef cattle under tropical conditions.  aEfeito Estufa  aGado Nelore  aMetano  aPecuária  aAquecimento global1 aMARTINS, E. C.1 aALVARENGA, R. C.1 aCAMPANHA, M. M.1 aALVES, B. J. R.1 aOLIVEIRA, L. G.1 aLOPES, L. S.1 aLANA, A. M. Q.  tLivestock Sciencegv. 295, 105694, 2025.