Forage intake and enteric methane emissions in N-fertilized or grass-legume pastures during cool and warm seasons

Authors: GARRCIA, LIZA - UNIVERSITY OF FLORIDA; DUBEUX, JOSE - UNIVERSITY OF FLORIDA; SOLLENBERGER, LYNN - UNIVERSITY OF FLORIDA; VENDRAMINI, JOAO - UNIVERSITY OF FLORIDA; DILORENZO, NICOLAS - UNIVERSITY OF FLORIDA; SANTOS, ERICK - UNIVERSITY OF FLORIDA; JARAMILLO, DAVID; QUEIROZ, LUANA - UNIVERSITY OF FLORIDA; RUIZ-MORENO, MARTIN - UNIVERSITY OF FLORIDA

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/9/2026
Publication Date: 4/11/2026
Citation: Garrcia, L., Dubeux, J., Sollenberger, L., Vendramini, J., Dilorenzo, N., Santos, E., Jaramillo, D.M., Queiroz, L., Ruiz-Moreno, M. 2026. Forage intake and enteric methane emissions in N-fertilized or grass-legume pastures during cool and warm seasons. Agronomy Journal. https://doi.org/10.1016/j.anopes.2026.100133.
DOI: https://doi.org/10.1016/j.anopes.2026.100133

Interpretive Summary: Grazing livestock are a major source of enteric methane emissions. This research was designed to estimate enteric methane emissions, animal performance, and feed intake when beef cattle grazed contrasting nitrogen-fertilized grass or grass-legume systems, in each of the cool and warm seasons across three consecutive years. The results from this study indicated that methane emission intensities were less during the cool season, as a result of greater forage quality, compared to the warm season. Within each season, methane emissions did not differ by treatment. Overall, this data can be used to generate carbon budgets to assess the carbon footprint of beef production in livestock systems typical of the southeastern US.

Technical Abstract: Grazing livestock are a major source of enteric methane (CH4) emissions. Enteric CH4 emissions were measured from steers grazing on three different systems (treatments) from 2016 to 2018. Treatments consisted of monocultures grasses (during the warm season) or grass-legume mixtures (overseeded during the cool season), as follows: 1) Grass+N, N-fertilized bahiagrass (Paspalum notatum) overseeded with a mixture of cereal rye (Secale cereale) and oat (Avena sativa); 2) Grass+CL, unfertilized bahiagrass overseeded with similar rye-oat mixture plus a mixture of clovers (Trifolium sp.); and, 3) Grass+CL+RP, rhizoma peanut (Arachis glabrata) and bahiagrass overseeded with a similar rye-oat-clover mixture. The objectives were to: (1) evaluate cattle performance; (2) estimate the cattle feed intake; (3) measure the cattle enteric CH4 emissions using the SF6 tracer technique; and (4) assess the relationship between forage intake and the production of enteric CH4 emissions. In either cool or warm seasons, enteric CH4 emissions did not differ among treatments (P > 0.05). However, emission intensity had a season × treatment interaction (P < 0.01), where emissions during the cool season were 58% lower across treatments. The increased forage quality in the cool season likely contributed to decreased CH4 emission intensity in grazing systems relative to the warm season. Overall, this data can be used to generate carbon budgets to assess the carbon footprint of beef production in livestock systems typical of the southeastern US.