| Summary: | Two experiments were conducted to evaluate the effect of replacing cottonseed meal with DDG on ruminal parameters, methane (CH<sub>4</sub>) emissions (Experiment 1), and animal performance (Experiment 2) of young Nellore bulls grazing Marandu grass during the rainy season. Four supplementation strategies were used in both experiments: (1) Mineral supplementation (MS); (2) conventional multiple supplement (energy/protein) with cottonseed meal and citrus pulp (CMS); (3) CMS with 50% cottonseed meal replaced by DDG (50DDG); and (4) CMS with 100% cottonseed meal replaced by DDG (100DDG). The 50DDG condition resulted in greater intake of dry matter (<i>p</i> = 0.033), organic matter (OM) (<i>p</i> = 0.050), forage (<i>p</i> = 0.035), and digestible OM (<i>p</i> = 0.031) than 100DDG. The supplemented animals presented greater final body weight (BW) and average daily gain than the animals consuming MS (<i>p</i> = 0.011), and lower pH, acetate, and acetate:propionate (<i>p</i> < 0.05). However, the treatments had no influence on stocking rate, gain per area, and enteric CH<sub>4</sub> emissions (<i>p</i> > 0.05). Replacing cottonseed meal with DDG does not result in great variations in ruminal parameters, animal performance, and enteric CH<sub>4</sub> emissions of grazing Nellore cattle during the rearing phase in the wet season. Both protein sources in 0.3% BW supplementation can be used to intensify beef cattle production in pastures.
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