| Summary: | Dairy cows are the highest daily and annual methane (CH<sub>4</sub>) producers among all cattle categories. So, the present study aimed to evaluate the effect of increasing supplementation levels of a low-quality forage on dry matter intake (DMI), DM digestibility (DMD), milk production, enteric CH<sub>4</sub> emission, gross energy, and protein partitioning in Holstein cows. In total, eight cows (112 ± 38 days postpartum; mean ± s.d.) were randomly assigned to 4 treatments composed of 4 dietary neutral detergent fibre (NDF) inclusion levels (40.2% (control), 43.3%, 46.5%, and 50.5%) in a 4 × 4 repeated Latin square experimental design. The cows were fed corn + alfalfa silage and a concentrate (60:40 forage:concentrate ratio). To increase the contents of low-quality NDF, part of the silage was replaced with maize stover (MSTV). The CH<sub>4</sub> production was measured in an open-circuit respiration chamber. The DMI increased significantly and linearly (<i>p</i> < 0.05) with increasing levels of MSTV. However, the CH<sub>4</sub> yield decreased (<i>p</i> < 0.0001) as the NDF level increased (32.1, 28.1, 23.1, and 21.3 CH<sub>4</sub> L/kg DMI, respectively). DMD decreased as NDF levels in the diet increased (<i>p</i> < 0.0001). The NDF digestibility (DNDF) explained the better (<i>p</i> < 0.0001) CH<sub>4</sub> production response than DMD. It was concluded that low-quality forages can be used to regulate CH<sub>4</sub> production in subtropical and tropical climate regions.
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