Impacts of Forage Maturity on Methane Production
Methane production in cattle represents a loss of gross energy intake. Any time energy can be repartitioned toward gain in the animal; the animal is more efficiently using its resources, which results in economic efficiency, but is also better for the environment.
Forage maturity has been shown to impact methane production. Many producers, with mono species pastures such as smooth brome or tall fescue, rotationally graze these pastures at increased stocking rates to keep forage from quickly maturing and thus resulting in decreased quality and subsequently, reduced cattle performance.
Research has shown that as digestibility decreased from 61.5% to 38.5% gross energy intake lost as methane increased (Boadi and Whittenberg, 2002; Boadi et al., 2002). Digestibility decreases as the plant matures and more soluble carbohydrates are converted to structural carbohydrates.
When pastures are stocked at appropriate levels for the amount of forage and grazing days for a given pasture, cattle can often be more selective of the plants and plant parts they consume and select the most digestible diet available. This is especially true in multi-species pastures which have differing maturity times. This also allows cattle to select a diet that has a tendency to produce less methane than when cattle are forced to eat mature plant parts. The ability of cattle to be selective may help explain why McCaughey et al. (1997) did not see methane emission differences in continuous vs. rotational grazing.
Researchers have also determined that increased forage retention time in the rumen increases methane production (Okine et al.1989). Mature forages generally have a longer retention time in the rumen than immature forages. This is due to the higher amount of structural carbohydrates in these mature plants. This concept is supported by research that has shown pastures containing grass legume mixes have higher digestibility and less methane production than grass pastures alone (McCaughey et al. 1999). The mixtures had less structural carbohydrate than the monoculture pastures.
Plant maturity has been shown to have some impact on methane production in the rumen with 11% of gross energy intake being lost on low quality forage (Ominski et al. 2004). When economically feasible to do so, producers should manage pastures to reduce plant maturity to maximize on cattle performance and reduce methane production.
Dr. Karla Jenkins
UNL Extension Cow-Calf/Range Management Specialist
Panhandle Research & Extension Center
University of Nebraska–Lincoln