Nutritive Value and Enteric Methane Production of Brachiaria spp. Under Elevated [CO2]

Despite tropical grasses being the main feed source for major part of ruminant livestock, information about nutritional quality changes under climate changes scenario are still scarce. The novelty of this work was to determine the effects of season and elevated CO2 under field conditions upon biomass production and nutritional value of Brachiaria decumbens during 2 years. The Free-Air Carbon Dioxide Enrichment was established in twelve rings: six of them being the control (current atmosphere) and others six fumigated with pure CO2 to achieve a higher concentration (e[CO2]). In each ring, two 0.25 m2 plots have been established with B. decumbens and after standardization cut, green forage yield was evaluated frequently. Plant samples were collected at 20 cm height and evaluated for determining the biomass production, nutritive value and in vitro enteric methane (CH4) production. Season and year had significant effect (P 0.05). Overall, e[CO2] and rainfall seasons significantly increased forage production, contributing to sequester carbon in plant biomass, but this C4 tropical grass must be grazed at its best protein and fermentable carbohydrate ratio for advantages in the rumen microbial synthesis and lowering CH4 production intensity of the production system.