Effect of easily fermentable carbohydrates on in vitro rumen methane emission at different pH

Focus has been on greenhouse gas (GHG) to a great extent because in the last 150 years they have increased and consequently affect the climate by skewing all of the global atmospheric concentrations and inducing a dramatic environmental impact to the world.

The greenhouse gases considered are mainly characterized by carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O). Approximately 20 and 35 % of the global greenhouse gas emissions originate from agricultural production and this production represents 40 and more then 50% of the anthropogenic emissions of CH4 and N2O, respectively (IPPC, 2001 and Monteny, 2005). The contribution of methane to global warming is 24%, while carbon dioxide contributes 49%, halocarbons 12% and tropospheric ozone 10% (Hansen et al., 2000).

Already prior to the formulation of the Kyoto protocol (1997) gas pollution was not under control and it was specifically possible to quantify that methane has a global warming potential of 21 times greater than CO2.

Methane is formed and released from biological processes in anaerobic environments and is particularly linked to the absorption of terrestrial infrared radiation that would otherwise escape into space.

This contributes to the warming of the atmosphere. Therefore from an ecological point of view as well as the CO2 reduction, it is still very important to reduce methane and the nitrous dioxide production from ruminants.

The total gas emission estimations should be improved since especially the methane emission has been identified as the largest single source of anthropogenic CH4 (Mathison et al., 1998; Monteny, 2005). Methane emission from agriculture (enteric fermentation, manure, rice production) contributes to as much as 43% of anthropogenic methane, of which enteric methane emission is the largest single source (Kruger, 2003). Particularly dairy cows produce roughly 118 kg methane/year, which is over twice that produced by other non-lactating cattle (beef cows, bulls, calves, growing steers/heifers, and feedlot cattle).

The methane emissions from enteric fermentation represent about 6% of dietary gross energy, but this varies with diet from about 2% (cattle in feedlots) to 12% (animals eating very poor quality forage) according to Johnson and Johnson (1995).