Strategies in grass silage production to mitigate enteric CH4 emissions from ruminants

About 2/3 of greenhouse gas (GHG) emissions in Norwegian agriculture come from ruminants, and most of the emissions are methane from the digestion of the ruminants. Forage constitutes a large proportion of the animals' feed ration. It is a national goal to increase the forage portion and the proportion of Norwegian-produced feed in the ration of the ruminants. It may have a major impact on GHG emissions from agriculture if characteristics of a low-emission forage is uncoverd. Grass silage, which is the predominant forage, is produced in various ways, resulting in a great variation of silage characteristics (eg botanical composition, digestibility and fermentation results). These characteristics can affect methane emissions from animals. At the same time, these must be characteristics that can be utilized to reduce methane emissions under both practical and economic conditions. The project includes 4 work packages (WP) which will contribute in achieving the main goal: Develop strategies in grass silage production that reduce methane emissions from digestion of ruminants. TINE has already established a database of silage samples (from 86 round bales collected from all over the country) that have a large variety of feed quality. These round bales are analyzed for chemical composition and digestibility. In addition, the NDF degradation profile of these round bales is determined. In WP1, characteristics of these silages that affect methane emissions have been analyzed by using a laboratory method (in vitro-method). The results showed that concentration of sugar (WSC) increased in vitro methane production, while concentration of NDF and undigestible NDF decreased methane concentration in grass silages. Silages that reduce in vitro methane production are, however, expected to lower animal production, thus it appears to be a contradiction between selecting silages that reduce methane production and those that support high levels of animal production. In WP2 some silage characteristics were studied in controlled field trials, where silage was produced with great variation for the certain characteristics and analyzed for in vitro methane production. The results showed that less frequent harvesting, extensive silage fermentation, and use of timothy as grass species reduced in vitro methane production. As in WP1, the methane-reducing silage characteristics will potentially reduce animal production, which must be confirmed with animal production data. In WP3 the results from the two previous WP’s were followed up, and some of the most interesting results from the in vitro studies were investigated in an experiment with dairy cows. The aim was to investigate the effects of grassland species (timothy, perennial ryegrass, and red clover) and cutting frequency (three vs. two cuts per season) for timothy on feed intake, milk production and enteric methane production. The results have not yet been published, but they indicate that increased cutting frequency of timothy and the use of timothy instead of ryegrass increased milk yield and reduced methane production per kg milk produced. Inclusion of red clover in the ration increased methane production per kg milk produced. Before introducing strategies in silage production into practice, it is important that potential side effects are evaluated. In WP4, results from the trials will be included in farm models, and it will be evaluated whether the strategies that reduce enteric methane emissions affect emissions of other greenhouse gases from ruminant production system. Also, the profitability and cost-effectiveness of implementing the strategies will be calculated.

Food production results in greenhouse gases (GHG) emissions. Today, GHG from the agricultural sector constitute 8.6 percent of the total emission from Norway. Enteric methane (CH4) is a significant contributor to GHG emissions as it accounts for almost half of the total GHG emissions from Norwegian agriculture. Grass silage is the dominating preserved forage in ruminant diets. The practice used for grass silage production is very diverse, resulting in wide variation in characteristics, and hence influence on enteric CH4 emissions. Thus, finding ways to produce grass silage that minimise enteric CH4 emissions is an important strategy to reduce GHG emissions from Norwegian agriculture. To be able to lower enteric CH4 emissions, new knowledge and competence on the effects of silage production are required. In the present project, research institutions will co-operate with the Agro-industries to: 1) Explore which silage characteristics that perform the largest effect on in vitro enteric CH4-emissions (these data complete the data bank (established by TINE) of grass silage samples that has a great variety of feed quality (botanical and chemical composition, digestibility and fermentation quality)). 2) Systematize the most promising silage characteristics regarding CH4 production in field experiments. 3) Determine the magnitude of enteric CH4 mitigation from dairy cows by the most promising silage characteristics. 4) Develop cost-effective silage production strategies to reduce GHG emissions from ruminant farming systems. These sub- goals will lead to the achievement of the primary objective: Develop strategies in silage production that mitigate enteric CH4 emissions from ruminants.