APPROACHES TO ESTIMATE RUMEN METHANE EMISSIONS AND STRATEGIES OF MITIGATION

The agricultural sector has long been criticized by public opinion of being among the major responsible for the climate-altering gas emissions, commonly known as greenhouse gases. These emissions are responsible for global warming and climate change. Within the agricultural sector, livestock farming is the larger contributor to methane emissions into the atmosphere. Methane, along with carbon dioxide and nitrous oxide, is one of the climate-altering gases, primarily produced and emitted by ruminants due to the unique structure and physiology of their digestive system. Cattle are the primary focus in this category, as they represent the most widespread ruminant species. Like other ruminants, they have three non-glandular pre-stomachs, which precede the true glandular stomach. Rumen is the larger pre-stomach and is populated by a microbial consortium of bacteria, protozoa, and fungi. These microorganisms are responsible for fermenting fibre, starch, and all dietary components, releasing volatile fatty acids and fermentation gases into the rumen as by-products. Through the rumen wall, the animal absorbs volatile fatty acids, which provide the energy needed for its metabolism, while it eructates and releases the fermentation gases, mainly carbon dioxide and methane, into the environment. Over the years, many studies have been conducted to find new substances, additives, or feeds capable of inhibiting methane production. At the same time, various screening, evaluation, and estimation methods for methane have been developed and proposed, in order to provide farmers with useful tools for assessing methane emissions from their livestock. Therefore, given the state of knowledge in the field, this thesis aimed to evaluate one of these methane emission estimation methods, while also seeking to characterize and analyse the effects of a feed additive and some officinal herbs on fermentation characteristics and the potential inhibition of methanogenesis through in vitro studies. To achieve this aim, several databases were used, one of which came from a previous project (“Cowability-Cowplus”), while the other two were specifically developed through various laboratory trials (“NoMethane” and “BIRD213117/21” projects). The results obtained from these studies demonstrate that there are molecules and substances capable of reducing ruminal methane emissions, but some of them need further study and understanding, not only in terms of their effect on methanogenesis but specially in their mechanism of action. Moreover, new simple, intuitive, and applicable screening methods must be developed based on easily accessible and routine information, so that farmers can use them effectively within their farms.