VN April 2021

Vetnuus | April 2021 6 Methane is a short-lived but powerful greenhouse gas and the second-largest contributor to climate change after carbon dioxide. And the majority of human-induced methane emissions comes from livestock. About 70%of agriculturalmethanecomes fromenteric fermentation – chemical reactions in the stomachs of cows and other grazing animals as they break down plants. The animals burp out most of this methane and pass the rest as flatulence. There are roughly 1 billion cattle around the world, so reducing enteric methane is an effective way to reduce overall methane emissions. But most options for doing so, such as changing cows’ diets to more digestible feed or adding more fat, are not cost- effective. A 2015 study suggested that using seaweed as an additive to cattle’s normal feed could reduce methane production, but this research was done in a laboratory, not in live animals. We study sustainable agriculture, focusing on livestock. In a newly published study, we show that using red seaweed ( Asparagopsis ) as a feed supplement can reduce both methane emissions and feed costs without affecting meat quality. If these findings can be scaled up and commercialised, they could transform cattle production into a more economically and environmentally sustainable industry. Plant-digesting machines Ruminant animals, such as cows, sheep and goats, can digest plant material that is indigestible for humans and animals with simple stomachs, such as pigs and chickens. This unique ability stems from ruminants’ four-compartment stomachs – particularly the rumen compartment, which contains a host of different microbes that ferment feed and break it down into nutrients. This process also generates by-products that the cow’s body does not take up, such as carbon dioxide and hydrogen. Methane- producing microbes, called methanogens, use these compounds to form methane, which the cow’s body expels. We first analysed this problem in a 2019 study, the first such research that was conducted in cattle rather than in a laboratory. In that work, we showed that supplementing dairy cows’ feed with about 10 ounces of seaweed a day reduced methane emissions by up to 67%. However, the cattle that ate this relatively large quantity of seaweed consumed less feed. This reduced their milk production – a clear drawback for dairy farmers. Our new study sought to answer several questions that would be important to farmers considering whether to use seaweed supplements in their cattle. We wanted to know whether the seaweed was stable when stored for up to three years; whether microbes that produce methane in cows’ stomachs could adapt to the seaweed, making it ineffective; and whether the type of diet that the cows ate changed the seaweed’s effectiveness in reducing methane emissions. And we used less seaweed than in our 2019 study. Feeding cows a few ounces of seaweed daily could sharply reduce their contribution to climate change while improving feed conversion rates Ermias Kebreab, Associate Dean and Professor of Animal Science. Director, World Food Center, University of California, Davis, and Breanna Roque, Ph.D. Student in Animal Biology, University of California, Davis (source: www.theconversation.com ) Leading Article A steer eats alfalfa pellets as equipments measures his gas emissions, including methane (Photo: Reanna Rogue, CC BY-ND)