Theme 3: Livestock--Oral Sessions

Description

Enteric methane (CH4) is a main source of agriculture-related greenhouse gasses. Conversely, pasture is increasingly demanded by customers due to both perceived and real benefits regarding animal welfare, environmental aspects and product quality. However, if implemented poorly, CH4 emissions can increase, thus contributing to climate change. One promising option to reduce enteric CH4 emissions are plant specialized metabolites (PSM), and particularly tannins. Consequently, we conducted two complementary experiments to determine to what extent enteric CH4 emissions can be reduced, and how this affects milk yields: a) an in vivo experiment with grazing Jersey cows, where CH4 emissions were quantified using the SF6 tracer technique, and b) an in vitro experiment using the Hohenheim gas test. In the in vivo experiment, a binary mixture consisting of perennial ryegrass (Lolium perenne) and white clover (Trifolium repens) was compared against a diverse mixture consisting of eight species, including birdsfoot trefoil (Lotus corniculatus), and salad burnet (Sanguisorba minor). In the in vitro experiment, the eight species from the in vivo experiment were combined in binary mixtures with perennial ryegrass in increasing proportions, to determine the mitigation potential of each species. Results show an increase in milk yield for the diverse mixture, although this is also accompanied by higher CH4 emissions. Nevertheless, these emissions are lower across both mixtures, when compared with similar trials. This is probably due to a very high digestibility of the ingested forage. With the in vitro experiment, we were able to confirm a substantial potential for CH4 reduction when including species rich in PSM. However, those forbs with the higher anti-methanogenic potential were only present in minor proportions in the pasture. Hence, further research will be required on how to increase the share of the bioactive species with lower competitiveness and confirm their potential in vivo.

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Assessing the Potential of Diverse Forage Mixtures to Reduce Enteric CH4 Emissions

Enteric methane (CH4) is a main source of agriculture-related greenhouse gasses. Conversely, pasture is increasingly demanded by customers due to both perceived and real benefits regarding animal welfare, environmental aspects and product quality. However, if implemented poorly, CH4 emissions can increase, thus contributing to climate change. One promising option to reduce enteric CH4 emissions are plant specialized metabolites (PSM), and particularly tannins. Consequently, we conducted two complementary experiments to determine to what extent enteric CH4 emissions can be reduced, and how this affects milk yields: a) an in vivo experiment with grazing Jersey cows, where CH4 emissions were quantified using the SF6 tracer technique, and b) an in vitro experiment using the Hohenheim gas test. In the in vivo experiment, a binary mixture consisting of perennial ryegrass (Lolium perenne) and white clover (Trifolium repens) was compared against a diverse mixture consisting of eight species, including birdsfoot trefoil (Lotus corniculatus), and salad burnet (Sanguisorba minor). In the in vitro experiment, the eight species from the in vivo experiment were combined in binary mixtures with perennial ryegrass in increasing proportions, to determine the mitigation potential of each species. Results show an increase in milk yield for the diverse mixture, although this is also accompanied by higher CH4 emissions. Nevertheless, these emissions are lower across both mixtures, when compared with similar trials. This is probably due to a very high digestibility of the ingested forage. With the in vitro experiment, we were able to confirm a substantial potential for CH4 reduction when including species rich in PSM. However, those forbs with the higher anti-methanogenic potential were only present in minor proportions in the pasture. Hence, further research will be required on how to increase the share of the bioactive species with lower competitiveness and confirm their potential in vivo.