Plant secondary metabolites for mitigating enteric methane in tropical small scale production systems
Feed supplementation with tropical plant species seems a rational, and practical approach for methane mitigation under the conditions of small-scale ruminant production systems in tropical regions.
This summary is from the paper “Role of Secondary Plant Metabolites on Enteric Methane Mitigation in Ruminants” where three students from the CLIFF-GRADS program, Sara Valencia Salazar, Isabel Molina Botero and Rafael Jiménez Ocampo are working together with scientists from CIAT and other universities.
The rumen microbiome plays a fundamental role in the digestion process of ruminants. Microbial consortia of the rumen result in a syntrophic relationship between them and of mutualism with their host. These microbial populations use cellulose, hemicellulose and starch in ruminant rations for their growth and produce volatile fatty acids, metabolic hydrogen and carbon dioxide. During this process archaeal communities use hydrogen and carbon dioxide as metabolic energy source and synthesize methane as a byproduct. Methane is then released to the atmosphere through belching and respiration.
In the search for mitigation strategies to reduce methane production from cattle in tropical livestock systems, plant secondary metabolites have shown to be a low-cost and effective strategy. Plant secondary metabolites are naturally produced by plants for their adaptation to environmental conditions and are found in the leaves, pods, tubers or seeds of the plants, especially those from tropical regions. These compounds are found to be effective[HT1] for the reduction of methane due to their capacity to reduce archaeal communities in the rumen or other microorganisms that are associated to the formation of methane. In laboratory conditions were ruminal fermentation is simulated through the in vitro gas production technique, plant secondary metabolites showed to modify some microbial communities in ruminal liquid. Also, under in vivo conditions were methane was measured from cattle housed in open circuit respiration chambers, the inclusion of these metabolites on the diet showed reductions of up to 20% on average. Some of the most studied secondary metabolites are condensed tannins, saponins and essential oils. However, the effects of these compounds on microbial communities and methane production depend on their chemical characteristics and quantity consumed in the ruminant’s feed ration.
Written by Sara Stephanie Valencia Salazar, 2020 CLIFF-GRADS Recipient