The Role of Chitosan as a Possible Agent for Enteric Methane Mitigation in Ruminants
Faculty of Veterinary Medicine and Animal Science, University of Yucatan, Carretera Merida-Xmatkuil km 15.5. Apdo. 4-116 Itzimna, C.P. 97100 Merida, Yucatan, Mexico
College of the Southern Border (ECOSUR), Livestock and Environment, Carretera Panamericana—Periferico Sur, C.P. 29290 San Cristobal de las Casas, Chiapas, Mexico
Faculty of Veterinary Medicine and Animal Science, Juarez University of Durango, Carr Durango—Mezquital km 11.5, C.P. 34307 Durango, Mexico
International Center for Tropical Agriculture (CIAT), km 17, Recta Cali-Palmira, Palmira C.P. 763537 Valle del Cauca, Colombia
Author to whom correspondence should be addressed.
Received: 28 September 2019 / Revised: 21 October 2019 / Accepted: 6 November 2019 / Published: 9 November 2019
Ruminant husbandry is one the largest contributors to greenhouse gas emissions from the agriculture sector, particularly of methane gas, which is a byproduct of the anaerobic fermentation of structural and non-structural carbohydrates in the rumen. Increasing the efficiency of production systems and decreasing its environmental burden is a global commitment, thus methane mitigation is a strategy in which to reach these goals by rechanneling metabolic hydrogen (H2) into volatile fatty acids (VFA) to reduce the loss of energy as methane in the rumen, which ranges from 2% (grain rations) to 12% (poor-quality forage rations) of gross energy intake. A strategy to achieve that goal may be through the manipulation of rumen fermentation with natural compounds such as chitosan. In this review, we describe the effects of chitosan on feed intake and rumen fermentation, and present some results on methanogenesis. The main compounds with antimethanogenic properties are the secondary metabolites, which are generally classified into five main groups: saponins, tannins, essential oils, organosulfurized compounds, and flavonoids. Novel compounds of interest include chitosan obtained by the deacetylation of chitin, with beneficial properties such as biocompatibility, biodegradability, non-toxicity, and chelation of metal ions. This compound has shown its potential to modify the rumen microbiome, improve nitrogen (N) metabolism, and mitigate enteric methane (CH4) under some circumstances. Further evaluations in vivo are necessary at different doses in ruminant species as well as the economic evaluation of its incorporation in practical rations.