Impacts of different condensed tannins structures on ruminal fermentation

Abstract

CCondensed tannins (CT) are a group of secondary phenolic compounds often found in forages, mostly legumes, which presents the ability of affecting some aspects of ruminal fermentation, such as the degradability of dietary nutrients and methane (CH4) production. The concentration of these molecules in diets is not the only parameter related to the occurrence of their effects on the metabolism of animals, the chemical structure of different CT from different sources may be even more crucial for the observation of such effects. Condensed tannins are found in plants as complex mixtures of homo- and heteropolymers containing different flavan-3-ols as terminal and extension units that usually include catechin (C), epicatechin (EC), gallocatechin (GC) and epigallotechin (EGC), with their relative proportions differing among plant types and species. Considering the hypothesis that the different chemical features from different CT sources may affect their biological activity in diverse ways, the objective of this project is to determine the CT structural features of CT sources and to evaluate the impacts of these on in vitro ruminal fermentation parameters. The flavan-3-ols terminal and extension units of CT (i.e. C, EC, GC and EGC) from various sources, including the forage legumes purple prairie clover (Dalea purpurea Vent), macrotiloma (Macrotyloma axillare) and the extract of black wattle (Acacia mearnsii) bark will be determined and afterwards, these CT sources will be evaluated in assays under in vitro ruminal fermentation conditions, using polyethylene glycol (PEG) to clearly estimate the impacts of CT on ruminal fermentation. Ruminal degradability, CH4 production, ammonia and short-chain fatty acids will be determined. The results obtained from these in vitro fermentation assays such as CH4 production and fermentation parameters will be correlated to the different CT structural properties, making it possible to associate correlations between flavan-3-ols terminal and extension units and the effects observed in studies using CT sources. During this collaboration, the candidate will be learning the methods for determination of CT structural features, which are still not employed in studies from research groups in this field of science in Brazil. During the execution of the project, the candidate should be able to apply these methods to different CT sources, including the forage legume macrotiloma, used in the main Post-Doctoral project in Brazil. The chronogram for the one-year period planned for this project is as follows:- First trimester (April 2019 - July 2019): To learn the laboratorial methods used to perform the CT structures analysis and apply them to different tannin sources;- Second trimester (August 2019 - October 2019): To perform in vitro ruminal fermentation studies;- Third trimester (November 2019 - January 2020): Data analysis and start writing of scientific papers and reports;- Fourth trimester (February 2020 - April 2020): Finalize papers and scientific reports.