The Use of Tannin for Enhanced Ruminant Production, Mitigation of Enteric Methane Emission and Alteration of Fatty Acid Profile in Beef

The role of tannin on ruminant production performance, reduction in enteric methane emission, and changes in rumen fatty acid profile were investigated. Specifically, the objectives were to screen and characterize common forage plants based on tannin and other chemical properties (Experiment 1), determine the rumen fermentation changes as affected by mixture of low and high tannin plants (Experiment 2), determine the effects of purified condensed and hydrolyzable tannins as feed additives on rumen fermentation and microbial population (Experiment 3), and determine the effect of tannin on the growth of beef cattle (Experiment 4).

In experiment 1, 27 tropical plant species were collected within Bogor, West Java, Indonesia, sampled and characterized for their chemical and nutritional composition. Rumen methane production and fatty acid (FA) profiles were analyzed. In experiment 2, 15 combinations of high and low tannin plants were prepared and subjected to in vitro gas production technique for measurement of methane emission and rumen fermentation parameters. In experiment 3, purified tannins were extracted from four high tannin plants, characterized into condensed or hydrolyzable tannins, and then used as feed additive to modulate methane emission and rumen microbial population structure in vitro. In experiment 4, 40 male Brahman cross cattle were divided into two experimental groups. The first group received a feedlot diet and the second group received a feedlot diet + chestnut tannin extract at 25 g/d.

Results revealed that plants rich in tannin have the property to mitigate methane emission. All phenolic fractions, i.e., non-tannin phenols, condensed tannins (CT), and hydrolyzable tannins (HT) appeared to contribute to suppressing CH4 formation as shown by negative correlations of the fractions in plants and CH4/total gas or CH4/digestible OM. Apart from decreasing CH4 emission linearly, combining plants rich in tannin with a high quality forage plant with negligible tannin provided additional benefits due to the presence of synergistic associative effects, which further decreased CH4. Incubation of tropical plants with additional linseed oil suggests the ability of plant tannin in modulating FA biohydrogenation by decelerating the process as indicated by lower disappearance of C18:3 n-3 and C18:2 n-6.

All tannin extracts decreased methane concentration either linearly or quadratically, but their magnitudes were different being greater for the HT than the CT, and correlated with their protein precipitation capacity. All purified HT and CT decreased total methanogen population. The addition of tannin at 25 g/d in the diet of crossbred Brahman cattle resulted in a 29.2 percent increase in growth rate from 1.20 kg/d to 1.55 kg/d. In conclusion, plant tannin in ruminant diet was able to modulate methanogenesis and fatty acid biohydrogenation and improve growth performance of cattle.