Ruminal biohydrogenation as affected by tannins in vitro

Area of Science:

• Animal Science
• Rumen Microbiology
• Nutritional Biochemistry

Background:

• Ruminal biohydrogenation significantly influences the fatty acid composition of ruminant products.
• Plant-derived tannins are known to interact with dietary components and microbial enzymes in the rumen.
• Understanding tannin effects on biohydrogenation is crucial for manipulating fatty acid profiles in meat and milk.

Purpose of the Study:

• To investigate the in vitro effects of carob (CT), acacia leaf (AT), and quebracho (QT) tannins on ruminal biohydrogenation.
• To determine how these tannins influence fatty acid metabolism, microbial protein synthesis, and specific enzyme activities.
• To elucidate the mechanism by which tannins affect the biohydrogenation process.

Main Methods:

• In vitro incubation of CT, AT, and QT (0.0, 0.6, 1.0 mg/ml) in cow buffered ruminal fluid (BRF) with hay or hay-plus-concentrate substrate for 12 hours.
• Analysis of branched-chain volatile fatty acids, branched-chain fatty acids, microbial protein, and specific fatty acids (vaccenic, stearic, CLA isomers).
• Assay of linoleic acid isomerase (LA-I) activity and product formation.

Main Results:

• Tannins significantly reduced branched-chain volatile fatty acids, branched-chain fatty acids, and microbial protein concentration (P < 0.05).
• Accumulation of vaccenic acid (+23%, P < 0.01) and reduction of stearic acid (-16%, P < 0.0005) were observed in tannin-treated fermenters.
• While total conjugated linoleic acid (CLA) isomers and LA-I enzyme activity were unaffected, the overall CLA production by LA-I was lower in the presence of tannins.

Conclusions:

• Plant-derived tannins, specifically CT, AT, and QT, inhibit ruminal biohydrogenation in vitro.
• The reduction in biohydrogenation appears to be mediated by the inhibition of ruminal microbial activity rather than direct enzyme inhibition.
• These findings suggest a potential strategy for manipulating fatty acid profiles in ruminants through tannin administration, warranting further in vivo investigation.