Modulatory effects of dietary tannins on polyunsaturated fatty acid biohydrogenation in the rumen: A meta-analysis

Abstract

BackgroundTannins are a group of phenolic compounds that can modify the rumen biohydrogenation (BH) of polyunsaturated fatty acids (PUFA), but to date results obtained have been inconsistent. This study therefore aims to conduct a meta-analysis of the scientific literature related to the effects of tannins on rumen BH and fermentation. MethodsA total of 28 articles were collected from various scientific databases, such as Scopus, Science Direct and Google Scholar, and the data were analysed using a random effects model and meta-regression for rumen BH. The publication bias on the main variables of rumen fermentation was assessed using a funnel plot and Egger's test. ResultsAn increase in tannin levels significantly reduced methane production (p < 0.001) and the population of Butyrivibrio fibrisolvens (p < 0.05). Dietary tannins also decreased the SFA proportion (p < 0.001) and increased (p < 0.001) the rumen monounsaturated fatty acid (MUFA) and polyunsaturated fatty acid (PUFA) proportions. In additions, there were negative relationships between dietary tannin levels and BH rates of C18:2 n-6 and C18:3 n-3 (p < 0.05). ConclusionDietary tannins modulate the rumen fermentation profile, mitigate methane emissions, and inhibit rumen BH of PUFA.