Sainfoin (Onobrychis viciifolia) is a forage legume with condensed tannins (CT), varying the content upon different factors such as the variety, phenological stage, forage preservation, etc. The CT can affect some parameters of the ruminal fermentation depending on their content and their chemical structure, the chemical composition of the diet and the ruminant species, among other factors. The objective of this review is to study the influence of CT, the phenological stage and the preservation of the sainfoin on the CT content and its fractions (free, protein‑bound and fibre‑bound), as well as in its structural characteristics (degree of polymerization, ratio of prodelphinidin:procyanidin and ratio of cis:trans in the flavanol unit) and their effects on ruminal fermentation in sheep and cattle. Condensed tannins mainly cause a reduction in the production of gas and methane and a reduction in the degradation of the protein that is showed by a reduction in the contents of ammonia and iso‑acids. However, there are still controversies in the studies using polyethylene glycol and in the studies that evaluate the phenological stage and preservation. It is difficult to ascribe the difference to changes in chemical composition and/or changes in CTs characteristics... As forage develops, a reduction in CT content can occur whereas preservation leads to changes in the distribution of CT fractions, especially in silage. However, the studies are not conclusive and show that other factors different to the CT content also affect the ruminal fermentation, such as type of diet, ruminant species or incubation time.

Rufino‑Moya PJ, Blanco M, Joy M (2021). Taninos condensados de la esparceta y su efecto sobre los parámetros de la fermentación ruminal. Influencia del estado fenológico y de la conservación. Revisión bibliográfica. ITEA‑Información Técnica Económica Agraria 117(3): 227-246. https://doi.org/10.12706/itea.2020.026