Silage quality as influenced by concentration and type of tannins present in the material ensiled: A meta‐analysis

Protein degradation during ensiling is a major problem. Tannins are known to prevent or decelerate protein degradation in the rumen and may be able to do so in silages as well. Therefore, the present evaluation aimed to analyse the influence of tannins on silage quality. This was done by integrating from all suitable experiments found in literature on the topic in a meta‐analysis approach. A total of 122 datasets originating from 28 experiments obtained from 16 published articles and one own unpublished experiment were included in the database. Tannins in the silages originated either from the plants ensiled or from supplementations of tanniferous plants or tannins extracted from such plants. Tannin concentrations ranged from 0 to 57.8 g/kg dry matter, and the ensiling period varied from 30 to 130 days. The analysis was based on the linear mixed model methodology in which the different studies were considered as random effects and tannin‐related properties (either concentration or type of tannins) were treated as fixed effects. Results revealed that greater concentrations of tannins were associated with a decrease of butyrate concentration in the silages (p