Can condensed tannins improve fermentation patterns and the nutritive value of sorghum silage?

Abstract

Context For an ensiling to succeed, the knowledge about the factors that might influence the fermentation dynamics and nutrient loss is mandatory. One of the strategies is the use of additives such as tannins, as they can decrease proteolysis and increase the total organic acids. Aims The aim was to investigate the effects of tannins on fermentation patterns and nutritional value of sorghum silage. Methods Silages containing 0.0, 7.5, 15.0, 22.5, and 30.0 g/kg of tannin on fresh matter were studied. To produce the silage, the tannin was added to the forage and manually homogenised before ensiling. The study was conducted in three experiments. In the first experiment, five replications of each level of inclusion were produced and assigned in a completely randomised design. The chemical composition and fermentation patterns of all experimental units were evaluated. The second experiment consisted of analysing the aerobic deterioration by using a PET bottles system. This experiment was conducted in a completely randomised split plot, with five replications and five treatments with the inclusion of different levels of tannin (main plots) and the hours of exposure of silage to air (subplot). In the third experiment, five levels of tannin (main plots) and incubation times (subplots) were evaluated as for in situ digestibility (ruminal degradability) in a randomised blocks design with three replications (animals). Key results The inclusion of tannins in sorghum silage caused quadratic effects on pH, acetic acid, lactic acid, total organic acids, ammonia nitrogen, dry matter content, crude protein content and in situ digestibility, when the level varied from 10.5 to 22.7 g tannin/kg fresh matter. There was a decreasing linear effect for aerobic deterioration as increasing levels of tannin in sorghum silage. Conclusions The inclusion of tannin as an additive in sorghum silage is recommended for the production of good quality silage. The use of condensed tannins optimise fermentation patterns (especially increasing lactic acid and decreasing ammoniacal nitrogen), chemical composition, providing less aerobic deterioration and improve digestibility. Implications This study revealed that condensed tannins can improve fermentation patterns and the nutritive value of sorghum silage.