Fermentation profile and hygienic quality of rehydrated corn grains treated with condensed tannins from quebracho plant extract

Abstract

The objective of this study was to evaluate the inclusion of a plant extract rich in condensed tannins on the fermentation profile, contents of biogenic amines and mycotoxins, chemical composition and aerobic stability of rehydrated corn silage. Kernels were milled (4.5-mm sieve), rehydrated (aiming for 350 g/kg moisture) and treated with a plant extract from the plant Schinopsis lorentzii at the following doses: 0, 5, 10, 30 and 50 g/kg dry matter (DM) before ensiling. Nylon-polyethylene vacuum-sealed bags were used as experimental silos (3 kg per silo). On the one hand, the additive reduced the DM losses and gaseous losses. On the other hand, the addition of the plant extract resulted in higher pH values due to the formation of less lactic acid, probably related to the inhibition of bacterial growth. The concentrations of ammonia, ethanol and acetic acid were also reduced due to the plant extract addition. The reduction in the acetic acid concentration led to higher counts of yeast and lower aerobic stability in silage treated with the highest dose of extract (50 g/kg). Silage treated with the plant extract had higher DM concentration as well as higher contents of condensed tannins, neutral detergent fiber and acid detergent fiber and lower contents of starch and protein. The application of the plant extract linearly decreased the ruminal in situ DM degradability of the corn grain silage. The plant extract reduced the proteolysis and the formation of putrescine, cadaverine, spermine, spermidine, and pyrrolidine, while increased histamine and isopropyl amine concentrations. A linear increase was detected in the aflatoxin concentration in the treated silages. Based on these results, condensed tannins may support the fermentation process especially the proteolysis. However, quebracho tannin are not recommended for addition to corn grain silage in dosages higher than 30 g/kg DM.