Effects of tannins on in vitro ammonia release and dry matter degradation of soybean meal

Abstract

The efficiency of quebracho (Schinopsis spp), acacia (Acacia spp) and chestnut (Castanea spp.) tannins to protect protein of soybean meal from in vitro degradation was determined. Each tannin was added to soybean meal at levels of 0, 2, 4, and 8% of dry weight and incubated by triplicate in ruminal liquor and McDougall buffer for 48 h (degradation by rumen bacteria) or 48 h plus 24 h of pepsin digestion (degradation by rumen bacteria plus pepsin). In vitro ammonia, isobutyric and isovaleric acid production decreased by addition of tannins to soybean meal. Reduction of ammonia and isobutyric acid per unit of tannin added (slope) was higher (P<0.05) for chestnut than for quebracho or acacia tannins. In vitro DMdegradation (DMD) by rumen bacteria plus pepsin decreased when tannins were added to soybean meal. Decrease in DMD by rumen bacteria per unit of tannin added (rate) was higher and decrease in DMD by rumen bacteria plus pepsin was lower for chestnut tannin than for quebracho or acacia tannin (P<0.05). Results suggest that chestnut tannins are more efficient in protecting soybean meal from in vitro degradation by rumen bacteria with the lowest negative effect on in vitro rumen plus pepsin degradation as compared to acacia or quebracho tannins.