Protein dietary efficiency and methane emission in cattle fed soybean meal treated with tannins

Abstract

Adding tannins to the dietary protein source will cause complexation between the tannin and protein, which may increase dietary ruminal undegraded protein. Thus, this study aimed to evaluate the effects of replacing soybean meal (SM) with soybean meal treated with tannin (SMT) on the intake, partial and total nutrient digestibility, and protein dietary efficiency of young cattle fed a high-concentrate diet. Five Nellore bulls with bodyweights of 290 ± 11.2 kg were fitted with ruminal and abomasal cannulas and were used in the study. The experimental diets included 7.5% SM, with a proportion of that SM (0%, 33%, 66% or 100%) replaced with SMT. Another treatment (SMT+urea) with only 2.5% SM treated with tannins was tested. The intake of ether extract and the intake of neutral detergent fibre ash and protein were the only parameters related to feed intake that were affected by the replacement of SM with SMT. Ruminal and intestinal digestibility each showed a linear effect on crude protein, which decreased with ruminal digestibility and increased with intestinal digestibility. The intake of ruminal undegraded protein and metabolisable protein showed a positive linear correlation with the amount of SMT in the diet. SMT substitution showed no effect on methane emission. The replacement of traditional SM with SM treated with 2.5% tannins (85% condensed tannins and 15% hydrolysable tannins) for cattle that were fed high-concentrate diets showed increased amounts of metabolisable protein and decreased nitrogen loss per unit of crude protein, without changing the methane emission.