Characterization of Nutritional Values, Ruminal and Total Digestibility of Nutrients and Predicted Metabolizable Protein Supply to Dairy Cows: Comparison of Tannin and Non-Tannin Faba Bean

The study was conducted to compare 1) chemical profile; 2) protein and carbohydrate subfractions fractionated by the Cornell Net Carbohydrate and Protein System (CNCPS); 3) energy values; 4) ruminal, intestinal and total digestibility of nutrients; and 5) protein supply predicted by the DVE/OEB system between tannin (var. Fatima) and non-tannin (var. Snowbird) faba beans, with comparison to starchy barley as a reference. The results showed that the brown-seeded Fatima faba bean showed higher contents of CP, ADF, NDICP, SCP and NPN and lower concentrations in EE and starch, compared with the white Snowbird bean. Subsequently, CNCPS protein and carbohydrate subfractions as well as energy values differed between these two beans. Although statistically significant, the differences on RUP, EDCP and TDP were found to be tiny between tannin and non-tannin faba beans. The DVE and OEB values of faba bean with presence of tannin were 6-15% greater than those of Snowbird bean. As a result, feed milk value (FMV) which is estimated from metabolizable protein was higher in Fatima. As for the control starchy barley, it showed significant differences in chemical compositions, CNCPS subfractions and energy values. Remarkable lower DVE and FMV were also found in the barley, compared with faba beans. The optimal OEB value is regarded to be zero or slightly above. In our study, the OEB was determined to be positive in faba beans (118 g/kg DM) and negative in the barley (-6.2 g/kg DM), indicating barley might be better than the beans if used as the unique ingredient in the ration for ruminants.