Ensiling and thermic treatment effects on nutrient content, protein solubility, and in vitro fermentation of partial crop faba beans

Legumes such as faba beans have a great potential to create local, independent, and high-quality protein resources for ruminant nutrition. Suitable methods for cost- and energy-effective preservation and protein stabilization against rapid fermentation in the rumen play an important role. Partial crop faba beans harvested with 500 or 708 g dry matter (DM)/kg were ensiled, toasted (160 °C, 60 min), or ensiled and toasted and it was investigated how this affects nutrient composition, protein solubility, carbohydrate fermentation, and in vitro organic matter digestibility (IVOMD). Non-protein nitrogen (NPN) concentrations increased and true protein (TP) concentrations decreased after ensiling, depending strongly on DM concentration of the plant (i.e., on maturity) – in NPN, from 15% to 35% (P < 0.001) and from 16% to 21% of crude protein (CP) (P > 0.05), and in TP, from 85% to 65% and from 83% to 79% of CP with 500 and 708 g DM/kg, respectively (P > 0.05) – whereas concentrations of soluble protein did not increase as much as expected. Toasting reduced soluble protein concentration in native faba beans from 56% to 29% and from 54% to 40% of CP with 500 and 708 g DM/kg, respectively (P < 0.001) and in ensiled faba beans from 58% to 38% and from 60% to 34% of CP with 500 and 708 g DM/kg, respectively, compared to the native material (P < 0.001). Ensiling and toasting slightly affected other crude nutrient or metabolizable energy concentrations, carbohydrate fermentation, and IVOMD.