Effect of toasting grain silages from field peas (Pisum sativum) and field beans (Vicia faba) on in vitro gas production, methane production, and post-ruminal crude protein content

Legume grains such as field peas and field beans can be produced on a local level, and may be reliable sources of dietary protein and energy apart from common soybean and rapeseed meals. In ruminants, protein, starch, and carbohydrates from peas and field beans are fermented in large part before reaching the small intestine. The objective of this study was to evaluate the effects of a combination of ensiling and hydro-thermic treatment (i.e., toasting at 160 °C for 30 min) of grains of peas and field beans on the concentrations of post-ruminal crude protein (PRCP) and rumen-undegraded protein (RUP). Moreover, 24-h gas production and methane production were measured. For this, an in vitro batch culture system with ruminal fluid from sheep was used. Rumen-undegraded protein was determined using the Streptomyces griseus protease test. Scanning electron micrographs were used to visualize morphological changes of starch granules and their joint matrices in peas and field beans after ensiling, toasting, or a combination of both. Native pea grains contained crude protein (CP) at 199 g/kg DM, PRCP at 155 g/kg DM at a ruminal passage rate of 0.08/h (Kp8), RUP at 33 g/kg DM at Kp8, and starch at 530 g/kg DM. Native field beans contained CP at 296 g/kg DM, PRCP at 212 g/kg DM at Kp8, RUP at 54 g of/kg DM at Kp8, and starch at 450 g/kg DM. The PRCP did not considerably differ among native and treated peas or field beans. Especially in the peas, RUP at Kp8 increased after ensiling by 10 g/kg DM (i.e., 30%; P