Effects of toasting temperature and duration on in vitro ruminal gas production kinetics and post-ruminal crude protein from field pea (Pisum sativum) legume grain silages

Abstract Field peas provide valuable starch and protein, but especially the latter is highly soluble in the rumen. Toasting of ensiled pea grains might reduce ruminal starch and protein degradation. The objective was to test this by measuring 24 h total gas production, gas production kinetics, and post-ruminal crude protein (PRCP) in an in vitro batch culture system. First, toasting temperature was varied with 120, 140, 160, 180, and 200°C stages, while keeping a constant treatment duration of 30 min, and second, toasting temperature was kept constant at 160°C, and the duration was varied with 10, 20, and 30 min. Rumen-undegraded protein (RUP) was measured using the Streptomyces griseus protease test. Moreover, ensiling and toasting effects on the morphology of pea starches were visually examined using scanning electron microscopy. In vitro gas production decreased with increasing toasting temperature or duration of heat exposure (P