Microwave Heat Treatment Induced Changes in Forage Hay Digestibility and Cell Microstructure

To investigate the effects of microwave (MW) treatment on hays nutritive value, five types of hay (50 g) were treated with MW for 0 (control), 20, 40, 60, and 80 s (0, 440, 880, 1320, and 1760 kJ kg−1 of MW energy, respectively) and analyzed for nutritive value prior to scanning by an electron microscope to observe microstructure changes. The dry matter (DM) % of hays were increased with increasing treatment time (p < 0.001). The improved DM and digestible organic matter in the DM were recorded from MW treated lucerne (60 s), wheat (40 s), and canola (20 s) (p < 0.001), which might have been due to the MW ruptured cell wall. The MW energy required for maximal DM digestibility improvement was linearly related to control hay crude protein content (r2 = 0.79; p < 0.001). Overall, the study showed MW treatment can increase some hays’ digestibility. In addition, the crude protein content from control hay may be a proxy to indicate DM digestibility improvement.