Joy likes peas. Joy really likes peas. "Peas" as in pod-and-all. She proved that this morning by eating the pea pods right off of the plants while I was watering them. It was amusing to see her rooting around in the plants for just the pea pods. Picture a pig rooting around in the dirt. Now translate that to a dog rooting around in the undergrowth of a raised bed of bush peas.
That said, mastiffs are not 1) picky eaters or 2) neat eaters, but they are omnivores. At one point Joy managed to tear off about a foot of plant along with her chosen pea pod. She ate the whole thing, plant and all.
Edit/additional: At the beginning of spring we fenced in the raised beds with welded cattle panels bent to shape around the boxes. The original intention was to annoy deer and other browsers (escaped goats). Happily, welded cattle panel is designed to thwart half-ton angry herbivores, and so is definitely a match for happy mastiffs. As such, Joy can only get to the pea plants that have escaped through the fence... thankfully.