@Mogima Many herbivores will partake of meat when the option presents itself; In general it takes less digestive work for animals to get nutrients out of meat, but most herbivorous animals don't have any good way of acquiring it regularly.
I recall an article a few years back about researchers in Canada using mist nets strung betwen trees to catch songbirds for banding, only to discover that in many of the nets, the songbirds were winding up being killed and eaten. Turns out the culprits were white-tailed deer.
https://io9.gizmodo.com/field-cameras-catch-deer-eating-birds-wait-why-do-deer-1689440870