I think a lot of this, as well as Orcs in general are derived from Mongols before, and under Ghengis. Their livestock and grazing pastures, ‘tribe’ interactions could be based on a lot of this. Mongols ate a lot of meat, cheese and milk, with the odd root vege etc. thrown in from their grazing lands and any imports they could get of tea or other items they could not produce themselves. Arguably the reason why they were so warlike was because of the amount of meat they ate, but obviously also political interferance from China was also a factor in getting them on the warpath under Ghengis.