While it might be tempting to let your guinea pig eat other pet food, particularly if they are a companion to a rabbit, even the best rabbit food and other pet foods are unsuitable for guinea pigs.

But M&S has managed to anger some Percy Pigs fans by completely removing gelatin from their main product - something described by one angry person online as "an assault on normal food".

Over the next 60 minutes, we see the wildlife biologist travel from ‘feedyards’ (cattle ranches), pig farms ... not able to eat grass, so compete with humans for plant-based foods.