I have two 7 year old female guinea pigs and I'm trying to help them gain weight. I've tried an apple puree with oats in but they don't like the oats, I used regular porridge oats. They eat their vedge, pellets and hay as normal but are still pretty thin. I was wondering can barley seed or grass help them gain weight, i grow it for them in the summer so I know they like it. Or what other vedge or any other methods of weight gain is there.one of them is currently ill(chest infection thats getting sorted) and really need her to gain weight as fast as possible