High-fibre diet for guinea pig with slow gut

A Rex with slow gut history at four and a half — that's exactly the kind of situation where diet really matters. The vet is right to push fibre: guinea pig digestion is almost entirely dependent on a constant supply of long-stem hay, and if gut motility is sluggish, high-quality hay becomes the most important thing in the enclosure. Before I point you toward anything specific, can you tell me what he's currently eating day-to-day? Particularly how much hay versus pellets, and whether he's on any supplements already?

Your vet has given you exactly the right steer. Pellets should be no more than one tablespoon per day for a guinea pig Barnaby's size, and the hay should genuinely be unlimited — the rack or pile should never fully empty. Timothy hay is the gold standard for fibre content and the coarser stem structure helps push things through a slow gut better than softer meadow hay. What I'd recommend is switching to Oxbow Western Timothy Hay. It's consistently high quality, has good stem length, and is specifically what vets and specialist rescues tend to reach for when gut motility is a concern. The 1.13kg bag is the practical starting size to see how Barnaby takes to it, though once you know he likes it the larger bags are much better value.

It matters more than you'd think. A lot of Timothy hay sold in pet shops is dusty, over-dried, or made up of mostly seed heads with very little actual stem — and it's the stems that do the digestive work. Oxbow sources consistently and has strict moisture controls, which means the fibre content is reliably high and the dust is low. Dusty hay can also aggravate respiratory issues, which are more common in older guinea pigs. For a guinea pig already on a vet's radar for gut issues, I wouldn't cut corners on hay quality.

Hay is the main fix, but if you're already reviewing the diet it's worth checking the pellets too. The Excel pellets you're using are fine for general use but they're a muesli-style mix, which means Barnaby can selectively eat the tastier bits and leave the fibrous pieces. For a guinea pig with gut history, a uniform pellet — where every piece has the same composition — removes that selective eating risk entirely. Oxbow Essentials Adult Guinea Pig Food is the one I'd point you toward: it's a uniform pellet, high in fibre, and formulated for adults, which suits Barnaby's age. But honestly, sorting the hay ratio first will make the biggest difference — that's the primary change.

Good news: unlimited high-quality Timothy hay and rationed uniform pellets is a completely appropriate diet for a healthy guinea pig too, so there's no issue feeding them the same way. Pickle will benefit from the better hay quality even if she doesn't have Barnaby's specific history. The only thing to watch is that Pickle doesn't edge Barnaby out of the hay rack — with a slow gut guinea pig you want to make sure he's actually eating freely and not being outcompeted. Two or three hay points around the enclosure solves that easily.