I hope he recovers soon x
When my little Alfred had an abscess he couldn't manage hay for about a month, and survived on soaked pellets and veg - he was (he went to the bridge in January 3 years after the abscess) intolerant of veg and normally anything other than a tiny portion would upset his tummy, but he was fine then bizarely, he had grated carrot, sprouts, spring greens, kale.