Hi Kerrie,
Here are some of my thoughts:
1. He doesn't seem to be drinking, the water level on the bottle is fuller than usual and I've not spotted him drinking.
Drinking becomes even more important with bladder issues, so you may want to consider syringing him some extra water. Is he getting water from elsewhere (are you giving him more cucumber than usual, for example?) Not drying his washed veggies before you give them to him can help keep his water intake up if you suspect he's not drinking enough.
2. I've not seen him eat hay or pellets, but I have seen him down his veg, in fact he was standing on the side of the cage when I walked in with it.
Lack of appetite is often a pain response, and usually the pellets are the first thing they'll stop eating. As you know, it's essential that he keeps eating hay so that he has the strength to fight this. You could try him on different sorts of hay to tempt him, and if you've never done it before I would start reading up on syringing food should you need to top-up his food intake or feed him entirely. Be aware that some piggies can respond badly to Baytril, with some developing anorexia. Keep a close eye on him and weigh him daily.
3. He's not crying in pain (I've not heard him)
This is a good sign, but if it is a UTI, and if it is a mild one, he may not cry each time he has a wee. Metacam would have been useful as it acts as a painkiller and an anti-inflammatory for the bladder wall.
4. We took him out of the cage with Big E and let him run around on a mattress pad on the floor to see if he had blood in his urine, but we didn't see any, will check again later. His poo looks smaller?
Smaller poo would be due to his lack of appetite.
5. He does seem to fluff himself up atm, I know they do that anyway, but this is sort of different to what he usually does.
Piggies fluff themselves up when they're not feeling well. Again, this can often be a pain response or a sign that they're not quite right.
6. The vet noticed Jericho has/had a saw bottom so gave us some wash for it.
Do we need to start hand feeding him and if so how much water/food should he get per feed with him eating veg? Is there anything else we need to do with him apart from weigh him and give probiotics?
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A word of warning with the veg, it's great that he's still eating it, but don't be tempted to give him vast quantities in place of his usual nuggets/hay as this can lead to stomach upsets and the last thing that you need right now is to deal with diarrhoea too!
Here's some info on hand-feeding. Sending lots of healing vibes.