I'm here !!!! Anke, please do phone this evening... as has been posted earlier the sooner this is stopped the better.
I would give 10-15ml of kaolin, with or without the morphine immediately, absolutely no milk at this stage whatsoever. Give water by bottle with some added glucose.. about 1 teaspoon per litre... for the next few 'feeds'. Wuthin 24 hours he will have stopped scouring. Don't weorry about acidosis at this stage.. it is unlikely to be the issue, I lean towards overeating therefore the gut has got to be rested. It can easily be restarted using yoghurt.... one small pot of live plain yoghurt syringed down the side of his mouth, he might even like it !!
Offer only very dry hay at this stage... no haylage, it is too rich for his gut.
But ring me anyway, am in all evening but going to bed early tonight.