I got 3 Soay Ewes (gift!!)...looked healthy when they arrived at a friends place then one just died in the field so they buried it, then I came home and they told me on was weak and ill so they separated it and were feeding it, it looked ok but wouldn't stand up. I took all the other sheep they got me up to my land. The 3rd Ewe looked really ratty but bright eyed, then the other Ewe arrived up as she seemed stronger. I put her in the field with the others and within 10 minutes she was sitting down, then she hid under a low platform in the shed (since removed). We built her a lean to emergency shelter up beside the house where I could nurse her back to health. I hand fed her...., gave whey in a bottle, green leaves, grass, hay , chopped veg etc ...she too it all, after 4 days I took her to the vet who kept her in hospital and tried lots of things to keep her alive but she died the following night. An autospy was done and it was plain to see that she died of starvation because her stomach had never formed. I assumed the other was the same as they were the same age etc. Apparently if you bucket feed Soay lambs using pellets or processed feed they will not live too long as their stomach does not form! They must be fed by the mother and if bucket fed only get whole grains, if they cannot be fed by the mother for some reason they must get colostrum from some other animal and then give them whey etc in a bottle. With the 3rd who had a really terrible cough, shitty arse, runny poo, rage coat etc I really researched nutrition etc for sheep and in particular Soay sheep.
The vet gave me some homeopathic remedy for scarring after pneumonia which gives them a terrible on off cough. I gave that for 3 days and then started a regime of feeding her lucerne/alfalfa hay in the morning and evening, gave her vit c and apple cider vinegar in her water and a homemade mixture of Nutritional yeast, whole wheat berries, whole popcorn kernels, whole adzuki beans, and Kelp flakes. That was last January , to our great surprise in May, she had twins , one died just at birth and the other is a super healthy strong ram. She has become so super healthy, no cough, no worms, good coat, lots of energy .....she is happy out. so now I feed her as the rest but continue with a small amount of the grain mix, without the yeast once a day, vinegar in her water and vit C once a week, small bit of hay in the morning and small bit of Lucern in the evening and left out to roam the fields with a shelter. Hope this tfroghs some light on it for you .....I was lucky in that our vet is a rare sheep nut!!