Sally do you usually keep the pigs in with the sheep? Are there any issue with it?
I am just wondering if I should try it next year
They're not together full-time, no - Bertha comes into the sheep's paddock for her feed, otherwise greedy Meg-pig eats her own and half of Bertha's too. Now of course, Bertha loses some of hers to the greedy fleece-sheep...

After she's eaten her cake, she potters about nibbling grass, checking the sheeps' trough for any they've missed (only fair!) and then, if I haven't returned by then to pop her back into her own field, takes that plough of a nose to any bit of soft ground she can find and turns as much of the sheeps' paddock into the Somme as she can before I get back to her!

So that would be the issue, I think - if you had a large enough area that there would still be enough ground to stay grassy for the sheep, the only other problems would be that
- the sheep would probably try to share the ark - not sure how that would play out, depending on the age and size of the pigs, and whether the sheep have and use their horns...
, - keeping each species off each others' feed,
- the amount of mud there is bound to be whereever there are pigs
If you do try it, please make sure you have a video camera in your pocket at all times!
