[tommytink]

Can sheep get looser faeces after being wormed?

[twizzel]

Some wormers have it listed as a side effect - levafas diamond in particular. Best to read the data sheet.

[Twotwo]

Maybe if the sheep had Haemonchus ( barber pole worm) which can cause constipation, the result would be runny poos. Just a thought -
The lots of Haemonchus about in this warm wet autumn.