Thanks everyone for your advice.
I have spoken to the very helpful equimins people, they're confident that there is no cause for alarm, however, like cptrayes suggests, this is one for the vet.
I am a long time lurker, so hi !
Had a bit of a fright this morning, Fin, aged 4 whom i've had since a yearling had ransacked the feed room and gobbled approx 3kgs of fast fibre and also approx 1kg equimins biotin 15.
He seems perky, certainly displaying no adverse symptoms. Question is...