sounds like the vet trip really upset him, what did he have done?

Try offering him ferretone or any type of oil if you havnt got tone, not many ferrets can resist this. give him a small lick while you pick him up, while he is still licking his lips put him down before he has time to even think about biting.

Do this as often as you can, it needs to be frequant and consistant.

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Tiggy, 13 yr old Collie x Alsation, Lucy 11 yr old epileptic cross breed, Kara, collie x whippet