Ortanord can give 1 slot pet 20-25 % of experience points. With peace buff +vet I was able to keep freshly bought horse alive. Ortanord should damage your goat to have gains.
Also can use UEV in Shame if your 2 slot triton will tank it. Very slow with not trained goat. Better rise resist on spellblinders first.
Or ask smb else to tank it. Your goat better be bonded anyway.
If it is for fisherman defense only - get 2* lowland boura. Tough and 0 taming needed. Just drop your boots in serpent corpses and they will go away.
If your fisherman have Bushido - use Lesser Hiryu. Eats fish.