Context: currently playing a cg goblin wizard (theurgy domain life) in a homebrew campaign. He has gotten his hands on an awaken scroll and has a pet ox. I would like to use the unearthed arcana for sidekicks (expert subclass) for the ox but I'm not sure what to make the ox an expert at, any ideas? 

Husbandry or agriculture.

I could see the potential in an cerebral nature expert (w/ wilderness survival as second skill), who likes to correct & educate everyone else - possibly claiming to have absorbed this knowledge all it's life, and in denial that it owes your character anything.

If you're after a practical long-term sidekick; investigation & perception combined with knowing when to keep it's mouth shut - no-one would ever suspect an eavesdropping ox...

If purely for a comedy cameo; stealth & deception, for an ox that considers itself stealthy and will earnestly try to convince someone who catches it that it is not in fact a talking ox.

I've got an ox, who wants to be an expert

Would he become an oxpert?

Stealth

Or Arcana

I like it