My yearling is a very picky eater. He was on antibiotics a few weeks ago and wouldn't eat them. The only thing I tried that worked was mixing in a little bit of maple syrup. The problem is, now he won't touch ANY feed (even sweet feed!) unless I add maple syrup. I don't add much, maybe 2 tbsp/day. Is there any potential side effects to doing this long term? I tried googling but I couldn't find any info on it.

Corn Syrup is a better than Maple Syrup.  I have used Maple Syrup to mix with medicine, but the horses like corn syrup better.  Corn syrup is an 'old cowboy' solution to get horses to gain weight and shed off better in the srping.

I would just quit using the syrup & put the feed out. Or quit giving him any graina t all for a few weeks & then try it plain again. Or reduce the amount daily until it's gone. If he doesn't want to eat just let him not eat it. At some point he should finally decide he's hungry enough to eat it 

I've found apple cider vinegar to be the best at hiding medicine. 

I started using it to cover up bute and now I feed it daily, whether I'm hiding medicine or not. My horses really like it. 

What feed are you feeding this yearling? 

totally agree  they like kids  you don/t eat it dn/t worry about we create picky eaters. let them decide  eat or die 

they will decide to eaty whats in front of them. or go hungry

Put the antibiotics in a syringe witha bit of water a touch of corn syrup and syringe it in their mouth and let them have their grain as normal.