any horses, ponies, donkeys or any other livestock that are not your own - there have been two cases this week alone of ponies dying in their fields due to the public feeding them - one was given a loaf of bread which it choked on and the other one is unknown so far. Grass cuttings especially are bad for horses as it ferments in their stomach. With more people taking exercise it seems that some are not following the country code so I beg you if you are walking where there are animals please don't feed them, and keep dogs on leads as lambing season is now starting.
I also grew-up with horses and my sister still has them; so I wouldn't make that sort of mistake. For people who didn't - I exhort you to listen to Lankeela.
When I was a kid many years ago, we used to feed horses sugar lumps.
Years after that, I would sometimes give them a bit of Mars Bar (I was told that was not good, so stopped).
These days, if I go for a walk, I will take a couple of carrots, and if I see any horses, give them a carrot.
Sunk while you mean well feeding carrots, please don't! Apart from making then snappy and encourage them to kick others in their attempt to get them they can choke on them - knowledgeable horse owners will slice carrots lengthways before feeding and if you feed whole or broken into lumps they can get stuck in the throat.