Katy Watts | Safergrass.org
Despite owning horses for over 20 years, I know next to nothing about grain/feed.
, Dr Kellon's site, feedxl.com & other good sites should provide you with enough good(up to date, scientific) info to help you understand what's what & what's needed. Generally, a natural diet is healthy & adequate, but this (esp with 'improved' fertiliser, grasses, etc) generally doesn't give a horse well balanced nutrition. Therefore a good complete supp or 'ration balancer' is important.
Given your horses are mostly 'easy keepers' on 24/7 pasture, keeping them healthy might be more about restricting grazing than adding anything much!
I'd like to have something around just to offer for a "treat" now and again. I've been told to just give plain oats. Is that a good idea?
If it's only very small quantities(like a handful) & occasional use, yes, oats are *generally*(wouldn't give them to an IR/laminitis prone horse or one with gut probs such as ulcers) OK. If you were thinking of larger quantities or regularly given, I'd be inclined to keep it low starch/sugar healthy treats. Eg. bits of apple or carrot(again sparingly or not at all to IR horses), rosehips, milk thistle, fruit tree leaves, bit of chaff.... or if you feed a pelleted feed or nutritional supp, some of what they're getting already.
Royale: 29 year old Arab gelding. I'm thinking he might start to need some sort of supplementing soon, due to his age. A friend of mine swears by Triple Crown Senior,
Yeah, I'd personally be looking for something without molasses, but TC seems OK apart from that. Older horses stop doing so well on hay/grass mostly due to their teeth. At 29yo you would hope they're not in bad disrepair yet, but he may need more frequent dental work. I would wait & see how he goes & not feed him extra in case of the possibility he may lose too much.
Cody: 22 year old QH gelding. Starting to get stiff in his rear legs.
Perhaps a joint supp, ACV or such added to his other supplements?
Warrior: yearling Shetland pony colt. He will be kept in a paddock with free choice shelter until the other horses get used to him.
While your other horses may need to be restricted, these little guys will most definitely need it. I wouldn't entertain the thought of putting them out on a couple of acres of unrestricted grazing, let alone 30! They may be OK turned out with the rest with grazing muzzles on though. You might gain some more insight into why from Equine Cushing's and Insulin Resistance Information
Eclipse: 7 year old Paint/TB gelding. He is being boarded and is on box stall board, which means he is turned out when it's nice and in a stall when it's not. ....his previous owner had been graining him daily.
I would personally get him out of the stall board ASAP & turned out 24/7. If you can't do that for some reason, I'd insist he was turned out every day for the full day at least, regardless of weather, &/or ensure you can take him out for walks, pref at least a couple of times daily. There are a number of reasons why it's bad for a horse's health & wellbeing to be kept cooped up, so this should be avoided unless absolutely necessary.
If he's healthy, a good weight, etc, he shouldn't need anything more than grass/hay and a nutritional supp either. If he does need more 'condition' then I'd personally choose a low starch, easily digestible alternative to grain, but if you are going to feed grain or other high starch feed, you can minimise the 'side effects' by ensuring you only feed as much as absolutely necessary, you feed well processed, not whole grain, and you feed it little & often(ie at least 2-3 small feeds daily minimum).