Hi! Flaxeed oil is the right thing. It is pricey in comparison with other oils but the best by my opinion.
I do not know what do you mean with equine ready form. Oil is oil - any oil, suitable for human consumption, is also OK for horses. The only thing - the refined is not as good as natural, cloudy ones but usually they are labelled organic, "natural" and so on - thus more expensive.The best thing- to contact farmstore wholesaler and order a gallon jar or something - it will be 10X cheaper than oil in small fancy bottle hrom healthy food shelfs at mall.
Actually the crushed Flaxeed itself is better but I do not know can you afford it timewise. The recipy is simple - crush 2 handfuls of flaxeed and pour over a very hot, nearly boiling water, and let it cool down. When it cools, it must look something like somebody tried to make milk jelly and something went wrong :D And then add it to your usual feed.
Time problem - you can not store crushed Flaxeed for long time, so it must be crushed at least onece a week and stored inside the house.
If you do not crush seeds, you loose about half of its goods as they go quickly through the horse, so it becomes really expensive.
This is also the pumpkin season. I am giving a good slice of pumpkin every day - pumpkin has a lot of great things but mainly I do use to support joints of the horses - it works like a natural glucosamine, also helps with hoof growth and as very mild natural de-wormer.
I'm quite worried about all these artificial supplements, especially for pregnant mares and I can afford timewise make my own food so I try to go as natural as it seems to be sensible.
I must add selen+minerals (my country does not have enough selen in the soil thus in plants) making your own probiotics would be silly as well, but other than that I collect herbs, dry them and store for winter. Nothing fancy - for example, nettles are greatsource of iron for pregnant mares, I order natural alfaalfa/timoty hay instead of giving pellets and so on.
And they do have free choice of hay, 24/7 - see, I believe that horses must eat all the time - they are more relaxed, full tummy with hay prevents from colics thus you can offer a bit more filling (like pellets) and not worry so much about colics. Fat ones who are on diet, gets poor nutrition hay or even straw (less calories) but still keeps tummies going.
Looked at pictures - they are in bad condition and needs a long term filling but nothing really to worry about - they are far from crucial line when happy recovery is nearly impossible. I believe - all will beOK with them if you will continue pampering them.
I do not how ard your winter temps will be but skinny ones might need blanketing if there is no shelter awailable to protect them from loosing calories due to the cold.