Brome is excellent hay for horses if it's put up right and not been rained on, However, your mare needs more than hay with nursing foal to provide for. Better than oats and the MarePlus would be a commercial feed formulated for lactating mares and foals. What brands can you get in your area?

 

alfalfa hay. Forage. Grass hay. what amount of hay are you feeding. and average horse needs about 10 lbs of forage every morning and night. Since she is nursing and dropping weight I would double that amount, or put it out as free feed.

 

I usually feed her Mare & Foal by Safe Choice but my TSC hasn't been selling it recently. So I'm hoping to find someone else who sells it. But while she was pregnant I fed her Mare & Foal with Senior feed also by Safe Choice and it's been very effective for her during the winter. I'm hoping I could move back to that but I can't seem to find it.

I usually feed her a bale a hay a day.

 

Any good quality hay can be fed as long as you are also feeding a concentrate designed for lactating mares at the rate recommended on the bag.

 

You can order it online from TSC and pick it up at the store.

 

In addition to what others have said, whatever the hay, if she's eating it all & going hungry for any length of time each day, I'd increase the amount. And if you've only been feeding oats(or whatever) for a couple of weeks, you should have started small(as with anything) & built up to however much she needs over a week or 2, so she will only have started getting the benefits after that time. And it's also important that she's fed little & often. You don't say how much oats & alfalfa you feed, but it should be in smaller meals & over at least 2, pref 3 or more meals daily. Changing feeds too suddenly, feeding rich feeds too infrequently or in large meals can cause digestive upsets such as acidosis/ulcers, which can also cause weightloss.

 

Agree that your regular hay (if good quality) should be fine. I was going to say alfalfa, but it may be overkill, then saw you're feeding the pellets so wouldn't bother.

Do find a good M&F feed. They should at least be willing to order something? Then keep that (you shouldn't need a supplement with that) and the alfalfa. You need to be careful with pregnant/lactating mares, when they drop it can happen overnight. That's why people often keep them a little on the heavy side. I know it's a little late at this point, but you really need to keep ahead of the curb. Worst case you wean the foal early. Really pour the food into her, free choice hay and a LOT of the M&F and pellets. There should be guidelines on the bag, and I would check in with your vet too.

I'd just really push the M&F instead of messing around trying to come up with something else that will put weight and give the right nutrients.