I’m looking for info on timothy/brome mix hay. Horses seems to have gained too much weight since they have been on it. Average horse eats about 20 lbs of hay a day. Grain varies by horse. Anybody have any experience with brome? This is the first time in 17 years that the barn has used it. My horse has also had lots of gas. Could just be age. She is 27.
I’ve fed it many years and my horses have kept weight similar to other hay types. Is your horse out on spring grass now? That would make a huge difference in gas production and in weight.
Pretty much impossible to say anything about why this would be happening without knowing what you were feeding before, and having a nutrition analysis of both the former and the current hay.
Is the current hay first or second cut? Was the former hay first or second cut?
A good second-cut timothy is a very nice hay; a first-cut can be as stalky and coarse as any other grass hay.
Some of the factors the hay analysis would show would be calories, protein, non-structural carbs (sugar levels), and overall digestibility.
When I switched over to a very nice timothy this past winter, I found that my horse was pooping considerably less. The hay was finer and more digestible, and she was using up more of it compared to, for instance, a coarse first-cut grass hay.
If your horse is putting on too much weight on a given diet, then you need to cut down the amount you are feeding.
I also wonder how you know she is getting 20 lbs of hay? Is anyone weighing the feedings? Different types of hay and different hay producers can put up very different weights of bale and of flake. The advertised weight of the bales is often not the real weight! If the barn is guesstimating weight by counting flakes, it is possible that they are feeding more now than they think, and less in the past than they thought.
IME, overfeeding by even 3 pounds a day can cause weight gain over time in an easy keeper, kind of like that unnecessary muffin every day at coffee break can put on 5 pounds in a month if you aren’t careful 
Only 15-20 minutes of grazing. A handful of grain and 20 lbs of hay.
Brome is an excellent hay.
I feed Brome to all my horses and ponies twice a day - all year - in their sheds or stalls respectively.
Use the huge round Brome bales in the pastures in the winter too.
Mine do not like straight Timothy nor Timothy mixes.
The one exception is Montana Timothy - very expensive - used by St. Louis area vet clinics and for Budweiser Clydes breeding farm in the Midwest.
ALL mine LOVE MONTANA TIMOTHY !
Weigh your hay and just cut down a bit.
Neither Brome nor Timothy should cause abnormal weight gain if fed appropriately - IMHO .
I think you’re lucky to have that Brome-Timothy mix available for your barn.
