They say it's 1 to 7 - one pound gain per seven pounds feed. I had a steer that did about 1 to 3 or 1 to 5 (on grain, not counting hay). When I added in the hay pounds it did come out to about 1 to 7.
Keep in mind the quality of the feed depends too on the conversion rate...poor quality grain and moldy grass hay won't put on the weight like top notch corn and 3rd cutting alfalfa hay. (Not that I think you're feeding her anything less than the best.)
Milk replacer - what type are we discussing here? and are you mixing it with water and bottle feeding her? I've gotten about 1lb/day gain (more or less) from calves on milk replacer at the standard 1/2lb milk + 2 quarts water twice a day. So I guess that would be 1lb milk replacer to 1 pound gain, right?
I'm not familiar with bermuda hay - up here we have alfalfa and grass. I usually figure alfalfa puts weight on and grass is a filler. At least that's how I feed it during the winter.
So figure the minimum - 10 to 14lbs grain at a 1-7 ratio is about 2lbs/day. Plus milk replacer is another 1lb/day. So you've got about (or at least) 3lb/gain per day right now. Make sense?
I'd say you're doing a good job - to put on 50lbs in what, 7, 10 days? - is at least a 5lb/day gain. You're asking a lot of her but she might be able to do it. I'd probably up the feed that matters (grain and milk) a little - but keep in mind if you up it too much it'll all come squirting out the back end and she won't put on weight.
Also if you change her routine too drastically (like keeping her penned up when she's used to going to pasture) she's not going to eat or put weight on since she's stressed.
Good luck - I hope she makes it and I wish you both the best.
