I've been using black oil sunflower seeds as treats for awhile and looked into using them for weight gain on my doe. I didn't realize the calcium/phosphorus ratio was so off on these. I don't think I'll be giving them to the boys anymore.
My does each get a cup of BOSS with their grain when they're on the milk stand. If you are only giving them as a treat (a small handful here and there) I wouldn't think the BOSS would hurt your boys.
I use chewable vitamin C tablets for treats. My goats love them! I buy huge bottles of them at Costco.
Another thing I use for treats is unsalted peanuts in the shell. The goats devour them!
As long as your ammonium chloride program is in place and they are getting what they need, you can fudge quite a bit on just about anything.
How bad is the ratio. I give each of my boys a cup a day?
All of the info I pulled up was a little different, but around 1:6.