Supplementing for weight gain
I have an awkward situation where my horse is not getting enough quality feed where he is boarded, and is consequently having diffiulty keeping weight on. He is in a paddock with a dozen or so other horses that are all eating off a round bale of mostly grass and timothy hay. There is no grass. The horses in his paddock also get some oats poured in piles on the ground once a day. Because he is a bit of a baby, he gets pushed around by the other horses and rarely gets to eat any grain. So far, he isn't ribby, but his hip bones stick out and he is very slight in his hindquarters.
I'm feeding him about 1-2 litres of complete feed and about 1-2 litres of mixed grain (barley and oats) about 3 times a week when I am out to ride. Unfortunately, I can't get out much more often than that. I am looking for a good feed supplement to help him gain some weight and particularly to help him build his topline. I am working him under saddle for about an hour 3 times a week.
Does anyone have any suggestions as to how I can put some weight on my guy, at least until I find a better boarding situation for him?