I agree that you can safely remove all concentrates from your horse's diet. He doesn't look in particularly poor condition in the picture and considering the time of year, I am quite sure that he will gain some weight over the spring, summer and autumn period. To ensure that your horse has a balanced diet, I personally would just feed him a broad spectrum vitamin & mineral supplement mixed in with a small handful of unmolassed chaff for extra platability. This diet would be low in energy and free of molasses, so as not to exaggerate your horse's natural temperament.
I have noticed that you feed a lot of different feeds and supplements. This could be contributing to your horse's excitibility as he will be receiving the same nutrients several times over. Bear in mind that the more different products you add to your horse's diet, the less he can absorb and use. It is healtier and more economical to feed more of less products, if you see what I mean!
It can be tempting to give a small volume of conditioning feed in an effort to encourage weight gain without excibility, but this will not provide your hrose with enough energy for weight gain, and won't be supplying him with all the vitamins & minerals he needs for a balanced diet. To encourage weight gain, you would need to feed the recommended daily volume of a conditioning feed that releases energy slowly, so as to discourage excitibility. However as I stated earlier, I suspect your horse doesn't really need a conditioning feed as such and would thrive on good grass, plenty of good quality forage and a vitamin & mineral supplement with a little chaff.
He's bound to feel pretty fresh considering that he is off box rest and the spring grass is coming through.
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