Somewhere around 300kg probably. You feed according to age, workload, temprement and condition. Initially I would either keep him on what he has now, or reduce him to forage only at least until you get used to one another. It may be that he never needs more than grass and hay.
You need to aim for 1 - 1.5% of his body weight in feed - probably closer to the 1% mark at least to begin with. And that is where the trick lies - because its really hard to estimate how much they consume when out at grass. What is your pasture like and how much turn out will he get?
