Hi, I tend to view sugar beet a bit like our potatoes i.e. it goes with most things and is eaten most days!  My horses usually stay on it all year, I feed alfa a oil so I usually reduce that a bit and with the summer grass they do fine.  My warmblood gets Allen and Page Calm and Condition and he gets a bit funny about eating his feed if it's not in it so I still give him enough to get a taste even though in summer he really doesn't need it.  I used to have an elderly thoroughbred who was difficult to get weight on and I didn't reduce his feed at all in summer so that he would go into the winter not too bad so it wasn't as bad if he lost some in the colder weather.