My horses during the winter are in probably an acre pen? I have a 160 acres so I'm not a 100% sure on our pen sizes, where I live we easily get 5 feet of snow during the winter, so I have one pen that is done up with steel panels to ensure the horses don't escape nor get hurt on wire they can't see through the snow, They have enough room to more around, kick up their heals and play with each other and seem to be content.
During the Summer their turned out which I have different fields I can put them in.
The only reason I'd divide the property would be to help grass growth, if you have two pens once one area is eaten to the max, I'd put them in the other pen hoping there would be new growth for the horses to eat, and once they ate all the grass in that pen put them back in the other one and so on.. but if that isn't a possible because one part is dirt, I'd leave it as one big pen, unless there is reasoning behind dividing them (wanting to try and produce grass, horses don't get along).
Home To: Pearl - 2010 AQHA Cremello Mare, Chloe - 2012 AQHA Dunskin Mare, Wyatt - 2015 AQHA Dun Colt.