Shade and shelter for livestock are a couple of the reasons for having big bushy hedges all around your fields. No help to you this time, but get them in now and you'll have them in a few year's time
Sally - I'm amazed your cattle didn't shove the gazebo over
A quick shelter from the sun for sheep can be made my knocking in four stobs, then placing a roof of some kind over it, a tarp, or tin sheets, or whatever you've got. This allows any breeze to blow through to keep it cool. At a later date it can be given 3 sides of weather board to help keep the rain out (except when it comes from the fourth direction of course

, then they sit round the back.