So, you have sheep, and cows (and rabbits and maybe goats?) on your land and leased land: do you have a feel for how many acres are needed per cow? Do you graze year round? To increase the diversity of species, would this be from overseeding or full-on tilling and reseeding? Sorry, lots of questions. I'm in an information gathering phase...
Yeah, we have all those things, and goats, ducks and dogs. The amount is acres per cow depends on cow size and quality of browse. So smaller cows like a Dexter can put more animals per acre. I would start at a cow per acre, then see how that works, paying close attention to body condition. If it starts to drop it's time to feed. If you are new to raising stock I would spend the first couple years feeding there are so many skills related to livestock increasing your chance of success is more important then doing it perfectly.
So far the latest we have browsed is into December. It is hard to have a perfect system on leased land, but as the herd increases the infrastructure we have will increase, this will make it easier to improve the pastures we use.
To increase pasture diversity I would just over seed. Try different mixes, and Forbes. There is alot of variety available, just gets expensive so typically not able to be done all at once.
Feel free to ask lots of questions, here or on our Facebook page, or I also offer consulting. My wife also dis a cool interview recently on the survival podcast about our failures, I would suggest listening to it.