Time to do some research, M! Find out exactly what you have in your pasture, and what the goats and cows will eat, and what they will eat that might harm them. You will find many plants listed as poisonous that well-fed animals simply won't touch, some that they have to gorge on massive quantities for there to be a problem, and some plants that they not only will eat but that a small quantity can be tragic. So start picking bits of plants and bringing them to the computer to identify. I really like the poisonous plant list for goats on
www.fiascofarm.com because it addresses the above problems with many lists out there.
As you know me from ss, I take a more natural and sustainable approach. That can take either more time or more money, but to me, is more cost effective in the long run if such ways are really important to you....balanced, of course, with the needs of your family.
I have been improving my "new" pasture bit by bit, year by year, with intensive grazing (I am the cow, with my scythe, as the goats can't keep up without the mare to help anymore...) and by finding out what the plants I want to encourage like and what the ones I want to discourage don't like. Mostly enriching the soil with a 3-4 inch layer of composted manure, leaves, yard waste, and anything I can get my neighbors to dump over the fence for me, along with what my animals supply me with. Also, lime is essential here. Since starting this project maybe five years ago, I have continued to adjust my thinking. I actually overseeded with dandelions a couple of years ago, as they are highly nutritious, and planted comfrey in one spot, and stopped gloving up and ripping out nettles. I now remove the large seed heads of plants like burdock rather than trying to eradicate them. Another nutritious plant. And I am not liming one end of the field to encourage a patch of wild raspberries that are growing there, since the goats love that stuff.
You can get more great ideas by researching Joel Salatin's methods of intensive grazing. I requested Salad Bar Beef from our local library for some winter reading to prepare for spring pasture improvement.