A good perennial pasture should include a mixture of nutrient dense grass varieties suited to your geography and soil type, with a combination of legumes to fix nitrogen and improve the stand longevity. The legumes should include sainfoin and vetch in the mix to reduce the risk of bloat from alfalfa. Ideally, you should rotate cattle through paddocks allowing rest periods after grazing.
The return on investment and productivity of a well managed perennial forage stand is difficult to beat. A perennial pasture requires a significant upfront investment, but when you amortize that investment over 10 or more years, it is an excellent option.