Your issue right now is likely that the plot productivity is too low to keep up with the browsing pressure. Put up some exclusion cages in your plots and see what they look like by spring.

It’s probably a little late now to spread any more seed. Just keep hitting it with low doses of nitrogen and look to the spring to get a good biomass crop growing. As the soil improves then so will the yield of your forage….as well as the plants ability to recover from browsing pressure.