Whitewing, be careful to add chicken/bovine manure mixes without first testing some soil where you'll be spreading it. You don't know if you've made progress if you don't know where you're starting point was. Test first, then apply, then retest the following year. You will then be able to see what elements rose and what did not, and use your eye to analyze the forage and see what coincides with the results on paper.
Don't be surprised if your chook/cow manure approach causes other elements to become bound up and unavailable for plant absorption. Nitrogen is far from the only element required, and if soil is truly balanced and healthy, it will create all the nitrogen the plant requires.