Yeah,  that "cow mosaic" term just went right over top of my head......

I looked closely into the distance of those pics - 2nd pic in particular - and I thought some of those darker green areas looked a bit larger than "a cow pile".  That was confusing me.

A couple of years back, I got a call from a guy who needed some soil sampling done. So, I went to see him.  In one of his fields he had some orchardgrass growing, and it was not doing well. So, he was thinking about taking it out.   So, we got in my truck and went to look at it.  Beautiful stand of orchardgrass.  Yellow as could be. But this stand density was nice and thick.   Looking closely, you could see small pockets of dark green orchardgrass scattered across the field of yellowish grass.  When I say "small", I mean maybe 6" in diameter.  I deduced these small pockets were areas where deer either urinated or defacated.  Either way, I figured he was getting a nitrogen response  from the deer manure.   I quizzed the guy a bit.  Found out he had applied swine manure for several years, until the soil P levels got high. So, he moved swine manure applications to other fields. He was trying to grow the orchardgrass on the fertility in the soil. That worked until he depleted the nitrogen out, and then yields went downhill.   So,   I recommended using commercial nitrogen to get that grass yielding again.   I have not talked with him since, and I don't know how it is working out. 

I have not forgotten that experience, and your situation looks similar.   I just didn't recognize the term "cow mosaic".