animal black blues cattle clouds cow dutch Friesian grass green holland Netherlands rural sky spring stock summer sun sunny Twente white agricultural agriculture animal-husbandry black-and-white bos Bos taurus bovine breed breeders calvers commercial cows dairy dairy-breed dairy-cattle dairy-cows dehorned domesticated-ungulates farming fertile field fodder graze grazing herd high-milk-yields Holstein-Friesian livestock longevity milk-production milkers milking-cows paddock pasture polled production quality reproductivity ruminant ruminating solid ungulates versatile