An ecopathological analysis of milk protein and fat contents in high lactating herds is described. In herds with a high milk protein content, cows had shorter dry periods and more cereal-based concentrates and fresh English rye-grass in the dry diet. In the early lactation period, these cows had a higher risk for milk fever, their body score was less decreased, and the duration of feeding with Italian rye-grass silage was lower. In herds with a high milk fat content, the cows had shorter dry periods, lower plasma magnesium levels, more dietary vitamins A,D and E before calving, a decreased risk for metritis, and calved less frequently in summer.