Association between Ruminal pH and Rumen Fatty Acids Concentrations of Holstein Cows during the First Half of Lactation oleh Georgios C. Kitkas, Georgios E. Valergakis, Maria Kritsepi-Konstantinou, Athanasios I. Gelasakis, Panagiotis D. Katsoulos, Emmanouil Kalaitzakis, Nikolaos K. Panousis