[Activity of lactate dehydrogenase in the milk serum of dairy cows in relation to the possitive response to the mastitis NK-test].

The level of total lactate dehydrogenase activity in dairy cow milk serum was studied in sets of quarter-udder milks showing different degrees of a positive response to Mastitis test-NK. The bacteriological examination for Streptococcus agalactiae, Streptococcus dysgalactiae, Streptococcus uberis, Staphylococcus aureus, and for coliform germs was performed at the same time. Increasing positiveness of the response to Mastitis test-NK was found to be accompanied by an almost proportionate increase of the total lactate dehydrogenase activity level in milk serum. The bacteriological finding was not correlated with increasing positiveness of the response to Mastitis test-NK. New aspects of various diseases of the mammary gland and the possibility to diagnose mainly the latent stages of these diseases are analysed in a discussion.