[Diagnostic significance of lactose level of milk. 2. Lactose level in first quarter milk samples in various udder disorders].

The behaviour of lactose levels in first quarter milk was studied in the context of a large dairy herd in the presence of various udder health defects. The results were related to other criteria generally used in mastitis diagnosis. The lactose level in first quarter milk was found to be a diagnostic criterion which was properly applicable to detecting and identifying clinical and subclinical mastitis. A limit value of 4.6 per cent has been commonly assumed in literature and proved to be a sound basis for udder health assessment, provided that the given phase of lactation is taken into due consideration (exclusion of cows in the first month post partum as well as of aged milking cows from the seventh month of lactation). Also reported in this paper are results regarding milk lactose and its correlations with other criteria for mastitis diagnosis. A close correlation was found to exist between lactose level and electric conductivity of first quarter milk.