This study was aimed at selected blood biochemical parameters in the male American mink before (September-November) and during the breeding (January-March) season. Blood from 143 Black and Sapphire male mink at one year age was collected. The plasma was assayed for the concentration of glucose, total protein, cholesterol, HDL and LDL fractions, triacylglycerides (TG), and the activity of ALT and AST. Concentrations of glucose, protein, total and HDL/LDL cholesterol, and AST activity were generally slightly higher during the breeding season than during the non-breeding season, but remained within the reference range. In the case of ALT activity and TG concentration, the relations were reversed. The parameters studied in the Sapphire mink showed greater variation, both in- and out of the season. In Black and Sapphire males of the American mink, the studied parameters revealed slightly higher values during the breeding season than the non-breeding season. This will vary depending on the color variety. The decrease in TG concentration during the breeding season may indicate an increased energy demand due to ambient temperature falls, and/or may be a sign of increased energy consumption associated with physical exertion during mating. Consideration should be given to the nutrition of male mink during the breeding season.

Key words: Blood parameters, Males, Mink, Reproduction, Season