Morphological characteristics of somatic cells from mammary glands of unbred heifers

Juvenile mammary glands of unbred heifers were chosen as the object for stu dies of resistance of the bovine mammary gland to infection. The purpose of this work was to recognise the functional state of juvenile mammary glands of unbred heifers as reflected in absolute and differential counts and mor phology of somatic cells. The results of determination of absolute and diff erential somatic cell counts of noninfected nonsecreting and noninfected ab errantly secreting mammary glands of unbred heifers, incl. morphologic cell characteristics are presented. The whole set included 160 mammary glands o f which 135 (84.4%) were noninfected and nonsecreting, 7 (4.4%) noninfected and aberrantly secreting, and 18 (11.2%) infected. Absolute counts of soma tic cells in lavages standardised on a constant volume (20 ml) were (0.985 +/- 0.882). 10(6)/ml and (2.713 +/- 1.514). 10(6)/ml for the noninfected no nsecreting and the aberrantly secreting glands, respectively. The differenc e was significant at P < 0.05. Macrophages of the nonvacuolised and vacuoli zed types predominated in the differential counts both in the nonsecreting (72%) and in the secreting (56.4%) glands. The vacuolized type represented degenerated macrophages and macrophages filled with fat globules in the non secreting and the aberrantly secreting glands, respectively. In addition to the typical polymorphonuclear leukocytes, cells showing a certain degree o f degeneration were observed. Functional alterations in aberrantly secretin g mammary glands were reflected in a marked increase in absolute somatic ce ll counts, in an increase of the proportion of polymorphonuclear leukocytes in differential cell counts, and a decrease in the proportion of lysed cel ls. Characteristics of absolute and differential somatic cell counts will b e analysed as potential markers of resistance of the mammary gland to infec tion.