We analyzed a large number of immune response parameters from quarter milk samples with distinct bacteriological and quarter somatic cell count (qSCC) statuses. Furthermore, we sought to explore and identify displayed immune response patterns in milk samples from mammary glands with nonspecific mastitis. Thus, 92 quarter milk samples from 28 cows were stratified into 4 groups, as follows: (1) 49 culture-negative control quarters with a low qSCC (<1 × 10 5 cells/mL) from 19 dairy cows (so-called healthy quarters); (2) 15 culture-negative quarters with high qSCC (>2 × 10 5 cells/mL; so-called quarters with nonspecific mastitis) from 10 dairy cows; (3) 8 culture-positive quarters with low qSCC (noninflammatory quarters with low qSCC) from 5 dairy cows; and (4) 20 culture-positive quarters with high qSCC (so-called truly infected quarters) from 8 dairy cows. Using flow cytometry, we evaluated the percentage of milk neutrophils and their viability, intracellular reactive oxygen species production, phagocytosis, and the expression of CD62L, CD11b, and CD44 for each of the 4 quarter strata. Furthermore, the percentage of monocyte/macrophages, B cells, and T lymphocyte subsets were evaluated by flow cytometry. Milk samples from bacteriologically negative quarters (both with a low and elevated qSCC) had a lower qSCC than those with bacteriologically positive outcomes (both with a low and elevated qSCC). As expected, the healthy quarters showed the lowest percentage of neutrophils and also showed a higher percentage of milk monocytes/macrophages and lower percentage of T lymphocytes than truly infected quarters. The most prominent result of the present study is that quarters with nonspecific mastitis showed the highest percentage of milk CD4 + T lymphocytes. The healthy quarters had a lower percentage of apoptotic neutrophils than noninflammatory and truly infected quarters, although it did not differ from those from the quarters with nonspecific mastitis. Our study supports the role of differential cell counting in the diagnosis of mastitis, as the milk leukocyte populations markedly fluctuate under healthy and inflammatory conditions. Furthermore, an increase in milk CD4 + T cells was associated with nonspecific mastitis, suggesting an increase in this leukocyte subpopulation is correlated with low bacterial shedding. Our study allows us to go further in our understanding of mammary gland immunity, providing further insights on potential protective mammary gland immunity, which we hypothesize can open new avenues for the development of novel targets that can promote bovine udder health.

The objective of the present study was to evaluate different methods for indirectly diagnosing mastitis during the postpartum period. These methods were: automatic and microscopic somatic cell counting (SCC), the California Mastitis Test (CMT) and Somaticell V R . A total of 538 milk samples from 34 cows were used. These were collected at six times: day of parturition (M1) and 3 (M2), 7 (M3), 15 (M4), 21 (M5) and 30 (M6) days after parturition. Automatic and microscopic SCC, CMT and Somaticell V R were all able to detect mastitis during the immediate postpartum period (up to 3 days postpartum). However, higher cut-off values should be applied to automatic and microscopic SCC. The negative score (score 0) of CMT was considered to be the best cut-off point at all times. Moreover, the values found using the Somaticell V R test should not be used to presume the automatic SCC values, since there are discrepancies between the values of Somaticell V R and automatic and microscopic SCC. It can be concluded that the different methods evaluated here to milk cellularity can be applied for diagnosing bovine mastitis, even during the immediate postpartum period, when there is greater cellularity, such as in the colostrum and transition milk. ARTICLE HISTORY

Inhibition of the growth of major mastitis-causing pathogens by non-aureus Staphylococcus isolates using the cross-streaking method [Comunicação: Inibição do crescimento dos principais patógenos causadores de mastite por isolados de estafilococos não aureus pelo método cross-streaking]

No abstract