Activity of cyclooxygenase-2 and nitric oxide in milk leucocytes following intramammary inoculation of a bio-response modifier during bovine Staphylococcus aureus subclinical mastitis

Abstract

The objective of the study was to evaluate the effects of intramammary infusion of a bio-response modifier (BRM) prepared from Nocardia globerula on certain inflammatory markers and percentage of neutrophil/lymphocyte in mammary secretions during bovine Staphylococcus aureus subclinical mastitis (SCM). The somatic cell count (SCC), total bacterial count (TBC) in milk, cyclooxygenase-2 (COX-2) activity, production of nitrite and nitrate (NOx) in milk leukocytes and neutrophil % and lymphocyte % in milk were evaluated before and after intramammary infusion of BRM in healthy and quarters inflicted with S. aureus SCM. Intramammary infusion of BRM significantly enhanced the SCC in earlier phase with subsequent reduction on day 7 after initiation of treatment. Whereas, the reduction of TBC was observed from day 3 onwards. The COX-2 activity and NOx production in milk cell increased initially on day 3 of post treatment but reduced on day 5 in SCM infected quarters following BRM infusion. The neutrophil % and lymphocyte % in milk also enhanced significantly on day 3 but reduced on day 5 in SCM infected quarters in response to BRM infusion. Initial influx of SCC, increased neutrophil%, lymphocyte % and enhanced COX-2 and NOx activity indicate the immunomodulatory potential of BRM in S. aureus SCM. Reduction of TBC could be due to increased leukocytosis or direct microbicidal activity of the activated milk cells. The beneficial effect of the BRM could be used as alternative therapy in the control of S. aureus SCM in cows, either alone or in conjunction with antibiotic therapy.