Morphology, viability and phagocytic activity of blood and milk neutrophils during peripartum and early lactation of Murrah buffaloes

Abstract

A comparative study of number, morphology, viability and activity in blood and milk neutrophils isolated from 10 Murrah buffaloes were carried out during different peripartum and early lactating days. Blood samples were collected from all buffaloes at days 30,15,7 before calving, on the day of calving and on days 7, 15, 30, 45 and 90 after calving. Colostrum and milk samples were collected on days 0, 5, 15, 30, 45, 60 and 90 days of early lactation.  Blood total leucocyte counts (TLC), milk somatic cell counts (SCC), viability and morphology of neutrophils were measured microscopically.  Blood and milk neutrophils were isolated and their in vitro phagocytic activity (PA) was estimated by Nitro Blue Tetrazolium assay. There were significant (P<0.05) increase in blood TLC and blood neutrophils percentage on the day of calving. Milk SCC and neutrophils in colostrums were significantly higher (P<0.05) than milk.   On comparison of the viability of neutrophils isolated from blood, colostrum and milk, blood neutrophils viability was significantly (P<0.05) higher than both. Partum blood neutrophils viability was significantly (P<0.05) higher than other peripartum days. Similarly colostrum neutrophils had significantly (P<0.05) higher viability than its milk counterparts during different postpartum days. Colostrum neutrophils had a significantly (P<0.05) higher PA than milk neutrophils on different early lactation days and also from blood neutrophils on the day of calving. Blood neutrophils on different peripartum days had a more lobed and matured nucleus when compared with the morphology of blood neutrophils observed at calving, where they showed band shaped nucleus. Milk neutrophils had more lobed nucleus as compared to blood neutrophils. Scanning Electron Microscopy revealed more ruffled surface of blood than milk neutrophils on early lactation days. This study shows the changes occurring in the shape, viability and PA of blood neutrophils once they cross the blood mammary barrier to become milk neutrophils. Further understanding the functions of neutrophils around peripartum period and early lactation may help to develop more efficient strategies to combat immunosuppression around this period.