Indigenous enzymes and leukocyte in sheep milk are markers of health status and physiology of the mammary gland

Abstract

Plasmin, plasminogen and plasminogen activator in ewe bulk milk were not significantly affected by stage of lactation probably as a consequence of the good health of the ewe udders throughout lactation as indicated by SCC which never exceeded 600,000 cells/mL. Elastase content increased significantly during lactation whereas cathepsin showed the highest content in mid lactation. Changes in macrophages and neutrophyls levels in ewe bulk milk during lactation were also investigated. Macrophages minimally contributed to leukocyte cell count in milk and had the highest levels at the beginning of lactation. An opposite trend was recorded for polymorphonuclear leukocytes (PMNL) that increased throughout lactation showing the highest value in late lactation. The increase of PMNL percentage and elastase content in milk, in spite of relatively low SCC, suggests that PMNL and elastase underwent a physiological increase associated to the remodelling of mammary gland in late lactation.