Submitted to: European Association of Animal Production Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: May 26, 2001
Publication Date: July 8, 2001
Citation: PAAPE, M.J., CONTRERAS, A., VAN OOSTVELDT, K., CAPUCO, A.V., MARCO, J.C. INTRAMAMMARY DEFENSE AND MILK SOMATIC CELL COUNTS 9MSCC0 OF GOATS AND SHEEP. EUROPEAN ASSOCIATION OF ANIMAL PRODUCTION PROCEEDINGS. 2001.
The first line of defence against intramammary infection is the teat canal. Bacteria that pass this barrier encounter the second line of defence: phagocytic leukocytes that consist of macrophages and polymorphonuclear neutrophil leukocytes (PMN). Toxins released by invading bacteria activate macrophages and epithelial cells causing the secretion of chemoattractants. .Soon PMN migrate directly from blood and initiate ingestion and killing of the bacteria. However, this PMN function is compromised because migration of blood PMN through the blood-milk barrier causes death of some PMN by apoptosis, and ingestion of milk fat globules and casein by PMN inhibits their ability to effectively ingest and kill bacteria. Potent oxidants released by PMN during ingestion of bacteria and milk components destroy not only bacteria, but also some of the secretory epithelial cells within the udder. Death of PMN and reduction in PMN function increases susceptibility of the udder to mastitis. Infection causes an increase in MSCC that could reach millions of cells/ml. Normal MSCC for sheep that are free from intramammary infection are <100,000/ml. For uninfected goats, MSCC are higher and can approach 2 x 106/ml. Non-infectious factors such as parity, stage of lactation, season and milk yield have been related to increased MSCC for goats.