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Vet. Res.
Volume 34, Number 5, September-October 2003
Mastitis of dairy ruminants
Page(s) 629 - 645
How to cite this article Vet. Res. (2003) 629-645
Vet. Res. 34 (2003) 629-645
DOI: 10.1051/vetres:2003021

Polymorphonuclear proteolytic activity and milk composition change

Yves Le Roux, François Laurent and Fatima Moussaoui

Laboratory of Animal Science, National Polytechnic Institute of Lorraine, ENSAIA-INRA, 2, avenue de la Forêt de Haye, 54505 Vand?uvre-lès-Nancy Cedex, France
(Received 31 October 2002; accepted 21 March 2003)

Relationships between Quarter Milk Cell Count (QMCC) and Tank Milk Cell Count (TMCC) with milk biochemical and technological parameters in milk and dairy products were investigated. All parameters measured were affected by the increase of TMCC and QMCC between 0 and 600 000 cells/mL. The variable effect of lactation stage which is different for different authors, is discussed. The three mechanisms, measured during the inflammation of the udder, implicated in the modification of milk quality are described (a decrease in synthesis, a decrease in the milk barrier permeability and an increase in proteolytic activities). The direct effect of plasmin in caseinolysis is well known; the specific role of the increase of somatic cells (especially PMN) in the modification of milk quality is described. Several specific proteolytic activities of PMN are described and the impact of these activities on caseinolysis is evaluated. Two hypothetical mechanisms of caseinolysis by PMN are suggested and a synthetic scheme of the role of plasmin, bacteria and somatic cells in caseinolysis is discussed.

Key words: caseinolysis / mastitis / milk / PMN proteases / SCC

Correspondence and reprints: Yves Le Roux

© INRA, EDP Sciences 2003