Characterizing the mammary epithelial cell exfoliation process during milking in dairy cows
Résumé
The presence of mammary epithelial cells (MEC) in milk indicates that some MEC are shed from the mammary
epithelium. The MEC exfoliation process in dairy cows likely participates in the regulation of MEC number
in the udder and thus in milk yield variations. The mechanisms that regulate the exfoliation process are
not known. However, we can hypothesize that milking, through its mechanical pressure on the mammary
epithelium, is a special time for exfoliation of the MEC. In order to characterize MEC exfoliation during
milking, 9 multiparous cows were milked and milk samples were collected each minute for composition
analysis. The samples collected at the beginning (after 1 and 2 min), in the middle and at the end of milking
were used for MEC purification using an immuno-magnetic method. Tight junction opening was assessed
by plasma lactose concentration and Na:K ratio in milk. Data were analyzed using the mixed procedure
of SAS. Milk flow increased until the 3rd minute and then decreased as the milking progressed (P<0.001).
Milk composition changed during the course of milking: the milk fat content increased (P<0.001) while the
milk protein content decreased (P<0.001). At the end of milking, the somatic cell count increased (P<0.001)
whereas the percentage of MEC in total somatic cells decreased (P<0.05), suggesting an influx of immune
cells. The concentration of MEC in milk decreased between the 1st and the 2nd minute of milking suggesting
that the milk of the 1st minute of milking contained MEC which were exfoliated before milking started. The
milk MEC concentration then increased from the 2nd minute to the end of milking. A decrease in the Na:K
ratio in milk (P<0.01) and an increase in plasma lactose concentration (P<0.01) during milking indicated a
disruption of mammary epithelium integrity. The results of this study show that MEC are exfoliated before
milking but also during milking. The exfoliation process during milking is concomitant with the disruption
of mammary epithelium integrity.
Domaines
Sciences du Vivant [q-bio]
Fichier principal
Abstract_Essai1_submitted_1.pdf (48.63 Ko)
Télécharger le fichier
Abstract_Essai1_submitted_2.docx (19.07 Ko)
Télécharger le fichier
Origine | Fichiers produits par l'(les) auteur(s) |
---|
Origine | Fichiers produits par l'(les) auteur(s) |
---|