MILK DIFFERENTIAL CELL COUNTS IN RELATION TO TOTAL COUNTS IN SARDINIAN EWES

Milk samples from 40 primiparous Sardinian ewes were examined during a whole lactation period in order to evaluate the dynamics of somatic c ell counts (SCC), differential cell counts (DCC) and bacteriological s tatus of the mammary gland. Only four samples out of 240 were bacterio logically positive and this was confirmed by the geometrical mean of S CC being always below 200 000 cells per ml. DCC during lactation showe d two different dynamics: one concerning polymorphonuclear neutrophil leucocytes (PMN) and macrophages, and the other one lymphocytes and ep ithelial cells. Macrophages and PMNs in particular showed a progressiv e increase as lactation went on, while lymphocytes and epithelial cell s showed a uniform decrease during lactation. The relationship between SCC and DCC indicated that PMN was the only cell type increasing when SCC rose. The progressive increase of SCC during lactation in absence of infection was probably an effect of cell concentration owing to th e physiological reduction of milk yield, while the increase of macroph ages and PMN was very likely a consequence of immune mechanisms approa ching the dry period. The results confirmed that DCC and particularly PMN rate could provide a more sensible method of identifying mammary i nflammations, particularly in well managed herds with low levels of in fections. (C) 1997 Elsevier Science B.V.