Facteurs de variation de la numération cellulaire du lait en exploitation

Abstract

Seventy-five dairy farms located in the northen Alps were included in a detailed survey involving the herd and farm structure, winter and summer feeding practices, milking and hygiene practices and cow characteristics and management. These data allowed the analysis of the variations of milk somatic cell count. Three groups of farms were realized according to their pattern of somatic cell count during the year. Fifteen farms had somatic cell counts always low (< 200 000 cells/ml). Twelve farms had somatic cell counts which were always high (> 200 000 cells/mL). Animal cleanness, mastitis frequency and milking machine maintenance differed between this two groups. Milking was carried out in the same place during winter and summer in group 1 and in two different places in group 2. However, milking hygiene, culling management and mastitis prevention pratices did not differ between the two groups. In most of the farms (group 3, n = 23) somatic cell counts were low in winter and high in summer. This pattern was difficult to explain. It may be the result of specific practices of some farmers of this group (mixing of cows from different herds during summer) or of factors unavailable in this survey (discarding practices of milk from mastitic cows).