Evolution of milk somatic cell count of cows grazing an alpine pasture according to the infection of udder by pathogens

The infection of udder by a pathogen and milk somatic cell count (SCC) of 2 20 quarters from 55 Abondance and Tarentaise cows coming from three Norther n Alps herds were analysed three times: in June when cows use a valley past ure before turning to highland pasture and in July and September, respectiv ely at the beginning and the end of highland pasture grazing period. During the three periods, 31% of the experimental quarters were free or infection , 61% were infected by a minor pathogen and 8% were infected by a major pat hogen. In quarters infected by a major pathogen, SCC was constantly high (> 1 600 000 cells/ml in the three periods). SCC of uninfected quarters remai ned below 60 000 cells/ml in the three periods whereas SCC of quarters infe cted by a minor pathogen averaged 89 000 cells/ml in June and 512 000 cells /ml in September. For the latter, SCC was all the higher as the infection w as older. Results are discussed according to the highland grazing condition s that may have had an impact on SCC.