Influence of different factors in milk production on standard plate count of raw small ruminant's bulk-tank milk in Switzerland

A total of 407 samples of bulk-tank milk, 344 of goat's milk and 63 of ewe's milk, collected from 403 different farms throughout Switzerland, were examined. The aim of this study was (i) to determine the microbiological status of goat's and ewe's milk by standard plate count (SPC) and (ii) to evaluate potential influence factors (management practices, herd characteristics) in Switzerland for the first time. Median SPC from small ruminant's bulk-tank milk was 4.68 log10 cfu/ml (4.69 log cfu/ml for goat's milk and 4.79 log cfu/ml for ewe's milk), with a minimum of 2.00 log cfu/ml and a maximum of 8.64 log cfu/ml. Statistical analysis showed significant differences within the months of sample collection, the number of milkings contained in bulk-tank milk, the different milking techniques applied and the flock size. Farms with flock size >25 animals, sampled in June, using mechanized milking systems (especially bucket milking without parlor) as well as farms with milk delivery every second or third day showed significant higher SPC levels, whereas the highest probability of a low SPC result was observed during July, in farms with flock size <6 animals, using hand milking and daily milk delivery. In consequence, smaller farms without high technology standards may reach a good milk quality. Improving hygienic conditions, checking the milking equipment, rapid cooling and refrigeration, as well as frequent milk collection are prerequisites for the production of good quality milk.