Abstract: Adopting the method of sedimentation, the research monitors three large-scaled dairy farm and three cow houses in Nanjing for comparison. The research showed that different cow houses, different sampling sites and different medium had different results. The bacteria amount on dairy farm was more than that within the cow house. The bacterial colony counted the NA culture medium being up to 33.81 ×103 CFU/m3. MAC and S.S culture medium had no bacterias growing. The research showed that F＞ E ＞B＞C ＞ A ＞ D in the total amount airborne bacteria. The bacteria amount had no relevance with the cow houses size, but had much relevance with the hygiene administration .From 270 samples separates 338 bacteria, A, B grazing land were staphylococcus mainly, account for 75.34% (55/73) and 60.61% (40/66) respectively in separation bacterium. C grazing land and E, F housing estate were nitrobacterium mainly, account for 51.22% (42/82), 62.16% (23/37), 61.11% (33/54) respectively in separation bacterium. In the D housing estate, staphylococcus accounted for 46.15% in separation bacterium (12/26), nitrobacterium and streptococcus accounted for 26.92% (7/26), respectivily. The scale-relation dairy had no obvious difference with the total air borne bacteria amount in milk cow houses.

Key words: large-scaled dairy farm; dairy cow houses; airborne bacteria mastitis