Bacteriology and somatic cell counts in milk samples from ewes on a Scottish farm

Milk samples from 50 sheep on a single Scottish research farm were collected weekly for 10 wk postpartum. Samples were analyzed for somatic cell counts (SCC) each week and bacteriologic culture was done for 7 of the 10 wk. A total of 492 udder half samples were cultured, of which 467 had corresponding cell count data. Statistical analysis on complete SCC and culture data showed no association between SCC and bacterial isolation, even when more than 10 colonies of a single bacterial species were present. Only 3.6% of the samples were simultaneously positive for high count (> 10 colonies from 0.01 mL of milk) of any one bacterial species and high SCC (> 1 x 10(6)/mL). The bacteria recovered were: Staphylococcus equorum (19 times), S. xylosus (7 times), S. simulans (6 times), Streptococcus uberis (3 times) and other streptococci (4 times), Mannheimia (Pasteurella) haemolytica (2 times), Staphylococcus aureus (1 time), S. capitis (1 time), and Enterococcus faecium (1 time). There was an association between the test day and SCC, with higher SCC values in the first 2 wk. In addition, significantly higher SCC values were found in the oldest animals compared to the other age groups.