TABLE 1.
Descriptive data of the farms included in the study grouped by geographical area and year of sampling.
| Dairy/year | A 2017 | A 2019 | B 2017 | B 2019 |
| Number of farms | 19 | 19 | 18 | 18 |
| Number of farms, type, and milking system | ||||
| Free stall automatic (AMS) | 9 | 12 | 6 | 6 |
| Free stall parlor (FSP) | 3 | 3 | 6 | 6 |
| Tie stall pipeline (TSP) | 7 | 4 | 6 | 6 |
| Mean number of cows (standard deviation, SD) | 41.1 (20.5) | 40.4 (23.6) | 33.9 (13.2) | 32 (12.1) |
| Number of small farms1 | 10 | 7 | 8 | 9 |
| Number of large farms1 | 9 | 12 | 10 | 9 |
| Mean (SD) average somatic cell count (SCC) (in 1,000) | 140.6 (52.2) | 129.3 (47.4) | 117.8 (39.6) | 115.1 (52.3) |
| Mean (SD) average bacterial load (TBC)2 | 4.2 (0.3) | 4.4 (0.3) | 4.1 (0.3) | 4.2 (0.4) |
| Average milk production per cow per year3 | 8064 (927) | 8415 (1233) | 7739 (726) | 8268 (1314) |
| Mastitis treatments, mean (SD)4 | 0.2 (0.2) | 0.2 (0.1) | 0.1 (0.1) | 0.1 (0.2) |
| Prevalence of SCC > 200.000, mean (SD)5 | 22.4 (11.2) | 26.7 (11.3) | 21.2 (6.2) | 19.5 (7.3) |
| Amount of concentrate, Mean (SD)6 | 24.3 (5.1) | 26.1 (5.8) | 31.7 (5.7) | 30.6 (9.9) |
| Average temperature (May–August, in°C)7 | 15.3 | 17.6 | 15.9 | 18.2 |
| Average precipitation (May–August, in mm)7 | 80.8 | 39.7 | 120.1 | 45.0 |
| Average Temperature (January–March, in °C) | −3 | −1 | −1.9 | −0.1 |
| Average precipitation (January–March, in mm) | 40.3 | 56.5 | 46.9 | 72.7 |
| Collection trucks8 | 3 | 3 | 1 | 1 |
1Farm sizes were divided in small and large if the number of cows were over the Norwegian average farm size (28 cows). 2Data in logarithm. 3Milk production per cow/year (kg energy corrected milk). 4Number of mastitis treatments per year, divided by number of cows. 5Percent of the cows with SCC > 200.000 on individual test days during the last year. 6Kg concentrate used per 100 kg produced milk (Energy corrected milk). 7Data from harvesting season previous summer 2016 and 2018, respectively. 8Number of trucks that collected the milk during each sampling.