Table 2.
Distribution of bacterial culture results in bovine milk samples in Norway (n = 36,431) analysed years 2019–2020
| Definition of cow-level diagnosis | ||||||
|---|---|---|---|---|---|---|
| Bacterial finding | Definition 1a | Definition 2b | Definition 3c | |||
| n | % | n | % | n | % | |
| Negatived | 7743 | 21.2 | 7743 | 21.3 | 7743 | 30.1 |
| Major pathogens | ||||||
| Staphylococcus aureus | 8918 | 24.5 | 7750 | 21.3 | 5028 | 19.6 |
| Streptococcus dysgalactiae | 4827 | 13.3 | 3618 | 9.9 | 2105 | 8.2 |
| Streptococcus uberis | 3269 | 9.0 | 2365 | 6.5 | 1411 | 5.5 |
| Escherichia coli | 1859 | 5.1 | 1493 | 4.1 | 936 | 3.6 |
| Trueperella pyogenes | 758 | 2.1 | 503 | 1.4 | 346 | 1.4 |
| Streptococcus agalactiae | 311 | 0.9 | 311 | 0.9 | 162 | 0.6 |
| Mixed majore | – | – | 2244 | 6.2 | – | – |
| Minor pathogens | ||||||
| Staphylococcus epidermidis | 3630 | 10.0 | 1790 | 4.9 | 1327 | 5.2 |
| Staphylococcus chromogenes | 2180 | 6.0 | 1022 | 2.8 | 766 | 3.0 |
| Staphylococcus simulans | 1697 | 4.7 | 704 | 1.9 | 508 | 2.0 |
| Staphylococcus haemolyticus | 670 | 1.8 | 277 | 0.8 | 195 | 0.8 |
| Other non-aureus staphylococcif | 5917 | 16.3 | 2647 | 7.3 | 2237 | 8.7 |
| Corynebacterium bovis | 3418 | 9.4 | 903 | 2.5 | 901 | 3.5 |
| Mixed minorg | – | – | 907 | 2.5 | – | – |
| Other bacteriah | – | – | 974 | 2.7 | 870 | 3.4 |
| Contaminationi | 2264 | 6.2 | 1180 | 3.2 | 1163 | 4.5 |
| Total | 47,461 | 1305j | 36,431 | 100 | 25,698 | 100 |
aDefinition 1: Each quarter sample diagnosis was included independent of the other quarter samples, meaning that cows with two different diagnoses at the same sampling occasion contributed to the frequency of both udder pathogens
bDefinition 2: Cows with at least one quarter with S. aureus, S. dysgalactiae, S. uberis, E. coli, T. pyogenes or S. agalactiae (“major” pathogens) were assigned this as cow-level diagnosis. Cows were given the cow-level diagnosis NAS, S. epidermidis, S. chromogenes, S. simulans, S. haemolyticus or C. bovis (“minor pathogens”) if they had no major udder pathogen at the same sampling event
cDefinition 3: Cow-level diagnoses in a subset with only one bacterial finding per sampling event
dNo growth in all sampled quarters
eCows with more than one major udder pathogen at the same sampling event
fNon-aureus staphylococci other than S. epidermidis, S. chromogenes, S. simulans, S. haemolyticus
gCows with more than one minor udder pathogens at the same sampling event
hBacteria other than presented in the table
iSamples with at least one quarter yielding more than two different colony types and no other udder pathogens in other quarters
jGiving on average 1.3 bacterial diagnoses per cow per sampling event