Table 1.
Distribution and percentage of milk samples and positive cultures for each sample type stratified by herd's region and herd's bulk milk tank somatic cell counts category (BMTSCC).
| Herd region (zone) | Herd BMTSCC (x 1,000/mL) | n Herds | Milk samples | p-valuea | p-valueb | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Overall | Mastitis | Int. C | Ext. C | |||||||||
| Total (n) | Positive; n (%)* | Total (n) | Positive; n (%)* | Total (n) | Positive; n (%)* | Total (n) | Positive; n (%)* | |||||
| NQLD (tropical) | ≤150 | 2 | 35 (25%) | 16 (11%) | 12 | 4 (3%) | 8 | 3 (2%) | 15 | 9 (6%) | ||
| 150–300 | 4 | 73 (51%) | 47 (33%) | 26 | 21 (15%) | 22 | 12 (8%) | 25 | 14 (10%) | |||
| >300 | 2 | 34 (24%) | 20 (14%) | 9 | 5 (4%) | 9 | 5 (4%) | 16 | 10 (7%) | 0.702 | ||
| Subtotal | 8 | 142 (100%) | 83 (58%) | 47 | 30 (64%) | 39 | 20 (51%) | 56 | 33 (59%) | 0.499 | ||
| SQLD (subtropical) | ≤150 | 2 | 62 (44%) | 33 (24%) | 25 | 17 (12% | 10 | 4 (3%) | 27 | 12 (9%) | ||
| 150–300 | 2 | 65 (46%) | 35 (25%) | 22 | 19 (14%) | 18 | 8 (6%) | 25 | 8 (6%) | |||
| >300 | 1 | 13 (9%) | 8 (6%) | 4 | 3 (2%) | 5 | 4 (3%) | 4 | 1 (1%) | 0.386 | ||
| Subtotal | 5 | 140 (100%) | 76 (54%) | 51 | 39 (76%) | 33 | 16 (48%) | 56 | 21 (38%) | <0.001 | ||
| Victoria (temperate) | ≤150 | 2 | 42 (31%) | 13 (10%) | 15 | 8 (6%) | 12 | 3 (2%) | 15 | 2 (1%) | ||
| 150–300 | 2 | 74 (54%) | 50 (36%) | 32 | 26 (19%) | 16 | 9 (7%) | 26 | 15 (11%) | |||
| >300 | 1 | 21 (15%) | 7 (5%) | 6 | 6 (4%) | 7 | 1 (1%) | 8 | 0 (0%) | 0.702 | ||
| Subtotal | 5 | 137 (100%) | 70 (51%) | 53 | 40 (75%) | 35 | 13 (37%) | 49 | 17 (35%) | <0.001 | ||
| Total£ | 419 (100%) | 229 (55%) | 151 (36%) | 109 (72%) | 107 (26%) | 49 (46%) | 161 (38%) | 71 (44%) | <0.001 | |||
Milk samples were collected from 151 clinical mastitis quarters and 268 apparently healthy control quarters from 18 dairy herds located in Northern Queensland (NQLD), Southeast Queensland (SQLD) and Victoria between March and June 2019.
Key: BMTSCC, Bulk milk tank somatic cell count; n, number; Int. C, Internal controls; Ext. C, External controls.
Chi square comparison of the distribution of sample types (mastitis, internal and external controls) by herd's bulk somatic cell count in the given herd region.
Chi square comparison of positive culture rates across the sample types within each region and in the total population.
Percentage of subtotal.
Percentage of total (n).