Table 3.
Descriptive statistics of explanatory variables in a study of herd-level risk factors for cow mortality in 4,252 Swedish dairy herds between September 2009 and August 2010.
| Variable | Category | n1 | No.1 with mortality, % | Mortality events per 100 cow-years |
|---|---|---|---|---|
| Calving interval, d | <391.8 | 3,098 | 59.7 | 5.5 |
| 391.8 to 407.3 | 3,152 | 61.0 | 6.1 | |
| 407.4 to 429.1 | 3,210 | 60.1 | 6.6 | |
| ≥429.2 | 3,126 | 61.0 | 7.4 | |
| Herd size, cow-years | 20 to 49.9 | 5,883 | 43.1 | 5.4 |
| 50 to 99.9 | 4,465 | 67.4 | 6.0 | |
| 100 to 199.9 | 1,823 | 90.9 | 7.0 | |
| ≥200 | 415 | 98.3 | 7.5 | |
| Housing system2 | Tie-stall | 8,188 | 50.9 | 5.8 |
| Freestall AMS | 1,941 | 76.7 | 6.9 | |
| Freestall CM | 2,457 | 79.7 | 6.5 | |
| Management type | Conventional | 11,473 | 61.0 | 6.4 |
| Organic | 1,113 | 55.9 | 5.3 | |
| Milk yield, kg of ECM | <8,421 | 3,132 | 55.5 | 6.7 |
| 8,421 to 9,279 | 3,153 | 61.1 | 6.7 | |
| 9,280 to 9,994 | 3,145 | 63.1 | 6.2 | |
| ≥9,995 | 3,156 | 62.0 | 6.0 | |
| Predominant breed | Swedish Holstein | 3,583 | 68.6 | 7.3 |
| Swedish Red | 3,105 | 50.0 | 5.0 | |
| Mixed/other breeds3 | 5,898 | 61.1 | 6.2 | |
| Region4 | Södra Götaland (1) | 1,175 | 68.4 | 7.4 |
| Östra Götaland (2) | 3,754 | 61.2 | 6.6 | |
| Västra Götaland (3) | 3,921 | 60.3 | 6.0 | |
| Östra Svealand (4) | 976 | 56.8 | 5.2 | |
| Västra Svealand (5) | 668 | 58.7 | 6.0 | |
| Norrland (6) | 2,092 | 57.3 | 6.5 | |
| Season5 | Autumn-winter | 4,251 | 56.8 | 5.9 |
| Winter-spring | 4,229 | 61.5 | 6.4 | |
| Summer | 4,106 | 63.2 | 6.7 |
1
Number of herd-seasons.
2
Tie-stall = tie-stall with pipeline milking; freestall AMS = freestall with automatic milking system; freestall CM = freestall with conventional milking (e.g., milking parlor or carousel).
3
Crossbreeds, Swedish Polled, and Swedish Jersey.
4
Numbers in parentheses refer to different regions identified in Figure 1.
5
Autumn-winter (September 1 to December 31), winter-spring (January 1 to April 30), and summer (May 1 to August 31).