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Table 2 Culling - characteristics of the study population (n = 644) and univariable analysis

From: Impact of foot-and-mouth disease on mastitis and culling on a large-scale dairy farm in Kenya

Variable Total population Culling
  N (col %) Rate per 1000 cattle-months (95% CI) HR (95% CI) P -value
FMD      
Yes 400 62.1 14.4 (11.2, 18.6) 2.2 (1.3, 3.7) 0.005
No 244 37.9 6.6 (4.1, 10.6)   
Age (quintiles) a      
−28- <227d 128 19.9 5.0 (2.4, 10.5) 1.6b (1.3, 1.9) <0.0001
227- < 577d 129 20.0 2.0 (0.66, 6.3)
577- < 974d 129 20.0 12.6 (7.8, 20.3)
974- < 1363d 129 20.0 17.1 (11.2, 25.9)
1364-3543d 129 20.0 23.2 (15.9, 33.8)
Parity      
0 381 59.2 4.8 (3.1, 7.4) 1.5b (1.3, 1.8) <0.0001
1 138 21.4 27.1 (19.5, 37.8)
2 77 12.0 11.6 (6.1, 22.4)
3 29 4.5 36.8 (19.2, 70.7)
≥4 19 3.0 18.2 (5.9, 56.6)
Days in milk      
Pre-lactating 373 57.9 4.9 (3.1, 7.6) 1.7b (1.5, 1.9) <0.0001
Early-lactation (<0-100d) 107 16.6 15.2 (9.3, 24.9)
Mid-lactation (101-250d) 85 13.2 18.8 (11.3, 31.2)
Late-lactation (>250d) 44 6.8 25.4 (13.7, 47.2)
Dry 35 5.4 46.0 (27.7, 76.3)
Breed      
100% Exotic breed 551 85.6 11.5 (9.0, 14.6) 0.7b (0.6, 1.3) 0.52
<25% Indigenous 53 8.2 14.6 (7.3, 29.2)
25% Indigenous 28 4.4 3.7 (0.5, 26.0)
50% indigenous 12 1.9 8.8 (1.2, 62.7)
  1. aNegative values reflect animals born during the outbreak period bIncluded as linear variables based on likelihood ratio tests.
  2. Univariable analysis examines putative associations with the primary outcome (culling) for cattle present during an outbreak of foot-and-mouth disease (FMD) on a dairy farm in Nakuru County, Kenya. Culling is defined as exiting the herd due to any disease or death. HR = Hazard ratio.