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Table 3 Clinical mastitis - characteristics of the study population ( n =409) and univariable analyses

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

Variable   FMD Clinical mastitis
  N (col %) N (row %) P -value Rate per 1000 cattle-months (95% CI) HR (95% CI) P -value
FMD        
Yes 323 79.0 - - 18.0 (13.7, 23.7) 1.3 (0.68, 2.5) 0.43
No 86 21.0 -   13.8 (7.6, 24.9)   
Age (quintiles)        
1.5- < 2.0y 81 19.8 54 (66.7) 0.0073a 3.4 (1.1, 10.6) 1.8b (1.5, 2.2) <0.0001
2.0- < 2.8y 82 20.1 61 (74.4) 7.5 (3.3, 16.6)
2.8- < 3.5y 82 20.1 71 (86.6) 17.8 (10.3, 30.7)
3.5- < 4.3y 83 20.3 73 (88.0) 18.1 (10.5, 31.2)
4.3-9.7y 81 19.8 64 (79.0) 50.8 (35.1, 73.6)
Parity        
0 146 35.7 107 (73.3) 0.042a 1.9 (0.6, 6.0) 1.7 b (1.4, 2.1) <0.0001
1 138 33.7 110 (79.7) 22.4 (15.3, 32.9)
2 77 18.8 67 (87.0) 33.2 (21.6, 50.9)
3 29 7.1 22 (75.9) 29.1 (13.1, 64.9)
≥4 19 4.7 17 (89.5) 55.6 (26.5, 126.0)
Days in milk c        
Pre-lactating 138 33.7 102 (73.9) 0.027 1.4 (0.34, 5.4) 1.7 b (1.4, 2.0) <0.0001
Early-lactation (<0-100d) 107 26.2 88 (82.2) 18.5 (11.5, 29.7)
Mid-lactation (101-250d) 85 20.8 75 (88.2) 27.7 (17.7, 43.5)
Late-lactation (>250d) 44 10.8 35 (79.6) 45.2 (26.8, 76.3)
Dry 35 8.6 23 (65.7) 37.8 (20.9, 68.2)
Breed        
100% Exotic breed 351 85.8 285 (81.2) 0.0046a 15.7 (11.9, 20.7) 1.3 b (1.0, 1.8) 0.053
<25% Indigenous 27 6.6 20 (74.1) 23.5 (10.6, 52.3)
25% Indigenous 19 4.7 10 (52.6) 12.8 (3.2, 51.1)
50% indigenous 12 2.9 8 (66.7) 54.8 (22.8, 131.6)
  1. aChi-square test for trend.
  2. bIncluded as linear variables based on likelihood ratio tests cDefined at the beginning of the outbreak period. Univariable analyses examine the associations with the primary risk factor (being a case of clinical FMD) and primary outcome (clinical mastitis) for cattle present during an outbreak of foot-and-mouth disease (FMD) on a dairy farm in Nakuru County, Kenya. Cattle are included in these analyses if over the age of 18 months at the start of outbreak, considered as the age when clinical mastitis becomes a possibility. HR = Hazard ratio.