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Table 1 Crude univariate analyses between seroprevalence of BVL and farm factors in seven prefectures in Japan

From: Risk factors associated with within-herd transmission of bovine leukemia virus on dairy farms in Japan

Variable and level Number of herds Median (IQR1) P2
Herd size    
< 30 head 35 43.3 (13.3, 60.0) 0.514
30--49 head 25 53.33 (16.7, 63.3)  
≥ 50 head 30 50.00 (26.7, 73.3)  
Cattle introduced into the herd within one year    
No 11 46.7 (27.3, 60.0) 0.286
Yes, self-bred cows only 33 52.2 (25.0, 78.0)  
Yes, including purchased cows 46 45.0 (13.3, 65.0)  
Housing conditions    
Tie housing 68 41.9 (13.3, 62.5) 0.001*
Loose housing 22 65.0 (52.2, 78.3)  
Availability of own grazing area    
Yes 65 43.3 (13.8, 63.3) 0.048*
No 25 52.2 (33.6, 78.0)  
Presence of horseflies in summer    
Never to seldom 28 26.7 (13.3, 51.8) 0.002*
Sometimes to often 29 47.6 (15.8, 65.0)  
Very high 33 63.3 (44.4, 83.0)  
Animal dehorning    
Yes 58 60.0 (39.2, 73.3) < 0.001*
No 32 20.0 (8.8, 43.0)  
Plastic sleeve used for rectal palpation    
One sleeve per cow 73 43.3 (14.5, 68.3) 0.012*
One sleeve for more than one cow 17 60.0 (47.8, 75.0)  
Needle used for vaccination    
One needle per cow 86 46.7 (16.7, 65.5) 0.100*
One needle for more than one cow 4 64.4 (50.5, 91.7)  
Colostrum feeding    
No 7 76.7 (60.0, 95.7) 0.003*
From dam to calves 63 42.1 (13.3, 60.0)  
Pooled 20 50.0 (36.7, 75.8)  
Overall 90 48.1 (17.1, 68.5)  
  1. 1Interquartile range
  2. 2Mann--Whitney U-test for two-level variables or Kruskal--Wallis test for all others
  3. *Incorporated into multivariate model
  4. Results of the Mann--Whitney U-test or the Kruskal--Wallis test showed that cattle housing conditions, availability of own grazing area, presence of horseflies in summer, dehorning, use of a plastic sleeve for rectal palpation, not changing needles between animals during herd vaccination, and colostrum feeding were possibly associated with seroprevalence (p < 0.15). These seven variables were incorporated in the multivariate model.