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Figure 5 | Veterinary Research

Figure 5

From: Quantification of the increase in the frequency of early calving associated with late exposure to bluetongue virus serotype 8 in dairy cows: implications for syndromic surveillance

Figure 5

Increase in frequencies of early calving. The increases were expressed as odds-ratios (OR), for cows in herds reported as cases of Bluetongue virus serotype 8 during the 2007 outbreak (black curve) and cows in herds located in the 2007 outbreak area but not reported as cases (gray curve). In both populations, cows with dates of exposure (reported or interpolated) within the last 10 weeks of gestation were selected. The different OR values correspond to each category of exposure, defined according to the dates of exposure during pregnancy. The reference population considered was composed of cows that calved in 2005 or 2006 from herds located in the 2007 outbreak area. Vertical bars around ORs correspond to their 95% confidence intervals. The histogram represents the distribution of gestation lengths for multiparous Holstein cows, with the gray area corresponding to early calving (defined as the interval between the expected percentile 1 and 25 of the Gaussian distributions of normal gestation lengths).

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