Herd-level seroprevalence of Fasciola hepatica and Ostertagia ostertagi infection in dairy cattle population in the central and northeastern Poland

Table 3 Multivariable linear regression model for herd-level exposure to Ostertagia ostertagi

Risk factor	Regression coefficient (B) and standard error (SE)	95% confidence interval (95% CI) for regression coefficient	t-statistics	p-value
Intercept	0.42 (0.02)	–	–	–
Length of grazing period (months)	0.05 (0.01)	0.03, 0.06	8.40	< 0.001 ^b
Grazing grass > 50% of all roughage	0.08 (0.03)	0.02, 0.13	2.60	0.010 ^b
The north-eastern province	0.06 (0.03)	0.01, 0.11	2.24	0.026^b
Grazing on pasture	−0.16 (0.08)	−0.31, − 0.01	−1.98	0.048^a
Hay or haylage as main roughage	−0.02 (0.03)	−0.07, 0.04	− 0.50	0.620
Herd size	0.01 (0.01)	−0.01, 0.01	−0.11	0.912

^a excluded for very strong correlation with the length of grazing period.
^b significant risk factor for herd-level exposure to Ostertagia ostertagi at a significance level of 0.05.

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