view - Department of Reproduction, Obstetrics and Herd Health

CHAPTER 6
EFFECT OF UFA AND CVUFA ON CRFI
Parameter estimates and odds ratios (OR) of the final multivariable logistic
regression model on CRFI are provided in Table 2. The variance partition coefficient
(VPC), representing the proportion of the total variation in the conception rate which
resides at the herd level, was estimated at 12.3%, calculated using the latent-variable
method (Goldstein et al., 2002; Snijders and Bosker, 1999).
Table 2. Final multivariable logistic regression model for conception rate to first
insemination, based on 8,247 first inseminations on 90 Belgian herds in 2008 and 2009
using herd as random effect in the model (λ = 0.46, SE = 0.1, P < 0.0001)
Covariate Class OR 1 95% CI of OR P-value
Cow level
Parity 1 1.00 2 2 0.73 0.65-0.83
DIM ≤60 d 1.00 0.0003
61-81 d 1.21 1.05-1.39
82 – 102 d 1.27 1.09-1.49
103 – 123 d 1.11 0.92-1.34
≥124 d 1.45 1.22-1.71
Relative M305 3 , % Cont. 4 0.98 0.98-0.99