In a cross-sectional study to determine the possible relationship between a positive antibody test to bluetongue vies (EiW) or Mjcoplasma b&s infections and repmductive performance of dairy cows, data wzre collected on 572 California dairy cows during December 1% for analysis. Serum samples were tested using an enzyme-linked immunosorbent assay (ELBA). Data on reproduction variables were extracted from the individual cow sheets of the California Dairy Herd Improvement Association records and interfaced with the semlogical results for analysis.
Similar data analyses for both E%TV and A4. bovis were performed to identify and quantitatively assess the association of tbepprcduction variables and each agent. These associations were evaluated unconditionally using the x for categorical variables and Student's &test for continuous variables. Logistic regression analysis was used to determine if reproduction variables with significant unconditional associations remained significant when adjusted for the effects of prxsible confounding facto=.
&th the BTV and M. bovis ELK.4 antibody titres indicated exposure to the agents. The results of the multiple logistic regxssion analyses indicated that cows seropositive for BTV were significantly older at first calving (p<O.O3). For M ti, sexopositive cows were more likely to have longer intervals from calving to last service and longer intervals from calving to pregnancy diagnosis than seronegative cows @<O.OS). The other reproduction variables examined were not significantly associated with ELK4 seropitivity.