TABLE 1.

Linear regression model evaluating factors associated with change in daily milk productiona

ParameterChange in daily production after challenge (kg of milk)btProbable associationc
EstimateSE
Intercept−0.92.11−0.410.702
Variables
    J5 vaccination6.73.332.000.102
    J5-specific antibody titerd2.81.431.930.111
  • a For the overall linear regression model, R2 = 0.50 and P = 0.18.

  • b The change in daily milk production was calculated by taking the difference between the mean of the 8 days before intramammary E. coli challenge and the mean of the 7 days following challenge.

  • c Values indicate the probability that the parameter is significantly related to the change in milk production; lower values indicate greater probability. Values were calculated by comparison of the calculated t value to the critical t value. The SAS program indicates this comparison by the shorthand notation “Pr > t,” where Pr is probability.

  • d Ratio of J5-specific IgG1 antibody to IgG2 antibody. Serum antibody titers were measured just after calving.