TABLE 1.

Linear regression model evaluating factors associated with change in daily milk production^a

Parameter	Change in daily production after challenge (kg of milk)b		t	Probable associationc
	Estimate	SE
Intercept	−0.9	2.11	−0.41	0.702
Variables
J5 vaccination	6.7	3.33	2.00	0.102
J5-specific antibody titerd	2.8	1.43	1.93	0.111

^aFor the overall linear regression model, R² = 0.50 and P = 0.18.

^bThe 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.

^cValues 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.

^dRatio of J5-specific IgG1 antibody to IgG2 antibody. Serum antibody titers were measured just after calving.