Effects of 2 commercially-available 9-way killed vaccines on milk production and rectal temperature in Holstein-Friesian dairy cows.

Veterinarians and farmers employing multivalent killed vaccines in lactating dairy cows have reported transient losses in milk production. Few studies have quantified this loss. In this report, effects of 2 commercially available 9-way vaccines on milk production and rectal temperature are examined. Repeated measures analyses of variance were used to compare changes in milk production and rectal temperature over time between treatment groups. There was a significant (P < 0.01) interaction among treatment and time when comparing vaccine- and placebo-treated animals. When pretreatment milk production (or days in milk) and pretreatment rectal temperature were considered, respectively, as covariates, a significant (P < 0.05) depression of milk production and a significant (P < 0.05) increase in rectal temperature were observed one day following injection. These effects were small and short-lived. The stage of lactation, level of milk production, and choice of product may be used as decision-making tools to decrease milk production losses in vaccine-candidate cows.