Effect of vaccination against foot-and-mouth disease on milk yield in dairy cows

• FMD vaccination temporarily reduces milk yield in high-producing Holstein cows. • FMD vaccination increases body temperature in dairy cows. • The impact of FMD vaccination on dairy yield depends on cows’ production level. This study aimed to assess the impact of foot-and-mouth disease (FMD) vaccination on milk production in dairy cows. In Experiment 1, 593 lactating Holstein cows (37.2 ± 0.3 kg/day), housed in a free-stall system, were randomly assigned to receive ( n =268) or not receive ( n =325) a dose of the FMD vaccine on Day 0 of the experiment. Milk yield was recorded from Day −3 to Day 9, and body temperature was measured from Day 0 to Day 3. Among cows producing ≥37.2 kg/day, vaccinated animals had a significantly lower milk yield than unvaccinated controls from Days 1 to 5 post-vaccination (40.7±0.3 kg/day vs. 42.9 ± 0.3 kg/day; P < 0.05). In cows producing <37.2 kg/day, milk yield was lower in vaccinated animals on Days 1 and 2 (31.0 ± 0.3 kg/day vs . 32.9 ± 0.3 kg/d; P < 0.05), with no differences detected thereafter. In a subset of cows from Experiment 1 ( n =96), vaccinated cows had higher body temperature on Day 1 (39.1±0.1°C vs. 38.2±0.1°C; P < 0.05). In Experiment 2, 146 lactating Holstein cows (20.3 ± 0.3 kg/day), managed on a pasture-based system, were randomly assigned to receive ( n =78) or not receive ( n =68) a dose of the FMD vaccine on Day 0. Milk yield was measured on Days 0 and 3, and milk composition, somatic cell count, and milk urea nitrogen were analyzed on Day 3. No significant differences were observed between experimental groups for any of these variables. In conclusion, FMD vaccination caused a transient milk yield reduction in high-producing cows (∼40 kg/day, free-stall system), but no significant effect was seen in lower-producing cows (∼20 kg/day, pasture-based system).