A booster vaccination for Salmonella spp. minimally affects feeding behavior in beef × dairy calves fed with automated milk feeders

Farmers can use automated milk feeders (AMF) to identify changes in the behavior of individual calves before they are clinically sick. However, other management factors, such as routine procedures, may affect group- and individual-level feeding behavior patterns in calves. This matched cohort study (n = 44; 22 pairs of booster-vaccinated calves matched to controls) evaluated the effects of a booster vaccination comprised of inactivated Salmonella Typhimurium and Salmonella Dublin on feeding behavior and relative changes in behavior of Angus × Holstein calves reared at one calf-rearing facility. All calves were vaccinated with Bovilis Bovivac S on d 1 after farm arrival. Booster calves received a booster vaccination at 15 d after farm arrival (d 0 of the study). Control calves did not receive the booster. We pair-matched booster-vaccinated calves to controls by sex, the first day they independently drank from the feeder, and arrival weight (±6 kg). Daily feeding behaviors (milk intake, drinking speed, and rewarded visits) were recorded by an AMF (Foerster-Technik, Engen, Germany). Calves were offered a maximum of 3.0 L of milk replacer per meal with no daily limit, using a 2-h block between meals to limit size. Mixed linear regression models assessed the effects of booster status, day (days -2 to 4), pair, and the day × booster status interaction on calf feeding behavior, with calf as a random effect and day as the repeated measure. Models also assessed effects on relative changes in feeding behavior using the same model structure. Relative change was calculated as [(day of interest behavior - baseline behavior on day -2) ÷ baseline behavior] × 100, giving the percent change at the individual calf level. Significant day × booster interactions had mean differences adjusted using the Tukey method. We observed a milk intake × day interaction: booster calves consumed more milk than controls on d 0, 2, 3, and 4. For example, on the booster day, control calves consumed 8.26 L/d (95% CI: 7.78 to 8.75; LSM) compared with 10.5 L/d (95% CI: 9.31 to 10.28) in booster calves. Booster status was also associated with greater rewarded visits and faster drinking speeds (control 0.49 L/min, 95% CI: 0.47 to 0.51 vs. booster 0.52 L/min, 95% CI: 0.50 to 0.54), but there was no day × booster interaction for these metrics. Interestingly, booster status was not associated with relative changes in milk intake, drinking speed, or rewarded visits. This suggests that although booster-vaccinated calves, as a group, consumed more milk and drank faster, the magnitude of the within-calf behavioral change after a booster shot was not significant. We suggest that calves injected with a booster vaccine for inactivated Salmonella Typhimurium and Salmonella Dublin did not experience individual changes in their behavior patterns, but group milk intake increases on the days after the booster shot.