PSXI-5 Evaluation of behavioral traits of beef calves inoculated with a bovine-derived blend of Lactic Acid Bacteria.

Abstract The gut microbiota influences animal behavior through bi-directional communication with the central nervous system. However, there is limited understanding of the use of microbial interventions with psychobiotics in beef cattle to alter stress-induced behaviors. We aimed to evaluate the effects of administering a bovine-derived mixture of Lactic Acid Bacteria (LAB) during early life on stress-related behavior in beef calves. Thirty-two crossbred beef calves [66 ± 11 kg of body weight; 60 ± 6 d of age] were stratified by age and sex and randomly assigned to receive either two doses of an orally administrated LAB cocktail (n = 16; 10^9 CFU; LAB) or saline solution (n = 16; CON) three-days apart. After first inoculation (d 0), cow-calf pairs were allocated to four different paddocks (two/treatment) for 15 d, and maintained in a single pasture until weaning, at ~202 d of age. After weaning, calves from both treatments were housed in a single pen. Two reactivity indicators were evaluated by a trained observer on d 0, 3, 143 (weaning), 146, and 157, including the reactivity inside the chute (RSC) within the first 30 seconds of entering the chute, adding up movement (1-5), tension (1-4), body posture (1-3), breathing (1-2), kicking (1-2), and vocalization (1-2) scores; and the flight speed (FS, m/s) measured electronically, as the speed at which each animal exits the chute. Total steps (TS), lying time (LT), and standing time (ST) were recorded using pedometers (IceRobotics) from weaning to d 157. Data was analyzed using linear mixed models with repeated measurements following a completely randomized design. Results indicated FS at weaning had the fastest speed (1.6 ± 0.08 m/s, p = 0.019) compared to d 0 (1.23 ± 0.09 m/s) and d 157 (1.15 ± 0.09 m/s) but did not differ from d 3 and d 143. A day effect was also detected for RSC (p = 0.004), where animals on d 0 had the highest value (4.28 ± 0.17) and was different from d 157 (3.47 ± 0.18); however, it did not differ from d 3, d 143, and d 146. The TS indicated that calves increased their number of steps (up to 7092 steps per day) for the three days following weaning (p < 0.001) and stayed under 1295 steps per day for the remaining days of the evaluation. Treatments did not impact any of the response variables measured (p ≥ 0.3), with calves from both treatments standing more and lying less time during the first three days post-weaning (p < 0.001) compared to the last eleven days of the recordings. While weaning influences calf behavior, our findings do not support that administering a bovine-derived LAB mixture during early life affects calves’ reactivity or stress-related behaviors.