Effects of Dietary Probiotics on Cattle Stress Behavior

The objective of this study was to evaluate if dietary probiotics alter stress behavior in cattle. Following a one week acclimation to treatment pastures, two treatments were evaluated; 1) control, receiving feed without probiotics and 2) probiotics, receiving feed containing 10 g per head per day of probiotics (Probios feed granules, Chr. Hansen, Inc.). Treatments were applied for 6 weeks to 33 female cattle ≥1 year old utilizing a randomized complete block design where cattle were blocked by age (control n=16, probiotics n=17). Cattle were housed in 4 pastures, allowed access to ad libitum fescue-based pasture and received a corn-based feed ration of 2.3 kg per head per day. Each week, chute exit velocity was measured using an electric sports timing system. During week 6, all cattle individually underwent a 5 min novel object test (NOT) where a green jolly ball was used as the novel object. Cattle were individually tested within a 3 x 4.7 m test arena within a barn, consisting of 4 zones. Behavior was evaluated using live observations by 2 trained observers between 08:00 and 12:00 h. Latency to first and frequency of novel object touches, duration of time within the zone containing the novel object, and frequency of zone line crossings, vocalizations, defecations, and urinations were recorded. Thermal images of the lacrimal region of the eye were taken before and after NOT and arena exit speed was recorded using an electronic sports timing system. Data were analyzed using the Glimmix procedure of SAS including the fixed effects of treatment, herd (2 herds were used in this study), NOT order, and the covariate of age. Prior to starting treatments, cattle fed probiotics tended to exit the chute faster than control cattle (P=0.09). However, during weeks 3-5 cattle fed probiotics exited the chute slower than control cattle (P<0.01). During NOT, cattle fed probiotics crossed zone lines more frequently (P=0.04), vocalized less often (P=0.002), and tended to take longer to first touch the novel object (P=0.06) compared to the control treatment. No treatment differences were observed in duration of time spent in the zone containing the novel object, frequency of novel object touches, defecations, urinations, or arena exit velocity (P>0.10). No treatment differences in eye temperature before or after NOT were observed (P>0.10). These results suggest that dietary probiotics may alter cattle stress behavior.