Effects of dietary probiotics on beef cattle performance and stress

Dietary probiotics have been shown to benefit cattle production; however, little is known about how they affect beef cattle temperament and stress. Therefore, the objectives of this study were to evaluate how dietary probiotics impact beef cattle performance and stress. Two treatments were used for this study: (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., Milwaukee, WI). Three groups of cattle were evaluated. Group 1 consisted of 7 weaned calves that were 7-10 months old and used a crossover experimental design where the calves were given each treatment for 3 weeks. Group 2 consisted of 33 female cattle ≥ 1 year of age and had treatments applied for 6 weeks using a randomized complete block design (control n = 16, probiotics n = 17). Group 3 consisted of calves that were nursing group 2 cows allocated to the control and probiotics treatment for 6 weeks (n = 8 per treatment). Weekly body weight, average daily gain, feed efficiency (group 2 only), chute exit velocity, behavior during a novel object test (group 1 and 2), and serum cortisol during weeks 0 and 6 (group 2) were measured. Group 1 cattle receiving probiotics had a greater overall change in body weight, average daily gain, and gain:feed (P ≤ 0.05). No differences in group 2 or 3 growth performance were observed (P > 0.10). No treatment effect was observed for group 1 weekly chute exit velocity; however, group 2 and 3 cattle of the probiotics treatment had an overall slower weekly chute exit speed compared with control cattle (P ≤ 0.02). No treatment differences were observed in serum cortisol concentrations in group 2 cattle during weeks 0 or 6 (P ≥ 0.72). During the novel object test, group 1 cattle receiving probiotics exited the arena slower and group 2 cattle receiving probiotics crossed zone lines more frequently and had less frequent vocalizations compared with control treatment cattle (P ≤ 0.05). These results suggest that dietary probiotics can improve performance in weaned, growing calves and may have benefits for cattle handling without negatively affecting cattle welfare with respect to stress.