Effects of Dietary Probiotics on Cattle Growth Performance

As the livestock industry shifts away from performance based antibiotics, probiotics may be a beneficial alternative for improving cattle growth and feed efficiency. Therefore, the objective of this study was to evaluate if dietary probiotics alter growth performance in cattle. Following a one week acclimation to treatment pens, two treatments were evaluated; 1) control, receiving feed without probiotics and 2) probiotics, receiving feed containing 10 g per head per day of probiotic granules (Probios feed granules, Chr. Hansen, Inc.). Two groups of cattle were used for this experiment. Group 1 had treatments 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). Group 2 had each treatment applied for 3 weeks to 7 weaned calves 7-10 months old (castrated males n=4, females n=3) using a crossover experimental design. Group 1 cattle were housed in groups of 8-9 cows per pasture within 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. Group 2 cattle were housed in groups of 2-3 calves per pen within three dry lots with access to a barn. Group 2 cattle were allowed access to ad libitum hay and received a corn-based feed ration of 4.5 kg per head per day. Weekly body weight and average daily gain (ADG) were measured for groups 1 and 2 and the gain to feed ratio was calculated for group 2. Data were analyzed using a mixed model in SAS including the fixed effects of treatment, herd (3 herds were used in this study) and covariate of age. No treatment differences were observed in group 1 on-test body weight, off-test body weight, or ADG (P>0.10). In Group 2, on-test body weight tended to be greater in the control treatment compared to the probiotic treatment (P=0.08); however, off-test body weight did not differ between treatments (P=0.85). Group 2 calves fed the probiotics treatment had a greater ADG and gain to feed ratio compared to the control treatment (P=0.04). In conclusion, probiotics did not alter performance in female cattle ≥1 year old. However, probiotics may improve growth performance in 7-10 month old calves.