Comparison of Feed Additives during Preconditioning on Growth and Performance of Beef Calves

The objective of this study was to evaluate the response of weaned calves to different feed additives within a preconditioning supplement. Specifically, alternatives to antibiotics and ionophores were evaluated to determine their effectiveness in improving calf performance and mitigating the stress response observed during the weaning process. Following stratification by bodyweight, sex, previous castration status, and breed, 160 calves were randomly allotted to one of four treatments (n = 40 calves/treatment): 1) control calves (CON) were supplemented without additives; 2) Chlortetracycline calves (CTC) were supplemented with added chlortetracycline at 350 g/hd/d; 3) Monensin calves (RUM) were supplemented with added Rumensin at 175 mg/hd/d; and 4) Actigen® calves (ACT) were supplemented with added Actigen® at 5 g/hd/d. Calf bodyweight was similar (P = 0.16) among treatments at the beginning of the trial period. Over the 52-d preconditioning period, ACT resulted in the greatest gain response. Chlortetracycline calves exhibited similar (P = 0.35) weight gains to ACT, which were both greater (P < 0.005) than weight gains exhibited by RUM. Control calves were similar (P > 0.13) to both medicated treatments, but did not gain more (P = 0.02) than ACT. Plasma concentrations of haptoglobin and ceruloplasmin were similar (P > 0.70) among treatments; however, a day effect (P > 0.0001) was observed in both acute phase proteins measured. Our results indicate Actigen® may improve calf performance as effectively as chlortetracycline during a preconditioning period of this length, but neither additive was effective at mediating stress postweaning.