Effects of antimicrobial or probiotics on growth performance of 6 to 25 kg nursery pigs

Two 44-d experiments were conducted to determine the effects of antibiotic or different probiotics on growth performance of 6 to 25 kg pigs. In Exp. 1 and 2, 297 and 315 pigs (21-d of age; DNA Line 241 × 600; initially 5.8 and 6.0 kg BW) were used with 6 and 7 replications/treatment and 5 or 6 pigs/pen. Dietary treatments included a control diet, or the control diet with either carbadox (Mecadox-2.5 Phibro Animal Health, Teaneck, NJ) at 55 mg/kg, 0.05% BioPlus 2B (Chr. Hansen USA, Inc., Milwaukee, WI), or 0.20% of 1 of 6 DSM Probiotics (DSM Nutritional Products, Inc., Parsippany, NJ). For Exp. 1, pigs fed carbadox had increased (P < 0.05; SEM = 15.1) ADG (473 g) compared to pigs fed the control (392 g) or DSM Probiotic 1 (391 g), 2 (387 g), 3 (397 g), or 6 (401 g), with pigs fed Bio-Plus 2B (421 g), DSM Probiotic 4 (437 g) and 5 (413 g) intermediate. Pigs fed carbadox had greater (P < 0.05; SEM = 23.1) ADFI (708 g) compared to those fed the control (586 g) or DSM Probiotic 1 (586 g), 2 (583 g), or 3 (606 g), with pigs fed DSM Probiotics 4 (656 g), 5 (634 g), and 6 (610 g), and Bio-plus 2B (625 g) intermediate. For Exp. 2, pigs fed carbadox had greater (P < 0.05; SEM = 15.3) ADG (542 g) than all other treatments. Pigs fed BioPlus 2B had greater (P < 0.05) ADG (463 g) compared to those fed DSM Probiotic 3 (396 g), with the control (412 g) and DSM Probiotic 1 (434 g), 2 (424 g), 4 (441 g), 5 (421 g), and (430 g) intermediate. Pigs fed carbadox had increased (P < 0.05; SEM = 22.9) ADFI (802 g) compared to the control (621 g) and DSM Probiotics 1 (665 g), 2 (656 g), 3 (621 g), 4 (686 g), 5 (659 g), and 6 (670 g), with BioPlus 2B (708 g) intermediate. Treatments did not influence G:F in either experiment. In conclusion, pigs fed carbadox consistently had improved ADG and ADFI when compared to pigs fed the other treatment diets. There was no consistent probiotic response, but pigs fed diets with BioPlus 2B or DSM probiotic 4 elicited the greatest response of the probiotics tested.