Effect of supplementing zinc oxide and biotin with or without carbadox on nursery pig performance

A 28-d nursery experiment was conducted to evaluate the effects of supplementing zinc oxide and biotin with or without a feed-grade antimicrobial agent (carbadox) on nursery pig performance, and plasma and fecal Zn concentrations. One hundred ninety-two crossbred pigs (initial BW = 5.94 +/- 0.03 kg; age = 17 +/- 2 d) were weaned and allotted to 1 of 8 dietary treatments based on BW, sex, and ancestry in a randomized complete block design (3 pigs/pen and 8 replications). Dietary treatments consisted of supplementation of ZnO at 0 or 3,000 mg/kg, d-biotin at 0 or 440 microg/kg, and carbadox at 0 or 55 mg/kg of diets in a 2 x 2 x 2 factorial arrangement of treatments. Phase 1 (d 0 to 14) and phase 2 (d 14 to 28) nursery diets were fed in meal form. Fecal samples were collected weekly, and blood samples were collected at d 0, 14, and 28 to determine fecal and plasma Zn concentrations, respectively. The basal diet contained 165 mg/kg of Zn as ZnSO(4) and 220 microg/kg biotin as d-biotin. Pigs supplemented with 440 microg/kg of d-biotin, independent of antibiotic and ZnO additions, had greater overall ADG (P = 0.02) than pigs fed no supplemental d-biotin postweaning. Overall ADG, ADFI, and G:F were not affected when pigs were supplemented with 3,000 mg/kg of Zn as ZnO or 55 mg/kg of carbadox. When pigs were fed 55 mg/kg of carbadox without supplemental biotin, plasma Zn concentration was less, whereas when biotin and carbadox were supplemented to nursery pig diets, plasma Zn concentrations did not decrease as with feeding carbadox alone (biotin x carbadox, P < 0.001). During wk 2, pigs fed 3,000 mg/kg of Zn as ZnO and 440 microg/kg of d-biotin had greater fecal Zn concentrations than pigs fed diets with only 3,000 mg/kg of Zn as ZnO (Zn x biotin, P = 0.04). In addition, pigs supplemented with 3,000 mg/kg of Zn as ZnO in combination with carbadox and d-biotin had greater fecal Zn concentrations compared with pigs fed diets containing no additional Zn during wk 2 (Zn x biotin x carbadox, P = 0.04). Fecal Zn concentrations increased over time (P < 0.001), and pigs fed supplemental ZnO had greater (P < 0.001) fecal Zn concentrations. These results indicate that feeding nursery pigs 440 microg/kg of d-biotin improved ADG, independent of zinc and carbadox supplementation, as well as increasing Zn excretion.