PSIV-18 Effect of sub-therapeutic antibiotics and pharmacological zinc oxide on nursery pig performance and intestinal integrity and function

Abstract

Abstract The objective of this study was to evaluate the impact of sub-therapeutic chlortetracycline (CTC) and pharmacological zinc oxide on nursery pig performance and intestinal integrity and function. Twenty-four newly weaned pigs (4.51 ± 0.21 kg BW) were randomly assigned to one of three dietary treatments for 21 d (n = 8/treatment): 1) Control diet (NC), 2) NC + Zinc oxide at 3000 ppm for 7 d followed by 2000 ppm for 14 d (ZnO), and 3) NC + 40 ppm CTC for 21 d (sCTC). Pig ADG, ADFI, and G:F were determined for the overall 21 d test period. At d 21, all pigs were euthanized for tissue collection. Jejunum and ileum ex vivo transepithelial resistance (TER), macromolecule (FD4) flux, and active glucose and glutamine transport were assessed in modified Ussing Chambers. Additionally, jejunum brush border enzyme and Na+/K+ ATPase activities were determined. Morphology and T-cell abundance were determined in all ileum sections by H&E staining and immunohistochemistry, respectively. Compared to the NC, sCTC and ZnO increased ADG (0.14, 0.20 and 0.23 kg/d, respectively, P = 0.020). Overall ADFI was increased by 150% due to sCTC compared to the NC and ZnO pigs (P < 0.05). G:F was increased due to ZnO and sCTC compared to the NC (0.82, 0.63 and 0.47, respectively, P < 0.01). Jejunum and ileum ex vivo function and integrity did not differ. Ileal villus height was increased in the NC compared to sCTC treatment (P < 0.01), but not different from the ZnO treatment. In the ileum, total T-cell number per unit area was significantly lower in the ZnO segments compared to sCTC and NC (0.95, 2.29 and 2.59 count per μm2, respectively, P = 0.05). These data indicate that ZnO and sCTC improved pig performance but did not directly alter small intestinal integrity and function. However, mucosal T cell abundance was altered.