Dietary bacitracin (Albac® and BMD®) improves ADG and FE in pigs in routine production environments (subjected to mixing and crowding stress)

Abstract Text: The primary objective of this study was to determine the effects of dietary Albac (bacitracin zinc) and BMD (bacitracin methylene disalicylate) on performance (ADG/FE) of pigs subjected to mixing and crowding stressors (MCS) seen in routine production.  In addition, changes in intestinal integrity and immunology were examined.  Ninety-six Yorkshire-cross barrows (~20 kg) were randomly assigned to 1 of 4 experimental diets: non-medicated (Control); non-medicated + MCS, 27.5 ppm bacitracin from Albac + MCS or 33.0 ppm bacitracin from BMD + MCS. Pigs were acclimated to diets and rooms for seven days, followed by 7 d of MCS. The MCS protocol included reducing pen size to 0.33m² per pig and co-mingling with unfamiliar pigs. Feed and water were provided ad libitum and body weights and feed intake were recorded over the 7 d experiment. On d 7, a subset (n=7-8 pigs/ treatment group) of pigs within each experimental group were euthanized for intestinal tissue collection and intestinal function and cytokine analyses. Ileum and proximal colon samples were collected and mounted on Ussing chambers to measure permeability via transepithelial electrical resistance (TER) and mucosal-to-serosal flux of FITC-Dextran, 4 kDa (FD-4 flux). Cytokines TNFα, IL-1β, and IL-8 were measured in ileal mucosal homogenates. Pigs subjected to MCS exhibited reduced (p<0.05) ADG but MCS had no effect on feed intake. Pigs fed BMD had greater ADG compared with MCS controls (ADG = 0.726±.03 kg/d and 0.895±.05 kg/d, for control MCS and MCS+BMD, respectively). Pigs subjected to MCS had reduced (p<0.05) ileal TER (TER, Ω.cm² = 46±2.9 and 35±2 for control and MCS controls pigs, respectively) and increased (p<0.01) FD-4 flux (ug.cm².min FD-4 flux = 0.005±0.0005 and 0.01±0.001 for control and MCS, respectively). Pigs fed either Albac or BMD had higher (p<0.05) ileal TER than MCS control pigs (TER, Ω.cm² = 35±2, 47±2, and 46±3, for MCS control, Albac and BMD, respectively). Pigs fed BMD had lower (p<0.05) intestinal FD-4 flux (ug.cm².min FD-4 flux = 0.01±0.001 and 0.006±0.0006 for MCS and MCS+BMD, respectively). lleal concentrations of TNFα, IL-1β, and IL-8 were reduced following MCS. Feeding Albac and BMD treatment prevented/restored MCS-induced suppression of TNFα (p<0.05).  These data demonstrate that Albac and BMD reduce the deleterious influence of MCS on pig ADG.  In addition, pigs subjected to MCS and consuming bacitracin exhibited improved intestinal barrier integrity. Albac^®and BMD^®are registered trademarks of Zoetis Florham Park, NJ

Keywords:

Bacitracin, Gut health, Production stress