ARS | Publication request: Effects of syndyphalin-33 on immune function during a Salmonella challenge in recently weaned pigs

Submitted to: Journal of Animal and Veterinary Advances
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 30, 2009
Publication Date: October 21, 2009
Citation: Jenkins, S.J., Cooper, T.A., Roberts, M.P., Mathew, A.G., Carroll, J.A., Kattesh, H.G., Kojima, C.J. 2009. Effects of Syndyphalin-33 on immune function during a Salmonella challenge in recently weaned pigs. Journal of Animal and Veterinary Advances. 8(12):2562-2567.

Interpretive Summary: The process of weaning pigs involves many stressors, and the proliferation and introduction of a pathogen occurs more readily in new weaned pigs moved to a nursery facility. Therefore, a collaborative study with scientists from ARS and the University of Tennessee was conducted to evaluate the effects of Syndyphalin-33 (SD-33), a synthetic enkephalin with prolonged analgesic activity that has the ability to increase feed intake (FI), on immune cell populations with and without a concurrent inoculation with a common enteric pathogen, Salmonella enterica. Collectively, the results of this preliminary study suggest that the synthetic opioid SD-33 may modulate the immune axis in recently weaned pigs. The results also demonstrate that although co-treatment with SD-33 during an immune challenge did not result in increased feed intake, SD-33 exerted effects relating to circulating populations of immune cells that may enhance the ability of newly weaned pigs to cope with pathogenic challenges during this stressful period. Further work is needed to determine if this compound could potentially be uses as a management tool to enhance the overall well-being and productivity of newly weaned pigs.

Technical Abstract: The objective of this experiment was to characterize the effect of Syndyphalin-33 (SD-33) on immune cell populations with and without a concurrent inoculation with a common enteric pathogen, Salmonella enterica (SALM) in recently weaned pigs. On d 0, pigs (8 barrows and 6 gilts, 24 ± 1 d of age, 8.43 ± 0.82 kg) were weaned and fitted with jugular catheters. The following day, pigs were administered either SD-33 (0.5 micromole/kg, given i.m.) or saline (VEH; 0.5 mL, given i.m.) and SALM (oral gavage of 5 x 500 million CFU) or sterile broth (CON; 3 mL oral gavage) in a factorial arrangement such that 4 treatment groups existed: VEH+CON (n = 4), SD-33+CON (n = 3), VEH+SALM (n = 3), and SD-33+SALM (n = 4). There were no differences in feed intake (FI) or body weight (BW) among the SALM treated animals over time (P > 0.05). Cumulatively, FI among the SD-33+CON pigs was greater (P < 0.05) compared to the SD-33+SALM pigs. White blood cell (WBC) populations increased (P < 0.05) over the 4 d post-injection period. On d 2 post-challenge, circulating neutrophils and lymphocytes were lower (P < 0.05) in VEH+SALM but not in SD-33+SALM pigs relative to VEH+CON and SD-33+CON pigs, demonstrating the ability of SD-33 to abrogate the affect of Salmonella. Also, on d 2 post-challenge, circulating monocyte populations were greater (P < 0.05) in pigs receiving SD-33 relative to controls regardless of Salmonella treatment. The results of this preliminary study suggest that the opioid SD-33 may modulate the immune axis in recently weaned pigs.