Interactions between corticotropin releasing factor signaling and prophylactic antibiotics on measures of intestinal function in weaned and transported pigs

Authors: MCCONN, BETTY - Oak Ridge Institute For Science And Education (ORISE); Kpodo, Kouassi; RIVIER, JEAN - Salk Institute; BEHAN, DOMINIC - Salk Institute; RICHERT, BRIAN - Purdue University; RADCLIFFE, JOHN - Purdue University; LAY, DONALD - US Department Of Agriculture (USDA); Johnson, Jay

Submitted to: Frontiers in Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/29/2023
Publication Date: 10/12/2023
Citation: Mcconn, B.R., Kpodo, K.R., Rivier, J.E., Behan, D.P., Richert, B.T., Radcliffe, J.S., Lay, D.C., Johnson, J.S. 2023. Interactions between corticotropin releasing factor signaling and prophylactic antibiotics on measures of intestinal function in weaned and transported pigs. Frontiers in Physiology. https://doi.org/10.3389/fphys.2023.1266409.
DOI: https://doi.org/10.3389/fphys.2023.1266409

Interpretive Summary: The weaning and transport process has the potential to induce stress and cause intestinal dysfunction in pigs. This may lead to an increased use of antibiotics in pig production that could contribute to antibiotic resistance. Improving our understanding of the mechanisms by which in-feed antibiotics improve biomarkers of intestinal health can assist in developing strategies to raise pigs with limited antibiotic use. Therefore, the study objective was to evaluate the interactions between the pig stress response and the efficacy of in-feed antibiotics on improving biomarkers of intestinal health and immune function in newly weaned and transported pigs. It was discovered that the physiological stress response played a role in the efficacy of in-feed antibiotics on improving intestinal health. Specifically, it was determined that eliminating the physiological stress response may decrease the need for providing pigs with in-feed antibiotics following potentially stressful events. Results from this study are expected to improve researcher’s understanding of the mechanisms by which in-feed antibiotics may improve pig health following exposure to stressors. This will allow for the development of alternative stress mitigation strategies.

Technical Abstract: Prophylactic antibiotics improve intestinal health and function in pigs; however, it is unknown whether their efficacy directly interacts with a pig’s stress response following weaning and transport. Therefore, the study objectives were 1) to evaluate the effects of corticotrophin releasing factor (CRF) receptor signaling on measures of intestinal function in weaned and transported pigs, and 2) to evaluate the interaction between CRF receptor signaling and a prophylactic antibiotic combination commonly provided following weaning and transport in the United States on measures of intestinal function in newly weaned and transported pigs. Mixed sex pigs (n = 56; 5.70 ± 1.05 kg body weight, BW) were weaned (20.49 ± 0.64 d), a blood sample was taken, pigs were given an intraperitoneal injection of saline (SAL; n = 28 pigs) or a CRF receptor antagonist (CRFA; n = 28 pigs; 30 µg/kg BW; Astressin B), and then were transported in a livestock trailer for 12 h and 49 min. Pigs were given second and third intraperitoneal injections at 4 h 42 min and 11 h 36 min into the transport process, respectively. Following transport, 4 SAL and 4 CRFA pigs were blood sampled and euthanized. The remaining 48 pigs were individually housed and assigned to a dietary antibiotics [AB; n = 12 SAL and 12 CRFA pigs; 50% castrated male and 50% female; chlortetracycline (441 ppm) + tiamulin (38.6 ppm)] or no dietary antibiotics (NAB; n = 12 SAL and 12 CRFA pigs; 50% castrated male and 50% female) treatment for 14 d post-transport. Blood was collected at 12 h and on d 3, 7, and 14, and then pigs were euthanized on d 7 (n = 24) and d 14 (n = 24) post-weaning and transport. Circulating cortisol was reduced (P = 0.05; 27.9%) in CRFA pigs when compared to SAL pigs post-weaning and transport. Circulating lipopolysaccharide was reduced overall (P < 0.01; 28.6%) in CRFA pigs when compared to SAL pigs during the transport phase. Adrenocorticotropic hormone tended to be reduced overall (P = 0.06; 12.0%) in CRFA pigs versus SAL pigs during the dietary treatment phase. On d 7, jejunal villus height and crypt depth was greater overall (P = 0.04 and 0.02, respectively; 22.5 and 14.4%, respectively) in AB-fed pigs versus NAB-fed pigs. On d 14, ileal crypt depth was reduced overall (P = 0.02; 5.1%) in CRFA pigs when compared to SAL pigs. Jejunal CRH mRNA abundance tended to be reduced overall (P = 0.09; 44.4%) on d 7 in CRFA pigs versus SAL pigs. Ileal CRH tended to be reduced overall (P = 0.07; 40.4%) on d 7 in AB-fed pigs when compared to NAB-fed pigs. On d 14, jejunal tumor necrosis factor alpha was reduced overall (P = 0.01; 30.7%) in AB-fed pigs versus NAB-fed pigs. On d 7, change in short-circuit current tended to be reduced (P = 0.07; 30.3%) in CRFA pigs fed NAB diet when compared to SAL pigs fed AB diet. In conclusion, CRFA pigs and pigs fed AB had similar biological intestinal function measures post-weaning and transport.