Location: Livestock Issues ResearchTitle: Weaned pigs experimentally infected with Salmonella display sexually dimorphic innate immune responses without affecting pathogen colonization patterns Author
|Carroll, Jeffery - Jeff Carroll|
|Gart, Elena - Texas A&M University|
|Bryan, Laura - Texas A&M University|
|Lawhon, Sara - Texas A&M University|
Submitted to: Translational Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/18/2016
Publication Date: 2/9/2017
Citation: Sanchez, N.C., Broadway, P.R., Carroll, J.A., Gart, E.V., Bryan, L.K., Lawhon, S.D. 2017. Weaned pigs experimentally infected with Salmonella display sexually dimorphic innate immune responses without affecting pathogen colonization patterns. Translational Animal Science. 1:69-76.
Interpretive Summary: A collaborative research effort was undertaken by scientists with the Livestock Issues Research Unit and Texas A&M University to determine whether sex influences the innate immune response to a Salmonella challenge in newly-weaned pigs. Pigs are susceptible to Salmonella challenge throughout the production cycle, but Salmonella infection may have more dire effects during the early post-weaning period. Further, previous research by our laboratory and others has observed sexually dimorphic responses to immune challenges in other livestock species. Thus, this study was designed to determine if the sex of weaned pigs influenced the response to an oral Salmonella challenge. Indeed, the results from this study suggest that sex of the pig influenced the innate immune response, with gilts producing a stronger response than the barrows. Specifically, gilts produced a greater intraperitoneal temperature response, altered cortisol response, greater lymphocyte response, yet decreased total white blood cell and neutrophil response. However, there was no effect of sex on the tissue translocation or shedding of the inoculated Salmonella within various tissues in the body. Therefore, these data provide further proof that sex can influence the innate immune response to a Salmonella challenge. Additionally, there may be benefits to managing male and female livestock differently. These data will be of interest to researchers in the field of stress and immune physiology, as well as swine producers.
Technical Abstract: Sexually dimorphic innate immune responses have been observed in several species, but have not been studied in response to a live pathogen challenge in pigs. This study aimed to elucidate sexually dimorphic innate immune responses along with Salmonella translocation patterns in newly weaned pigs orally inoculated with Salmonella. Newly weaned pigs (n = 8 gilts and 12 barrows; 6.2 ± 0.2 kg BW) were obtained from a commercial swine facility and were maintained in an environmentally-controlled facility in individual pens equipped with feeders and nipple waterers. Pigs were allowed ad libitum access to a commercial non-medicated starter ration and water throughout the study. On d 12, pigs were anesthetized to allow placement of a temperature measuring device (TEMP) in the abdominal cavity. On d 17, pigs were anesthetized and fitted with indwelling jugular vein catheters. On the following day (d 18), pigs were orally inoculated with 4.7x10^9 Salmonella Typhimurium. Blood samples were collected at 0.5-h intervals from -2 to 8 h, and at 8-h intervals from 8 to 72 h post-challenge. Whole blood was analyzed for complete blood cell counts using a ProCyte Dx Hematology Analyzer. Serum was isolated for measurement of cortisol. Following collection of the 72 h sample, pigs were humanely euthanized and tissues were collected for Salmonella isolation. There was a sex x time interaction (P < 0.001) for TEMP such that gilts had a greater TEMP response to the Salmonella challenge compared to barrows. There was also a sex x time interaction (P = 0.03) for serum cortisol with gilts having decreased cortisol at 16 h yet greater cortisol at 32 h than barrows. Barrows had greater total white blood cells (17.8 vs. 16.2 ± 0.4 103 cells/µL; P < 0.01; respectively) and neutrophils (7.8 vs. 6.1 ± 0.4 103 cells/µL; P < 0.01; respectively) than gilts. However, gilts had greater lymphocytes (9.6 vs. 9.0 ± 0.2 103 cells/µL; P = 0.05; respectively) than barrows. While immune parameters were influenced by sex, there was no effect of sex (P > 0.05) on Salmonella concentrations from fecal shedding 4 d post-inoculation in the cecum, mesenteric and subiliac lymph nodes, liver, spleen, gallbladder, or kidney tissues. These data demonstrate that weaned gilts produced a stronger immune response to a Salmonella challenge compared to barrows, without affecting the tissue translocation or shedding of Salmonella.