ARS | Publication request: SOCIAL STRESS INCREASES FECAL SHEDDING OF SALMONELLA TYPHIMURIUM BY EARLY WEANED PIGLETS

Submitted to: Proceedings of Allen D Leman Swine Conference
Publication Type: Proceedings
Publication Acceptance Date: September 15, 2003
Publication Date: September 15, 2003
Citation: CALLAWAY, T.R., MORROW, J.L., EDRINGTON, T.S., GENOVESE, K.J., DOWD, S.E., DAILEY, J.W., ANDERSON, R.C., NISBET, D.J. SOCIAL STRESS INCREASES FECAL SHEDDING OF SALMONELLA TYPHIMURIUM BY EARLY WEANED PIGLETS. PROCEEDINGS OF ALLEN D. LEMAN SWINE CONFERENCE. 2003. V. 30(SUPPL.). P. 19.

Technical Abstract: Weaned pigs are often transported to grower facilities in groups and may be co-mingled without regard to farm of origin. The present study was designed to determine the effect of mixing and social stress on populations of Salmonella typhimurium in early weaned pigs. Piglets (7 d old; n = 14, in each of 2 replicates) were separated into 2 groups (control and mixed groups). One 'seeder' pig from each group was removed and inoculated via oral gavage with 10**9 CFU of S. typhimurium. Each seeder was placed into a pen (n = 4 pens), containing (n = 6) non-inoculated piglets. Each day, one piglet was exchanged between both mixed groups, to simulate mixing stress (long term); control pigs were not exchanged. Pigs were mixed daily for 5 d, and behavior was recorded continuously. Groups had significant behavioral differences; mixed pigs devoted significantly (P< 0.05) less time to eating (P< 0.05), to rooting (P< 0.05) and performed less agonistic (defensive) behavior (P< 0.05), indicating that they were under a form of social stress. Fecal swabs were enriched each day to qualitatively monitor shedding of S. typhimurium; more mixed pigs shed Salmonella than did control groups. Upon slaughter, rectal Salmonella concentrations in mixed pigs were greater (P< 0.05) than in control pigs but cecal Salmonella concentrations were not altered by mixing. When tissues from the tonsils, ileo-cecal lymph node, cecum and rectum were enriched for Salmonella, the mixed group demonstrated more susceptibility to tissue invasiveness (i.e., Salmonella-positive tonsils and lymph nodes) than did control pigs. Additionally, more pigs in the mixed group shed Salmonella 5 d after inoculation. These results indicate that social stress induced by mixing groups of weaned pigs may increase susceptibility to and/or fecal shedding of foodborne pathogenic bacteria.