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ARS Home » Midwest Area » West Lafayette, Indiana » Livestock Behavior Research » Research » Publications at this Location » Publication #338057

Research Project: Safeguarding Well-being of Food Producing Animals

Location: Livestock Behavior Research

Title: Feed withdrawal and transportation effects on Salmonella enterica levels in market weight pigs

Author
item Eicher, Susan
item Rostagno, Marcos
item Lay, Jr, Donald - Don

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/10/2017
Publication Date: 7/13/2017
Citation: Eicher, S.D., Rostagno, M.H., Lay Jr, D.C. 2017. Feed withdrawal and transportation effects on Salmonella enterica levels in market weight pigs. Journal of Animal Science. 95:2848-2858. doi:10.2527/jas.2017.1454.

Interpretive Summary: Feed withdrawal and transport commonly occur together in pigs. Objectives were to determine if pre-slaughter stressors, feed withdrawal and transportation, affect the levels of a common foodborne pathogen (Salmonella), stress hormone concentrations, and immune functions in infected market pigs. Pigs were subjected to; no stress, feed withdrawal only, transportation only, or feed withdrawal followed by transport. Feed withdrawal by itself or followed by transportation caused an increase of Salmonella levels in the intestinal pouch that is similar to the human appendix. Very low levels of Salmonella were detected in feces. The stress hormone increased in pigs from all 3 stress treatments. Immune responses demonstrated immune suppression caused by the stressors and inflammatory responses. It is concluded that some typical pre-slaughter practices, such as feed withdrawal and transportation, lead to greater intestinal Salmonella levels and gut inflammation in market pigs, and consequently, to an increased food safety risk.

Technical Abstract: Feed withdrawal and transport commonly occur together in pigs. Objectives were to determine if these pre-slaughter stressors, feed withdrawal and transportation, affect the levels of Salmonella, stress hormone concentrations, and immune functions in infected market pigs. A 2 x 2 factorial analysis of a randomized complete block design with feed withdrawal and transport as fixed effects was used. Sixty market-weight pigs were individually inoculated with Salmonella enterica serovar Typhimurium. The experiment was replicated 3 times (blocking factor) with 20 pigs per replicate. Three days post-innoculation, the pigs were randomly assigned to 1 of 4 treatments (5 pigs per treatment in each /replicate), including; 1) control (Control, or no stress), 2) feed withdrawal (FW) for 12 h, 3) transportation (T) for 2 h, and 4) feed withdrawal for 12 h followed by transportation for 2 h (FWT). Feed withdrawal by itself or followed by transportation caused an increase of Salmonella levels in ileal contents (P < 0.05), whereas only FWT caused an increase of Salmonella levels in cecal contents (P < 0.05). Rectal contents (feces) consistently contained very low levels of Salmonella with no difference among treatments (P > 0.10). Cortisol increased in pigs from all 3 stressed treatments (P < 0.001) with T and FWT pigs having greater concentration than Control pigs (P < 0.05). While total white blood cell counts were lower for FWT pigs compared to Controls (P > 0.03). Each granulocyte percentage (neutrophil, eosinophils, and basophils) increased (P < 0.05) following transport but was attenuated (P > 0.05) by feed withdrawal with transport. Lymphocytes were suppressed (P < 0.05) by all stressors and the greatest suppression occurred when pigs were transported (T and FWT). However, monocytes were only suppressed (P < 0.05) from controls by FWT. Expression of IL-1 (produced by monocytes/macrophages) from the spleen cells, increased (P < 0.05) with FW compared with Controls, while its receptor antagonist was suppressed by FWT (P < 0.05). It is concluded that some typical pre-slaughter practices, such as feed withdrawal and transportation, lead to greater intestinal Salmonella levels and gut inflammation in market pigs, and consequently, to an increased food safety risk.