Impact of Commercial Preharvest Transportation and Holding on the Prevalence of Salmonella enterica in Cull Sows

Abstract

The objective of this study was to examine the prevalence of Salmonella enterica in cull sows at various stages from the farm to the abattoir. Cull sows (n=181) were sampled over 10 weeks. Fecal samples (10 g each) were collected on the farm ca. 24 h before loading and at the live-hog market ca. 3 h before loading. Samples (ileocecal lymph nodes, cecal contents, feces from the transverse colon, ventral thoracic lymph nodes, subiliac lymph nodes, sponge swabs of the left and right carcass sections, and chopped meat) were collected at the abattoir. The percentages of positive fecal samples on the farm and at the live-hog market were 3% (5 of 181 samples) and 2% (3 of 181 samples), respectively. After transport from the live-hog market (10 h) and holding at the abattoir (6 h), 41% (74 of 180) of cull sows yielded S. enterica in one or more sampled tissues. The isolation rate for total cecal contents (33%; 60 of 180 samples) was significantly (P<0.05) higher than those for ileocecal lymph nodes (7%; 12 of 181 samples), feces (11%; 20 of 181 samples), and ventral thoracic and subiliac lymph nodes (2%; 4 of 181 samples). Before a 2% lactic acid carcass wash (lasting 8 to 9 s), 14% (25 of 180) of carcasses were positive, compared with 7% (12 of 179) after the wash (P<0.05). Two S. enterica serotypes, Derby and Infantis, were found on the farm and at the live-hog market. At the abattoir, 12 serotypes that had not previously been found on the farm or at the live-hog market were recovered. The results of this study demonstrate that transport and holding practices may contribute to an increase in S. enterica infection prior to slaughter to levels much higher than those found on the farm.

Sub-Iliac Lymph Nodes at Slaughter Lack Ability to PredictSalmonella entericaPrevalence for Swine Farms

“…Although other studies have correlated Salmonella prevalence on farm with abattoir-collected samples from naturally infected farms (Hurd et al, 2001(Hurd et al, , 2002Korsak et al, 2003;Kranker et al, 2003;Larsen et al, 2003), the present study is unique because it matched individual pigs on the basis of fecal samples collected on farm with sub-iliac lymph node samples collected at slaughter. To the best of our knowledge, this type of individual animal sample matching in Salmonella and swineproduction-related research has not been reported previously.…”

“…The gutassociated lymph nodes can also be readily collected at slaughter, but these tissues are poor predictors of on-farm Salmonella status. The association is confounded by transient Salmonella introduced into the gut from the lairage environment immediately before harvest (Hurd et al, 2001(Hurd et al, , 2002Larsen et al, 2003).…”

“…Limited small studies with relatively large variation in prevalence suggested that nongut-associated lymph nodes may be a candidate tissue for evaluation: 0% in 300 superficial cervical lymph nodes (Bahnson et al, 2006b); 0.4% (1 of 272); and 2% (4 of 181) in ventral thoracic lymph nodes and sub-iliac lymph nodes (Hurd et al, 2001;Larsen et al, 2003). On the basis of these data, sub-iliac lymph nodes were selected as the tissue for evaluation as a screening tool as these tissues are rarely positive and easy to collect.…”

Prevalence, Enumeration, Serotypes, and Antimicrobial Resistance Phenotypes of Salmonella enterica Isolates from Carcasses at Two Large United States Pork Processing Plants

“…Known Salmonella contamination sources prior to entering the processing plant include swine production farms, transport trailers, and lairage pens (25,26,35,42,43,55). Transportation and lairage are likely sources of contamination, since exposure of uninfected swine to contaminated transport trailers or lairage pens results in rapid infection of lymph nodes, cecal contents, and rectal contents (26,28,45,46,55,57,59). Other potential sources of prescald carcass contamination include belts or elevators colonized by Salmonella.…”

Dose Determination for Acute Salmonella Infection in Pigs

“…Transmission of Salmonella from pigs with subclinical infections to naïve pigs during transportation and lairage has been proposed to be a major source of Salmonella introduction into the food chain (5,10). Events immediately prior to slaughter have been shown to correlate with an increased rate of Salmonella isolation from pig carcasses (5,6) and from pork products (2,8,12).…”