Variable Abattoir Conditions Affect Salmonella enterica Prevalence and Meat Quality in Swine and Pork

Abstract

Research suggests that abattoir holding pens pose significant Salmonella enterica risk to swine immediately preharvest. The goal of this study was to evaluate those factors related to holding that increased the prevalence of S. enterica in swine at slaughter. To accomplish this goal, we focused on holding time and flooring. Our objectives were to (1) compare Salmonella enterica prevalence among pigs held for short (15-45 min) versus long (up to 4 h) periods before slaughter; and (2) determine the impact of flooring (slatted vs. concrete) as it relates to the prevalence of S. enterica. The study consisted of seven repetitions at a large volume (11,000 head/day) Midwest abattoir. Each repetition consisted of one truck load of pigs (n = 170) sorted into one of three groups: (1) animals held for a short time (15-45 min) on solid floors (short-hold); (2) animals held for 4 +/- 0.5 h on slatted floors; and (3) animals held for 4 +/- 0.5 h on solid concrete floors. At slaughter, samples were collected from 30 pigs in each group. Cecal contents (20 mL), feces (20 g), and the ileocecal lymph node were cultured for S. enterica. Additionally, the effect of holding time on meat quality parameters (loin pH at 35 min and 6 h, color, drip loss) was evaluated for the first four replicates. The proportion of S. enterica-positive samples was highest (p < 0.05) in the cecum of pigs held on solid concrete floors (72.4%), and slightly less for pigs held on slatted floors (63.3%). Animals held for less than 45 min before slaughter demonstrated the lowest proportion of S. enterica-positive samples (52.9%). The pig prevalence, as measured by any one of the three samples being positive, was significantly different (p < 0.05) between animals held on solid floors (81%) and those animals held for 45 min or less before slaughter (69%). Meat quality, as measured by multiple parameters, was adversely affected by lack of a rest period. The mean 24-h pH was significantly lower for the short-hold group compared to the other two groups. The mean Minolta L and the drip loss were significantly higher in the short-hold group. From this and other studies, it appears that elimination of the holding process is not feasible S. enterica control option, given current U.S. harvesting systems.

The role of transport, lairage and slaughter processes in the dissemination of Salmonella spp. in pigs in Ireland

“…Holding pigs in lairage for extended periods increases the contamination rate with Salmonella spp. because of the high prevalence of this pathogen in the lairage environment (Hurd et al, 2005;Larsen, Hurd, McKean, Griffith, & Wesley, 2004). Therefore, in the current study, a greater percentage of positive lymph node and caecal samples were expected to be linked to the lairage which suggests that other factors such as the farm may have had a role to play.…”

“…within some abattoir environments and in the current study PFGE analysis showed the same Salmonella serotypes were isolated from the lairage environment within abattoirs on different sampling days. Previous authors have shown lairage pens to be highly contaminated before pigs entered (Hurd, Gailey, McKean, & Griffith, 2005;Rostagno et al, 2003;. Furthermore, Hurd et al (2005) demonstrated differences between solid concrete and slatted floors with 95% of solid and 68% of slatted testing positive for Salmonella spp.…”

“…Previous authors have shown lairage pens to be highly contaminated before pigs entered (Hurd, Gailey, McKean, & Griffith, 2005;Rostagno et al, 2003;. Furthermore, Hurd et al (2005) demonstrated differences between solid concrete and slatted floors with 95% of solid and 68% of slatted testing positive for Salmonella spp. which is consistent with our findings in which the isolation rates were significantly higher in the lairage pens of abattoirs 1 and 3, both of which had solid concrete floors and were subjected to a daily washing routine with an intensive cleaning programme in place at the weekends.…”

Effect of feed texture, meal frequency and pre-slaughter fasting on behaviour, stomach content and carcass microbial quality in pigs

“…The standing position and the scarce exploratory behaviour seemed to have prevented the contamination of pigs' body or mouth with the faeces present on the vehicle floor. Furthermore, despite this behaviour, the short exposure of pigs to manure might have limited their contamination anyway as it is known that the risk for carcass faecal contamination increases with the animals' exposure time to manure in the surrounding environment (Hurd et al 2005). For personal use only.…”

“…The environmental factors contributing to the contamination of the mouth are not fully understood. However, it is expected that mouth contamination can result, at least in part, from the pigs' contact with manure present on the pen floor or walls while performing their natural exploratory behaviour (Hurd et al 2005). The presence of manure on the truck or lairage pen floor is a likely source of faecal bacteria (e.g., E. coli, Salmonella) and shedding rate of animals is known to be influenced by feed withdrawal time and stress (Gregory 1998;Reid et al 2002).…”