RESTING ON TRANSPORT TRAILER REDUCES SALMONELLA AT HARVEST

A potential intervention strategy to reduce the prevalence of Salmonella enterica at harvest was evaluated, which consisted of resting pigs prior to harvest on their transport vehicle, instead of in the abattoir holding pen. Individual fecal samples were collected at the farm and at the abattoir (n= 120 pigs), where half of the pigs were unloaded, and moved to a holding pen, whereas the other half stayed in the transport trailer. After approximately 1.5 hour of resting, both groups were harvested on the same line and samples collected. The overall S. enterica prevalence was higher for pigs held in the abattoir pens (40.7% versus 13.3%, p<0.05). This study demonstrates that resting pigs on the transport vehicle as a method to avoid exposure to contaminated holding pens has the potential to decrease S. enterica levels entering the abattoir. Introduction Prior to harvest, pigs are held for a period of time to recover from the physiological changes attributed to handling and transport, improve meat quality, and to maintain a constant supply for the harvest line (Fortin, 2002; Warriss et al., 1992). However, we have demonstrated (Hurd et al., 2001; Hurd et al., 2002, Rostagno et al., 2003) that; 1. abattoir holding pens are highly contaminated with S. enterica, 2. swine exposed to a S. enterica-contaminated environment can become rapidly infected, and 3. much of the pre-harvest S. enterica infection in pigs occurs immediately before harvest during this rest period in the contaminated abattoir holding pen. Consequently, at harvest, the intestinal tract of the pigs and its associated lymph nodes are frequently contaminated or infected with S. enterica and provide the main source from which the bacteria may be spread in the abattoir. The more S. enterica pigs carry into the abattoir greater the risk of equipment and final product contamination. Intervention strategies to reduce the occurrence of S. enterica infections during the pre-harvest holding period are necessary, in order to reduce the number of pigs carrying the bacteria into the harvest process, consequently reducing the risk of pork and pork products contamination. Therefore, the main objective of this study was to evaluate a potential intervention strategy to reduce the prevalence of S. enterica-positive pigs at harvest, which consisted of resting pigs prior to harvest on their transport vehicle, instead of in the abattoir holding pen. Additionally, a secondary objective of this study was to evaluate the effect of transport on S. enterica prevalence. Many believe that the number of pigs shedding S. enterica will be increased after transportation and its associated stress. However, limited investigations have been conducted on the potential effects of transportation stress on S. enterica shedding in swine (Isaacson et al., 1999; Williams and Newell, 1970). Currently, there is still no conclusive data showing a direct association between transport and increased shedding of S. enterica. Materials and Methods A total of 120 grower-aged pigs (~25kg) were included in the experiment, divided in 4 replicates (n=30 pigs per replicate). This study was conducted in a very small commercial abattoir (~80 pigs per day) and using young pigs to control several logistic-related variables (e.g., unloading and moving pigs to the holding pen, moving pigs from the holding pen to slaughter, slaughter line speed, cross-contamination, and others) present in large commercial abattoirs that may interfere in the experiment. The small size of the plant allowed for moving the pigs very quickly from the transport trailer to the holding pen, and from the holding pen or transport trailer to the harvest line (~2 minutes). On the farm, prior to loading, five floor swabs were collected from the transport trailer, and a 1g fecal sample was collected from each pig (directly from the rectum). Pigs were loaded and immediately transported for 3-4 hours. Upon arrival at the abattoir, a 1g fecal sample was again collected, and 15 randomly chosen pigs were unloaded, and moved to a holding pen, whereas the remaining 15 pigs stayed in the transport trailer. Before placement in the holding pen, five floor swabs and one water sample from the drinker were collected to verify pre-existing contamination. After approxi-