Can Virus Transfer Be Reduced by a Staged Loading Procedure?

( National Pork Board and the Pork Checkoff )

The swine industry has made great efforts to improve biosecurity in breeding herds, but more work is needed to assess biosecurity protocols in wean-to-finish growing sites. As pork producers look for ways to continually improve biosecurity in light of increasing foreign animal disease threats, the Swine Health Information Center (SHIC) funded a study conducted by Iowa State University’s College of Veterinary Medicine to assess viral contamination during market hog load-out.

For pigs left in the barn after a load-out event, viral contamination may be transferred from the contaminated livestock trailer, driver or other carrying agents. How frequently does this occur? Is there a way to reduce frequency of viral contamination?

Researchers evaluated if implementing a staged loading procedure for market pigs is effective at preventing transfer of swine pathogen contaminated particles from livestock trailers to the barn using fluorescent powder (Glo Germ) as a marking agent to be able to see traffic patterns. According to a SHIC release, the study compared a conventional method of loading and a staged loading procedure.

The study revealed that four out of the five measuring points in the center alleyway of the barn had a level of contamination that measured significantly lower (p

In standard loading protocols, there is typically one line of separation between the livestock trailer and the end of the load-out chute. The protocol is that load-out crew members cannot cross over this line into the livestock trailer and the driver cannot cross over onto the chute. 

However, in a staged loading protocol, a second line of separation is implemented. One member from the load-out crew is stationed between the two lines of separation in which he or she cannot cross onto the livestock trailer or cross the second line of separation into the center alleyway of the barn. The remaining load-out crew members within the barn cannot cross the second line of separation into the load-out alleyway or chute. In the study, there were 10 replicates per loading procedure, SHIC said in the release.

Glo Germ was mixed with obstetric gel and dry wood chips and spread evenly on the floor of the livestock trailer, just inside the opening to the chute. Once load-out was observed and completed, researchers evaluated the Glo germ contamination using a grid of eight different measuring points within the chute after the first line of separation, two within load-out alleyway before the second line of separation, and five within the center alleyway.

The staged loading procedure completely eliminated contamination within the center alley measurements in one replicate, but, did not completely eliminate contamination in all other replicates, SHIC reports. Four out of the five points in the barn’s center alleyway had a level of contamination significantly lower in the staged loading protocol as compared to the conventional loading protocol. The difference at the fifth measuring point in the center alleyway of the barn was nearly significant (p=0.0573). The level of contamination measured at all other measuring points were not statistically significant between the two study groups.

“This study highlights the importance of additional layers of biosecurity. Adding layers of biosecurity can reduce the frequency that contamination is conveyed from the livestock trailer to the barn. When contamination crosses the first line of separation, the second line of separation serves as a backup to reduce contamination transfer from the loadout chute to the center alleyway in the barn,” the researchers noted in their report.

The study was carried out by Iowa State University College of Veterinary Medicine’s Derald Holtkamp, DVM; Chelsea Ruston, DVM; and Daniel Linhares, DVM. Further research will utilize this proof of concept. Work to develop an objective evaluation of swine health as affected by conventional vs. staged loading is in process, SHIC reports.

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