Monitoring for Enterobacteriaceae (EBAC) within feed mills is a demonstrated way to predict the risk of Salmonella spp. also being present. Viral pathogens in swine feed are a high interest health issue but there is little information available on how the presence of EBAC correlates with viral pathogen presence, especially on farms or in feed mills. The first step is to evaluate the efficacy of mill or farm level feed biosecurity. The purpose of a study conducted by Kansas State University and funded by the Swine Health Information Center (SHIC) was to identify EBAC presence in the feed manufacturing facilities and farms of a multi-farm system. That information was then used as a method of identifying feed-related and other biosecurity gaps in the feed mill and on the farm. Results showed compliance with biosecurity protocols had a substantial impact of EBAC prevalence and distribution throughout the feed mill. The results also emphasize the need for producers to evaluate feed ingredients as potential swine disease vectors, using resources provided by SHIC and industry partners to examine their suitability for use in rations.
For this study, three separate feed manufacturing facilities were evaluated and sampled, with a biosecurity evaluation and audit performed during each visit. A total of 573 samples were taken over the course of four days, with 381 of those samples consisting of feed ingredient or finished feed, and the remaining 192 samples environmental swabs, collected across the sites. Each swab was assigned one of four zones, including direct feed or ingredient contact surfaces (Zone 1), close proximity non-contact surfaces (Zone 2), non-contact surfaces without close proximity (Zone 3), and transient surfaces, such as moveable tools, employees, and vehicles (Zone 4). Swabs taken from a fourth facility, a multiplier farm, were assigned zones based on proximity to pigs. This included direct feed-contact surfaces (Zone 5), direct pig-contact surfaces (Zone 6) including pen flooring, pen walls, feeders, and waterers (pig contact), and non-pig contact surfaces (Zone 7) including employee walkways, work areas, feed storage, and fans (non-pig contact).
After collection, samples were shipped to the Iowa State University Veterinary Diagnostic Lab. Three types of bacteria with largest growth for each sample were identified and reported by assigning a growth index value. Bacterial growth results were assigned an index value of either 0, 1, 2, 3, or 4, based on reported growth, representing no, few, low, moderate, or high growth, respectively.
Audit scores for each facility were Site 1 – 83%, Site 2 – 67%, and Site 3 – 42%. Site 1, 83%, utilized locked exterior doors, required employees to change clothes and shoes prior to entry, and had handwashing stations located inside the doorway. The scale was located within a fenced perimeter and was used to weigh company-owned pigs occasionally. In Site 1, the scale, receiving pit, finished feed bin, and finished feed truck were the only feed-contact surfaces with detected EBAC. At Site 2, 67%, exterior doors were not locked and handwashing stations were not used except for restroom purposes, but employees changed clothes and shoes prior to entry. There was no perimeter fence and the scale was routinely used to weigh animals. There was a moderate quantity of EBAC detected in all feed contact surfaces tested, with high levels on the floor of the manufacturing area. At Site 3, 42%, exterior doors were not locked and handwashing stations not used except for restroom purposes, but employees changed clothes and shoes prior to entry. There was no perimeter fence and the scale was routinely used to weigh company-owned animals, as well as those from other sites within the region. While it was difficult to obtain samples from feed contact surfaces in Site 3, those collected all had high levels of EBAC.
There was significant evidence of a weak correlation (r = 0.201, P ≤0.0001) between EBAC presence and site. There was evidence of moderate correlation noted (r = 0.463, P ≤0.0001) between the zone and presence of EBAC, but no evidence of correlation (r = 0.028, P > 0.05) between zone a presence of fecal indicator bacteria.
Clearly, compliance with biosecurity protocols had a substantial impact of EBAC prevalence and distribution throughout the feed mill. As facilities begin to transition biosecurity from the farm to the feed mill, using environmental monitoring to evaluate risk for biosecurity gaps, as well as success in their mitigation, will be useful and necessary.
Funded by America’s pork producers to protect and enhance the health of the US swine herd, SHIC focuses its efforts on prevention, preparedness, and response. As a conduit of information and research, SHIC encourages sharing of its publications and research for the benefit of swine health. Forward, reprint, and quote SHIC material freely. For more information, visit http://www.swinehealth.org or contact Dr. Sundberg at psundberg@swinehealth.org.