Lawsonia intracellularis (Li) has been shown to be a causative agent in the development and onset of porcine enteropathy (PE). This intracellular organism needs energy from host cells to replicate and, in turn, cause a thickening of the mucosa of the intestines. This can lead to significant lesions in the intestines and decreased growth performance.
A presentation on the effect of flooring type and post-weaning production method on the timing of seroconversion of Li was presented at the 2009 meeting of the American Association of Swine Veterinarians. The research was performed by Peter Lasley, Dr. Rodger Main and Dr. Ginger Pelger.
Both clinical and subclinical infection can lead to a decreased growth rate, say the researchers, and Li has been correlated to poor performance in herds where chronic diarrhea was both present and absent. The costs related to increased feed costs and increased time to reach market weight due to Li can be significant.
The researchers note that understanding the age of seroconversion to Li and the prevalence within groups of pigs can aid in treatment decisions. It has also been suggested that management and environmental factors can play 
a role in the onset of disease, but there was little information regarding how production method (wean-to-finish compared to nursery-to-finish) affected the seroconversion of Li. Therefore, a study was developed to evaluate the effects of partially slatted (PS) versus fully slatted barns (FS), as well as wean-to-finish (WF) versus nursery-to-finish (NF) production on the timing of seroconversion to Li.
Methods
The researchers report that a total of 1,920 pigs in 64 growing pig sits (30 pigs/site) were bled to capture a representative sample of pigs in each age group (12, 15, 18, and 21 weeks of age), flooring type (PS or FS) and post-weaning production method (NF or WF). All growing pig sites were located in western Iowa and sampling was organized into manageable geographical regions with sites sampled over a four-week period in the summer of 2008.
All pigs were from the same production system and were fed a common feed-medication scheme. They were randomly sampled and distributed throughout the specified barn at each production site.
Results
The percentage of animals seroconverting to Li increased from 12 to 21 weeks of age, note the researchers. There was a tendency for NF pigs to have seroconverted at a higher rate than WF pigs, however, there was no effect of flooring type (PS vs. FS) on the rate of serconversion to Li. In addition, there were no significant interactions between pig age, flooring type or post-weaning production method.
In this study, the date suggested that at 12, 15, 18, and 21 weeks there was no difference in the seroconversion of pigs in PS and FS barns. The researchers report that this is in agreement with a study by Bane et al. where there was no significant association observed with porcine proliferative enteropathy (PPE) and either partially- or fully-slatted floors.
The researchers note that one reason for the discrepancy could be that the surveys included comparisons of pigs raised outdoors as well as indoors on PS and FS floors. It was also suggested that differences occurred when flooring was not cleaned sufficiently between groups of pigs.
Furthermore, say the authors, the data in this study suggest that pigs in traditional three-site production (NF) may seroconvert to Li at a faster and/or higher rate than pigs reared in a wean-to-finish (WF) production scheme. While further research may be warranted, this knowledge may be valuable to producers and veterinarians when determining appropriate and timely Li control strategies.
Editor’s Note: This commentary is sponsored by Boehringer Ingelheim Vetmedica, Inc. and was derived from proceedings of the 2009 AASV meeting in Dallas, TX. For more information, go to www.bivi.com
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