“We observed that in Salmonella challenged piglets the supplementary feeding of Enterococcus faecium NCIMB 10415 resulted in a significantly increased number of intraepithelial lymphocytes. The results indicate an immunomodulatory effect of E. faecium,” said the authors, writing in this month’s edition of writing in the journal, Veterinary Immunology and Immunopathology.
The study is part of a wider project, supported by the German Research Foundation (DFG) and involving a range of research institutes, looking at feed additives, probiotics and the role nutrition plays in the functioning of the intestines in the pig.
Lead researcher, Juliane Rieger, who is based at the Department of Veterinary Medicine at FU Berlin, told FeedNavigator the immune modulatory effect noted in this study was interesting but minimal.
“However, we did not carry out a phenotypic type analysis, so while the most prominent differences in IEL numbers were found in the population located at the enterocytes nuclear level, we still need to clarify whether it is a special IEL subpopulation involved in the maintenance of epithelial integrity,” she added.
Antibiotic alternatives
Salmonella Typhimurium infection is usually a self-limiting disease in pigs, said the study’s authors. Nevertheless, they note the pathogen represents a threat due to its potential to persist hidden in the porcine body for long periods.
“Formerly, auxinic antibiotics were used as feed additives to prevent infection outbreaks in pig production. Increasing rates of microbial resistances against such antibiotics have led to the ban on their usage in the European Union since 2006. Since then, much interest has been raised in the pursuit of potential alternatives such as probiotics,” add the team.
Probiotics are believed to have a beneficial effect on the gastrointestinal tract of animals, in terms of immune system modulation as well as regulation of the surface epithelium's cellular growth and apoptosis (Kreuzer et al 2012, Resta-Lenert and Barrett 2003, Walsh et al 2012 and Yan et al 2007).
Rieger said the results of the wider evaluation of E. faecium, under the DFG backed project, indicate there is little benefit from its inclusion in piglet diets in terms of weight gain or FCR. She said the research also underscores the importance of understanding the potential of a particular strain of probiotics when looking to achieve a health or productivity gain in pigs.
However, some of the teams found E. faecium increased the absorptive and secretory capacity of jejunal mucosa (Klingspor et al, 2013) and reduced levels of cytotoxic T cells in the jejunal epithelium (Scharek et al., 2005), while mucosal morphology, villus height, crypt depth and the enlargement factor were not influenced (Martin et al 2012 and Reiter et al 2006).
The study details
The goal of this study was to see whether the probiotic E. faecium strain improved histomorphological and immune system-related parameters of gut function after a Salmonella challenge in weaned pigs.
Weaned piglets were challenged with Salmonella enterica serovar Typhimurium DT 104, and half of them also received E. faecium NCIMB 10415 in their diets. Animals were sacrificed at day 2 and day 28 post infection (DPI), said the team.
The researchers said they calculated villus length and width, crypt depth and width as well as the actual enlargement of the intestinal epithelial surface and they evaluated the number of IEL was evaluated in sections of the porcine gut.
They said the effect of the factors of time post-infection and age and probiotic treatment on jejunal morphology and IEL numbers and distribution was evaluated by light microscopy.
The time post-infection had significant effects in both feeding groups. Animals sacrificed at DPI 28 had longer and wider villi, deeper and wider crypts, a higher villus enlargement factor, a higher ratio between villus and crypt enlargement factors as well as more IEL, noted the authors.
Higher IEL populations
The scientists said the probiotic treatment resulted in longer villi, a higher ratio of villus surface/crypt circumference enlargement factors and significantly more IEL.
“The larger total number of IEL displayed by the probiotic group resulted from significantly higher numbers of IEL at the nuclear and apical levels of the intraepithelial compartment but not from the number of IEL situated at the basement membrane. The probiotic effects were only measurable 28 DPI…
It is proposed that Enterococcus faecium NCIMB 10415 exerts an immune modulatory effect by increasing the numbers of intraepithelial lymphocytes,” they concluded.
Rieger is seeking funding to continue exploration of the effects of probiotics in livestock.
Source: Veterinary Immunology and Immunopathology
DOI: doi:10.1016/j.vetimm.2014.12.013
Title: Intraepithelial lymphocyte numbers and histomorphological parameters in the porcine gut after Enterococcus faecium NCIMB 10415 feeding in a Salmonella Typhimurium challenge
Authors: J. Rieger, P. Janczyk, H. Hünigen, K. Neumann, J. Plendl