Contents lists available at ScienceDirect Research in Veterinary Science journal homepage: www.elsevier.com/locate/rvsc Dietary supplementation of encapsulated organic acids enhances performance and modulates immune regulation and morphology of jejunal mucosa in piglets Georgios A. Papadopoulos a , Theofilos Poutahidis b , Nicola Tallarico c , Alexandros Hardas b , Konstantinos Teliousis b , Georgios Arsenos a , Paschalis D. Fortomaris a,⁎ a Laboratory of Animal Husbandry, Faculty of Veterinary Medicine, School of Health Sciences, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece b Laboratory of Pathology, Faculty of Veterinary Medicine, School of Health Sciences, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece c Kemin Europa N.V., Toekomstlaan 42, 2200 Herentals, Belgium ARTICLE INFO Keywords: Organic acids Weaned piglets Performance Jejunal immune regulation Jejunal morphology ABSTRACT The aim of the study was to test two encapsulated regimens containing organic acids and/or zinc oxide (ZnO) on weaned piglet performance and jejunal mucosa morphology and immunity. For that, weaned piglets were allocated to treatments including control, supplemented with encapsulated organic acids (ACID group), and supplemented with organic acids and ZnO, both encapsulated (ACIDplus group). Antibiotics were used at similar concentrations in all groups during the first two weeks, but withdrawn from the ACIDplus group during the last three weeks of the experiment. ZnO was given with feed in the Control and ACID groups only during the first two weeks. The experimental period lasted 5 weeks. Piglets from the ACID group exhibited higher average daily gain compared to other groups during the last 3 weeks of the experiment (P< 0.05). The ACIDplus group performed similarly with controls. The mucosal height of jejunum was higher in both ACID (P < 0.01) and ACIDplus groups compared to controls (P < 0.05). Immunohistochemical analysis of jejunal mucosa, showed higher numbers of neutrophils in ACID and ACIDplus groups compared to controls (P < 0.01 and P < 0.001, respectively). Treatments had the opposite effect on mucosal regulatory T-cells (Foxp3-positive cells) in jejunum, being higher (P < 0.001) in control group compared to ACID and ACIDplus groups. The number of CD3-positive cells was higher (P < 0.05) in the ACIDplus and control groups compared to the ACID group. In conclusion, the encapsulated products used had beneficial effects on growth performance coexisting with improvements on jejunal histomorphology and modulation of mucosal immunity. 1. Introduction The weaning period is one of the most stressful phases in the life of the growing pigs (Kim et al., 2012). Technological improvements in housing, nutrition, health and management have been used to minimize some of the adverse effects of weaning stress (Campbell et al., 2013). Nonetheless, weaning remains a major predisposing factor of intestinal barrier dysfunction, digestive disorders and impaired performance (Kim et al., 2012). Weaning-associated diseases damage the intestinal mucosa resulting in decreased functional surface area for nutrient absorption (Hu et al., 2012), and therefore it is important to maintain a healthy mucosa and a selective intestinal barrier in this critical phase (Grilli et al., 2015). Despite the ban of using antibiotics as growth promoters in EU, they are still being used to prevent infections during the post-weaning period. The most frequently used antimicrobials applied were colistin (30.7%) and amoxicillin (30.0%) (Callens et al., 2012). Plausible explanations on their mode of action in piglets include the reduction of total bacterial load and pathogens, the enhancement of the mucosal layer and the direct modulation of the immune system (Allen et al., 2013). Single alternative substance treatments have so far failed to compete antibiotics in their performance-enhancing functions (Allen et al., 2013). This is probably the reason why a mixture of different dietary supplements is often used during the post-weaning period. In practice, the most common dietary supplements, are organic acids and ZnO. Particularly, ZnO has been shown to improve piglet growth performance and decrease the incidence of diarrhea (Carlson et al., 1999; Hill et al., 2001). However, feeding high levels of Zn by means of dietary supplementation of ZnO results in large quantities of Zn residues in manure and poses an environmental problem (Poulsen http://dx.doi.org/10.1016/j.rvsc.2017.04.014 Received 19 December 2016; Received in revised form 23 March 2017; Accepted 21 April 2017 ⁎ Corresponding author. E-mail address: fortomap@vet.auth.gr (P.D. Fortomaris). Research in Veterinary Science 115 (2017) 174–182 0034-5288/ © 2017 Elsevier Ltd. All rights reserved. MARK