J Anim Physiol Anim Nutr. 2019;00:1–7. wileyonlinelibrary.com/journal/jpn | 1 © 2019 Blackwell Verlag GmbH Received: 25 January 2019 | Revised: 17 July 2019 | Accepted: 20 July 2019 DOI: 10.1111/jpn.13182 ORIGINAL ARTICLE Microstructure of the small intestine in broiler chickens fed a diet with probiotic or synbiotic supplementation Joanna Bogucka 1 | David Miguel Ribeiro 2,3 | Monika Bogusławska‐Tryk 1 | Agata Dankowiakowska 1 | Rosário Plácido Roberto da Costa 2,4 | Marek Bednarczyk 5 1 Department of Animal Physiology, Physiotherapy and Nutrition, UTP University of Science and Technology in Bydgoszcz, Bydgoszcz, Poland 2 Polytechnic Institute of Coimbra, Agricultural College of Coimbra, Coimbra, Portugal 3 LEAF Linking Landscape, Environment, Agriculture and Food, Instituto Superior de Agronomia, University of Lisbon, Lisbon, Portugal 4 CERNAS ‐ Research Centre for Natural Resources, Environment and Society, Coimbra, Portugal 5 Department of Animal Biotechnology and Genetic, UTP University of Science and Technology in Bydgoszcz, Bydgoszcz, Poland Correspondence Monika Bogusławska‐Tryk, Department of Animal Physiology, Physiotherapy and Nutrition, Faculty of Animal Breeding and Biology, UTP University of Science and Technology, Mazowiecka 28, 85‐084 Bydgoszcz, Poland. Email: Monika.Boguslawska‐Tryk@utp.edu.pl Abstract The aim of the study was to determine the effect of dietary supplementation of a probiotic and a synbiotic on the morphometric parameters of the small intestine of broiler chickens. The experiment was conducted on three hundred sixty, one‐day‐old female Ross 308 chicks, which were randomly selected from 20,000 birds and divided into three treatment groups (n = 120) with ten replicates per treatment. The control group (C) was fed a commercial diet, the probiotic group (PRO) was fed the same diet with an added 1% of the probiotic Lavipan® (Lactococcus lactis, Carnobacterium di- vergens, Lactobacillus casei, Lactobacillus plantarum and Saccharomyces cerevisiae), and the synbiotic group (SYN) was fed the commercial diet with an added synbiotic: 0.8% of the prebiotic RFO (extracted from lupin seeds) and 1% Lavipan®. According to the manufacturer's data, apart from the typical probiotic action,microorganisms con‐ tained in the preparation release anti‐bacterial substances (hydrogen peroxide and bacteriocins) and, therefore, are antagonistic towards pathogenic bacteria present in the gut of animals. Supplementation took place in the first seven days of rearing, and all birds had ad libitum access to water and feed during the 42 days of the experiment. On the last day, all birds were slaughtered and samples from three segments of the small intestine were taken. Villi area, height, width and crypt depth ratios were read using Multiscan software. Synbiotic supplementation increased the BWG of broilers from first to tenth day of rearing, compared to the control group. The PRO group had improved villi morphometric parameters of the duodenum. In the jejunum and ileum, both bioactive substances improved villus width and villus surface area. Crypts were deeper in the small intestine of birds supplemented with bioactive substances, which allows greater renewal of the villi. As expected, the intestinal morphometric parameters of broiler chickens benefited from bioactive substance supplementation. KEYWORDS broiler chicken, probiotics, small intestine morphology, synbiotics 1 | INTRODUCTION The European ban on the use of antibiotics as growth promoters (AGP) introduced by the European Union has increased the interest of re‐ searchers in new and safer alternatives (European Union, 2006). In this respect, three new concepts are gaining importance: probiotics, prebiot‐ ics and synbiotics. Probiotics are preparations or products containing viable, de‐ fined microorganisms, which alter the gut microflora (by implan‐ tation or colonization), and thereby exert beneficial health effects