# Assessment of Postbiotic, Mundticin-like Substance EM 41/3 Application in Broiler Rabbits
## 1 Introduction  
Nowadays, various innovative routes have been searched to sustain the healthy status of animals, including food-derived animals. Among food-derived animals also broiler rabbits can be included because of their easily digestible meat [1]. It could be recommended for people, e.g., in the period after illness convalescence. Rabbits can convert an approximately 20% of the protein they eat into edible meat, which is a higher amount than, e.g., in pig meat (16-18%) [2]. Taking into account innovative strategies, the use of probiotics, postbiotics, parabolics and other beneficial natural substances has dominated [3]. Recently, posbiotics have been aimed more frequently for this purpose. Postbiotic components arediverse and outperform live probiotics in terms of technology, safety, cost due to their sufficient absorption, metabolism and organismal distribution [4]. This term has been officially established by the ISAPP (The International Scientific Association of Probiotics and Prebiotics consensus statement on the definition and scope of postbiotics) [5]. A wide range of future perspectives for postbiotics has been reported, including health care.  
Mundticin-like substance (MLS) EM 41/3 is a thermo-stable substance of proteinaceous character. It is produced by horse-derived strain _Enterococcus mundtii_ EM 41/3. This MLS producer strain was isolated from Slovak horse breed [PERSON] from Muran. It possess a gene for Enterocin P and a gene for Mundticin KS [6]. Under in vitro conditions, MLS EM 41/3 has shown a broad antimicrobial (inhibitory) spectrum also inhibiting the growth of listeriae and staphylococci with activity up to 800 AU/mL [6]. Based on the origin of the MLS EM 41/3 producer strain, MLS EM 41/3 has been aimed predominantly for use in horse breeding [6]. However, before its use in horses, its functionality has been assessed in broiler rabbits. Rabbits are a food-derived animal category and they also represent suitable model animals. Reasons for this are, e.g., the small body size, short generation interval, rapid growth rate, high productive capacity, and their meat as has already been mentioned [1,7]. Resulting from our previous experiments using broiler rabbits and, e.g., postbiotics characterized at our laboratory (Enterocin M, Durancin ED 26E/7) and/or their producer strains, we have hypothesized that MLS EM 41/3 would have beneficial effects in animals without side effects [7; 8; 9; 10]. Enterocin M and Durancin ED 26E/7 application lead to a decrease in coliforms and pseudomonads (\(p<0.05\)) (\(p<0.001\)) in feces of rabbits. Both postbiotics (bactericons) mentioned stimulated enzymatic activity in caecum [7; 8; 9; 10]. In the case of Ent M, higher daily weight gains were also noted in rabbits, and stimulation of phagocytic activity (PA) (\(p<0.01\), \(p<0.001\)) not only in the case of Ent M but also in the case of its producer strain EFAL41 = CCM8558 [9]. Therefore, the aim of this study was to test the effect/functionality of MLS EM 41/3 in broiler rabbits with a focus on the following parameters: microbiota, phagocytic activity (PA) as a non-specific immunity parameter, glutathione-peroxidase activity (GPx) to assess oxidative stress, growth parameters, biochemistry in blood serum, jejun morphology, organic acids in cecal chyme, fecal enzymatic activity, and meat quality. Based on previous achievements with our enterocins and hypothesis formerly indicated, the study aim was to find if this new entercin can have similar effect in rabbits to previously detected and tested enterocins. In addition, these tests have been conducted to ensure rabbit health as food-derived animals and their meat as functional food. And as mentioned, the aim was also to test MLS EM 41/3 in a broiler rabbit animal model before its use in horses.