Caecal microbiota of chickens fed diets containing propolis

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For many years, subtherapeutic levels of antibiotics were widely used to promote gastrointestinal health and improvements in broiler performance. It is known that many natural products, for example, can positively modify the intestinal microbiota due to their antimicrobial properties without affecting human health (Windisch et al., 2008). Propolis, a substance produced by honeybees, has received special attention due to its antimicrobial, antioxidant, immunomodulatory, anti‐inflammatory and antiviral effects, among other biological and pharmacological properties (Silva‐Carvalho et al., 2015). The presence of aromatic acids, diterpenic acids, phenolic compounds and flavonoids in propolis may be responsible for improvements in the digestive and absorptive functions of broiler chicken gastrointestinal tract by modifying the intestinal microbiota (Mahmoud et al., 2014). In this context, propolis has been found to increase the presence of some beneficial bacteria (Mahmoud et al., 2014), such as the genus Lactobacillus spp. and Bifidobacterium, in faecal samples of chickens, while decreasing the incidence of pathogenic bacteria such as E. coli and Clostridium in the chicken gastrointestinal tract (Kačániová et al., 2012) and faecal samples (Abdel‐Mohsein et al., 2014).
Studies to evaluate the changes of the microbial population in the gut associated with propolis inclusion in the diet have primarily been realized by bacterial cultures (Abdel‐Mohsein et al., 2014; Mahmoud et al., 2014), but these methods have limitations, especially among the strict anaerobic micro‐organisms. In fact, only a proportion of the micro‐organisms present in the gut can be cultivable under standard laboratory conditions (Gong et al., 2007). However, more sensitive technologies are available, such as next‐generation sequencing (NGS) or qPCR, the fluorescence in situ hybridization using probes followed by flow cytometry has been efficient for detection of complex bacterial communities (Amann et al., 1990; Liao et al., 2012).
The majority of the studies on the effects of propolis have examined the effects of EEP on intestinal microbiota of chickens (Kačániová et al., 2012; Abdel‐Mohsein et al., 2014; Mahmoud et al., 2014). In order to extract the biologically active compounds from the solid portion of raw propolis and produce the ethanolic extract of propolis (EEP), raw propolis (RP) is processed using solvents (grain alcohol). High costs are associated with this process.
Morphophysiological changes in the gastrointestinal tract of chickens fed raw propolis were reported by Duarte et al. (2014) and it is possible that this product could also modulate the intestinal microbiota, with lower cost compared to EEP. It is important to evaluate the effects of both propolis‐derived products, due to differences in the concentration of active compounds to obtain a dose adjustment in order to promote a stimulation of such beneficial bacteria and protection against pathogenic micro‐organisms.
Lactobacillus, Clostridium and Bacteroides have been considered as important bacteria groups identified in caecal microbiota (Stanley et al., 2012); thus, it was chosen to determine the caecal population related to Lactobacillus spp., Bacteroidaceae, Clostridiaceae, Gammaproteobacteria and Enterobacteriaceae to evaluate the effects of inclusion of ethanolic extract of propolis and raw propolis in chicken diets on intestinal microbiota.
Thus, two experiments were conducted to evaluate the effects of different levels of EEP (trial 1) and RP (trial 2) in the diet from 1 to 21 days of age on broiler performance and on selected bacterial groups in the caecal microbiota using fluorescent in situ hybridization (FISH) measured by fluorescent activated cell sorting.
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