Molecular analysis of the caecal and tracheal microbiome of heat-stressed broilers supplemented with prebiotic and probiotic

Abstract

The gastrointestinal tract commensal microbiome is important for host nutrition, health and immunity. Little information is available regarding the role of these commensals at other mucosal surfaces in poultry. Tracheal mucosal surfaces offer sites for first-line health and immunity promotion in broilers, especially under stress-related conditions. The present study is aimed at elucidating the effects of feed supplementations with mannanoligosaccharides (MOS) prebiotic and a probiotic mixture (PM) on the caecal and tracheal microbiome of broilers kept under chronic heat stress (HS; 35 ± 2°C). Day-old chickens were randomly divided into five treatment groups: thermoneutral control (TN-CONT), HS-CONT, HS-MOS, HS-PM and HS synbiotic (fed MOS and PM). Caecal digesta and tracheal swabs were collected at day 42 and subjected to DNA extraction, followed by polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE) and pyrosequencing. The PCR-DGGE dendrograms revealed significant (49.5% similarity coefficients) differences between caecal and tracheal microbiome. Tracheal microbiome pyrosequencing revealed 9 phyla, 17 classes, 34 orders, 68 families and 125 genera, while 11 phyla, 19 classes, 34 orders, 85 families and 165 genera were identified in caeca. An unweighted UniFrac distance metric revealed a distinct clustering pattern (analysis of similarities, P = 0.007) between caecal and tracheal microbiome. Lactobacillus was the most abundant genus in trachea and caeca and was more abundant in caeca and trachea of HS groups compared with the TN-CONT group. Distinct bacterial clades occupied the caecal and tracheal microbiomes, although some bacterial groups overlapped, demonstrating a core microbiome dominated by Lactobacillus. No positive effects of supplementations were observed on abundance of probiotic bacteria.

Farm Stage, Bird Age, and Body Site Dominantly Affect the Quantity, Taxonomic Composition, and Dynamics of Respiratory and Gut Microbiota of Commercial Layer Chickens

“…The bacterial microbiota of the chicken gut has been studied extensively, mainly because of its association with weight gain in broilers (7,8,10,41,42) and egg production in layers (2)(3)(4)43). However, chicken respiratory bacterial microbiota studies are scarce (7,(23)(24)(25), and chicken layers have been reported in only two studies (23,25). The two studies on layers have provided much-needed data on respiratory microbiota, but they were limited in terms of sample sizes, sampling time points, and use of management systems that are not widely applied in commercial settings (23,25).…”

“…It was not possible to determine which OTUs corresponded with these pathogens, because numerous OTUs identified to the same genus by the SILVA database were often present in the same samples and those present rarely found matches of Ͼ99% identity within the NCBI 16S database. The persistence of bacterial pathogens at subclinical levels is common in commercial chicken flocks (7,15,24,57); this deserves further study, since these pathogens have the potential to exacerbate the effects of superinfecting transkingdom pathogens such as respiratory and enteric viruses (58)(59)(60). Furthermore, nonbacterial domains (archaea, protists, fungi, and viruses) should be considered if the roles of microbiota in chicken health and performance were to be fully understood.…”

“…Unlike the gut microbiota, the respiratory microbiota of both broilers and layers are understudied (7,(23)(24)(25). The respiratory microbiota of layers have been reported in only two studies, which showed variable results, possibly due to the effects of inadequate sample sizes and sampling time points, differences in sampling sites and techniques, layer breeds, and the use of management systems which are not widely applied in commercial settings (23,25).…”

“…The respiratory microbiota of layers have been reported in only two studies, which showed variable results, possibly due to the effects of inadequate sample sizes and sampling time points, differences in sampling sites and techniques, layer breeds, and the use of management systems which are not widely applied in commercial settings (23,25). In broilers, a 16S rRNA-based microbiota analysis revealed wide differences between tracheal and cecal microbiota in 42-day-old birds (24). In a previous paper, we defined the broiler trachea microbiota and found relationships to microbiota in the gut (cecum and ileum) and environment (litter) over several life cycles (7).…”

Effects of oxidative stress induced by high dosage of dietary iron ingested on intestinal damage and caecal microbiota in Chinese Yellow broilers

“…() demonstrated that excess dietary vanadium induced oxidative stress and altered the amount and diversity of intestinal bacteria in broilers (Wang et al., ). In addition, heat stress which is tightly linked with oxidative stress (Altan, Pabuçcuoğlu, Altan, Konyalioğlu, & Bayraktar, ; Lin, Decuypere, & Buyse, ) also resulted in change of the caecal microbiome in broilers (Lan, Sakamoto, & Benno, ; Sohail et al., ). In the current trial, there was no direct evidence to support that the excess iron itself or/and its induced oxidative stress disrupted the intestinal microbiota, because iron plays an essential role in virulence and colonisation of some bacteria such as Salmonella and Mycobactin, and their virulence is enhanced by excess iron (Schaible & Kaufmann, ).…”