Abstract
Cross-talk between the gut microbiota and neurochemicals affects health and well-being of animals. However, little is known about this interaction in chickens despite their importance in food production. Probiotics and live Salmonella vaccines are microbial products commonly given orally to layer pullets to improve health and ensure food safety. This study’s objective was to determine how these oral treatments, individually or in combination, would impact the gut environment of chickens. White Leghorn chicks were either non-treated (CON) or orally given probiotics (PRO), a recombinant attenuated Salmonella vaccine (RASV; VAX), or both (P+V). Birds were fed with probiotics daily beginning at 1-day-old and orally immunized with RASV at 4-days-old and boosted 2 weeks post-primary vaccination. At 5 weeks, ceca content, ceca tissues, and small intestinal scrapings (SISs) were collected from ten birds/group post-euthanasia for analyses. Catecholamine, but not serotonergic, metabolism was affected by treatments. Dopamine metabolism, indicated by L-DOPA and DOPAC levels, were increased in P+V birds versus CON and PRO birds. Based on 16S sequencing, beta diversity was more similar among vaccinated birds versus birds given probiotics, suggesting live Salmonella vaccination has a major selective pressure on microbial diversity. Abundances of Akkermansia muciniphila and Enterobacteriaceae positively correlated with levels of tyrosine and norepinephrine, respectively. Both enumeration and 16S sequencing, determined that PRO exhibited the greatest levels of Enterobacteriaceae in the ceca and feces, which was associated with greater IgA production against E. coli virulence factors as tested by ELISA. In summary, we demonstrate that using probiotics alone versus in combination with a live vaccine has major implications in catecholamine production and the microbiota of layer pullets. Additionally, unique correlations between changes in some neurochemicals and specific bacteria have been shown.
Highlights
The gut microbiota directly regulates host activities through the brain-gut-enteric microbiota axis (Rhee et al, 2009)
Microbial endocrinology research is virtually absent in chickens (Villageliú and Lyte, 2017), and no study has investigated the impact of oral vaccination on neurochemical synthesis in the gut of any animal model
Ceca content from P+V birds had the highest levels of 3,4-dihydroxyphenylacetic acid (DOPAC) compared to both chicks were either non-treated (CON) and PRO birds (P < 0.05; Figure 3B)
Summary
The gut microbiota directly regulates host activities through the brain-gut-enteric microbiota axis (Rhee et al, 2009). Live Salmonella vaccines are commonly used to reduce colonization of broad-host Salmonella enterica serovars in poultry (Hassan and Curtiss, 1997), the primary vehicle of human salmonellosis (Batz et al, 2012). These vaccines successfully reduce Salmonella ceca colonization (Muniz et al, 2017) and environmental contamination (Dórea et al, 2010). We establish a foundation for microbial endocrinology in the chicken gut by evaluating (i) neurochemical production and (ii) microbiome in the ceca of chickens given probiotics, a recombinant attenuated Salmonella vaccine (RASV), or both. We hypothesize that each treatment group will have a unique neurochemical and microbiome profiles
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