Abstract
Salmonellosis is a poultry industry and public health concern worldwide. Recently, Salmonella enterica serovar Heidelberg (SH) has been reported in broilers in Brazil. The effect of feeding a blend of three strains of Bacillus subtilis (PRO) was studied in broilers orally challenged (107 CFU/chick) or not with a SH isolated in south of Brazil (UFPR1 strain). Twelve male Cobb 500 broilers per pen were randomly assigned to six treatments in a 3 × 2 factorial experiment where PRO was added at 0, 250, or 500 g/ton of broiler feed and fed to either SH-challenged (SH Control, SH + PRO 250, and SH + PRO 500) or non-challenged birds (Control, PRO 250, and PRO 500). Broiler performance, histologic alterations in intestinal morphology, Salmonella quantification and immune cells counts in liver (macrophages, T CD4+ and T CD8+) were analyzed. Changes in the intestinal microbiota of broilers were also studied by metagenomics for Control, SH Control, SH + PRO 250, and SH + PRO 500 only. Feeding PRO at 250 or 500 g/ton reduced SH counts and incidence in liver and cecum at 21 days of age. It was observed that PRO groups increased the macrophage mobilization to the liver in SH-challenged birds (P < 0.05) but reduced these cells in the liver of non-challenged birds, showing an interesting immune cell dynamics effect. PRO at 250 g/ton did not affect gut histology, but improved animal performance (P < 0.05) while PRO at 500/ton did not affect animal performance but increased histologic alteration related to activation of the defense response in the ileum in SH challenged birds compared to control birds (P < 0.05). SH + PRO 500 group presented a more diverse cecal microbiota (Shannon–Wiener index; P < 0.05) compared to Control and SH Control groups; while SH + PRO 250 had greater ileal richness (JackkNife index) compared to Control (P < 0.05). PRO was effective in reducing Salmonella colonization in liver and cecum when fed at 250 or 500 g/ton to broilers inoculated with SH strain UFPR1. PRO promotes positive alterations in performance (at 250 g/ton), immune modulatory effect in the gastrointestinal tract, SH reduction, and intestinal microbiota modulation.
Highlights
Despite advances in the treatment of infectious diseases, pathogenic microorganisms such as Salmonella are an important threat to both human and animal health worldwide [1]
Probiotics are well documented to increase modulation of adaptive immunity [19]. These findings suggest a specific immune interaction of each probiotic strain used, and its abilities to improve protection against certain pathogens, maintaining health and homeostasis through intestinal and systemic immunomodulation, in order to enhance animal performance and health
The addition of PRO at 250 g/ton increased (P < 0.05) feed intake (FI) and body weight gain (BWG) from 1 to 21 days compared to Control (Table 2)
Summary
Despite advances in the treatment of infectious diseases, pathogenic microorganisms such as Salmonella are an important threat to both human and animal health worldwide [1]. Salmonella is a pathogen but it has the ability to live in animals and poultry as a transient member of the intestinal microbial population without causing disease. Colonization of most types of Salmonella enterica does not often affect poultry performance and asymptomatic infections may increase the likelihood of zoonotic transmission to humans through the food chain [2]. B. subtilis modulates the intestinal microbiota and favors the growth of lactic acid bacteria with recognized health-conferring properties [12]. B. subtilis has been studied and used as a feed additive to improve broiler performance [13, 14], modulate immune response [15, 16] and act as a prophylactic agent against bacterial diseases, by balancing gut microbiota [17, 18]
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