Abstract
Applying probiotics to improve gut health and growth performance of pigs is considered an effective approach to reduce use of antimicrobial growth promoters in swine production. Understanding the properties of these probiotics is a prerequisite for the selection of probiotic strains for pigs. Host-adapted probiotic strains were suggested to exert probiotic effects by different mechanisms when compared to free-living or nomadic probiotic strains. This study assessed the effect of probiotic intervention with Limosilactobacillus reuteri TMW1.656, a host-adapted species producing the antimicrobial compound reutericyclin, its isogenic and reutericyclin-negative L. reuteri TMW1.656ΔrtcN, and with Limosilactobacillus fermentum and Lacticaseibacillus casei, two species with a nomadic lifestyle. Probiotic strains were supplemented to the post weaning diet in piglets by fermented feed or as freeze-dried cultures. The composition of fecal microbiota was determined by high throughput sequencing of 16S rRNA gene sequence tags; Enterotoxigenic Escherichia coli and Clostridium perfringens were quantified by qPCR targeting specific virulence factors. Inclusion of host-adapted L. reuteri effectively reduced ETEC abundance in swine intestine. In contrast, nomadic L. fermentum and L. casei did not show inhibitory effects on ETEC but reduced the abundance of Clostridium spp. In addition, the increasing abundance of Bacteriodetes after weaning was correlated to a reduction of ETEC abundance. Remarkably, the early colonization of piglets with ETEC was impacted by maternal-neonatal transmission; the pattern of virulence factors changed significantly over time after weaning. Probiotic intervention or the production of reutericyclin showed limited effect on the overall composition of commensal gut microbiota. In conclusion, the present study provided evidence that the lifestyle of lactobacilli is a relevant criterion for selection of probiotic cultures while the production of antimicrobial compounds has only minor effects.
Highlights
The stress triggered by weaning and the immature immune system contributes to the susceptibility of weanling pig to gut microbial dysbiosis and pathogen infection (Katsuda et al, 2006; Gresse et al, 2017)
Clostridium perfingens Type C infections are common in neonatal piglets within 7 days of farrowing; infections with enterotoxigenic Escherichia coli (ETEC) are the most significant cause of post-weaning diarrhea (Kyriakis et al, 1996; Fairbrother et al, 2005)
Freeze-dried cultures of L. casei K9-1 and L. fermentum K9-2 with 109 CFU/g vegetative cell were provided by CanBiocin Inc. (Edmonton, AB, Canada), which were stored at 4◦C until use
Summary
The stress triggered by weaning and the immature immune system contributes to the susceptibility of weanling pig to gut microbial dysbiosis and pathogen infection (Katsuda et al, 2006; Gresse et al, 2017). Alternatives for protection against pathogen infection are required for early weaned pigs after the interrupted protection from maternal immunity. Probiotic bacteria are one of those alternatives and the primary trait required for the application of probiotics in weanling pigs is the ability to inhibit colonization of pathogen. Probiotic bacteria have been shown to reduce the pathogen load, Salmonella enterica and ETEC, in suckling and weaned piglets (Liao and Nyachoti, 2017; Wang and Gänzle, 2019). Lactic acid bacteria and lactobacilli have been used experimentally to reduce the pathogen load in suckling and weaned piglets (Liao and Nyachoti, 2017). Probiotic effects of strains that were administered to swine by these two methods of delivery methods, have not been compared directly
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