Microbiome Modulation by a Precision Biotic in Broiler Chickens: a Field Study Validation

The increased recognition of antimicrobial resistance as a public health risk and, therefore, the imposed restrictions on the use of antimicrobial growth promoters (AGP), has driven the search for novel nutritional strategies for broiler chickens. The advances in molecular biology, analytics, and data science in the past years have enhanced our understating of the gastrointestinal tract (GIT) microbiome of chickens (Oakley et al., 2014; Sun et al., 2021). These novel approaches have led to the development of precision biotics (PB) that are able to specifically modulate microbiome pathways of the GIT of chickens (Walsh et al., 2021). It has been found that the targeted modulation of microbiome pathways, mainly related to protein metabolism and utilization, and short chain fatty acid (SCFA) production, improves the growth performance of chickens (Walsh et al., 2021; Jacquier et al., 2022), and increase the resistance against enteric stress (Blokker et al., 2022).

Precision biotics (PB) are glycans with specific glycosidic linkages (Jacquier et al., 2022) that can redirect the functions of the microbiome towards increased beneficial outputs, such as higher propionate production and nitrogen utilization (Walsh et al., 2021), regardless of the taxonomic composition of the microbial community. The objective of the present study was to evaluate the effect of the supplementation of PB on the growth performance, and cecal microbiome modulation of broiler chickens raised under field conditions.

A field trial was carried out at a commercial farm in Weifang City, Shandong Province, China. A total of 190,000-day-old Ross 308 straight-run broilers were randomly assigned to two dietary treatments. There were 5 houses per treatment with 19,000 birds per house. The two dietary treatments included a control diet (a commercial broiler diet) and a PB supplemented diet at 0.9 kg/MT (SymphiomeTM, DSM Nutritional Products, Switzerland).

At 42 d of age, the bird weight (BW) and feed intake (FI) of each house were recorded, the feed conversion ratio (FCR) was calculated and corrected with the final body weight (cFCR). Additionally, 40 birds/experimental group (80 birds in total) were randomly selected and the cecal content was aseptically collected. The samples were then sent to the lab and frozen at -80o C until further processing (DNA isolation and sequencing).

The microbial DNA from the cecal content sample was extracted using MagPure Stool DNA KF Kit B (Magen, Wuhan, China) following the manufacturer’s instructions. After DNA extraction, DNA was sequenced on the Illumina Hiseq platform (BGI-Shenzhen, China). The Functional Metagenomic Profiling and Microbiome Protein Metabolism Index (MPMI) was done as following: top microbial metabolic reactions (EC Numbers) and KEGG pathways responsible for distinguishing PB treated birds from Control were identified by sorting EC Numbers by “Mean Decrease in Accuracy” using the truncated random forest classifier. Each EC Number was then annotated and regrouped by KEGG Pathway.

Growth performance data were subjected to a student’s t-test using JMP Pro v. 16.0 (SAS Institute, Cary NC). House served as the experimental unit. Statistical significance was considered at P ≤ 0.05.

The supplementation of PB significantly improved the cFCR by 2.2 points (P = 0.04) and the EPI by 13 points (P = 0.04; Table 1).

The Local Fisher Discriminant Analysis (LFDA) of functional profiles (Figure 1A), showed a clear and significant qualitative separation in the cecal microbiome metabolism between control and PB supplemented birds. The abundance of pathways modulated by PB involved those associated with amino acid fermentation and putrefaction, particularly from lysine, arginine, proline, histidine and tryptophane (Figure 1B). Other pathways of importance related to purine, vitamins, carbohydrates, and ABC transporters were also modulated by the supplementation of PB. It was observed that the supplementation of PB significantly reduced the abundance of pathogen groups (Escherichia coli and Salmonella enterica) in the cecal microbiome (Figure 1C).

The PB used in the present study has been previously shown, in experimental research settings, to modulate the pathways of the cecal microbiome (Walsh et al., 2021), led to improved growth performance and welfare (Jacquier et al., 2022), and improved resilience of chickens against enteric stress (Blokker et al., 2022). This is the first study, however, conducted in field conditions where we demonstrated that the output obtained in research trials with the supplementation of chickens with PB are translated into field conditions.

In a previous meta-analysis by Walsh et al. (2021) it has been reported how the PB used herein consistently improved the growth performance of broiler chickens. Also, Jacquier et al. (2022) demonstrated that this PB not only improved the growth performance of chickens, but also had positive effects on the litter quality, which translated into enhanced gait score. In the present study, it was also observed that the supplementation of PB improved the cFCR by 2.2 points. The overall growth performance of the control group in the present study was satisfactory (final FCR of 1.457 vs 1.611 as the breed target) suggesting a good overall health of the birds. However, the cFCR was improved by 2.2 extra points with PB, which shows that by harnessing the full potential of the intestinal microbiome, precision nutritional ingredients may improve the performance of chickens to reach or to go beyond their genetic potential.

In conclusion, the results presented herein prove that the PB can efficiently modulate the intestinal microbiome of broiler chickens towards a beneficial metabolism related to protein metabolism and utilization with positive effects on the growth performance of the birds.