Enhancing broiler gut health with compound probiotics
Several studies have shown probiotics can improve broilers’ production performance and economic benefits. In a recent study, researchers explored the benefits of compound probiotics on broiler gut health and growth performance.
Probiotics are live microbial feed supplements that have been reported to improve feed efficiency and immunity as they promote nutrient utilisation, regulate cellular and humoral immunity and improve intestinal microbial diversity. Probiotics as feed additives that improve gut health have the potential to replace antibiotic growth promoters in broilers, as they enhance growth performance and reduce the incidence of diseases without harming the environment or endangering consumer health.
Lactobacillus casei (L. casei), Lactobacillus acidophilus (L. acidophilus), and Bifidobacterium are beneficial gut microbiota as they help develop the gut’s immune system by activating the innate and adaptive immune responses. Studies have demonstrated that L. acidophilus, L. casei, and their metabolites have antibacterial activity that combat a variety of enteric pathogens and may enhance the composition of the intestinal flora by boosting the growth of more beneficial bacteria such as Bifidobacterium in the intestine. Bifidobacterium, which mainly exists in the large intestine in chickens, is a major producer of short-chain fatty acids (SCFAs). Besides their role as key substrates for energy production, SCFAs play a significant role in the regulation of intestinal health as they can inhibit the invasion and colonisation of pathogens by reducing intestinal pH.
Compound probiotics in broiler diet
To investigate the effects of compound probiotics, researchers used Arbor Acres broilers in four dietary groups:
- Control group: a basal corn-soybean meal diet without probiotics
- Probiotics I, probiotics II, and probiotics III were fed a basal diet plus 1, 5, and 10 g/kg compound probiotics (Lactobacillus casei: Lactobacillus acidophilus: Bifidobacterium = 1:1:2), respectively.
The density of viable probiotics was 1 × 1010 CFU/g. They evaluated the intestinal barrier function, intestinal immunity, and growth performance benefits of the compound probiotics for the experimental duration of 42 days (measurements were performed on days 21 and 42).
Enhancing intestinal barrier function
Tight junctions are an integral part of the intestinal barrier as they control the selective passage of molecules through cell channels by opening or closing the space between adjacent intestinal epithelial cells. This protects the host from external pathogens and endotoxins. Occludin, Claudin, and ZO-1 are the main tight junction proteins that regulate intestinal epithelial integrity and permeability. In addition to tight junction proteins, MUC2, a mucin produced by goblet cells, also has a key effect on intestinal homeostasis, and its destruction links to a variety of diseases and can lead to chronic intestinal inflammation such as leaky gut syndrome.
Results (Table 1) showed significantly higher Claudin, Occludin, MUC2, and ZO-1 mRNA expression levels in the broiler’s caecum at days 21 and 42 when compound probiotics were added, compared to the control group. The upregulation of the tight junctions was more pronounced with the highest inclusion level of 10 g/kg, especially for Occludin and ZO-1; the observed upregulation of the tight junction components was attributed to the increase of viable Bifidobacteria with a higher dosage that could produce more SCFAs, thus regulating the intestinal barrier function. “Compound probiotics can enhance intestinal barrier function by increasing the synthesis of tight junction proteins and mucins,” the researchers said.
Effects on intestinal immune function
Toll-like receptors (TLRs) are a class of proteins that play a key role in the innate immune system and the induction of adaptive immunity. For example, TLR4 and TLR2 can induce the nuclear factor (NF-κB) signal pathways through lipopolysaccharide (LSP) activation leading to the up-regulation of proinflammatory cytokines such as Interleukin-1 beta (IL-1β), and Interleukin-2 (IL-2). The release of pro-inflammatory cytokines leads to the activation of immune cells and their further production. In the current study, researchers found an increased relative expression level of intestinal immune-related genes in the probiotic groups; in the highest dosage of the compound probiotics (probiotics III, 10 g/kg), the TLR2, TLR4, IL-1β, and IL-2 mRNA relative expression levels increased most significantly. They concluded that supplementation of compound probiotics improves the gut microbiota and increases the intestinal health of broilers.
Promoting beneficial microbes
In this study, the researchers found the dominant flora of the caecum of 42-day-old broilers to be Firmicutes, Bacteroidota, and Proteobacteria. The addition of compound probiotics increased the relative abundance of beneficial microbes Firmicutes, Bacteroidota, and Verrucomicrobiota and reduced the relative abundance of harmful microbes such as Proteobacteria.
Improving growth performance
Supplementing compound probiotics promoted the growth performance of broilers in both the pre-growth phase (day 1-21) and late growth phase (day 21-42), and the promotion effect on the pre-growth period increased with the increase of probiotic dosage. The researchers suggested that compound probiotics as feed additives promote the growth performance of broilers by enhancing fibre digestion and enzyme activity, in addition to causing improvements in gut health.
Probiotics and essential oils
Research work is also evaluating the possible benefits of combining probiotics and other additives to assess the possibility of synergistic effects in promoting growth and gut health. In a recent broiler study published in the Indian Journal of Animal Sciences, researchers supplemented broiler diets with a combination of essential oil formula (mainly thymol, linalool and carvacrol) and probiotic (Lactobacillus fermentum), and found significant benefits on growth performance, immunity status, gut health and intestinal morphology in broilers fed the combination additive, compared to the individually supplemented additives.
Probiotics and MCFAs
In a conversation with Feed Innovation Services, a Dutch advisory and research partner in the feed and food chain, it came to light that the growing concern for feed-food competition is pushing stakeholders in the feed industry to focus on the utilisation of by-products (those not used as human food) for animal feed. As the project initiator, Feed Innovation Services is working with a consortium of companies involving feed producers, fatty acid producers and probiotic producers in the preparation phase for the development of products that combine probiotics and medium-chain fatty acids as additives in poultry diets to better utilise by-products not used as human food.
In conclusion, supplementation of compound probiotics in broiler diets improves the growth performance, intestinal barrier and intestinal immune function of broilers. In the face of the current feed-food competition, the exploration of the synergistic effects of probiotics and other feed additives could be valuable for sustainable feed production.
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