Negative consequences of reduced protein diets supplemented with synthetic amino acids for performance, intestinal barrier function, and caecal microbiota composition of broiler chickens.

The consequences of feeding broiler chickens with reduced protein (RP) diets for gut health and barrier function are not well understood. This study was performed to elucidate the effect of reducing dietary protein and source of protein on gut health and performance parameters. Four experimental diets included 2 control diets with standard protein levels either containing meat and bone meal (CMBM) or an all-vegetable diet (CVEG), a medium RP diet (17.5% in growers and 16.5% in finisher), and a severe RP diet (15.6% in grower and 14.6% in finisher). Off-sex Ross 308 birds were assigned to each of the 4 diets and performance measurements were taken from d 7 to 42 post-hatch. Each diet was replicated 8 times (10 birds per replicate). A challenge study was conducted on additional 96 broilers (24 birds per diet) from d 13 to 21. Half of the birds in each dietary treatment were challenged by dexamethasone (DEX) to induce a leaky gut. Feeding birds with RP diets decreased weight gain (P < 0.0001) and increased feed conversion ratio (P < 0.0001) from d 7 to 42 compared with control diets. There was no difference between CVEG and CMBM control diets for any parameter. The diet containing 15.6% protein increased (P < 0.05) intestinal permeability independent of the DEX challenge. Gene expression of claudin-3 was downregulated (P < 0.05) in birds fed 15.6% protein. There was a significant interaction between diet and DEX (P < 0.05) and both RP diets (17.5% and 15.6%) downregulated claudin-2 expression in DEX-challenged birds. The overall composition of the caecal microbiota was affected in birds fed 15.6% protein having a significantly lower richness of microbiota in both sham and DEX-injected birds. Proteobacteria was the main phylum driving the differences in birds fed 15.6% protein. At the family level, Bifidobacteriaceae, Unclassified Bifidobacteriales, Enterococcaceae, Enterobacteriaceae, and Lachnospiraceae were the main taxa in birds fed 15.6% protein. Despite supplementation of synthetic amino acids, severe reduction of dietary protein compromised performance and intestinal health parameters in broilers, evidenced by differential mRNA expression of tight junction proteins, higher permeability, and changes in caecal microbiota composition.

Reduced environmental bacterial load during early development and gut colonisation has detrimental health consequences in Japanese quail.

Gastrointestinal colonisation by commensal microbiota is essential for the health and well-being of the host. We aimed to evaluate the influence of a reduced bacterial load environment on microbiota development and maturation, and the possibility of targeted colonisation via at-hatch administration of a selected bacterial strain. Japanese quail (Coturnix japonica) were inoculated within 1 h of hatch with a freshly grown culture of a Lactobacillus agilis isolate derived from a healthy adult quail. Hatchlings were kept in a mouse isolator for one week and then housed between one and four weeks of age, with a flock of normally grown adult quail to expose the bacteria-restricted birds to normal commensal quail bacteria. The bacterial isolate used to inoculate the birds was found to completely dominate the microbiota of the intestine of L.agilis at-hatch inoculated birds. Despite 3 weeks of co-housing of the test birds with an adult flock harbouring normal rich gut microbiota, neither the Lactobacillus inoculated nor PBS inoculated birds reached the level of bacterial diversity seen in birds raised under normal conditions. Neither PBS nor Lactobacillus inoculated birds were able to adopt normal quail microbiota after one week of restricted exposure to bacteria, indicating that contact with diverse microbiota during the early days of gut development in birds is critical for the establishment of healthy intestinal community. Very early intervention in the form of a suitable bacterial probiotic inoculant immediately post-hatch protected birds grown in extreme hygiene conditions from developing anomalous gut microbiota and intestinal damage. Our data shows that it is possible to induce dominance of desired strain using simple timed manipulation.

Oregano: A potential prophylactic treatment for the intestinal microbiota.

Prophylactic use of antibiotics in poultry diets has been identified as a problematic practice because of its potential to exacerbate the spread of antibiotic resistance to human pathogens. A range of countries have opted to completely ban the use of antibiotics in animal feed. The animal production industries are looking for alternative ways to effectively control pathogens while providing the performance benefits previously secured by antibiotics in feed. Here, we present evidence that oregano (Origanum vulgare) could be a potential alternative for pathogen control in the poultry industry. Broiler diets were supplemented with oregano powder (0%, 0.5%, 1%, and 2%) for six weeks. The capacity for pathogen control was estimated by microbiota profiling of the jejunum, ileum, and caecum content, and in the faeces, by 16S rRNA gene amplicon sequencing. The concentrations of short-chain fatty acids in the caecal content were also measured, as were villus/crypt parameters in the ileum. There were no differences among treatments in weight gain, feed intake, or the concentration of short-chain fatty acids. The height, width, and the surface area of villi in the ileum were not influenced by oregano addition. However, 1% and 2% of oregano produced a significant increase in the villus height to crypt depth ratio. There were no visible histopathological changes in the liver in control and treated groups. Although oregano had no significant effect on overall microbial diversity and gross composition, some specific genera, like Proteus, Klebsiella and Staphylococcus, which include known pathogens, were reduced in relative abundance by oregano treatment. Bifidobacterium, recognized as a beneficial and probiotic genus, was also suppressed by the oregano treatment.

At-hatch administration of probiotic to chickens can introduce beneficial changes in gut microbiota.

Recent advances in culture-free microbiological techniques bring new understanding of the role of intestinal microbiota in heath and performance. Intestinal microbial communities in chickens assume a near-stable state within the week which leaves a very small window for permanent microbiota remodelling. It is the first colonisers that determine the fate of microbial community in humans and birds alike, and after the microbiota has matured there are very small odds for permanent modification as stable community resists change. In this study we inoculated broiler chicks immediately post hatch, with 3 species of Lactobacillus, identified by sequencing of 16S rRNA and pheS genes as L. ingluviei, L. agilis and L. reuteri. The strains were isolated from the gut of healthy chickens as reproducibly persistent Lactobacillus strains among multiple flocks. Birds inoculated with the probiotic mix reached significantly higher weight by 28 days of age. Although each strain was able to colonise when administered alone, administering the probiotic mix at-hatch resulted in colonisation by only L. ingluviei. High initial abundance of L. ingluviei was slowly reducing, however, the effects of at-hatch administration of the Lactobacillus mix on modifying microbiota development and structure remained persistent. There was a tendency of promotion of beneficial and reduction in pathogenic taxa in the probiotic administered group.