Effect of salt and water balance on colonic motility of white leghorn roosters

Intestinal nutrition: role of vitamins and biofactors and gaps of knowledge

The role of the microbiota in the health of the host is complex and multifactorial. The microbiota both consumes nutrients in competition with the host, but also creates nutrients that can be used by other microbes, but also the host. However, the quantitative impact of the microbiota on nutrient supply and demand is not well understood in poultry. The gastrointestinal tract is one of the largest points of contact with the external environment, and the intestinal microbiome is the largest and most complex of any system. Although the intestinal microbiota has first access to consumed nutrients, including vitamins, and is potentially a major contributor to production of various vitamins, the quantification of these impacts remains very poorly understood in poultry. Based on the human literature, it is clear that vitamin deficiencies can have systemic effects on the regulation of many physiological systems, beyond the immediate, direct nutrient functions of the vitamins. The impact of excessive supplementation of vitamins on the microbiota is not well understood in any species. In the context of poultry nutrition, in which substantial dietary excesses of most vitamins are provided, this represents a knowledge gap. Given the paucity of studies investigating the vitamin requirements of modern, high-producing poultry, the limited understanding of vitamin nutrition (supply and utilization) by the microbiome, and the potential impacts on the microbiome of the move away from dietary growth-promoting antibiotic use, more research in this area is required.

The microbiota also contributes a vast array of other metabolites involved in intramicrobiota communication, symbiosis and competition that can also have an impact on the host. Myo-inositol and butyrate are briefly discussed as examples of biofactors produced by the microbiota as mediators of intestinal health.

Comparison of fecal and cecal microbiotas reveals qualitative similarities but quantitative differences

Background

The majority of chicken microbiota studies have used the ceca as a sampling site due to the specific role of ceca in chicken productivity, health and wellbeing. However, sampling from ceca and other gastrointestinal tract sections requires the bird to be sacrificed. In contrast, fecal sampling does not require sacrifice and thus allows the same bird to be sampled repeatedly over time. This is a more meaningful and preferred way of sampling as the same animals can be monitored and tracked for temporal studies. The commonly used practice of selecting a subset of birds at each time-point for sacrifice and sampling introduces added variability due to the known animal to animal variation in microbiota.

Results

Cecal samples and fecal samples via cloacal swab were collected from 163 birds across 3 replicate trials. DNA was extracted and 16S rRNA gene sequences amplified and pyrosequenced to determine and compare the phylogenetic profile of the microbiota within each sample. The fecal and cecal samples were investigated to determine to what extent the microbiota found in fecal samples represented the microbiota of the ceca.

It was found that 88.55% of all operational taxonomic units (OTUs), containing 99.25% of all sequences, were shared between the two sample types, with OTUs unique for each sample type found to be very rare. There was a positive correlation between cecal and fecal abundance in the shared sequences, however the two communities differed significantly in community structure, represented as either alpha or beta diversity. The microbial populations present within the paired ceca of individual birds were also compared and shown to be similar.

Conclusions

Fecal sample analysis captures a large percentage of the microbial diversity present in the ceca. However, the qualitative similarities in OTU presence are not a good representation of the proportions of OTUs within the microbiota from each sampling site. The fecal microbiota is qualitatively similar to cecal microbiota but quantitatively different. Fecal samples can be effectively used to detect some shifts and responses of cecal microbiota.