Abstract
BackgroundThe porcine gastrointestinal microbiota has been linked to both host health and performance. Most pig gut microbiota studies target faecal material, which is not representative of microbiota dynamics in other discrete gut sections. The weaning transition period in pigs is a key development stage, with gastrointestinal problems being prominent after often sudden introduction to a solid diet. A better understanding of both temporal and nutritional effects on the small intestinal microbiota is required. Here, the development of the porcine ileal microbiota under differing levels of dietary protein was observed over the immediate post-weaning period.ResultsIleal digesta samples were obtained at post-mortem prior to weaning day (day − 1) for baseline measurements. The remaining pigs were introduced to either an 18% (low) or 23% (high) protein diet on weaning day (day 0) and further ileal digesta sampling was carried out at days 5, 9 and 13 post-weaning. We identified significant changes in microbiome structure (P = 0.01), a reduction in microbiome richness (P = 0.02) and changes in the abundance of specific bacterial taxa from baseline until 13 days post-weaning. The ileal microbiota became less stable after the introduction to a solid diet at weaning (P = 0.036), was highly variable between pigs and no relationship was observed between average daily weight gain and microbiota composition. The ileal microbiota was less stable in pigs fed the high protein diet (P = 0.05), with several pathogenic bacterial genera being significantly higher in abundance in this group. Samples from the low protein and high protein groups did not cluster separately by their CAZyme (carbohydrate-active enzyme) composition, but GH33 exosialidases were found to be significantly more abundant in the HP group (P = 0.006).ConclusionsThe weaner pig ileal microbiota changed rapidly and was initially destabilised by the sudden introduction to feed. Nutritional composition influenced ileal microbiota development, with the high protein diet being associated with an increased abundance of significant porcine pathogens and the upregulation of GH33 exosialidases—which can influence host-microbe interactions and pathogenicity. These findings contribute to our understanding of a lesser studied gut compartment that is not only a key site of digestion, but also a target for the development of nutritional interventions to improve gut health and host growth performance during the critical weaning transition period.
Highlights
The porcine gastrointestinal microbiota has been linked to both host health and performance
Less studies have been done on the small intestinal microbiota, primarily due to the challenge of Pollock et al anim microbiome (2021) 3:58 obtaining samples and the assumption that faecal material can be considered a proxy for upstream gut microbiota interactions [1]
We have shown that both enterotoxigenic Escherichia coli exposure and an increase in dietary crude protein (CP) level have a significant impact on ileal microbiota composition in weaner pigs, in the absence of changes at faecal level [1]
Summary
The porcine gastrointestinal microbiota has been linked to both host health and performance. We have shown that both enterotoxigenic Escherichia coli (an important causative agent of postweaning diarrhoea) exposure and an increase in dietary crude protein (CP) level have a significant impact on ileal microbiota composition in weaner pigs, in the absence of changes at faecal level [1]. In our previous work [1], we considered the spatial variation in the gut microbiota in response to dietary CP manipulation and enterotoxigenic Escherichia coli exposure but have yet to explore temporal changes in ileal microbiota composition. We compared ileal bacterial communities from pigs fed a low CP (LP) and a high CP (HP) diet to gain information on the effects of CP nutrition on ileal microbiota composition and function through the immediate post-weaning period, with consideration of how weight gain may be linked to ileal microbiota composition
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