Abstract
This review summarises the evidence for a link between the porcine intestinal microbiota and growth and feed efficiency (FE), and suggests microbiota-targeted strategies to improve productivity. However, there are challenges in identifying reliable microbial predictors of host phenotype; environmental factors impact the microbe–host interplay, sequential differences along the intestine result in segment-specific FE- and growth-associated taxa/functionality, and it is often difficult to distinguish cause and effect. However, bacterial taxa involved in nutrient processing and energy harvest, and those with anti-inflammatory effects, are consistently linked with improved productivity. In particular, evidence is emerging for an association of Treponema and methanogens such as Methanobrevibacter in the small and large intestines and Lactobacillus in the large intestine with a leaner phenotype and/or improved FE. Bacterial carbohydrate and/or lipid metabolism pathways are also generally enriched in the large intestine of leaner pigs and/or those with better growth/FE. Possible microbial signalling routes linked to superior growth and FE include increased intestinal propionate production and reduced inflammatory response. In summary, the bacterial taxa and/or metabolic pathways identified here could be used as biomarkers for FE/growth in pigs, the taxa exploited as probiotics or the taxa/functionality manipulated via dietary/breeding strategies in order to improve productivity in pigs.
Highlights
The pig intestinal microbiota is undeniably of critical importance to its host, conferring numerous services, such as nutrient digestion, disease resistance and production of vitamins and beneficial metabolites [1]
As with pig growth and composition traits, evidence of a link between the pig gut microbiota and feed efficiency (FE) comes from association studies in pigs ranked on measures of FE: Either feed conversion ratio (FCR) or residual feed intake (RFI)
(better FE) in the faeces [23], but was less abundant in a different cohort of feed-efficient pigs in the McCormack et al study [24]. It appears that bacterial taxa involved in nutrient processing and energy harvest, as well as those associated with anti-inflammatory effects and improved gut health, are enriched in more feed-efficient pigs, while potential pathogens are less abundant
Summary
The pig intestinal microbiota is undeniably of critical importance to its host, conferring numerous services, such as nutrient digestion, disease resistance and production of vitamins and beneficial metabolites [1]. Data on the role of Prevotella as a determinant of FE in pigs are conflicting (see section) Treponema is another genus that was higher in abundance in the caecum of leaner pigs [6], and a 16S rRNA gene (V4) sequencing study by Bergamaschi et al [18] found it to be associated with growth and fatness parameters. Looking at other 16S rRNA gene sequencing studies not represented, other bacterial taxa commonly associated with increased BW and leanness include Roseburia (another core member of the pig gut microbiome [16]) in the caecum [12,15] and faeces [20], probably due to its role in carbohydrate degradation and as a butyrate producer [21] It was less abundant in leaner pigs in the Yang et al study [6]. This is most likely due to the study’s lack of identification of taxa to the species level, an issue commonly encountered across the studies reported here due to the lack of use of shotgun metagenomics
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