December 03, 2018

Interpretive Summary: Gut microbiota, diet, sex and feed efficiency in grow-finish pigs.

Interpretive Summary: Fecal microbial composition associated with variation in feed efficiency in pigs depends on diet and sex.

By: Anne Wallace

In this paper published in the April 2018 issue of the Journal of Animal Science, researchers studied the correlation between commercial grower-finisher pigs’ gut microbiota, diet, sex, and feed efficiency (FE).

Gut microbiota can be a critical factor to consider in livestock health and production. Fecal microbes play multiple roles that influence an organism’s health, immune system, digestion, and in livestock animals, FE. Microbes can break down indigestible feed fibers via anaerobic fermentation. Some fermentation byproducts, such as volatile fatty acids (VFA), are absorbed and used as an additional energy source by the host animal. Studying how fecal microbes may influence FE in pigs is therefore a very important area of study in the area of animal science.

A total of 160 grower-finisher pigs were separated into two groups based on feed. An American-based corn/soybean meal (CS) diet, and an EU/China-based wheat/barley/byproduct meal (WB) diet were used. Animal weights were taken at days 0, 56, and on the day of slaughter, when pigs’ weight reached approximately 120 kg. Fecal samples were collected on the day before slaughter and analyzed via 16S ribosomal RNA (rRNA) sequencing. Data from pigs with the 25% highest and lowest FE were evaluated to determine potential associations between microbiota and FE.

The authors reported significant differences in the fecal microbes of pigs at the phyla, class, genera and operational taxonomic unit (OTU, a proxy for microbial species) levels, based on diet. At the OTU level, for instance, Butyricicoccus pullicaecorum was more abundant in pigs fed the CS diet, whereas Blautia wexlera was more abundant in pigs fed the WB diet. Microbial fermentation abilities and the starch and fiber composition of the two diets likely accounted for these differences. The WB diet was reported to be higher in dietary fiber than the CS diet. The authors additionally reported a correlation between fecal microbes and FE for pigs fed the WB diet, but not for pigs fed the CS diet. For sex, fecal microbe differences at the genera and OTU level were noted, possibly explained by steroid sex hormones.

The results of this study do support the findings of prior studies that diet can influence fecal microbiota composition. In grower-finisher pigs, this study also suggests there may also be sex-based differences in microbes at the genera and OTU levels. This study also supports a further look into how WB diets may influence FE. However, the specific reasons for these diet and sex-based differences need to be studied in more detail (e.g. are VFA byproducts, or changes to gut barrier integrity or pig metabolism contributory? Which specific dietary fibers may influence the observed microbial changes?). The authors additionally note that their study is representative of only a single fecal sample collected from pigs’ colon. More in-depth studies collecting multiple samples over multiple time points and/or from different areas of the digestive tract (e.g. gut mucosa or ileum) may help to better and more comprehensively understand the relationship diet and gut microbes may have on FE.  

To view the article, “Fecal microbial composition associated with variation in feed efficiency in pigs depends on diet and sex,” visit the Journal of Animal Science.