Friday, 21 July 2017 16:45

Pig microbiome makeup may influence animal growth rate

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Published in mBiosphere

The high cost of raising livestock to their slaughter weight drives some farms to provide antibiotics to their animals to promote growth: administering subtherapeutic doses of antibiotic drugs increases animal weight more quickly, which is good for the business of selling meat. The clear association of this practice with drug-resistant infections in people has led scientists to investigate alternative ways to increase animal feed efficiency (turning calories into fat and muscle), including exploring the role of the microbiome. A new Applied and Environmental Microbiology study finds a set of gut microbial biomarkers in pigs that may be associated with increased feed efficiency.

AppEnvMicro: Exploring a possible link between the intestinal microbiota and feed efficiency in pigs

Pig microbiomeCorrelations between bacterial taxa and pig physiological measures in order of residual feed intake Source.

In the study, first author Ursula McCormack and senior scientist Peadar Lawlor found microbial compositional differences that associate with feed efficiency. The experimental design used 16S rRNA gene sequencing of both fecal and intestinal samples to associate bacterial taxa with the residual feed intake (the difference between an animal’s actual and expected feed intake based on size and growth; a lower value indicates more efficiency). Eight bacterial genera correlated with low residual feed intake (higher feed efficiency), and five genera correlated with high residual intake (lower feed efficiency) at various times and locations in the pig intestine (see table, right). These bacterial genera may therefore help or hinder caloric intake from food (though the study establishes no causative link).

Physiological factors other than microbiome composition can also affect feed efficiency. The research team tested saliva levels of the hormone cortisol, another possible feed efficiency biomarker, but found no differences associated with residual feed intake. Nutrient absorption, and thus efficient caloric uptake, is also influenced by Intestinal architecture, but of the pig intestinal characteristics measured, only the number of goblet cells was found to associate with higher feed efficiency.

The researchers then used bioinformatics to predict functional differences associated with identified microbiome constituents that may explain greater or lesser feed efficiency. Biosynthesis of secondary metabolites, thiamine metabolism, and expression of the phosphotransferase system all associated with higher feed efficiency, as did lower abundance of a pathway involved in bacterial invasion of epithelial cells. These functions give the researchers manipulable pathways to test in future studies.

Microbiome research is a relatively new branch of microbial sciences with still-developing technologies, but this study highlights the power of potential applications. Understanding the microbial functions that lead to increased feed efficiency, combined with research on pre- or probiotic manipulation of pig gut flora, may someday lead to a satisfactory compromise both for the farming industry, which wants larger animals quickly, and for the public health officials seeking to fight antibiotic resistance by reducing the use of these drugs in agriculture. 

Pig photo credit

Last modified on Monday, 24 July 2017 13:35
Julie Wolf

Julie Wolf is the ASM Science Communications Specialist. She contributes to the ASM social media and blog network and hosts the Meet the Microbiologist podcast. She also runs workshops at ASM conferences to help scientists improve their own communication skills. Follow Julie on Twitter for more ASM and microbiology highlights at @JulieMarieWolf.

Julie earned her Ph.D. from the University of Minnesota, focusing on medical mycology and infectious disease. Outside of her work at ASM, she maintains a strong commitment to scientific education and teaches molecular biology at the community biolab, Genspace. She lives in beautiful New York City.