The Beauty of Butyrate
When it comes to the products of rumen fermentation, butyrate is a beneficial fatty acid superstar.
On a recent episode of the “Have You Herd?” podcast from the American Association of Bovine Practitioners, rumen microbiologist Dr. Jane Leedle discussed the products of rumen fermentation, and how they influence the stability and function of the gut microbiome.
In traditional rumen fermentation, she said feedstuffs are broken down into the “big 3” short-chain fatty acid end products – acetate, propionate, and butyrate. All three support critical functions in the ruminant animal.
“Acetate is important for milkfat production and cell membrane development,” she shared. “Propionate is the base molecule that forms glucose, which is central to nearly every metabolic process in mammals.”
Those activities are indeed important, but Leedle said it’s butyrate that really shines as a metabolic and immunological powerhouse.
“Butyrate is the key to keeping the animal’s intestinal lining intact,” said Leedle. “It is the supporting substrate that feeds the enterocytes, which are the cells that line the entire gastrointestinal (GI) tract.” She added that butyrate helps maintain a high mitotic index so the healthy development, shedding, and replacement of cells in the epithelium can carry on naturally.
Additionally, butyrate promotes immune function by stimulating epithelial cell receptors and helps support cells that maintain tight junctions in the epithelial lining, which are protective against disease-causing pathogens. A functional epithelium allows animals to neutralize invasive pathogens and maintain the integrity of the gut, so nutritional absorption can occur, feeding the desired functions of tissue growth and milk production.
Finally, butyrate partners with its fatty acid cousin, acetate, to synthesize longer-chain fatty acids that also are important for animal growth and productivity. Leedle added that the beneficial contributions of butyrate to the GI tract have been widely embraced by the human health and nutrition sector as of late.
But what happens when the GI microbiome is thrown out of balance? Leedle said both the beef and dairy industries struggle to walk the fine line between healthy rumen function and optimal animal performance.
“Rumen microorganisms are often balancing on the knife’s edge,” stated Leedle. She said the highly digestible feedstuffs of today and high-concentrate rations that are designed to support high levels of tissue production also can send the rumen environment into disarray by creating excessive levels of lactic acid and dramatically dropping the rumen pH.
Lactic acid is 10 times more acidic than the short-chain fatty acids. In that highly acidic environment, animals must channel their resources to neutralizing their blood pH as the rumen products are absorbed. As a result, milk, and butterfat production, along with appetite and dry-matter intake, can suffer.
Normal absorption of the short-chain fatty acids, including butyrate, also can be disrupted. This may result in insults to the rumen epithelium, sloughing of damaged tissues, and unprotected patches and lesions in the GI tract lining that can disrupt the healthy, protective process fueled by butyrate.
There are ways to prevent this acid overload, noted Leedle, including stepping up animals gradually onto high-performance rations so the rumen microbes have time to adjust. Consistent feed particle size, adequate bunk space, and preventing slug feeding also can help to maintain digestive consistency.
Boosting the rumen microbial population with a dose of an indigenous rumen organism, Megasphaera elsdenii, or “Mega e” in the dry cow period and again in early lactation also can help cows bridge the adjustment to a higher-concentrate diet. Megasphaera is an aggressive consumer of lactic acid and is native to the rumen environment.
As starch and sugar fermenters step up their game to digest readily fermentable feedstuffs and thus produce more lactic acid, naturally present Megasphaera will do the same to digest it – but it takes a while to catch up, during which the overwhelming effects of lactic acid can occur.
Leedle said providing an external boost of “Mega e” helps kickstart the rumen fermentation to devour the high levels of lactic acid, and convert it into beneficial acetate, propionate, and/or the ultimate GI good guy, butyrate.
