Thermodynamics of Rumen VFA Studied

Researchers at Virginia Tech University have investigated what effects infusing extra acetate or propionate, or lowering the pH, would have on thermodynamics of VFA in the rumen.
Researchers at Virginia Tech University have investigated what effects infusing extra acetate or propionate, or lowering the pH, would have on thermodynamics of VFA in the rumen.
(ResearchGate)

Acetate, propionate, and butyrate make up about 95% of the volatile fatty acids (VFA) in the rumen. In turn, they provide about 75% of total metabolizable energy (ME) for ruminants.

Researchers at Virginia Tech University have investigated what effects, if any, infusing extra acetate or propionate, or lowering the pH, would have on thermodynamics of VFA in the rumen. Their studied, was published recently in the Journal of Dairy Science.

The team wanted to explore rumen VFA thermodynamics to determine whether or not ruminal efficiency could be manipulated and improved. Their work was based on previous research indicating  that the stoichiometry of production of the three major VFA determines the amounts of methane (CH4) and carbon dioxide (CO2) that are generated.

That research also noted that the profile of VFA formed in the rumen reflects different fermentation pathways and partially determines the efficiency of energy utilization. They also cited previous work indicating that thermodynamics control which pathway branches are available during ruminal fermentation, and thus the final VFA produced.

Their in vitro analysis started using ruminal fluid as a base substrate. Using dual-flow continuous culture, included 4 study groups:

  1. Control – pH buffered to an average of 6.75
  2. Control plus 20 mmol/day of infused acetate
  3. Control plus 7mmol/day of infused propionate; and
  4. A 0.5-unit decline in pH, created by adjustment of the buffer

 

All four fermenters were fed 40 grams a daily “diet” of a 50/50 mix of whole alfalfa pellets and concentrate mix pellets.

After 7 days of this feeding routine, sequential, continuous infusions were fed to all four batches, containing a consistent mix of sodium acetate (3.5 mmol/day); sodium propionate (2.9 mmol/day); and sodium butyrate (0.22 mmol/day).

Filtered, liquid effluent was extracted and evaluated from all 4 fermentation chambers 8 times per day. A larger filtered sample was drawn to quantify aqueous concentrations of hydrogen and methane. Headspace hydrogen and methane also were monitored continuously.

Significant results included:

  • The digestibility of neutral detergent fiber (NDF), acid detergent fiber (ADF), and starch in continuous cultures was not affected by low pH, acetone infusions, or propionate infusions.
  • Microbial carbon sequestered from VFA was not affected by any treatment.
  • Reduction in pH increased net propionate production and decreased emissions of hydrogen and methane.
  • VFA interconversions were not affected by any treatment.

           

Ultimately, the Virginia Tech researchers concluded that thermodynamics might not be a primary influencer of metabolic pathways used for VFA formation.


For more on nutrition, read:

 

Latest News

AABP Creates 'Using Credentialed Veterinary Technicians  in Bovine Practice' Guidelines
AABP Creates 'Using Credentialed Veterinary Technicians in Bovine Practice' Guidelines

Utilizing credentialed veterinary technicians (CVTs) in bovine practice can assist veterinarians in providing additional and efficient services to their large animal clients.

Get the Facts Straight on Highly Pathogenic Avian Influenza
Get the Facts Straight on Highly Pathogenic Avian Influenza

Now that the mystery illness impacting some dairy herds has been revealed as the same strain of Highly Pathogenic Avian Influenza that has been impacting the U.S. poultry flock, pork producers are asking questions.

New Guide Helps Producers Maximize Values of Cull Cows
New Guide Helps Producers Maximize Values of Cull Cows

A new resource developed by the National Cattlemen’s Beef Association and CattleFax helps cattle producers maximize profitability from their culling decisions.

"Boring" Technology Will Reshape Dairy Over the Next 10 Years
"Boring" Technology Will Reshape Dairy Over the Next 10 Years

Once a technology becomes a boring experience it means it has become proven, well-adopted, and easy to utilize. There are three "boring" technologies silently shaping the industry.

Meat Institute: Properly Prepared Beef is Safe to Eat; HPAI is not a Food Safety Threat
Meat Institute: Properly Prepared Beef is Safe to Eat; HPAI is not a Food Safety Threat

According to the Centers for Disease Control and Prevention (CDC) and USDA food safety experts, properly prepared beef is safe to eat and is not a food safety risk to humans.

BREAKING: Mystery Illness Impacting Texas, Kansas Dairy Cattle is Confirmed as Highly Pathogenic Avian Influenza Strain
BREAKING: Mystery Illness Impacting Texas, Kansas Dairy Cattle is Confirmed as Highly Pathogenic Avian Influenza Strain

USDA says genetic sequencing revealed the mystery illness impacting Texas dairies is the same strain of Highly Pathogenic Avian Influenza (HPAI) that's been in the U.S. The virus is carried by wild waterfowl.