Veterinary is preparing to give dairy cow an oral supplement

Unlocking Livestock Feed Efficiency with Isoacids

Livestock | August 2025

Written by:

Jennifer Ryan has been writing about veterinary topics for nearly 20 years. She has a master’s degree in journalism, a bachelor’s degree in agricultural communications and decades of experience caring for both livestock and pets.

Isoacids have been studied since the 1960s. Today, the nutrient is again being recognized for its ability to boost feed efficiency and productivity in dairy cattle.

The benefits of isoacids in dairy diets have been investigated since the 1960s. Today, the nutrient’s popularity is being revived alongside precision feeding technology that allows nutritionists to anticipate nutrient deficits and tailor rations for optimal performance.

Older and wiser nutritionists might remember the tell-tale smell of isoacids. Modern versions are protected to remove that drawback. However, the benefits remain.

“The effects we’ve seen equate to two to four pounds of energy-corrected milk,” said Andrew LaPierre, Ph.D., dairy technical specialist with Zinpro. “A lot of that is driven by enhanced fiber digestion in the rumen.”

Isoacids are an essential nutrient resulting from degrading amino acids in the rumen. Isoacids feed fiber-digesting microbes in the rumen. By enhancing fiber digestibility, cows can improve milk production and efficiency with less dry matter intake.

Isoacid basics

Isoacids are a collective term for a group of volatile fatty acids that cows naturally produce in their rumen as starch and sugar-degrading bacteria break down protein and peptides through proteolysis. However, some ration formulations may be lacking this important nutrient.

“In modern diets, our nutritionists are doing a good job of bringing in fermentable ingredients and soluble proteins, which helps to create an endogenous, or internal, source of isoacids,” LaPierre said. “Some diets with a high level of fermentability can actually have a deficit and enhancement is a good option.”

LaPierre noted that diets including brown midrib (BMR) silage, triticale, wheat or rye may allow nutrients to degrade rapidly in the rumen. Rations with higher inclusions of these forage ingredients, such as those in the Northeast and Midwest, should consider isoacids.

“This really drives what I call a competitive rumen environment. Certain bacterial populations will out-compete when diet fermentability is high and nutrients for growth may be limited. Adding isoacids through the diet can alleviate some of these limitations,” LaPierre said. “There are dietary formulation tools that can predict isoacid deficiencies. Including this nutrient in your diet can help bridge the nutrients needed to overcome this deficiency and drive rumen efficiency.”

Beyond the lactating cow

Isoacids aren’t only for lactating cows. Transition cows can benefit from isoacids to help prepare for the energy demands of upcoming lactations.

“This really helps when those lactating animals have a negative energy and protein imbalance. Research has shown that supplemented isoacids can mitigate bodyweight loss and improve dry matter intake in the transition period,” he says.

Isoacids can easily be incorporated into precision feeding, and LaPierre is seeing more isoacid precision feeding in the field.

“I think precision nutrients are an exciting topic,” he said. “Isoacids can take a good diet to the next level. It requires a well-managed herd that is feeding a solidly built diet as the foundation, but most diets can see a 2-to-1 return on investment when we can both enhance digestibility and performance in the rumen and remove excessive dietary ingredients where producers may have been supplementing protein or energy directly to the animal.”

1 Redoy, M. R. A., Ahmed, S., Urbina, J. B., Kleinschmit, D. H., Socha, M. T., Salunke, P., & Uddin, M. E. (2025). Supplementation of isoacids to lactating dairy cows fed low- or high-forage diets: Effects on performance, digestibility, and milk fatty acid profile. Journal of Dairy Science, 108(2), 1408–1418. https://doi.org/10.3168/jds.2024-25358

2 Gouveia, K. M., Beckett, L. M., Casey, T. M., & Boerman, J. P. (2024). Production responses of multiparous dairy cattle with differing prepartum muscle reserves and supplementation of branched-chain volatile fatty acids. Journal of Dairy Science, 107(12), 11655-11668. https://doi.org/10.3168/jds.2024-24915

 

Dairy cattle grazing with barn in the background

 

Key points

  • Forage can be utilized by cattle with the help of cellulolytic bacteria in the rumen to synthesize volatile fatty acids and microbial protein.
  • Cellulolytic bacteria grow from the cross-feeding of branched-chain volatile fatty acids by other proteolytic bacteria in the rumen.
  • Isoacids include the branched-chain volatile fatty acids isobutyrate, 2-methybutyrate and isovalerate, either individually or in combinations with another straight-chain fatty acid, valerate.
  • Feeding isoacids significantly improves cellulolytic bacterial growth in the rumen environment.

 

Photo credits:

istockphoto.com/JackF

istockphoto.com/Natallia Saksonova

>