Oleic Acid Challenges Traditional RUFAL Limits in Dairy Diets

Dairy cow nutrition strategies may need a closer look at how dietary unsaturated fatty acids are evaluated, as emerging research highlights the different effects of oleic acid compared with other fatty acids on rumen health, energy metabolism and milk production.

In an article published by Feedstuffs on October 30, 2026, Essi Evans of E+E Technical Advisory Services examines the role of oleic acid (C18:1) in dairy diets and questions whether the traditional Rumen Unsaturated Fatty Acid Load (RUFAL) calculation adequately distinguishes between different types of unsaturated fatty acids.

Understanding RUFAL in Dairy Nutrition

RUFAL represents the combined dietary supply of three major unsaturated fatty acids:

• Oleic acid (C18:1)
• Linoleic acid (C18:2)
• Linolenic acid (C18:3)

The calculation considers their contribution from all feed ingredients and is generally expressed as a percentage of total dietary dry matter.

RUFAL was developed to help nutritionists manage the risk of rumen fermentation disturbances and milk fat depression associated with excessive unsaturated fatty acid intake. A commonly used target is to keep RUFAL below 3.5% of dietary dry matter.

However, the three fatty acids do not necessarily have the same effects on rumen microorganisms and milk fat synthesis.

Why Oleic Acid May Need Different Consideration

The Feedstuffs article highlights that polyunsaturated fatty acids, particularly linoleic and linolenic acids, are more likely to disrupt rumen microbial activity and contribute to the formation of biohydrogenation intermediates associated with milk fat depression.

Oleic acid, a monounsaturated fatty acid, behaves differently. It is generally biohydrogenated to stearic acid and has shown comparatively high digestibility in research involving lactating dairy cows.

A large Dairy Herd Information Association dataset involving 4,205 records also found that the relationship between RUFAL and milk fat depression was more strongly associated with linoleic acid, followed by linolenic acid, while oleic acid was unlikely to have a similar negative effect.

Potential Benefits for Digestibility and Energy Balance

Research from Michigan State University has identified several potential benefits of oleic acid supplementation:

• Improved fat digestibility: Oleic acid may act as an emulsifier, helping improve the digestibility of other fatty acids.
• Greater energy availability: Better fatty acid digestibility may increase the energy available to dairy cows.
• Support during early lactation: Studies have reported increased feed intake and reduced body-weight loss in early lactation.
• Milk production: Oleic acid supplementation has been associated with improvements in milk production in certain studies.

A 2025 review published in the Journal of Dairy Science also examined oleic acid's role in lipid metabolism, insulin signalling, oxidative stress and inflammation, particularly in transition dairy cows experiencing negative energy balance.

Implications for Dairy Feed Formulation

The discussion raises an important question for dairy nutritionists: should every unsaturated fatty acid contribute equally to the assessment of rumen fat load?

The Feedstuffs article suggests that the current RUFAL calculation may penalise ingredients rich in oleic acid, even when they could offer nutritional benefits. Canola meal, peanut meal and high-oleic soybean varieties are identified as potential dietary sources.

For feed manufacturers and dairy nutritionists, this could encourage more detailed evaluation of fatty acid profiles rather than relying only on total unsaturated fatty acid load.

However, this does not mean that RUFAL should be ignored or that oleic acid can be included without limits. Overall dietary composition, rumen function, production stage and the balance of individual fatty acids remain important considerations.

Moving Towards More Precise Dairy Nutrition

The growing body of research points towards a more targeted approach to dairy cow nutrition—one that considers the individual functions of fatty acids rather than treating all dietary fats as equivalent.

For dairy producers, the practical objective remains the same: maintain rumen health, support milk fat production, improve energy utilisation and sustain productivity, particularly during the challenging transition period.

As research advances, a more differentiated understanding of oleic acid could help nutritionists refine fat supplementation strategies and improve the precision of dairy feed formulation.

Source:  Read full story here 01 Nov, 2026 Edited and Reported by