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Fatty acid nutrition: More than bringing added calories into your diet

John Goeser for Progressive Dairyman Published on 06 August 2018

Often when nutritionists think of fatty acid nutrition, our minds turn to fat supplements. However, the area is much broader than dairy cattle diet fat supplements and should be recognized as such.

Milkfat concentration has now become a focal point for nutritionists and farms, given the value per pound has eclipsed that of protein and, in some months, accounted for well over half the milk check. When I think of fatty acid nutrition now, I think of several distinctly different areas within animal and dairy nutrition.



The three nutrition management areas within the fatty acid discipline include TMR fat supplements, milkfat depression and now also milk fatty acid profile.

TMR fat supplements

Fatty acid-rich supplements have historically been brought into diets to bring calories and increase energy density without adding more grain. Nutritionists often bring fat into diets during summer months, when intakes may drop, or during colder months where cows may be burning more energy for maintenance and, in some cases, losing body condition score.

Fat derived from plant or animal sources has about two times the energy value per pound corn grain does, thus packing an energetic punch on a pound-for-pound basis. While research over the past 20 years suggested animal-based fat supplements (tallow) interact with both intakes and fiber digestion within the rumen, today’s fat supplements (outside of tallow) are generally rumen-inert, meaning they do not negatively interact with other feeds or nutrients.

Beyond bringing energy into diets, field-leading researchers have recognized other aspects to fat supplements that contribute to dairy cattle health and performance. Supplementing specific omega-3 and omega-6 fatty acids during transition and breeding periods has been shown to improve animal health and reproductive success.

Further, Adam Lock and others are also recognizing functional effects such as increasing insulin levels in dairy cows or changing how energy is partitioned by the cow when feeding oleic acid-rich supplements. These functional fatty acid effects do not surprise me and are intriguing.


Reason being, in graduate school I learned how omega-3 and -6 fatty acid supplementation has been heavily researched and found to benefit human health and nutrition in several diverse ways, such as improved cardiovascular health and blood triglyceride levels. Hence, I supplement my own diet with omega-3 and -6 fatty acid-rich supplements (flax and fish oils) daily.

Milkfat depression

Beyond functional fat effects, recognize fat metabolization in the rumen has a substantial impact upon mammary gland function. Moreover, fatty acids flowing out of the rumen have a marked impact on milkfat synthesis and content.

I think of fat metabolism by the rumen much like I think of intermeshing gears within an engine, in that the rumen needs to be functioning with all gears in contact, properly processing fats, to successfully function and permit maximum milkfat creation.

In scientific terms, unsaturated fatty acids (fatty acids with bent configurations) in the rumen need to be biohydrogenated (turned into saturated fatty acids with a more linear configuration) by bacteria.

If the rumen unsaturated fatty acid load (RUFAL) isn’t processed correctly, a specific fatty acid (conjugated linoleic acid, C18:2 Trans-10, cis-12) starts to be created through an alternative metabolism process. As little as a few grams (picture a teaspoon) of this fatty acid can drop milkfat percentage from 3.8 to less than 3 percent.

Lock has also analogized rumen fat metabolism and function to that of a funnel, in that RUFAL (like oil dumped into a funnel) needs to flow through the saturation process (like oil running down a hose into the container).


Like how the flow through the funnel is limited by the hose size, the fat metabolization process in the rumen is slowed by several factors, including depressed rumen pH or feed-borne or feed management factors that negatively affect rumen function (i.e., spoiled feed or variable feeding times).

To avoid overflowing the funnel, nutrition consultants are now better recognizing RUFAL load and then limiting the RUFAL (grams per cow) during nutrition or management situations. Ask your nutritionist to discuss your dairy’s RUFAL and recognize the critical threshold is different from farm to farm.

Milk fatty acid profile

The prior two fatty acid nutrition areas discussed here are often addressed prior to feeding through feed analyses and formulation. This third management area is retrospective, much like following the butterfat, protein, milk urea nitrogen and somatic cell content on the prior loads of milk shipped. Advanced laboratory techniques are becoming more routinely available and allow managers to better understand milk fatty acid profile.

Why does this matter? The de novo fatty acid content in milk (those only created by the mammary gland, four to 16 carbons in length) has been suggested as a herd-level management tool to help understand milkfat opportunities.

Mammary gland de novo fatty acid synthesis and milk concentration has been found tightly correlated to milkfat content, and researchers are now looking to tie nutrition and management strategies to de novo synthesis.

Great interest exists within this area, although further research is warranted to continue helping us understand what further insight de novo fatty acid content can provide beyond simply knowing butterfat content alone. Consult with your nutritionist and advisory team on this evolving nutrition topic.

In summary, like how amino acid nutrition has evolved over the past 15 years and we now balance for specific amounts of amino acid, fatty acid nutrition is evolving as well.

Nutrition consultants are better recognizing specific fatty acids’ impact on the rumen, dairy cow’s body and milkfat synthesis. We can now better balance for specific fatty acid amounts and ratios to benefit animal health and performance and, ultimately, the dairy farm’s bottom line.  end mark

John Goeser earned a Ph.D. in animal nutrition from the University of Wisconsin – Madison, where he currently serves as an adjunct professor in the dairy science department. He also directs animal nutrition, research and innovation efforts at Rock River Lab Inc. based in Watertown, Wisconsin.

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John Goeser
  • John Goeser

  • Director of Nutrition, Research and Innovation
  • Rock River Laboratory Inc.
  • Email John Goeser