Research Note

Risk vs. Opportunity:

Fat Sources & High Performance

High quality forages and stable rumen fermentation will always be the best support for the cow’s de novo synthesis of milk fat. However…

The cow also needs dietary fat for milk fat synthesis. And, given advancing dairy genetics and component-oriented milk marketing, optimal dietary fat can be a moving target. Where is research pointing?

As Penn State’s Dr. Kevin Harvatine notes, about 45% of milk fat comes from digestible fiber via de novo synthesis (acetate, glucose, butyrate), but roughly 55% comes from preformed fatty acids (FA, including 85% directly from absorption).

Biofuels boosting cost

Dietary fat sources and fat supplements are increasingly expensive, with more competition from biofuels given today’s global fuel-food-feed marketplace.

Fortunately, Harvatine says, if de novo synthesis is able to compensate, then decreasing dietary fat will not necessarily reduce milk fat. “However, if de novo synthesis hits its maximum capacity, then we will lose milk fat yield.”

MFD risk still there

Harvatine cautions that trying to optimize dietary FA for milk fat can still increase the risk of diet-induced milk fat depression (MFD), despite many factors today that help mitigate the risk, including lower fat distillers (DDGS), better forages and feed management, and less use of high-moisture corn.

The genetic potential for milk fat has been increasing and average milk fat has followed with many farms performing much better than just a few years ago. However, this begs the question: “Are we missing diet-induced MFD because we have not adequately adjusted to the new genetic potential?”

Yet, if we have minimized diet-induced MFD, Harvatine suggests, then it’s likely that “in some herds and cows” we are missing opportunities for greater energy intake, milk yield, and diet cost savings.

Pointing to oilseeds

“We need to think about all the sources of fat in our diets,” Harvatine advises, “which includes first feeding relatively inexpensive sources of rumen available fat, then selecting fat supplements based on your goal and specific situation, such as energy intake, milk fat, reproduction, etc.”

Harvatine points to opportunities in the mid-range of dietary fat — sources that are rumen available and relatively economical — for example, oilseeds like high-oleic soybeans and cottonseed.

High oleic soybeans have a lower risk of milk fat depression and recent experiments at Penn State and other universities report roughly a 5% increase (about 65 g/d) in milk fat versus conventional soybeans.

Cottonseed has been well established in dairy nutrition programs for decades. A recent Penn State experiment revealed differences in milk fat yield between first lactation and multiparous cows. A second experiment, feeding whole cottonseed at 15%, increased milk fat concentration and yield. Nutritionists sometimes worry about undigested seeds in the manure, but this was only 1% to 4% of seeds fed with less found in first lactation cows.

Plug in smarter energy

Next month, the Penn State 2023 Dairy Nutrition Workshop (Nov. 8-9, Hershey, PA) includes a Diamond V-sponsored pre-conference on dairy nutrigenomics and a Phibro-sponsored post-conference on controlled energy diets and fully-acidogenic, DCAD diets for transition cows and their calves.

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