Podcast Topic
Dr. Weiss and his guest discuss Milk Responses to Fatty Acid Supplements in Low and High-Fat Basal Diets on this episode.
Episode 131: Milk Responses to Fatty Acid Supplements in Low and High-Fat Basal Diets
Timestamps:
In this study, two basal diets were fed, one low-fat and one high-fat. The low-fat diet contained cottonseed meal and cottonseed hulls and the high-fat diet contained whole cottonseed. This balanced fiber and protein to try and make the difference between the basal diets and just the fatty acids. Basal diets were supplemented with two different fat supplements that had different ratios of palmitic and oleic acids. The applied question at hand was “Does fat need to be supplemented to a high-fat basal diet?” (5:32)
The low-fat diet contained 1.93% fatty acids and the high-fat diet contained 3.15% fatty acids. Fatty acid supplements were fed at 1.5% of dry matter and replaced soyhulls. The palmitic acid supplement contained 80% palmitic acid and 10% oleic acid. The palmitic + oleic acid supplement contained 60% palmitic acid and 30% oleic acid. Thirty-six cows were used in a split-plot Latin square design, with half the cows on each basal diet. Under each split-plot, cows were allocated to a 3×3 Latin square, evaluating a control treatment (no fat supplement), palmitic acid supplement, and palmitic + oleic acid supplement. (8:46)
Bill, Adam, and Clay discuss the increase in milk components the industry has experienced recently due to the powerful combination of genetics and nutrition. Hoard’s Dairyman reported that 2024 was the first year that the U.S. had averaged over 4% milk fat going back to 1924 when records began. (13:01)
Both fat supplements increased milk yield in low-fat and high-fat basal diets, but the magnitude of the increase was larger in the low-fat diet. The high palmitic acid diet increased milk yield more in cows fed the low-fat basal diet than the palmitic + oleic supplement did. High-fat basal diet cows had similar milk yield responses to both fatty acid supplements. The panel discusses the industry emphasis on milk components and if/when a threshold in performance might happen given the advancement of genomics and nutrition. (15:51)
Clay asks Adam to remind the listeners about the relationship between fatty acids and crude fat or ether extract. Adam recommends moving away from ether extract and focusing solely on fatty acid content. Bill, Adam, and Clay talk about the variability in the fatty acid content of various feedstuffs. (25:33)
Bill asks if the feed efficiency improvement with the fat supplementation was due to more of a gross energy or digestible/metabolizable energy effect. Adam suggests it may be a little of both. The diet is more energy-dense, but we also know now that some of those specific fatty acids have specific effects. Improvements in NDF digestibility are consistently observed with palmitic acid supplementation. Oleic acid improves fatty acid absorption and impacts adipose tissue metabolism and insulin sensitivity. Bill and Adam talk more philosophically about the best way to measure feed efficiency in dairy cows. (29:02)
If Adam could repeat this experiment, he would have pushed the basal fat levels a bit more and had both lower-producing and higher-producing cows in the experiment. This leads to a discussion of how the results might have differed if distiller grains or soybeans were used instead of cottonseed in the experiment. Listeners should be careful not to extrapolate the results from this experiment to other fat sources. (33:55)
Adam emphasizes that we shouldn’t be afraid of feeding high-fat diets, either basal or supplemental fatty acids, especially to high-producing cows. We should be very mindful about where those fatty acids are coming from. We could provide the same nutrients by feeding either cottonseed or distillers grains, but how those ingredients feed out could be very different. (38:38)
In summary, Clay agrees we should take a fresh look at how much fat we’re feeding cows in basal diets and underlines the importance of the source of supplemental fatty acids. Bill concurs and commends Adam’s group for basically making cottonseed without fat in the low-fat basal diet, which allowed for very clean interpretations of the fatty acid supplement results. Adam underlines that we can feed higher fat diets, but the fatty acid profile of all of those ingredients we might use is going to be key. In addition to fatty acids in diets and supplements, de novo synthesis of milk fat from acetate is the other half of the equation. Bringing those together might be a strategy to keep up with genetic improvements and drive higher milk fat yield. (47:43)
You can find this episode’s journal club paper from JDS Communications here: https://www.sciencedirect.com/science…
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