Q: What Makes Fat Sources Different?
A: Many dairy producers think they are getting the same value from different fat sources, but that’s not necessarily true.
Fats are derived from a variety of dietary ingredients, like grains, oilseeds and forages, as well as supplemental sources. Differences in production response among various fat sources are due to different true energetic content and the fact that fatty acids have profound biological effects on animals outside of their energetic effects.
Fat is a key source of storage for energy since tissues use stored fat when cows are in negative energy balance. Cows have the ability to synthesize fat for tissue storage and milk fat, but it is more efficient to use fat obtained from the diet for these purposes.
A recent 12-week trial at the University of Delaware1 examined two supplemental fat sources—Palmitic acid (C16:0) and MEGALAC® Bypass Fat—and their effects on milk production and component production to show the differences between these two supplemental fat sources.
Q: What Were the Results?
A: In short-term research studies, fat yields have decreased, increased or stayed the same. In this longer, 12-week trial, no differences were seen in results between the two treatment groups until cows had been on treatment for at least four weeks. However, the final results outlined in these charts show that MEGALAC increased milk production, milk components and was more persistent in its effects than C16:0 over the course of the trial.
Q: What Do These Results Mean?
A: A few short-term studies have been conducted with these products. Most of the studies compared added palmitic acid to no added fat. The inclusion of any supplemental fat tends to increase energy density and therefore improve feed efficiency.
This study helps explain the role of palmitic acid in dairy diets in several ways:
- Short-term trials can be misleading. If this trial had ended after five weeks or less, there would have been no differences between treatments, even though final results show MEGALAC outperformed C16:0.
- Palmitic acid as a sole source of supplemental fat, while promising in the short term, might not provide the fatty acids needed to support the cow in the longer term.
- There is reason to believe that there is a maximum amount of certain fat sources that can be effectively utilized in milk and component synthesis.
That means it’s important to remember that while rumen inert fatty acid supplements provide a concentrated source of energy to cows and cows respond to added fatty acid supplements, time is needed to see the real response. When evaluating diets on-farm, keep in mind that pounds of fat, and not changes in fat percentage, are the defining standard of ration success.
Click here to hear more from Dr. Limin Kung about this research.
1 Block E, Kung L, Merrill C. Production performance parameters of early lactation dairy cows fed a diet supplemented with MEGALAC or a fatty acid prill containing high levels of palmitic acid. Available at: http://jtmtg.org/2013/abstracts/235.pdf. Accessed June 20, 2013.