Some Fatty Acids Work--Others Not So Much

"Just as we recognize that not all protein sources are the same, it is important to remember that not all fatty acid supplements are the same," says Adam Lock, Michigan Sate University. ( Wyatt Bechtel )

Fatty acid supplementation in dairy rations have gotten a bad wrap. Sometimes they work, sometimes they don’t work out quite as expected.

The key is to realize that long-chain fatty acids, due to their chemical make-up and how they release energy in the cow’s digestive tract, are not created equal. While dairy researchers still don’t fully understand those mechanisms, feeding trials are starting to sort out differences.

“Just as we recognize that not all protein sources are the same, it is important to remember that not all fatty acids or fatty acid supplements are the same,” says Adam Lock, a dairy nutrition specialist with Michigan State University.

The results of stearic acid (C18:0) supplementation show mixed results both in early and mid-lactation diets. But palmitic acid (C16:0) supplementation shows more promise, says Lock.

Our results, and those of others, indicate that palmitic supplementation has the potential to increase yields of energy corrected milk and milk fat as well as the conversion of feed to milk, independent of production level when it was included in the diet for soyhulls or stearic acid,” he says.

For example, when it was offered in the fresh period from one to 24 days in milk, Lock saw no differences in dry matter intake or milk yield. But energy-corrected milk increased about 10 lb/cow/day due to higher milk fat yield. At the same time, cows fed palmitic acid lost about 1 ¾ lb more body weight per day and had reduced body conditions scores compared to non-supplemented cows.

During the peak milk period (25 to 67 days in milk), feeding palmitic acid increased milk production by 7.5 lb/cow/day and energy corrected milk by 10 lb. Over the period, cows tended to lose about 22 lb of body weight during this period compared to cows not fed palmitic acid.

Lock also compared feeding a combination of fatty acid supplements. “When we compared combinations of palmitic, stearic and oleic (cis-9 C18:1) in fatty acid supplements, a supplement containing more palmitic acid increased energy partitioning toward milk due to the greater milk fat yield response compared with other treatments,” he says.

“In contrast, a fatty acid supplement containing palmitic and oleic acids increased energy allocated to body reserves compared to other treatments. The fatty acid supplement containing a combination of palmitic and stearic acids reduced nutrient digestibility, which most likely explains the lower production responses compared with other treatments.”

To complicate the matter further, Lock found fatty acid supplements containing both palmitic and oleic acids fed to post-peak cows produced more milk if the supplement had more palmitic acid and if the group was producing less than 100 lb of milk per cow per day. But if the group was producing more than 130 lb/cow/day, cows performed better with more oleic in the supplement. In both cases, cows fed oleic acid increased body weight.

Interestingly, during early lactation, feeding a combination of palmitic and oleic acids increased milk production while not affecting body weight loss compared to cows not fed supplemented fat, Lock says.

More research is needed to fully understand the mechanism of fatty acid metabolism. In the meantime, Lock recommends dairy farmers work with their nutrition consultants in formulating rations if they are considering fatty acid supplements.

“Identify what you are trying to achieve, then design your nutritional program (including fatty acid supplementation) around those objectives,” he says. “The key is to know what fatty acids are present in the supplement, particularly fatty acid chain length and their degree of unsaturation.”