Some Fatty Acids Work–Others Not So Much
Fatty acid supplementation in dairy rations have gotten a bad wrap. Sometimes they work, sometimesthey 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 releaseenergy in the cow’s digestive tract, are not created equal. While dairy researchers still don’t fullyunderstand 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 allfatty acids or fatty acid supplements are the same,” says Adam Lock, a dairy
nutrition specialist withMichigan State University.
The results of stearic acid (C18:0) supplementation show mixed results both in early and mid-lactationdiets. 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 increaseyields of energy corrected milk and milk fat as well as the conversion of feed to milk, independent ofproduction 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 differencesin dry matter intake or milk yield. But energy-corrected milk increased about 10 lb/cow/day due to highermilk fat yield. At the same time, cows fed palmitic acid lost about 1 ¾ lb more body weight per day andhad 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 by7.5 lb/cow/day and energy corrected milk by 10 lb. Over the period, cows tended to lose about
body weight during this period compared to cows not fed palmitic acid.
Lock also compared feeding a combination of fatty acid supplements. “When we comparedcombinations of palmitic, stearic and oleic (cis-9 C18:1) in fatty acid supplements, a supplementcontaining more palmitic acid increased energy partitioning toward milk due to the greater milk fat yieldresponse compared with other treatments,” he says.
“In contrast, a fatty acid supplement containing palmitic and oleic acids increased energy allocated tobody reserves compared to other treatments. The fatty acid supplement containing a combination ofpalmitic and stearic acids reduced nutrient digestibility, which most likely explains the lower productionresponses compared with other treatments.”
To complicate the matter further, Lock found fatty acid supplements containing both palmitic and oleicacids fed to post-peak cows produced more milk if the supplement had more palmitic acid and if thegroup was producing less than 100 lb of milk per cow per day. But if the group was producing more than130 lb/cow/day, cows performed better with more oleic in the supplement. In both cases, cows fed oleicacid increased body weight.
Interestingly, during early lactation, feeding a combination of palmitic and oleic acids increased milkproduction 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 areconsidering fatty acid supplements.
“Identify what you are trying to achieve, then design your nutritional program (including fatty acidsupplementation) around those objectives,” he says. “The key is to know what fatty acids are present
the supplement, particularly fatty acid chain length and their degree of unsaturation.”