Fatty acid study shows ‘carry-over’ effect in fresh cows

Evidence is strengthening that daily milk yields from fresh cows supplemented with fatty acids remain elevated in the peak period after fat supplementation has been withdrawn.

This is according to a growing body of research evaluating specific fatty acids and their role in dairy cow diets in lactation, which has found a “carry-over” effect.

Cows at Michigan State University produced 8% more energy-corrected milk (ECM) in the fresh period (1-24 days in milk) when given a calcium salt fatty acid supplement, in a study presented at this summer’s virtual American Dairy Science Association annual meeting.

However, the cows continued to yield 7.7% more ECM in the peak period (25-67 days in milk) once fatty acid supplementation was stopped, compared with the control group that had no fatty acid supplementation at all.  

See also: Three tips on feeding fats in dairy rations 

The blend 

The optimal blend of fatty acids appears to be close to a mix of palmitic acid (C16:0) and oleic acid (C18:1) at a ratio of 60:30 in a product called Mega-Max, according to Dr Adam Lock, Michigan State University department of animal science.

Dr Lock and colleagues have advised farmers that palmitic acid aids milk fat production, while oleic acid helps yields and promotes body weight gain after peak lactation.

Importantly, the university’s research is in agreement with on-farm observations and other trials that the right blend of palmitic and oleic acids can increase milk yield without increasing body condition loss in early lactation.

This is an improvement on feeding palmitic acid on its own, which has been shown to bring higher milk yield but also increased body condition loss in early lactation.

Currently the advice is as follows:

• Fresh to peak lactation: A fatty acid balance of 25-30% oleic and the rest palmitic acid.
• After peak lactation: Depending on cow body condition score, oleic acid should be dropped back to 10%, with 80-90% palmitic acid.

“Don’t just think of it as a bag of fat,” Dr Lock told a recent webinar organised by nutrition specialist Volac. “In the same way we have moved away from crude protein to talk about amino acids, we need to talk about fatty acids rather than fat.”

Dr John Newbold, professor of dairy nutrition at Scotland’s Rural College (SRUC), said the fact that the extra milk came with no change in dry matter intakes and no mobilisation of body fat reserves suggested oleic acid helped fat digestibility.

“It’s a very key finding that we can achieve an increase in performance without pushing the cow into a deeper negative energy balance,” he said.

“Providing more C18:1 to the ovary is also beneficial for development of embryos, and the improved digestibility provides an additional boost in megajoules.” 

The trial

Researchers at the University of Michigan have blended commercially available products, to test 80:10, 70:20 and 60:30 mixes of palmitic and oleic acids.

As well as observing the carry-over effect, the trials adding oleic acid in the fresh period had the following three key findings:

• Yield response: 3.1kg a cow/day more ECM was produced in the fresh period and 5.1kg more in the peak period. Fat content lifted 0.2% (1.76-2.07kg cow/day).
• Less bodyweight loss: Importantly, by supplying oleic acid, the extra milk fat and milk yield can be produced without increasing body weight loss, suggesting C18:1 improves nutrient absorption and energy partitioning to body fat stores.
• Dry matter intakes remain the same: Many people in the industry believe that feeding fat to fresh cows is risky, as dry matter intakes will fall. Feed intakes remained stable in the trial.

The cost

Dr Richard Kirkland of Volac said the economics of feeding supplemental fatty acids would depend on individual farm contracts, nutrition, and herd and fertility performance.

He said feeding about 500g a cow/day of Mega-Max (1.8% inclusion of dry matter), as in the Michigan study, up to day 67 of lactation would cost about 35p a cow/day to give a five-litre milk yield increase.