Changing the thinking on fat inclusion in dairy cow diets
Adam Lock, an associate professor specialising in fat and fatty acid nutrition in the Department of Animal Science, Michigan State University, USA, outlined the “sea change” at the recent Transitioning from Fats to Fatty Acids seminar at the Volac Wilmar conference in Co. Cork recently.
“Typically a bag of fat was thought as a bag of fat and it was to just bring in calories – extra energy – to the cow.
“But what we are starting to understand is the effects of individual fatty acids can be quite different in the dairy cow on the yield of milk and milk components; energy partitioning; body condition and reproduction; and health.
“The next time that someone is looking to sell you a new fat supplement, the number one question is what type of fatty acids are in it because that’s going to determine what type of response you will expect to see from it,” he told delegates at the Volac Wilmar organised conference.
The fatty acid profile in a fat supplement is going to be the first factor in determining the response to it.
Lock’s research programmes focus on both dairy production and human nutrition and health. The central theme is fatty acid digestion and metabolism in the dairy cow and the impact of bioactive acids on animal production.
Over recent years, he has lead research looking at the impact of including numerous fatty acids in the diet of dairy cows – most notably palmitic acid (C16:O), stearic acid (C18:O) and oleic acid (C18:1).
“All three of these are important for dairy cow metabolism and what we are trying to understand is if there is an ideal ratio among these fatty acids that may help us optimise their utilisation in dairy cow rations and what interactions they may have with other animal and dietary factors,” he said.
A paper published earlier this year highlighted the impacts of feeding palmitic acid, a palmitic acid / stearic acid blend and a palmitic acid / oleic acid blend at 1.5% of diet dry matter to mid-lactation, high-producing cows. All three of these treatments were compared to a “control” or a diet not supplemented with additional fat.
“We saw an improvement in NDF (neutral detergent fibre) digestibility with palmitic acid, but we also saw a slight improvement with our palmitic acid / oleic acid treatment.
“But when we take out half of the palmitic acid and add in stearic acid, we actually see a decline in NDF digestibility.”
In terms of the digestibility of fatty acids, Lock noted that there was no difference between the control and the palmitic acid treatment. However, when half of the palmitic acid was replaced with stearic acid, a significant reduction in fatty acid digestibility was observed.
On the other hand, when oleic acid was added into the diet (the palmitic acid / oleic acid treatment) an improvement in fatty acid digestibility was observed.
Referring to the results observed when oleic acid was added to the diet, Lock said: “This was a little bit surprising. We were feeding 1.5% more fatty acid in the diet compared to the control, but we actually improved the fatty acid digestibility.”
Commenting further, he said: “All three of the treatments gave a nice increase in milk yield over the control – about 2.5kg.
“But then when you look at the effects on milk fat percent, you can see that it’s only the high palmitic acid treatment that’s improving milk fat percent; the other two fat treatments did not improve fat percent at all.”
Presenting the data as energy corrected milk – which takes into account not just milk yield, but protein and fat yield as well – all three treatments improved energy corrected milk compared to the control; the increase was greatest for the high palmitic acid treatment.
“Also what intrigued us in this study was when we looked at body weight change. Our palmitic acid and our palmitic acid / stearic acid treatments did not result in body weight change; that’s important in terms of that extra milk yield not coming at the expense of cows gaining body weight.
“What’s really interesting is the palmitic acid / oleic acid treatment actually increased body weight gain over the control treatment and also the palmitic acid / stearic acid treatment.
“That’s kind of interesting when you think of that palmitic acid / oleic acid treatment increasing energy corrected milk compared to the control and gaining more body weight compared to the control without eating more diet.
“We’ve been following up on the effect of this palmitic acid / oleic acid treatment. We have a number of lines of evidence that led us to conclude that we don’t really want stearic acid in a fat supplement.
“But we are very interested in the palmitic acid / oleic acid blend – the effects of what each of these fatty acids have and what the impact may be if we have different blends and ratios of these.”
Further studies have been undertaken using blends of palmitic acid and oleic acid – including a 80:10 ratio and a 60:30 ratio.
Comparing high-producing and low-producing (40-45kg/day at peak), post-peak, mid-lactation cows, the body weight effects of adding oleic acid to the cows’ diet were also observed.
“In the low-producing cows, it was actually the higher palmitic acid treatment (80:20) that gave us the best energy corrected milk response, mostly through increased milk fat yield.
“However, in the high group of cows (started at 50kg/day of milk), we saw a clear relationship as you increased the oleic acid content of the fat supplement; it gave us an increase in energy corrected milk.”
This, he said, indicated that cows at different levels of milk production respond differently to these different blends.
“The high-producing cows benefit from a higher blend of oleic acid than palmitic acid, whereas lower-producing cows benefit from a more palmitic acid enriched supplement,” he added.
A study was also completed to examine the effect of supplementing cows with palmitic acid in the first three weeks of lactation; the study was carried on to see what impact this had during the first 10 weeks of lactation. Again, a control group was used as part of the study.
Key results of palmitic acid supplementation:
- No difference in terms of dry matter intake;
- Cows fed palmitic acid during the peak period (weeks three-to-10 of lactation) increased milk yield by 3.5kg compared to the control cows – energy corrected milking increased by approximately 5kg;
- Cows fed palmitic acid during the fresh period lost more body weight (approximately 25kg compared to the control).
The results of the above study focused the research efforts to looking at the impacts of using supplements with various ratios of palmitic and oleic acid. The initial findings of this research were presented at dairy science meetings this summer.
Along with a control group, high-producing, fresh cows were offered diets containing palmitic acid / oleic acid blends at different ratios – 80:10, 70:20 and 60:30.
Lock explained that the responses to the 80:10 ratio were similar to previous studies undertaken; but as the oleic acid content was increased, “fascinating” results were obtained.
“As you increase the oleic acid content in the diet, you are seeing increases in feed intake – more feed intake going into the cow and hopefully more energy going into the cow.
“By week two, those higher oleic acid treatments (70:20 and 60:30) are producing 4.5kg more energy corrected milk than the control group. And when we look at body weight, particularly for the 60:30, as we provide more oleic acid into that diet, those cows are not losing any more body weight than the control cows.”
The Irish Context
When questioned on the possible response from oleic acid supplementation in pasture-based, lower-producing cows – typical of the Irish system, he said:
“The cows in our study were pretty high production. What I would expect is the partitioning differences we see would hold true in terms of the differences between palmitic and oleic acid.”
In the fresh cow, he added: “I would suspect that you would see some similar results. If you can get the same amount of milk while minimising body loss, I think that’s an attractive proposition and opportunity. It would be good to see that type of study under your situations.”
Lock’s presentation coincided with the launch of MegaMax – a fat supplement from Volac Wilmar – next week. The company already supplies a number of fat supplementation products, but the fatty acid profile in MegaMax is based on the work outlined above.
With this, Volac Wilmar hopes to provide its customers with a product containing a blend of palmitic and oleic acids, which will be targeted at early-lactation cows to minimise the effect of body condition loss.
Volac offers a strong technical back up through Dr. Richard Kirkland, technical director of Volac Wilmar, and Dr. John Newbold, technical director of Volac, who are available to support millers with any queries around fat usage.