Evolution of the Western diet
Today, many American and other populations consume a primarily Western diet. This diet is characterized by high consumption of refined sugars and saturated fats, which leads the population to an obesity epidemic.
In the '50s, some researchers realized that Eskimos also eat a high-fat diet, mainly due to the fatty fish they consume. But, unlike the Western population, they had very few cardiac diseases. The researchers concluded that the kind of fat they ate was different from Western populations. Arctic native peoples eat high amounts of PUFAs, and this diet makes them the population with the healthiest hearts.
There is a slow but marked tendency to consume healthier foods in recent decades. Changing from sugars and saturated fats to fruits, vegetables and healthy unsaturated fats. This situation is reflected in the increase of healthy products in the market. One type of product that has increased the most on the market is those high in omega-3s. Now we find a wide range of milk, eggs, butter and other products with high amounts of omega-3 fatty acids.
What are omega-3 fatty acids and what effects do they have?
Omega-3s are polyunsaturated fatty acids (PUFAs), which means they have more than one double bond in their structure. The three main types are alpha-linolenic acid (ALA) from vegetable origins (for example, linseed oil), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from animal origins (mainly fish oil). The ALA is an essential fatty acid (FA) because it cannot be synthetized in the body, and it must be consumed in the diet. Through the action of desaturase and elongase enzymes, ALA can be converted into EPA, and the latter can be converted to DHA after peroxisomal oxidation.
Several studies have shown the beneficial effects of omega-3 fatty acids on human health. Different effects have been demonstrated, for example, on the cardiovascular system, at a neurological level in elderly people and in improving psychiatric disorders. Omega-3 fatty acids are important for embryological development both in humans and animals. It has been observed that consumption of milk enriched with omega-3s, folic acid and vitamin E reduces levels of triglycerides, total cholesterol and LDL cholesterol in human patients with metabolic syndrome. The main mechanism of action is through the alteration of the composition and function of the membranes (phospholipids) and also through gene expression.
How to increase omega-3 content in milk
The fatty acid profile of milk is determined by two factors. Fifty percent of milkfat is synthesized in the mammary gland and has a very defined fatty acid profile, rich in short-chain fatty acids and palmitic acid. The other 50% of milkfat comes from feed fat, so it has a fatty acid profile very similar to the feed. If we want to increase the content of omega-3 in milk, we should increase the intake of feeds rich in fatty acids.
The problem is that PUFAs are harmful to some rumen bacteria strains, especially those that degrade fiber. These bacteria try to defend themselves by adding hydrogen to the fatty acid and saturating the carbon chain (a process called biohydrogenation). This is why the direct addition of unprotected PUFAs to the diet of dairy cows is risky and doesn’t have a big impact on the fatty acid profile of the milkfat. The main problem with the use of PUFAs is that it can cause milkfat depression (MFD). This situation is caused by intermediate metabolites (trans-10 fatty acids) that are made during the biohydrogenation process.
For best use, PUFAs must be protected to avoid their interaction with ruminal bacteria. One of the ways to protect the PUFAs is to coat them with vegetable-based saturated fats that are rumen inert. With this technology, we have two objectives. The first is to take care of the rumen bacteria and avoid MFD. The second is to try to maximize the amount of omega-3 PUFAs available in the gut. To reach these goals, we created a bypass omega-3 fatty acid supplement.
Modifying the milk fatty acid profile
Our department carried out a field test (presented at the American Dairy Science Association Annual Meeting 2019) to evaluate the effects of the product on the performance of dairy cows and the omega-3 content of milk.
In our study, we used a base diet with three different supplemented fats. The control group (CTR) received 500 grams per day of hydrogenated palm fatty acids distillate (HPFAD), the second group (EXT) received 350 grams per day of extruded linseed (unprotected) and 390 grams per day of HPFAD, and the third group (HFL) was supplemented with 500 grams per day of a bypass omega-3 fatty acid (HI-FLAX). Both, HFL and EXT diets provided the same amount of linolenic acid.
We found that milk yield and milk protein content did not differ among treatments. One of the most interesting findings was that milkfat content was lower in EXT cows compared with CTR cows. This means that cows fed unprotected extruded linseed went through milkfat depression. There was no difference between HFL cows and the CTR ones, supporting the fact that our product does not cause milkfat depression. The key finding was related with the profile of fatty acids of milkfat; both groups supplemented with flax products (EXT and HFL) showed significatively higher amounts of ALA and total omega-3 fatty acids (Figure 1) when compared with the CTR cows. With this study, we concluded that bypass omega-3 fatty acids are safe and do not modify yield or the amount of protein and fat in milk. However, the content of omega-3 in milk was increased significantly.
Another important improvement: reproductive performance
There are several studies that affirm that omega-3 FAs have an important effect on reproductive performance. Nevertheless, other authors suggest that the reproduction variables improve if the omega-6-to-omega-3 FA ratio decreases. One study proposed that omega-3 FAs cause an inhibition of prostaglandin PGF2α synthesis. And, because of the known luteolytic properties of PGF2α, a reduction in endometrial PGF2α secretion would prevent the regression of the corpus luteum. Also, the mean diameter of the ovulatory follicle and corpus luteum was higher when dairy cows were fed diets high in omega-3 fatty acids. Oocyte maturation in vivo was improved with the inclusion of omega-3 FAs. Finally, the establishment and maintenance of pregnancy was improved by the increase progesterone secretion by the corpus luteum.
The increase in the consumption of healthy products is a situation that encourages farmers to adopt new technologies like the addition of bypass omega-3 fatty acids in the diet of farm animals. This also brings other extra benefits, not less important, such as improving the reproductive efficiency of herds.
Leandro Royo is the ruminant product manager at Norel S.A. Email Leandro Royo.
Mónica Puyalto is a research and development director for Norel S.A. Email Monica Puyalto.
References omitted but are available upon request. Click here to email an editor.