By Elton Alisson | Agência FAPESP – The inclusion of canola oil in the diet of dairy cows can make the milk they produce healthier and deliver other non-nutritional benefits, such as reducing the risk of cardiovascular, autoimmune and inflammatory disorders.
These are the findings of a study performed by researchers at the University of São Paulo’s Animal Science & Food Engineering School (FZEA-USP) in Pirassununga, São Paulo State, Brazil.
Resulting from a research project and a master’s degree project supported by FAPESP, the study led to the publication of an article in the journal PLoS One.
“We succeeded in improving the nutritional quality of the fat in cows’ milk by adding canola oil to the animals’ diet,” said Arlindo Saran Netto, a professor at FZEA-USP and principal investigator for the project.
Saran Netto told Agência FAPESP that canola oil was included in the dairy cows’ diet to measure its effect on milk yield and composition. A key goal was to enhance the quality of milk fat by reducing the proportion of saturated fatty acids and increasing the proportion of omega-3 and omega-6, which are unsaturated fatty acids.
Saturated fatty acids have been identified as precursors of cardiovascular disease, whereas unsaturated fatty acids such as omega-3 and omega-6 are known to reduce low-density lipoprotein (LDL) cholesterol, commonly referred to as “bad cholesterol,” mitigating the risk of cardiovascular disease.
“Milk and other animal products are often seen as bad for human health because of the significant saturated fat content and low omega-3 or unsaturated fat content,” Saran Netto said.
“Research prior to ours had already shown that including vegetable oils such as canola, which is a source of omega-3, could alter the fatty acid profile of milk, increasing the amount of unsaturated fat and reducing the amount of saturated fat. However, most of this research failed to measure the effects of including high levels of canola oil, for example, in the diet of dairy cows.”
To evaluate the ideal dosage of canola oil in the diet of dairy cattle, the researchers selected 18 non-pregnant Holstein cows with an average daily milk yield of approximately 22 liters. The cows were in the middle stage of lactation and were milked twice a day.
The cows were fed three different diets, each lasting 14-21 days for adaptation and 7 days for the collection of blood and milk samples.
The control diet had no added oil and consisted of soybean meal, ground corn and maize silage. The other two diets included 3% or 6% canola oil.
The results of the experiments showed that including 6% canola led to a 20.24% reduction in saturated fatty acids in the milk produced by these cows. It also reduced the ratio of saturated to unsaturated fatty acids by 39.20% and increased the proportion of omega-3, reducing the ratio of omega-6 to omega-3 by 39.45%.
“We set out to improve the omega-6 to omega-3 ratio in cows’ milk as a better balance between these unsaturated fatty acids is beneficial to human health, helping to prevent cardiovascular, autoimmune and inflammatory disorders, for example,” Saran Netto said.
The researchers also estimated that the 6% canola diet led to a 48.36% reduction in milk atherogenicity (potential arterial plaque buildup) and a 39.86% decrease in thrombogenicity (tendency to form blood clots, potentially causing a heart attack or stroke) compared with the control diet.
Furthermore, the 6% canola diet led to a 94.44% increase in the ratio between hypocholesterolemic and hypercholesterolemic fatty acids (h/H) – the higher the ratio, the lower the probability of cardiovascular disease.
As for milk composition, the 6% canola diet increased the unsaturated fatty acid content by 34.08% and raised the omega-3 level by 115%.
“The inclusion of canola oil in the diet of lactating cows made the fat profile of their milk healthier for human consumption,” Saran Netto said.
The downside was that the 6% canola diet led to a reduction of 2.5 liters per day in milk yield compared with the control diet.
The results of the analysis showed that milk yield fell in line with the proportion of canola oil added to the cows’ diet, falling from 23.5 liters for the control diet to 22.46 liters per day when 3% was added and to 20.99 l/d when 6% was added.
“This may be because any oil added to diet reduces ruminal degradability, impairing the cow’s capacity to digest dry matter and nutrients. The flow of nutrients to the mammary gland decreases, and this in turn reduces milk production,” Saran Netto said.
“Now we’re interested in finding ways to compensate for this effect to avoid a decrease in milk yield while still producing milk with these characteristics.”
UHT milk with extra omega-3 content is sold in some countries, but the omega-3 is added to the product during factory processing. According to Saran Netto, the advantages of adding canola oil to the animals’ diet so that they produce milk with higher unsaturated fatty acid content include greater bioavailability and hence more effective intake by human consumers.
“Another advantage is cost,” she said. “Milk from cows fed an omega-3-supplemented diet can cost a little less than when it’s added to the milk during factory processing, albeit more than conventional milk.”
None of the products developed by the researchers in recent years, such as milk with added omega-6, selenium and vitamin E, has come to market yet because this requires changes to farm and factory logistics, according to Saran Netto.
Milk produced by cows fed a diet with added canola or sunflower oil has to be received and processed separately by factories, for example.
“Right now, there isn’t enough demand to justify the production of this premium-priced type of milk by dairy farms,” she said.
The researchers have not yet tested milk with omega-3 on consumers to assess the health benefits of regular consumption, but they plan to conduct a study using cows fed a diet with added soybean and canola oil to measure the effects of milk with higher omega-3 and omega-6 content on pigs, whose physiology is similar to that of humans, according to Saran Netto.
“We’ve seen the benefits of including canola oil for milk fat quality, which can be extended to human health via the consumption of milk with more omega-3,” she said. “Now, we’re going to take a closer look at the real effects using pigs as a model.”
The article “Canola oil in lactating dairy cow diets reduces milk saturated fatty acids and improves its omega-3 and oleic fatty acid content” (doi: 10.1371/journal.pone.0151876) by Saran Netto et al. can be read in the journal PLoS One at journals.plos.org/plosone/article?id=10.1371/journal.pone.0151876.
Productivity and quality
For several years, Saran Netto and colleagues at FZEA-USP have focused on improving the productivity and nutritional quality of animal products, such as milk and meat, by supplementing animal feed with vitamins, minerals and antioxidants, among other functional ingredients.
As part of a previous project, also funded by FAPESP, they added sunflower oil with organic selenium and vitamin E to the cows’ diet, successfully improving their health and milk yield and resulting in product conservation and increased levels of selenium and vitamin E in the blood of children who consumed the product (read more at agencia.fapesp.br/14748).
In early 2014, as part of another project, they produced low-cholesterol meat by adding vitamin E, selenium and sunflower oil to cattle feed (read more at agencia.fapesp.br/18613).
More recently, also as part of a project supported by FAPESP, they added vitamin E, canola oil and selenium to the diet of beef cattle in order to study the effects of this supplementation on gene expression, meat quality, and the animals’ immune systems.