A Look at the Fatty Acid Profile of Milk from Ontario Organic Dairy Farms

Consumers are becoming more focused on the importance that food can play in maintaining a healthy lifestyle. Mounting evidence from research and consumer awareness about the potential health benefits of various components in our foods has given rise to the concept of functional foods and has created a demand for foods with improved nutrient profiles.

Milk fat contains approximately 400 different fatty acids, which make it the most complex of all natural fats. Fatty acids such as EPA (eicosapentaenoic acid), DHA (docosahexaenoic acid) and CLA (conjugated linoleic acid) are examples of such functional food components that are found in cows' milk. One of the goals of the dairy industry in the last 25 years has been to enhance the concentration of these fatty acids that may have beneficial effects in humans. To achieve this, the main objective has been to improve the ratio of unsaturated fatty acids to saturated fatty acids.

The consumption of more omega-6 fatty acids than omega-3 fatty acids is a well-known risk factor for a variety of health problems, including cardiovascular disease, cancer, excessive inflammation, and autoimmune diseases. The higher the ratio of omega-6 to omega-3, the greater the associated health risks. Western diets typically have a ratio of about 10- to -1 to 15- to -1or more, while a ratio of 2.3- to -1 is thought to maximize heart health. Considerable research has taken place in recent years that is focused on strategies that are capable of altering the fatty acid profile of cow's milk to achieve a fatty acid profile consistent with consumer perceptions and health recommendations. The nutritional enhancement of omega-3 and CLA are of particular interest because of their potential benefits to human health.

The milk fatty acids are derived almost equally from two sources, the feed and the microbial activity in the rumen of the cow. Generally speaking, concentrations of CLA can be more easily enhanced through diet formulation and nutritional management of dairy cows, than EPA and DHA. However, many factors are associated with the variations in the amount and the fatty acid composition of the fat component of cow's milk. These factors may be of animal origin, i.e. related to genetics (breed and selection), stage of lactation, mastitis and ruminal fermentation, or they may be feed-related factors, i.e. related to fibre and energy intake, dietary fats, and seasonal and regional effects.

The predominate feed sources of polyunsaturated fatty acids in ruminant diets are linolenic acid, derived principally from forage crops, and the other is linoleic acid, a major component of oilseeds and concentrates that are fed to dairy cows. The predominate form(isomer) of CLA in milk is referred to as rumenic acid and it is produced by the biohydrogenation of linoleic acid. Vaccenic acid is another isomer of CLA formed from both linoleic acid and linolenic acid.

A large body of research has shown that grass and legume forages can promote cow health as well as potentially enhance the fatty acid profile of the milk fat. The feeding and management protocols of organic milk production, where there is a greater reliance on pasture and forage-based feeds and less reliance on grains, should theoretically result in the production of milk with a fatty acid profile that is potentially healthier for consumers.

Researchers Alan Fredeen and Payam Vahmani from Dalhousie University recently reported on a project where they set out to test the assumption or hypothesis that the fatty acid profile in organic milk is improved relative to conventionally produced milk, with the difference being related to feed. This project involved the participation of 36 dairy farms in Ontario, with 14 of those farms being organic (Org) and 22 being conventional (Con). Milk samples from the bulk tank and feed samples from the major forages fed were taken between September 2011 and November 2011 and referred to as the fall period (F), samples taken from April 2012 to May 2012, were referred to in this study as the spring group(S). Both milk and feed samples were analyzed for fatty acid composition. Researchers found large variations in feed composition due to the wide range in feeds used in the cows' diets. The average forage composition of the diets is shown in Table 1. On average, organic farms in this study milked 74 cows per farm while the conventional farms milked 60 cows.

MAIN FORAGE

Table 1: Average Forage Composition of Diets

Table 1: Average Forage Composition of Diets

Highlights of the Ontario Study

  • Differences in milk fatty acid profiles between organic and conventional in this study were small.
  • Milk content of rumenic and vaccenic acid (CLA isomers) were highest in the OrgF milk (Table 2)
  • The forage content of alpha linolenic acid was highest in the OrgF group (25.8+/-4.0%) followed by Con-F (8.6+/-4.5%); Org-S(5.7+/3.2%); Con-S(3.70+/-1.36%)
  • Organic milk had a higher content of stearic acid and alpha linolenic acid compared to the conventionally produced milk.
  • The ratio of Omega 6 to Omega 3 fatty acids in the organically produced milk was much lower - which is considered healthier.
% of Total FAs
% Rumenic Acid
% Vaccenic Acid
Organic Fall
5.19
.68
1.79
Organic Spring
4.09
.45
.91
Conventional Spring
4.51
.47
.89
Conventional Fall
4.33
.45
.90

Table 2: Rumenic and Vaccenic Acid (CLA isomers) Content in Milk Samples.

Based on the results of several previous studies, providing cows with fresh pastures resulted in a two to three fold increase in the CLA content of milk fat, but this effect diminished as the pastures matured. Another interesting point is that the enhanced levels of CLA in milk cannot be totally accounted for by the fatty acid composition and supply of polyunsaturated fatty acids that fresh grass provides. Therefore, other unknown factors or components of grass are thought to promote the production of vaccenic acid (CLA) in the rumen.

While the conclusions of this Ontario study of comparing the fatty acids of organically produced milk versus conventionally produced milk suggest that the organically produced milk is slightly more healthful for consumers, further research to improve the knowledge about the effects of different grass and forage species; the importance of fresh grazing and the possible effects of the season would be useful to organic dairy producers who have an interest in enhancing the content of beneficial fatty acids in the milk that they produce.

References

Lock, Adam. L. and Bauman, Dale E. 2004, Modifying Milk Fat Composition of Dairy Cows to Enhance Fatty Acids Beneficial to Human Health,Lipids,Vol.39,no.12 (2004)

Fredeen, A., Tucker, A., Levison, L., Bergeron, R., Vahami, P., and Devries, T., Milk Fatty acid profile of organic farms in Ontario. Canadian Journal of Animal Science, 2014 94(1):175-222


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