Take home messages:
- Omega 3 fatty acids are linked to many health benefits for consumers
- Omega 3 levels in milk can be influenced by the cow’s diet, such as increasing fresh forage feed intake
- Consumer demands for organic dairy products and healthier foodstuffs means that farmers may be able to gain additional profits by increasing the level of fresh forage feeds within the production system
Omega 3 fatty acid concentrations in milk
Omega 3 fatty acids have been linked with many health benefits for consumers, such as
reducing the incidence of cardiovascular disease (CVD) and improved neurological function.
Milk contains over 400 different fatty acids, in particular, omega 3 and 6 are essential fatty
acids that are not produced in the human body therefore need to be included in the diet.
Omega-6 is often included at high levels in many western diets, which can lead to increased
risk of CVD, cancer, and inflammatory diseases. The recommended omega-6: omega-3 ratio
is in the range of 1-4:1, although in some western diets the ratio can be greater than 10:1.
However, lower ratios can be present in milk from pasture fed dairy cattle. The composition
of milk fatty acid profiles depends on the fatty acids consumed by the animal and the
biohydrogenation process occurring in the rumen. Hence there are a range of factors that
affect the fatty acid profile, such as breed, season, location and feed. The omega-3
composition of milk can be influenced by the cow’s diet, hence plant types at pasture are
important. Pasture management also plays a large role in the fatty acid composition of
forage with younger plants containing higher levels of fatty acids than older plants. Season
also has an effect on fatty acid concentration, increasing in the plant during early spring and
autumn.
Increasing Omega-3 levels in milk
Omega-3’s are polyunsaturated fatty acids (PUFA’s) consisting of three main types, ALA
(alpha-linolenic acid), DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid). ALA is an essential fatty acid, which needs to be included in the diet as it cannot be made within
the body. From ALA the body can make DHA and EPA. By substituting saturated fatty acids
(SFA) in the human diet for PUFA’s can reduce the incidence of disease and mortality rates.
Thereby, reducing the level of SFA and increasing the concentration of PUFA in milk can
boost the health benefits of milk and dairy products. To increase omega-3 intake the
fortification of commonly consumed foods is increasing. Milk can be fortified with plant
based omega-3’s, however, by fortifying the cow’s own diet can influence the level of
omega-3 in milk.
The nutrition of the cow is a natural and economical way for farmers to modulate the fatty
acid composition in milk. However, the proportion of pasture grass in cow’s diets has
declined in recent years, with an uptake of supplementary feeds in the form of grain or
pelleted concentrates to improve milk yield. Arguably, grazing is a more sustainable system
than the indoor feeding of animals, although this does depend on farm and herd size. Much
research has shown that milk from grazing animals has higher levels of PUFA than indoor
housed animals, although supplementing indoor fed animals with such food as oilseeds or
algae can also increase PUFA content in milk. Cereals are rich in linoleic acid and oleic acid,
whereas fresh grass contains around 50 to 75% of its total fatty acid content as ALA.
However, it has been shown that any processing conducted on the plant (e.g. ensiling) will
reduce the ALA content of the feed thus effecting the ALA concentration in milk.
The types of plant that are available at pasture are important, with more diverse pasture
shown to produce higher PUFA concentrations in milk, through the inhibition or
modification of biohydrogenation in the rumen. Clovers have been shown to have a greater
ALA concentration than ryegrass, with red clover containing a greater ALA concentration
than white clover. Higher levels of omega 3 fatty acids may be achieved from certified
organic milk as many organic dairy farms graze their animals on clover. In a study
conducted by Ellis et al., (2006), they aimed to determine a difference between FA
composition of bulk tank milk from organic and conventional farms in the UK, also looking at
nutritional and seasonal effects. Results supported the hypothesis that organic milk had a
higher omega 3 content compared to conventional milk. Their results showed a number of
factors influencing the FA content of milk including, an increase in omega 3 during the
summer months and higher omega 3 content from mixed breed herds, which are also
related to differences in FA profiles. In Wales, a study investigated the difference in omega 3
content from a conventional high intensity system (CH), and organic medium-intensity
system (OM) and a conventional low-intensity system based on the New Zealand production
system (CL). As expected the highest amounts of omega 3 was determined from the OM
system, attributable to the greater level of clover intake. These studies show that switching
to pasture based dairy systems enables an increase in the health benefits of omega 3 in milk
whilst reducing unwanted levels of SFA.
Potential for profitability on farm
There is no doubt that over recent years there has been growing interest in improving the
health benefits of milk by moving away from grain and concentrate based feeds to rations
consisting of fresh forages, such as grass and legumes. Consumer demands for organic dairy
products and healthier foodstuffs means that farmers may be able to gain additional profits
by increasing the level of fresh forage feeds within the production system. For example, the
Piedmont Noble Milk project produced in Italy, showed the possibility to differentiate farm
production and promote a new drinking production model. Four dairy farms were involved
in the project, where during the summer cattle were fed fresh forage only. Piedmont Noble
milk showed highest concentrations of omega 3 FA during the summer, with desirable
omega 6 to omega 3 ratios compared to commercial milk. Upon consumer evaluation 88%
of testers could identify Noble milk, which was considered to have more freshness, flavour
and higher taste intensity and persistence. It has been suggested that the model used for
Piedmont Noble Milk might also be utilised by other extensively managed farms. Therefore,
enhanced milk as created from altering the cows’ diet to include more fresh forages can be
an alternative marketing strategy for a healthier consumer diet.