Since the high profile publication of Benbrook (et al 2013) in PLoS one, research into organic milk has continued. This found “organic production enhances milk nutritional quality” by improving the omega three to six fatty acid ratio in a statistically significant way.
Indeed, as Ferrerio et al (2015) say “Milk from organically managed cows contains higher levels of vitamins, antioxidants, and unsaturated fatty acids than conventionally produced milk”, as though this is standard, accepted thinking in the field.
It’s important to note that, inevitably, with different breeds, seasons, feeding regimes to take into account in different countries, it can be difficult to compare organic and conventional milk. Studies also differ in how they are set up, as Schwendel et al point out in an invited review of research comparing organic and conventional dairy:
"Lack of research on interactions between several influential factors and differences in trial complexity and consistency between studies" means more research is needed before making robust conclusions, Schwendel et al (2015) say.
(An invited review shares similarities with a meta-analysis. However there is no compulsion on a meta review to be as systematic. Instead a leading expert is invited to review what he or she deems to be the important literature.)
Schwendel (et al 2015) do note some consistency of results for six different fatty acids across countries and seasons in relation to organic milk. “This result might suggest, that independent of origin, organic cows consume a different diet (higher amount of pasture and other forages) than conventional cows. This can be seen as a direct result of regulations mandating that organic dairy cows in the United States and European countries ...have access to pasture and outdoor areas.”
However in the main, they list a range of studies which back up their central point that breed, feed, seasonality and a range of other factors are the crucial components in determining the nutritional content of milk, rather than its being organic per se.
While it is no doubt true that all these other considerations need to be taken into account, it is also the case that the factors which lead to positive fatty acid and antioxidant levels for organic milk and nutrition tend to be outdoor, grass feeding. In Ireland, while cows in general are very grass fed and outdoors by global standards, organic cows also of course are too. With organic, however, there are also specific rules to limit the amount of feeds other than grass the cows can get.
As Schwendel (et al 2015) add, even this grass fed dimension can be complicated by the addition of supplements to concentrated feeds. They also emphasise how important the different grass swards are (in table 4 on fatty acids).
But again, organic farming leads the way in developing more complex grass swards. Organic farmers do this to compensate for the lack of mineral fertilizers. Organic farmers can have, not just white and or red clover in their grass swards, but a range of bespoke grasses to optimise each field's performance. This, combined with mandated outdoor grasing time, makes organic quite specific and very grass and other plant based in diet for cows.
Indeed Kusche (et al 2014) emphasise low input outdoor organic as the optiminal, in a published paper called "Fatty acid profiles and antioxidants of organic and conventional milk from low- and high-input systems during outdoor period". This paper is contextualised by the emergence of more conventional style maize (a cereal crop) silage and concentrated feeds in organic farming – a high input system - and examines whether this is effecting milk quality. Comparing low and high input systems for each of organic and conventional, it concludes that the “highest concentrations of nutritionally beneficial compounds” namely fatty acids and antioxidants “were found in the low-input organic system”
In other words, outdoor animals fed more on grass than on concentrated feeds – and that’s exactly how organic milk is produced in Ireland.
As research moves on, it will be possible to do more studies of the grass species in organic swards themselves. Adler (et al 2013) analysed 4 different types of silage (that's grass cut in the summer and kept for feeding animals in the winter) including 2 organic ones. The first organic grass was a mix of the first and third cut of organically managed short-term grassland with a grass type called timothy and with red clover. The second was a longer term grassland with what they described as “high proportion of unsown species” (i.e. wild grasses). This is a typical organic grass sward, as organic farmers need a wider variety of plants to do the work 'chemicals' (i.e mineral fertilizers) do. The researchers concluded that both organic diets, because of these extra plant components, “increased milk fat proportions of beneficial fatty acids,” while also having other positive effects (ruminal biohydrogenation).
Of course, it would be most beneficial to Irish consumers if research into organaic milk in Ireland was conducted. While this has been done for the biodiversity performance of organic dairy farms, alas no published work has yet studied organic milk from Irish dairy farms – either in the tank or in the carton.