Can dairy cows get enough vitamins from their diet, or are supplements required? Here is a summary of some of the latest findings.
In the early 2000s, the EU imposed a ban on giving supplements of synthetic vitamins to ruminants in organic production. Despite the ban, it was understood that there was a lack knowledge on how cows' health and production would be affected by not giving vitamin supplements. Therefore, a dispensation was given to continue using mainly synthetic vitamin A, D and E. From 2006 the ban was removed completely. But still, if there are natural vitamins available, they should be used first.
Several studies on the need for vitamin supplements
Natural vitamins come mainly from forage (silage) and oilseeds. The content in plants varies depending on climate and other factors. Therefore, there have been a number of studies in Sweden to explore the basis for the use of vitamins to Swedish organic cows.
In a recent published study from an attempt at the experimental farm Tingvall, half of the cows were given a mineral mixture without vitamin supplements for two years. In a comparison of vitamins in cow's blood, researchers could not see any big differences between cows and cows that had not received vitamin supplements, except for vitamin D, and then only during the cold season. But cow health deteriorated so that those who did not receive supplementation had more treatments for mastitis year 2 than in year 1 and in addition more mastitis than those who received vitamins the second year They also had higher cell content of the milk in the second year.
The cows in the above experiments were fed with silage with good content of vitamins. But the content of the silage has been shown to vary widely among crops and years. In another two-year trial (e.g. published in a thesis from 2012) the cows got so-called semi-natural vitamin supplements (vitamin E, which is on the market) in a high rate around calving, when cows have the highest vitamin needs. The content of vitamins in the silage was almost twice as high the first year compared with the second, and the supplement seemed to have much less effect on vitamin levels in cow's blood when the vitamin content of the silage was high than when it was less vitamins in the silage.
The current recommendations is based on the cow's total needs, but with a feeding high doses of silage with a high vitamin content, cows should be able to support themselves with vitamins without supplementation, at least in the medium-and late lactation. The problem is to know the vitamin content of the silage and to order a vitamin analysis is expensive. The above-mentioned thesis also includes studies on the factors that can influence the content of vitamins in ley crops.
It is not only the cow that is affected by access to vitamins. The Swedish Farmers' Foundation for Agricultural Research reports from a study that showed a correlation between high levels of vitamin E in 2–7 day old calves and low calf mortality. By feeding heavily pregnant cows with vitamin-rich feedstuffs, they get a higher vitamin content in the blood, leading to a vitamin-rich colostrum, which in turn improves the vitamin status of the calves.
Johansson, B., Persson Waller, K., Jensen, S. K., Lindqvist, H. and Nadeau, E. 2014. Status of vitamins E and A and β-carotene and health in organic dairy cows fed a diet without synthetic vitamins. Journal of Dairy Science, 97: 1682-1692.
Thesis from 2012: α-tocopherol and β-carotene in forages and their utilisation by dairy cows in organic production