Measured per kilo milk produced Danish cows have developed into some of the best in the world at utilising their feed and lowering their climate impact. Over the last 30 years, surplus nitrogen and emissions of greenhouse gases from cattle farming have fallen drastically. This development may be able to continue if research results from Aarhus University are anything to go by.

The development from 1950 to 2010, the future prospects until 2040 and new research results that can carry the development forward were presented at the annual seminar on dairy cow nutrition, which was arranged by the Department of Animal Science at Aarhus University and held at the AU Foulum.

The presentations from the seminar have been published in a report by DCA – Danish Centre for Food and Agriculture. Here one of the topics you can read about is the extrapolation of the results to 2040, which shows that the positive development will continue but will rely on changes to animal genetics, feeding and management.

Fat and nitrate give lower impact

Danish cows are currently responsible for 45 percent of the total emission of nitrogen and 56 percent of the total emission of methane from livestock farming. One way whereby farming could reduce its environmental impact is via feeding strategies. Scientists from the Department of Animal Science have tested different feeding strategies that combine increased productivity with a reduced impact, including lower emissions of methane and nitrogen.

In one of the experiments they found that a feeding strategy based on a high energy and protein level in the mobilisation phase followed by a drop in the energy and supplementation with 5-6 percent fat in the deposition phase can reduce the environmental load from dairy cows. Feeding high-quality roughage means you can increase the proportion of roughage, particularly following the mobilisation phase.

Another experiment showed that increasing the nitrate concentration in the feed can reduce methane emissions by up to 23 percent without adversely affecting the digestibility of the feed.

New alternative feed ingredients on the menu

One of the ways of increasing sustainability is to use waste products from other productions. An example of this is distiller’s grain. The production of ethanol from grain and maize generates the waste product distiller’s grain, which can be used as a feed ingredient. Dried distiller’s grain is increasingly available on the Danish market.

Experiments at the Department of Animal Science show that cereal-based distiller’s grain is a good protein feed that does not have any negative effect on milk production or quality and can make up to 15 percent of the dry matter content of the feed ration. The dried distiller’s grain can substitute half of the protein sources such as soy pellets and rapeseed cake in the ration for dairy cows.

An alternative product, which scientists at Aarhus University have tested and which is included in the report from the seminar, is glycerine. This is a liquid, syrupy feed ingredient which originates from the production of biodiesel using plant oils. The supply of this product is expected to increase.

The scientists found that glycerine can replace up to 12 percent of the dry matter of starchy sources of energy in the feed ration for dairy cows such as barley without any negative effects on the cow’s productivity or milk quality and that it even has a positive effect on feed uptake and milk content of fat and protein.

Vitamin D requirements

In the last 10 years, scientists at the Department of Animal Science have studied intensively the vitamin D supply and physiology in cattle. The results of this research were also presented at the seminar.

Vitamin D affects a number of physiological processes in the body and has, for example, a large effect on the risk of calving problems and the incidence of mastitis in cows. Vitamin D is produced in the skin with the help of sunlight. The scientists have studied the cows’ vitamin D status when they are indoors and outdoors.

It turns out that summer sunlight is a very important source of vitamin D for dairy cows and that there is a direct link between how long they stay in the sun and how much vitamin D is measured in their blood. If the cows do not have access to sunlight, they will need to be given a vitamin D supplement. The studies indicate that the existing recommendations for the allocation of vitamin D to dairy cows are too low.

The report also includes presentations on the possibility of increasing the protein value of grass silage, the use of feed additives that are expected to have a positive effect on efficiency, and the most up-to-date knowledge on production response and the optimal feed level in the Nordic feed evaluation system NorFor.

The seminar “Malkekoens ernæring” (”Dairy cow nutrition”) was the seventh in the series of seminars on the subject.

The report (in Danish) ”Malkekoens ernæring – fodringsstrategier målrettet produktivitet og miljøhensyn”, DCA report no. 60, April 2015 can be downloaded here.

For further information please contact: Senior Scientist Peter Lund, Department of Animal Science, e-mail: peter.lund@anis.au.dk, telephone: +45 8715 8072, mobile: +45 4015 7673