HEUMILCH – Chemical markers in milk for the detection of silage addition in feed of dairy cows

Funded by:

European regional development fund (ERDF 2014–2020)

Purpose of the project:

In the production of “Heumilch” (literally “hay milk”), in the diet of dairy cows the use of fermented feed, i.e. grass and maize silage, is prohibited. The HEUMILCH project focused on the development and optimisation of a standardised and reliable method for distinguishing between standard milk and “hay milk”. It is based on an official analytical method developed for the differentiation of Parmigiano Reggiano from Grana Padano. In particular, it considers specific fatty acids (CPFA) that have been identified in cheeses made from milk produced with the use of maize silage (i.e. Grana Padano), but not in Parmigiano Reggiano, which is made without the use of silage. The HEUMILCH project aimed to test whether the presence of these molecules could also be detected in milk when silage was included in the diet. A novelty of the project is the analysis of milk obtained with grass silage (i.e. not only maize silage), which is widely used in South Tyrol and on which, to date, no research for CPFA has been carried out.

Expected results:

Development of an analytical method for identifying the difference between standard milk and “hay milk”, particularly in relation to the addition of silage in the ration of dairy cows, by:
I. Development of an analytical method for the determination of CPFA in milk and evaluation of the detection limit of CPFA in “hay milk"
II. Development of rapid and effective methods for screening of CPFA or any other compounds in milk.
III. Identification of possible new chemical markers in milk that are associated with the presence of silage in the feed of dairy cows using high resolution mass spectrometry (HR-MS).


The results of the joint project show that milk from cows that were not fed silage contains no cyclopropane fatty acids (CPFA). In contrast, CPFA are detectable in milk from cows fed both maize and grass silage. The average concentration of CPFA in milk is higher when maize silage is used, but the developed analytical method can also detect the use of grass silage. In this case, the average CPFA concentration is lower and, in a few cases (about 7%), the use of grass was not detectable in the milk samples. The experiments also showed that CPFA are detectable in the milk as early as 3 days after the introduction of maize silage in the cow’s diet. Furthermore, it was demonstrated that these molecules remain in the milk until up to 2 months or 2 weeks from when respectively maize silage or grass silage have been removed from the diet.

The developed analytical method can guarantee with a certain margin of reliability that no silage feed is used for the production of “hay milk”.

The CPFA detection method developed in the project will be offered in future as a routine analysis at the Laimburg Research Centre.

Link to the final event of the project and presentation of the results




Project duration:

01.01.2019 - 31.03.2022


Project team:

The HEUMILCH project involved an interdisciplinary approach and close collaboration between all project partners. Specifically, the Laboratory for Flavours and Metabolites of the Laimburg Research Centre was responsible for the analysis of the specific marker in milk and silage samples. The Food Technology sector and the Mountain Agriculture sector of the Laimburg Research Centre contributed to drawing up the experimental plan, the sampling of milk and fodder at the farms, data processing as well as carrying out silage trials. The mountain agriculture consulting company BRING calculated the fodder ration. The Forage Analysis Laboratory analysed the forage quality. The Free University of Bozen/Bolzano dealt with the screening of compounds in milk and the search for alternative markers to differentiate “hay milk” from standard milk. The South Tyrolean Dairy Federation was not only responsible for sampling and sample management/storage, but also played a liaison role between the research institutions and that of the 32 South Tyrolean producers involved.

Lead Partner - Laimburg Research Centre:




Free University of Bolzano:


Federazione Latterie Alto Adige:


Ex collaborators: