Funding for this research was provided by:
Contribution of this author was funded by the University of Groningen and the FrieslandCampina company.
Contribution of this author was funded by FrieslandCampina, the Dutch ministry of Economic Affairs and the Provinces of Groningen and Drenthe.
Received: 15 February 2018
Accepted: 18 October 2018
First Online: 14 November 2018
: The authors declare no competing interests.