This is what it probably is.

Often there is nothing derelict or abandoned about it.
A great many Danish farms have become too small to be viable on their own in the last ten or twenty years, and so farmers have bought up the land from neighbouring farms.

The houses are then sold off as country houses, possibly with a couple of hectares of land for the owner to keep horses on, or to run a plant nursery or the like.

While some are run down or derelict, many are well-kept, attractive houses. It is sometimes possible to buy a home with space for children and a garden for the same price as a small town appartment.

The owners work in the nearby towns and either enjoy the countryside and garden or carry on ´weekend farming´.

Google for more if this link no longer works (because the house has been sold!)
http://www.edc.dk/Sag/?pid=85519173

Lystejendom, beliggende i udkanten af Tvede med udsigt over markerne og med 7.566 m2 grundareal med plads til en hest. ... Ideelt for naturelskeren eller jægeren. Til ejendommen hører et fritliggende stuehus i god stand med pudsede ydermure og eternittag ... Stuehuset indeholder: Bryggers, vaskerum med vask, køkkenalrum med god stor spiseplads, viktualierum og en dejlig stor opholdsstue med fransk dør til spisestuen. Badeværelse med bruser, 3 værelser og opgang til 1. salen ... Kan overtages med det samme.



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Note added at 18 hrs (2010-11-08 10:40:50 GMT)
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A special point about some of these houses is that there are regulations about the owner living on the property if it is run as a farm. (Bopælspligt/beboelsespligt) These regulations no longer apply to a house designated as a ´nedlagt landbrug´. The rights and obligations will have been transferred along with the land, or simply cancelled if the owner already lives in a neighbouring house with bopælspligt.