The number of dairy cows put outside to pasture remained steady at 1.1 million last year,  the national statistics office CBS said on Monday.

Between 2001 and 2011, the number of cows with access to fields and fresh grass fell from 90% to 70%. The percentage was still 70% last year.

The main reason for keeping cows indoors is the size of farms. Last year, the Netherlands had 2,900 farms with more than 125 cows, four times the 2000 figure, the CBS said.

Farmers with large herds prefer to keep them indoors because it is cheaper. They also claim to be better able to monitor the health of their cows and the quality of their milk.