Does body size of dairy cows, at constant ratio of maintenance to production requirements, affect productivity in a pasture‐based production system?

This study compared productivity of dairy cows with different body weight (BW), but a constant ratio of maintenance to production requirements in their first lactation, in a pasture‐based production system with spring calving. Two herds, Herd L (13 and 14 large cows in 2003 and 2004 respectively; average BW after calving, 721 kg) and Herd S (16 small cows in both years; 606 kg) [Correction added after online publication 14 January 2011: 16 small cows in both years; 621 kg was changed to 16 small cows in both years; 606 kg], all in their second or following lactations, were each allocated 6 ha of pasture and rotationally grazed on 10 parallel paddocks with equal herbage offer and nutritional values. Winter hay, harvested from the same pastures, was offered ad libitum in the indoor periods in a tied stall barn. Each herd received, per lactation and year, approximately 2000 kg dry matter (DM) of concentrates and of fodder beets, equally distributed to every individual. Indoors, the L‐cows ingested more DM than the S‐cows (18.7 vs. 16.3 kg DM/cow per day; p