Milk production of fall-calving dairy cows during summer grazing of grass or grass-clover pasture

Milk production of fall-calving dairy cows during subsequent summer grazing was evaluated in two consecutive years using a total of 80 mid- to late-la ctation Holsteins. Cows calved during September and October and grazed from April to August in the following year. In yr 1, 27 cows grazed a native gr ass pasture and 13 cows grazed a native grass-clover mixed pasture containi ng 26% red clover and white clover. In yr 2, 40 cows grazed native grass pa sture as one group. Also, cows in yr 2 were administered bovine somatotropi n, whereas in yr 1, no bST was used. Grazing cows also were fed concentrate supplements at 6.2 kg/d of dry matter (DM) in yr 1 and 7.9 kg/d of DM in y r 2 to provide 35 to 40% of total intake. Average daily milk during the gra zing period decreased 3.6 kg in yr 1 and 7.7 kg in yr 2 when compared with milk yield extrapolated from the lactation curve established 10 wk before b eing turned out to pasture. Estimated DM intake during grazing was also les s than what would have been expected had cows continued on a total mixed ra tion in confinement. Cows grazing the mixed pasture of grass and clover yie lded 1.3 kg/d more milk than those grazing the grass pasture in yr 1. A dec rease in milk resulting from the change from total mixed ration fed in conf inement to grazing supplemented with concentrates was not avoided with thes e mid- to late-lactation cows, but the cumulative loss over the lactation w as less than with early lactation cows in a companion study. Clover enhance s the grazing value of pasture when grown with grasses.