Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/4/2000
Publication Date: N/A
Citation: Interpretive Summary: Some dairy producers have turned to intensive rotational grazing to lower milk production costs, and are also practicing seasonal calving to manage labor needs. Most producers who practice seasonal calving are calving in the spring just before the pasture is available, and then graze during the early-mid part of lactation. An alternative would be to calve in the fall, and feed cows in the early and mid part of lactation in confinement during the winter, followed by grazing for late lactation and the dry period. Since cows usually produce more milk under confinement feeding, it might be advantageous to feed cows in confinement during the early part of lactation rather than at the end. this experiment was conducted to answer this question. Milk production of fall-calving cows during subsequent summer grazing was evaluated in 2 consecutive years using a total of 80 mid- to late-lactation Holsteins. In year 1, there were two treatment groups, with one group grazing grass only, and a second group that grazed grass paddocks containing 26 percent red clover and white clover combined. In year 2, the paddocks contained only grass. Cows grazing the mixed pasture of grass and clover in year 1 yielded 1.3 kg/day more milk than those grazing grass alone. Decreased milk production resulted when cows in mid- to late-lactation were switched from confinement feeding to grazing, but the loss in milk production was less than for cows in early lactation in a companion study. We concluded in this study that farmers who practice rotational grazing with seasonal calving will likely have higher milk production with fall calving than spring calving. This research will be of benefit to dairy producers who practice intensive rotational grazing, and who may wish to consider seasonal calving.
Technical Abstract: 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-lactation Holsteins. Cows calved during September and October, and grazed from April to August in the following year. In year 1, 27 cows grazed a native grass pasture, and 13 cows grazed a native grass-clover mixed pasture containing 26 percent red clover and white clover. In year 2, 40 cows grazed native grass pasture as one group. Grazing cows also were fed concentrate supplements at 6.2 kg/d of DM in year 1 and 7.9 kg/d of DM in year 2 to provide 35 to 40 percent of total intake. Average daily milk decreased 3.6 kg in year 1 and 7.7 kg in year 2 during grazing when compared to milk yield extrapolated from the lactation curve established ten weeks before being turned out to pasture. Estimated DMI during grazing was also less than what would have been expected had cows continued on a TMR in confinement. Cows grazing the mixed pasture of grass and clover yielded 1.3 kg/d more milk than those grazing the grass pasture in year 1. A decrease in milk, resulting from the change from TMR fed in confinement to grazing supplemented with concentrates, was not avoided with these mid- to late-lactation cows, but the cumulative loss over the lactation was less than with early-lactation cows in a companion study. Clover enhances the grazing value of pasture when grown with grasses.