Layout for Field Experiments
Lactating cows within the Pasture Dairy Center herd are divided into two long-term ‘farmlet systems’: 1) High Stocking Rate and 2) Low Stocking Rate. Within these farmlets, researchers study the effects of dairy management on cow behavior, nutrition and health; forage production and utilization; ecosystem services; and overall productivity. All research involving these animals and the pastures that they graze must fit within the farmlet systems.
The High Stocking Rate farmlet consists of 60-65 lactating cows grazing 40 acres during a six-month grazing season. Cow numbers remain constant during the non-grazing period (winter). During the grazing season, 60% of the dry matter intake (DMI) comes from pasture with the remainder coming from conserved feeds [20% as a partial mixed ration (pTMR) and 20% concentrate]. During the winter months, the ration consists of 80% from a Total Mixed Ration (TMR), with the remainder being concentrate. Targets of 2.8 milkings and 65 pounds of milk per cow per day have been set for this group during the grazing season and 3.1 milkings and 75 pounds of milk per cow per day during the winter.
The Low Stocking Rate farmlet consists of 75-85 lactating cows grazing 80 acres during a 7-8 month grazing season. Cow numbers are reduced to 60-65 during the winter. Approximately 60% of this group calve in the spring to allow for the greater cow numbers during the grazing season. During the grazing season, 80% of the DMI is provided by pasture with the remainder coming from concentrate (20%). During the winter, the ration is similar to that of the High Stocking Rate farmlet group. Targets of 2.0 milkings and 55 pounds of milk per cow per day have been set for this group during the grazing season. During the winter, target production is similar to that of the High Stocking Rate farmlet.
Within both farmlet systems, two contrasting forage mixes (simple and complex) are available within the pastures. The simple pasture mix includes perennial ryegrass (Lolium perenne) and white clover (Trifolium repens); while the complex mix includes perennial ryegrass (Lolium perenne), orchardgrass (Dactylis glomerata), tall fescue (Festuca arundinacea Schreb.), alfalfa (Medicago sativa), red clover (Trifolium pratense), birdsfoot trefoil (Lotus corniculatus), and white clover (Trifolium repens). Both the simple and complex pasture mixes contain approximately 40% legumes.
The lactating herd consists of approximately 80% U.S. Holstein genetics, with the remaining animals being New Zealand Friesian. The North American Holsteins have a mature body weight of 1400 to 1500 pounds; mature body weight of the Freisians is around 1,000 pounds.
A more detailed description of the farmlet systems, and a pasture map: