Pastured Holstein cows are as productive as their haylage-fed counterparts in an Arlington Agricultural Research Station study.
The study is comparing milk production and fat and protein composition in intensive, rotational grazing systems and a conventional stored-feeding system. Researchers are also evaluating yield, quality and persistence of forages on pure alfalfa and mixed grass/legume pastures.
“At least in the system we’re running now, the data tend to suggest that we’re not seeing lower milk production on pasture,” says UW-Madison dairy scientist Dave Combs.
Combs is conducting the study with dairy science graduate student Kim Vaughan and UW-Madison agronomist Ken Albrecht. The study is part of a larger rotational grazing project conducted jointly with farmers and non-profit groups from Wisconsin and Minnesota and University of Minnesota scientists. It is supported by the USDA Sustainable Agriculture Research and Education program. The project includes on-farm research in rotational grazing and an economic comparison between conventional farmers and rotational grazers. CIAS and Wisconsin Rural Development Center staff are coordinating the project.
The research station study included 18 first-calf heifers and 24 cows in 1991 and 18 first-calf heifers and 27 cows in 1992. Half of the animals grazed either on a pure alfalfa pasture or on a mixed grass-alfalfa pasture. The other half received alfalfa silage and feed concentrate in a stanchion barn.
All cows also were fed protein supplements according to their milk production, lactation period and quality of forage they received. Rations were balanced to meet fiber, energy, protein, and mineral requirements.
Initial pasture seeding took place in April, 1990. In the pure alfalfa stand, researchers seeded 15 pounds per acre. In the mixed pasture, they seeded 7 pounds of alfalfa, 3 pounds of red clover, 1.5 pounds of orchardgrass and 6 pounds of smooth-bromegrass per acre.
In 1991, pastured cows grazed from May 8 to August 1. Severe winter kill of alfalfa during the winter of 1991-1992 forced researchers to reseed pastures with 12 pounds of alfalfa and 3 pounds of red clover in the spring of 1992. As a result, cows pastured on pure alfalfa could not start grazing until July 3. Cows on the mixed pasture started grazing May 22, primarily because the grasses survived the winter much better than alfalfa. Cows pastured until September 18 on the alfalfa pasture and October 1 on the mixed pasture in 1992.
Milk production and quality in 1991 and 1992 varied little across the three systems, with a few exceptions. (See accompanying tables.) Confinement cows averaged 3.41 percent fat in 1991, compared to 3.16 percent for cows on alfalfa pasture and 3.23 for cows on mixed pasture. In 1992, heifers of mixed pastures had a slightly higher milk fat percentage, averaging 3.55 percent fat compared to 3.38 percent for the alfalfa pasture heifers and 3.34 percent for heifers in confinement. Milk protein levels were similar both years.
The 24 acres of pasture in the study are divided into six 4-acre paddocks using a New Zealand fencing system. Animals rotated every 22 to 30 days and are moved onto new forage twice a day. The back fence is moved twice a week so cows can’t regraze and trample pastures.
“As long as we maintain that type of rotation, the quality of forage on pastures is nearly as consistent as alfalfa silage,” says Combs.
Harvesting excess forage is also important to maintain quality, especially during the early-season lush growth, he adds. In a farm situation, the excess forage could be used for winter feeding.
In both years, dry matter yields in the mixed pasture were higher than in the alfalfa pasture. About 3 tons per acre of dry matter in 1991 and slightly less than 3 tons in 1992 were available for grazing in the mixed pasture. In the alfalfa pasture, about 2.8 tons of dry matter were available for grazing in 1991, and about 2.2 tons were available in 1992.
Researchers harvested 1.5 tons of dry matter off the alfalfa pasture and 2 tons of dry matter off the mixed pasture per acre in 1991. In 1992, they harvested about 1/2 ton of feed off the mixed pasture and 1.3 tons from the alfalfa pasture.
Crude protein averaged 22 percent in the alfalfa pasture, 21 percent in the mixed pasture and 20 percent for the alfalfa silage in 1991. Fiber content also was a little lower in the alfalfa pasture. Combs notes, however, that adding brome and orchardgrass to legume pastures did not reduce pasture quality enough to hurt milk yields.
“We expect over time that the composition of the mixed pastures will be more grasses and less legumes,” he says.
In addition, grasses offer a lot of advantages in pastures, says Combs. Grasses may protect the alfalfa plants from heaving and winter kill and help to suppress weed growth. They also persist better and can reduce bloat problems. A heavy rain in late August 1991 led to lush regrowth on the pure alfalfa pasture and bloated several cows.
Because forage quality in the pastures was higher than the alfalfa silage, pastured cows received less grain than the confined cows.
Project researchers and farmers are conducting grazing demonstrations and field trials on a number of pasture grasses on 15 Wisconsin and Minnesota farms. In addition, information on economics, management and labor requirements is being collected.
“We’re hoping that with our data and their (on-farm) data we can put together some general picture on rotational grazing,” Combs notes.
Contact CIAS for more information about this research.
Published as Research Brief #13