Controlling pasture growth is an ongoing struggle in many pasture systems. Yet, it is often a major determinant of livestock performance.
The balancing act of offering enough forage quantity to provide adequate energy intake while also maintaining a high plane of forage quality is a major challenge.
Eric Mousel, an extension beef specialist with the University of Minnesota, recently completed a study with cow-calf pairs that contrasted four different grazing strategies on perennial cool-season grass pastures. He reported his results in the most recent issue of the Midwest Forage Association’s Forage Focus magazine.
The study was conducted on upland, improved pasture consisting largely of orchardgrass, quackgrass, timothy, and Kentucky bluegrass.
The treatments, which all included 20 cow-calf pairs, were as follows:
1. A season-long continuously grazed pasture (80 acres) with pairs turned out June 1 and pulled off on October 1.
2. Four 20-acre pastures with pairs turned out May 15 and pulled September 15 to maintain a vegetative stage of growth.
3. Four 20-acre pastures with pairs turned out June 15 and pulled October 15 to maintain an elongation stage of growth.
4. Four 20-acre pastures with pairs turned out July 1 and pulled November 1 to maintain grass in the seedhead stage.
The season-long continuous grazing and the seedhead stage treatments were similar in terms of body weight (BW) gain (Table 1). Only grazing at the elongation stage significantly improved cow BW. Calf BW at the end of grazing in the elongation stage was 7% higher than other treatments.
“Moisture concentration among the treatments varied widely, Mousel notes. “Feed moisture concentrations over 70% to 75% seem troublesome for grazing ruminants. As moisture goes down, performance increases as long as corresponding nutrients are available.”
Mousel explains that the “washy grass” effect observed in the northern and eastern U.S. has a big impact on performance. Not only does cow weight gain suffer on immature, high-moisture grass without supplement, milk quantity and/or quality to the calf also declines.
“There is also a focus on nutrient concentrations rather than nutrient yield in grazing situations,” Mousel asserts.
“This nutrient yield improvement, in combination with the performance data, suggests cows, and to a lesser degree calves, are short of energy in the season-long and vegetative stage treatments,” he explains. “Therefore, grazing strategies adhering to keeping vegetation short may in fact be limiting energy and total intake at certain times of the grazing season, even at recommended stocking rates.”