Rotational Stocking of Caucasian Bluestem and Switchgrass Produced Good Dairy Heifer Gains
Crop and Soil Environmental News, December 1997
Paul Peterson, Extension Specialist, Forages
Steve Hutton, Research Specialist
Bob James, Associate Professor, Dairy Science
Ozzie Abaye, Extension Specialist, Alternative Crops
Holstein heifers gained 2.1 lb/day with rotational stocking of Caucasian bluestem during 3 months of grazing last summer at Virginia Tech's Kentland Farm at Whitethorne. A similar group of heifers rotationally stocked on switchgrass gained 1.5 lb/day over 3.5 months. These gains were achieved by grazing warm-season grass pasture and 1 lb/day of a supplement containing corn, mineral, salt, and Bovatec. Total supplement cost was just 6 cents per head per day.
Twelve Holstein heifers averaging about 530 lbs were placed on 3 acres of well- established Cave-in-Rock switchgrass on June 4. An additional 12 heifers were placed on 3 acres of Caucasian bluestem on June 17. This corresponds to initial stocking rates of 4 heifers or 2120 lb per acre. Switchgrass was about 20 inches tall and vegetative when the heifers were turned in whereas the Caucasian bluestem was only about 6 inches tall with some winter annual weeds present. Given delayed spring growth of these species following the cool spring, turn-in dates in 1997 were probably 7-10 days later than would have occurred in a typical year.
A front and back fence of single-strand, electrified polywire was used to allocate 2 days of pasture forage at a time throughout the trial on both grasses. A portable 60-gallon waterer was used to provide water in every paddock as the heifers were rotated. One hundred pounds per acre of N as ammonium nitrate was applied in split applications to both grass species.
The goal was to try to maximize the quality of pasture forage that could be obtained from these grasses. Switchgrass stubble height was about 7 inches initially, and increased to about 14 inches as the forage matured and stems became coarser within each grazing cycle. Caucasian bluestem was grazed to a 2-4 inch stubble height throughout the trial.
Initial stocking rates were too high to maintain satisfactory performance throughout the trial, especially on the Caucasian bluestem. This may have been due to the below average precipitation during the trial. Only 10.3" of rain fell during the trial. Thus, 3 heifers were removed from the Caucasian bluestem on July 16, and 2 more were removed on August 14. The seven remaining heifers grazed until September 16. Only 3 heifers were removed from the switchgrass on August 14, with the remaining 9 heifers grazing until September 16.
Although Caucasian bluestem produced greater daily gains, switchgrass had a greater carrying capacity in this trial (381 heifer grazing days per acre of switchgrass compared to 279 grazing days per acre of Caucasian bluestem). Turn-in on the Caucasian bluestem may have been too early, resulting in its reduced carrying capacity. The greater carrying capacity of the switchgrass resulted in similar total gain per acre for the 2 warm-season grasses, about 580 lbs/acre.
Forage samples were obtained throughout the trial to measure forage yield, quality, and utilization. These results will be reported in a future issue of The Virginia Forager. The grazing trial will be repeated next year.
Rotational stocking with a 2-day rotation and high stocking rates enabled us to achieve high levels of forage utilization and gain on these grasses despite the dry summer. It will be interesting to see if the intensive pasture utilization imposed in 1997 has any adverse effects on stands and vigor of these grasses next year.