|Mitchell, Robert - Rob|
Submitted to: Crop Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/23/2005
Publication Date: 9/25/2005
Citation: Mitchell, R., Vogel, K.P., Klopfenstein, T., Anderson, B., Masters, R.A. 2005. Grazing evaluation of big bluestems bred for improved forage yield and digestibility. Crop Sci.45;2288-2292. Interpretive Summary: Big bluestem is a perennial grass native to North America, and was one of the primary species of the tallgrass prairie. 'Pawnee' and 'Kaw' big bluestem are commercially-available cultivars, and Pawnee C3 and Kaw C3 were bred for increased yield and digestibility from the parent populations. The objective of this study was to compare beef cattle average daily gain (ADG) and gain per acre on pastures seeded to two big bluestem strains bred for increased yield and digestibility. Averaged over the 3 years, Pawnee C3 and Kaw C3 produced 16% and 7% greater ADG, respectively, than their parent populations. Pawnee C3 pastures produced 14% more gain per acre than Pawnee pastures, and Kaw C3 pastures produced 5% more gain per acre than Kaw pastures. Average beef production per acre for the 3 years of the study ranged from 355 pounds for Pawnee to 405 pounds for Pawnee C3. The results of this 3-year grazing trial demonstrate the productivity of big bluestem pastures in the eastern Great Plains, and document the positive livestock response to moderate increases in grass digestibility. Pawnee C3 and Kaw C3 have been released as the big bluestem cultivars 'Bonanza' and 'Goldmine' respectively, and represent the first big bluestem cultivars developed specifically for increased animal performance by increasing forage yield and digestibility, and validated by grazing trials.
Technical Abstract: Two big bluestem (Andropogon gerardii) strains (Pawnee C3 and Kaw C3) developed by three breeding cycles for increased forage yield and in vitro dry matter digestibility (IVDMD) were compared to the base populations of 'Pawnee' and 'Kaw' in a 3-y grazing trial. Pastures were seeded in May 1998 near Mead, NE. Experimental units were three 0.4 ha pastures of each strain or cultivar in a randomized complete block design. Pastures were burned and fertilized with ammonium nitrate at 112 kg N ha-1 in the spring of 2000, 2001, and 2002 prior to grazing. Each pasture was stocked with three crossbred yearling steers ('350 kg) in mid-June 2000, 2001, and 2002 to provide a stock density of 7.5 steers ha-1. Pawnee C3 and Kaw C3 produced 16% and 7% more average daily gain (ADG), respectively, than the base populations during this 3-y study. Additionally, Pawnee C3 and Kaw C3 produced 14% and 5% more kg of beef ha-1, respectively, than the base populations. Pawnee C3 ADG was 1.30 kg h-1 d-1 and it produced more than 455 kg of beef ha-1 y-1 during a drought period in eastern Nebraska. Pawnee C3 pastures had more available forage and its forage had higher IVDMD, cell soluble, cell wall digestibility, and lower lignin concentration than forages from Pawnee pastures. Kaw C3 pastures differed from Kaw pastures by producing forage with greater crude protein concentration. Pawnee C3 and Kaw C3 are adapted to USDA Plant Hardiness Zones lower 4 and 5 and lower 5 and 6, respectively, east of 100 W. Long. Pawnee C3 has been released as the cultivar 'Bonanza' and Kaw C3 has been released as 'Goldmine'.