Grazing Evaluation of Big Bluestems Bred for Improved Forage Yield and Digestibility

the peak spring and autumn production periods for coolseason forages in the eastern Great Plains (Mitchell et Two big bluestem (Andropogon gerardii Vitman) strains (Pawnee al., 1994; Moser and Vogel, 1995). Krueger and Curtis C3 and Kaw C3) developed by three breeding cycles for increased forage yield and in vitro dry matter digestibility (IVDMD) were com(1979) in South Dakota reported monocultures of pared with the base populations of ‘Pawnee’ and ‘Kaw’ in a 3-yr Pawnee big bluestem grazed by yearling steers had an grazing trial. Pastures were seeded in May 1998 near Mead, NE. average daily gain (ADG) of 0.70 kg hd 1, and produced Experimental units were three 0.4-ha pastures of each strain or cultivar 138 kg total BW gain ha 1. They concluded that big in a randomized complete block design. Pastures were burned and bluestem forage can be used successfully for beef profertilized with ammonium nitrate at 112 kg N ha 1 in the spring of duction during summer. Conard and Clanton (1963) 2000, 2001, and 2002 before grazing. Each pasture was continuously reported similar results from big bluestem pastures in stocked with three crossbred yearling steers (Bos taurus) (380 38 kg) eastern Nebraska. in mid-June 2000, 2001, and 2002 to provide a stock density of 7.5 Pawnee and Kaw are cultivars of big bluestem that steers ha 1. Pawnee C3 and Kaw C3 produced 16 and 7% more are widely grown for forage in the central Great Plains. average daily gain (ADG), respectively, than the base populations during the 3-yr study. Additionally, Pawnee C3 and Kaw C3 produced Pawnee was originally collected in Pawnee County, NE, 14 and 5% more total body weight (BW) gain ha 1, respectively, than and was released jointly by the Nebraska Agricultural the base populations. Pawnee C3 ADG was 1.30 kg hd 1 and produced Experiment Station (AES) and USDA-ARS in 1963 greater than 455 kg total BW gain ha 1 during a drought period in (Alderson and Sharp, 1994). Kaw is a synthetic variety eastern Nebraska. Pawnee C3 pastures produced more available forthat originated from several lines collected near Manage with higher IVDMD, cell soluble, cell wall digestibility, and lower hattan, KS, and was released in 1950 by the Kansas AES lignin concentration than forages from Pawnee pastures. Kaw C3 (Alderson and Sharp, 1994). Pawnee is best adapted to pastures differed from Kaw pastures by producing forage with greater USDA Plant Hardiness Zones 4 (lower half) and 5, crude protein concentration. These results demonstrate the productivwhereas Kaw is best adapted to Zones 5 (lower half) ity of big bluestem pastures in the eastern Great Plains and document and 6 (Moser and Vogel, 1995). Kaw is usually 7 to 10 d the positive livestock response to moderate increases in forage IVDMD. The strains bred for increased yield and IVDMD provided later in maturity than Pawnee at the latitude of Mead, as much as 26% more total BW gain ha 1 at no additional cost. NE, which is near the northern limit of its recomPawnee C3 was released as the cultivar Bonanza and Kaw C3 was mended use. released as ‘Goldmine’. Increasing forage yield and digestibility in perennial grasses may increase livestock performance and profitability of grasslands (Anderson et al., 1988; Hopkins et B bluestem is a C4 perennial grass native to North al., 1993; Vogel and Sleper, 1994; Casler and Vogel, America (Weaver, 1954) and accounts for over 1999). The objective of this study was to compare beef 25% of the basal cover and over 40% of the herbaceous cattle ADG and total BW gain per hectare on pastures biomass of the tallgrass prairie (Weaver and Fitzpatrick, seeded to two big bluestem strains developed by three 1934; Masters et al., 1993). The importance of big bluegenerations of breeding for increased forage yield and stem in extensively managed native grasslands is recogin vitro dry matter digestibility (IVDMD) with the base nized by grassland scientists, including Weaver (1954) populations from which the two strains were derived. who called it, “the best prairie grass for both pasture We hypothesized that the strains bred for increased and hay.” Big bluestem pastures provide productive, forage yield and IVDMD (Pawnee C3 and Kaw C3) high-quality forage during late spring and summer and would produce superior ADG and total BW gain per may fill the forage availability gap that occurs between hectare when compared with the parental cultivars. Additional objectives were to determine if the strains difR.B. Mitchell and K.P. Vogel, USDA-ARS, Wheat, Sorghum and fered in stand persistence under grazing, available forForage Res. Unit, Univ. of Nebraska, PO Box 830937, Lincoln, NE age (AF), and nutritive value of AF. 68583; T.J. Klopfenstein, Dep. of Animal Science, Univ. of Nebraska, Lincoln, NE 68583; B.E. Anderson, Dep. of Agronomy and Horticulture, Univ. of Nebraska, Lincoln, NE 68583; and R.A. Masters, Dow MATERIALS AND METHODS AgroSciences, 8049 Nob Hill Road, Lincoln, NE 68516. This paper Seed of Pawnee C3 and Kaw C3 used to establish the pasis published as Journal Series No. 14873 of the Agric. Res. Div., Univ. ture trial was produced in seed increase nurseries at the Uniof Nebraska. Mention of trade names or commercial products in this versity of Nebraska Agricultural Research and Development publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the USDA Center (UNL-ARDC) near Mead, NE. Certified seed of Kaw or the University of Nebraska. Received 9 Dec. 2004. *Corresponding and Pawnee was obtained from commercial vendors. Pastures author ([email protected]). were seeded in May 1998 at the UNL-ARDC (41.17 N. Lat., Published in Crop Sci. 45:2288–2292 (2005). Forage & Grazinglands Abbreviations: ADG, average daily gain; ADL, acid detergent lignin; AF, available forage; CP, crude protein concentration; CW IVDMD, doi:10.2135/cropsci2004.0716 © Crop Science Society of America cell wall digestibility; DM, dry matter content; IVDMD, in vitro dry matter digestibility; NDF, neutral detergent fiber. 677 S. Segoe Rd., Madison, WI 53711 USA 2288 Published online September 23, 2005