摘要：

In the central Great Plains, crested wheatgrasses (Agropyron cristatum(L.) Gaetner and A. desertorium (Fischer ex Link) Schultes] arebest utilized for early spring and late fall grazing. The principal objectiveof this study was to determine if beef (Bos taurus L.) yearlingsgrazing 'Ruff' (A. cristatum) during the spring grazing season hadhigher average daily gains and gains per hectare than cattle grazing`Nordan' (A. desertorum). These cultivars were evaluated in grazingtrials (four replications) in eastern Nebraska in 1985, 1986, and 1987.The 0.8-ha pastures were seeded in the fall of 1983 on a Typic Argiudollsoil and were fertilized annually with 68 to 90 kg N ha-1. Grazingwas for 6 wk each spring by yearling steers with a beginning averageweight of 250 kg. Averaged over 3 yr, Ruff produced higher gainsper hectare than Nordan (272 vs 245 kg ha-1) probably because itproduced more herbage because of its better persistence. At the endof the trial, the averge basal cover of Ruff and Nordan were 21 and6%, respectively. Three-year mean average daily gains were Ruff =1.28 vs. Nordan = 1.34 kg d-1, which were unexpected, because Ruffgenerally had higher forage quality as measured by an array of parameters.Ruff forage had a higher, less desirable grass tetany ratio[K/(Mg +Ca)) than Nordan (2.6 vs. 2.3) averaged over 3 yr. Cattlegrazing Ruff had lower blood serum Mg levels than cattle grazingNordan (15.4 vs. 16.2 mg L-1, both of which were below the hypomagnesemiathreshold of 18 mg L-1. This condition may have reducedintake and animal gains. These results indicate the need for evaluatingpasture and range grass cultivars under grazing conditions.

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