• Comparison of seeded and native pastures grazed from mid-May through September

      Hofmann, L.; Ries, R. E.; Karn, J. F.; Frank, A. B. (Society for Range Management, 1993-05-01)
      Cool-season introduced grass species are not recommended for season-long grazing in the northern Great Plains. They mature earlier than native species, which leads to an earlier loss in forage quality and palatability. A study conducted at Mandan, N.D., compared liveweight gains of yearling steers grazing crested wheatgrass [Agropyron desertorum (Fisch. ex Link) Schult.], smooth bromegrass (Bromus inermis Leyss.), and western wheatgrass [(Pascopyrum smithii (Rydb.) Love] and level native prairie (Class II and III land) and hilly native prairie pastures (Class IV and VI land), season-long. A set stocking rate of 1.5 AUM ha-1 was used from mid-May through late September in 1988, 1989, and 1990. Caged standing crop was higher from the seeded pastures than from the native pastures but liveweight steer gain was highest from the level native. Three-year average gains were 124, 114, 108, 106, and 105 kg per steer for level native, smooth bromegrass, western wheatgrass, hilly native, and crested wheatgrass pastures, respectively. The seeded cool-season grass pastures, grazed season-long at a rate 25% higher than that recommended by the SCS for native range, produced acceptable liveweight steer gains without additional inputs. Season-long grazing may provide an alternative use for marginal cropland and other highly erodible land that has been reseeded to cool-season species.
    • Influence of ruminally dispensed monensin and forage maturity on intake and digestion

      Fredrickson, E. L.; Galyean, M. L.; Branine, M. E.; Sowell, B.; Wallace, J. D. (Society for Range Management, 1993-05-01)
      Eight ruminally cannulated crossbred steers (average weight 336 kg) grazing native blue grama (Bouteloua gracilis [H.B.K.]) rangeland were used in a repeated measures design to evaluate effects of monensin ruminal delivery devices (MRDD) and forage phenology on ruminal digestion. Three periods were assessed: mid-August (Aug.), early October (Oct.), and mid-November (Nov.). One MRDD was placed in the reticulum of 4 steers via the ruminal cannula 21 days before each period. Intake was estimated using total fecal collections. Diet samples were collected using 3 esophageally fistulated steers. Ruminal fill was measured by ruminal evacuation; rate and extent of in situ ruminal neutral detergent fiber disappearance were estimated before ruminal evacuations. Ruminal passage rates, retention time, and apparent total tract organic matter digestibility were estimated using indigestible neutral detergent fiber. In vitro organic matter disappearance of esophageal masticate did not differ (P > .05) in Aug. and Oct. (average of 53.7%), but declined (P < .05) in Nov. (48.7%), whereas organic matter digestibility was greater (P < .10) in Aug. (62.3%) than in either Oct. (55.2%) or Nov. (53.9%). Release of monensin from the bolus (68 mg day-1) was less than expected (100 mg day-1). Intake, organic matter digestibility, ruminal passage rates, retention time, pH, and ammonia were not affected (P > .10) by MRDD. In situ neutral detergent fiber disappearance at 96 hours was decreased (P < .10) by MRDD (68 vs 65% for control and MRDD, respectively). As the grazing season progressed, intake declined (P < .10), whereas ruminal fill and retention time increased (P < .05), and passage rate of indigestible neutral detergent fiber decreased (P < .05). At 48 hours in situ neutral detergent fiber was greatest (P < .05) in Aug. and least (P < .05) in Nov.