Persistence of perennial cool-season grass and legume cultivars under continuous grazing by beef cattle

Persistence of highly productive forage species in pastures is essential to maximize economic returns from grazing livestock, However, most forage cul tivars are neither developed nor evaluated under grazing. The objective of this study was to evaluate several cool-season forage species and cultivars to determine their tolerance to continuous grazing. Three grazing experime nts were established in 1996 in central Iowa: (i) 20 cultivars and populati ons of alfalfa (Medicago sativa L.), (ii) 15 cultivars representing five co ol-season legume species, and (iii) 25 cultivars and germplasms of six tool -season grass species. Beef cattle (Bos taurus) continuously grazed the exp eriments for about four months in 1997 and 1998. Alfalfa yield was measured in adjacent plots. Stand survival ratings were taken each year. Among the alfalfa entries, grazing-tolerant 'Alfagraze' showed high persistence but m oderate yield. Several new alfalfa populations combined excellent grazing t olerance with yield equal to the best hay-type cultivar, Kura clover (Trifo lium ambiguum Bieb.) and white clover (T. repens L.) persisted better than alfalfa, birdsfoot trefoil (Lotus corniculatus L.), and red clover (T. prat ense L.), with no loss of stand after two grazing years. Orchardgrass (Dact ylis glomerata L.) and tall fescue (Festuca arundinacea Schreb.) persisted well, though considerable variation was present among orchardgrass cultivar s after the second grazing year. Reed canarygrass (Phalaris arundinacea i,. ) and smooth bromegrass (Bromus inermis Leyss.) stands were reduced to <10% after one grazing year. Although the severe, continuous grazing used in th ese experiments is not recommended, it clearly and quickly differentiates a mong species and cultivars for grazing tolerance.