CATTLE GRAZING A RIPARIAN MOUNTAIN MEADOW - EFFECTS OF LOW AND MODERATE STOCKING DENSITY ON NUTRITION, BEHAVIOR, DIET SELECTION, AND PLANT-GROWTH RESPONSE

Twelve ruminally cannulated and six intact crossbred beef steers were used in a randomized complete block design to evaluate the effects of stocking density of a riparian pasture in the Sierra Nevada mountains on grazing behavior, dietary selection, forage intake, digesta kinetic s, and growth rates of Caret nebraskensis and Juncus balticus. Nine .5 -ha pastures were assigned to one of three treatments: ungrazed (CON) or grazed to leave either 1,500 kg/ha (LOW) or 1,000 kg/ha (MOD). Two collections were conducted during the summer of 1992 (following winter drought) and 1993 (following above-average winter precipitation). Sta nding crop biomass was greater (P < .05) in grazed pastures than in CO N pastures at initiation of grazing in 1992 but not in 1993. After gra zing in both 1992 and 1993, a treatment x intrapasture location intera ction was noted (P < .05). Tiller growth rates in both 1992 and 1993 w ere affected (P < .05) by a treatment x growth period interaction. Sto cking density did not alter (P > .10) botanical or chemical compositio n of the diet in 1992, and only minor differences were noted (P < .05) in 1993. Forage intake, passage rate measures, and total time spent l eafing did not differ (P > .10) between LOW and MOD steers. Within the mid-meadow area in 1992, leafing time was greater (P < .05) for MOD s teers than for LOW steers. In 1993, a treatment x trial interaction wa s noted for leafing time in all three areas. Total time spent grazing was greater (P < .05) for MOD steers than for LOW steers in 1992 and w as affected (P < .05) by a treatment x trial interaction in 1993. In 1 992 grazing time along the streamside was greater (P < .05) for LOW st eers than for MOD steers, and significant treatment x trial interactio ns were noted for grazing time spent along the forest edge and mid-mea dow areas. In 1993, only streamside grazing time was influenced by tre atment being greater (P < .05) for MOD steers than for LOW steers. In general, our data suggest that management decisions to reduce stocking densities may force cattle to congregate along streambanks and to con centrate grazing and leafing activities in those areas.