Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/16/1995
Publication Date: N/A
Interpretive Summary: In recent years there has been increasing interest in streamside zones on western rangelands. Grazing by livestock can impact streamside vegetation, and there have been efforts to reduce or remove livestock from streamside areas on both public and private land. However, there is relatively little experimental information on how moderate or light stocking rates of cattle influence their behavior and impact on streamside zones. Most research has focused on heavy stocking rates. We found that cattle selected similar diets when grazed at light and moderate stocking rates, and production of the vegetation at the beginning of grazing was higher in the two grazed treatments compared to an ungrazed control. At the light stocking rate cattle spent relatively more time at the streamside location than those grazing at the moderate intensity. Thus, simply reducing number of livestock may not reduce impacts to streamside vegetation. Timing of grazing and other management considerations may be more important at the stocking rates used for this study.
Technical Abstract: 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 and digesta kinetics. Nine .5-ha pastures were assigned to one of three treatments: ungrazed (CON); 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). Standing crop biomass was greater (P<.05) in grazed pastures than CON pastures at initiation of grazing in 1992 but not in 1993. Stocking density did not alter botanical or chemical composition of the diet in 1992, and only minor differences were noted (P<.05) in 1993. Forage intake, passage rate measures and total time spent loafing did not differ (P>.10) between LOW and MOD steers. Total time spent grazing was greater (P<.05) for MOD steers than LOW steers in 1992 and was affected (P<.05) by a treatment x trial interaction in 1993. In 1992 grazing time along the streamside was greater (P<.05) for LOW compared with MOD steers. In 1993, streamside grazing time was influenced by treatment, being greater (P<.05) for MOD steers than LOW steers. In general, our data suggest that management decisions to reduce stocking densities may force cattle to congregate along streambanks and to concentrate grazing and loafing activities in those areas.