Huber S A, Judkins M B, Krysl L J, Svejcar T J, Hess B W, Holcombe D W
School of Veterinary Medicine, University of Nevada, Reno 89557-0104, USA.
J Anim Sci. 1995 Dec;73(12):3752-65. doi: 10.2527/1995.73123752x.
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 kinetics, and growth rates of Carex 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). Standing crop biomass was greater (P < .05) in grazed pastures than in CON pastures at initiation of grazing in 1992 but not in 1993. After grazing in both 1992 and 1993, a treatment x intrapasture location interaction was noted (P < .05). Tiller growth rates in both 1992 and 1993 were affected (P < .05) by a treatment x growth period interaction. Stocking density did not alter (P > .10) 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. Within the mid-meadow area in 1992, loafing time was greater (P< .05) for MOD steers than for LOW steers. In 1993, a treatment x trial interaction was noted for loafing time in all three areas. Total time spent grazing was greater (P < .05) for MOD steers than for 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 steers than for MOD steers, and significant treatment x trial interactions were noted for grazing time spent along the forest edge and mid-meadow areas. In 1993, only streamside grazing time was influenced by treatment 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 concentrate grazing and loafing activities in those areas.
12头装有瘤胃瘘管的杂交肉牛和6头未装瘘管的杂交肉牛，采用随机完全区组设计，以评估内华达山脉沿岸牧场的放牧密度对放牧行为、日粮选择、牧草采食量、消化动力学以及内布拉斯加苔草和波罗的海灯心草生长率的影响。9个0.5公顷的牧场被分配到三种处理之一：不放牧（对照）或放牧至剩余1500千克/公顷（低密度）或1000千克/公顷（中密度）。在1992年夏季（冬季干旱之后）和1993年夏季（冬季降水量高于平均水平之后）进行了两次采集。1992年放牧开始时，放牧牧场的立枯生物量比对照牧场更大（P < 0.05），但1993年并非如此。1992年和1993年放牧后，观察到处理×牧场内位置的交互作用（P < 0.05）。1992年和1993年，分蘖生长率受到处理×生长时期交互作用的影响（P < 0.05）。1992年，放牧密度未改变（P > 0.10）日粮的植物学或化学组成，1993年仅观察到微小差异（P < 0.05）。低密度和中密度组的肉牛在牧草采食量、通过率指标以及躺卧总时间方面没有差异（P > 0.10）。在1992年的草甸中部区域，中密度组肉牛的躺卧时间比低密度组更长（P < 0.05）。1993年，在所有三个区域都观察到处理×试验的交互作用对躺卧时间的影响。1992年，中密度组肉牛的总放牧时间比低密度组更长（P < 0.05），1993年总放牧时间受到处理×试验交互作用的影响（P < 0.05）。1992年，低密度组肉牛在溪边的放牧时间比中密度组更长（P < 0.05），在森林边缘和草甸中部区域的放牧时间观察到显著的处理×试验交互作用。1993年，只有溪边放牧时间受处理影响，中密度组肉牛的溪边放牧时间比低密度组更长（P < 0.05）。总体而言，我们的数据表明，降低放牧密度的管理决策可能会迫使牛群聚集在河岸，并将放牧和躺卧活动集中在这些区域。
