Browsing Journal of Range Management, Volume 47, Number 2 (March 1994) by Subjects
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Bite characteristics of wapiti (Cervus elaphus) in seasonal Bromus-Poa swardsWe used a cubic sampling quadrat to study the 3-dimensional structure of volunteer Bromus-Poa swards, and explored the relationship of bite depth and sward height as a determinant of bite sizes of wapiti (Cervus elaphus) in the mixed-wood parklands of central Alberta, Canada. The vertical biomass distribution of the sward was pyramidal with leaves dominating the top stratum. Bite depths of yearling and adult wapiti were not significantly different but both were influenced by sward height and season. Wapiti selected bites in both vertical and horizontal dimensions. In spring, wapiti selected vertically, taking green leaves in the top layer of the sward. They selected forbs horizontally in summer and selected leaves vertically in mature autumn swards. Based on the relationships among bite depth and sward height, biomass and sward height, as well as vertical biomass distribution, we calculated expected bite sizes of wapiti on seasonal pasture. We also predicted changes of dietary protein and neutral detergent fiber with increasing bite depth. On spring swards, calculated dietary protein decreased and fiber increased as animals grazed deeper into the swards. In summer and autumn, dietary protein peaked as wapiti cropped about half of the height of the sward whereas dietary fiber was relatively constant. Wapiti adjusted their bite depth to select forage containing at least 14% protein in spring, summer, and autumn. The sacrifice of bite size in tall summer and autumn swards was compensated by diet quality.
Social facilitation influences cattle to graze locoweedMany ranchers claim that if a cow starts eating locoweed, she will teach others to eat it. Three grazing trials were conducted to evaluate the role of social facilitation in starting cattle to graze locoweed. The first trial was conducted near Gladstone, N.M., using mature cows grazing woolly locoweed (Astragalus mollissimus var. mollissimus Torr). The second trial was conducted on the Raft River Mountains in northwestern Utah, using yearling cattle grazing white locoweed (Oxytropis sericea Nutt). The third trial was conducted to determine if aversion-conditioned yearling cattle would consume white locoweed when placed with cattle that were eating locoweed (loco-eaters). Cattle conditioned to eat locoweed and naive animals in trials 1 and 2 first grazed in separate pastures to evaluate their initial acceptance of locoweed. The groups in the respective trials then were placed together to evaluate the influence of social facilitation on locoweed consumption. Locoweed consumption was quantified by bite count. Naive cattle in trials 1 and 2 sampled small quantities of locoweed while grazing separately. However, they greatly increased locoweed consumption when placed with the loco-eaters. Aversion-conditioned cattle in trial 3 did not consume locoweed while grazing separately. When placed with loco-eaters, they gradually increased consumption of white locoweed, in contrast to the immediate acceptance of locoweed by naive cattle in trials 1 and 2. The aversion extinguished and averted animals eventually accepted white locoweed at levels comparable to loco-eaters. Results of this study demonstrate that social facilitation can cause cattle to start eating locoweed.