Browsing arid rangeland shrubs under multispecies management strategies

TitleBrowsing arid rangeland shrubs under multispecies management strategies
Publication TypeConference Paper
Year of Publication1991
AuthorsAnderson D.M., Gibbens, Robert P., Hulet, Clarence V., Havstad K, Estell R.E.
Conference NameIV International Rangeland Congress
Date Published1991
AbstractThe deciduous shrub tarbush (Flourensiacernua DC.) grows on fertile clay loam soils of 5 to 6 x 106 ha of North America's Chihuahuan Desert. Blooming tarbush is toxic to ruminants, whereas vegetative tarbush can be safely browsed. Under conventional management strategies tarbush seldom exceeds 15% of free-ranging animal diets. In an attempt to defoliate tarbush cattle, sheep, Spanish goats and Angora goats (8:20:17:2; 23 AU/ha) were used to stock eight 0.6 ha paddocks, four at a time, for 8 to 9 days during vegetative growth between August and September 1989. Mean tarbush canopy cover, estimated using line-point transects, was 17% and 11% before and after stocking, respectively. Daily tarbush defoliation was monitored on 120 plants randomly chosen among the eight paddocks. In addition, 20 tarbush plants, adjacent to the paddocks, were hand-harvested and -separated. Mean annual tarbush leaf, flower and twig production was 385 kg/ha. Individual tarbush plant defoliation ranged from 5 to 99%. Cattle refused to browse only tarbush and were the first animal species removed due to a lack of other available forage. Sheep consistently lost liveweight (2.3 to 3.0 kg/hd) and body condition (0.8 unit) regardless of paddock. Goat body condition did not change overall. In four of the paddocks, Spanish goats gained 0.5 kg/ha while Angoras lost 1.4 kg/hd. Goat liveweight in the remaining four paddocks did not change (P > 0.05). Overall, 48, 67, 82 and 84% of cattle, sheep, Spanish goat and Angora goat diets were tarbush, respectively. Short intervals of high-density multispecies stocking reduced tarbush foliage. However, unique plant and animal differences existed which affected tarbush use.