• Temperature and Water Stress Effects on Growth of Tropical Grasses

      Bade, D. H.; Conrad, B. E.; Holt, E. C. (Society for Range Management, 1985-07-01)
      Coastal bermudagrass (Cynodon dactylon (L.) Pers.) and Kleingrass "75" (Panicum coloratum L.) were grown under controlled environments to evaluate the effects of high growth temperatures and water stress on forage growth. Plants were grown under a controlled environment with 14/10 hour day/night temperatures of 30/20, 35/25, and 40/30 degrees C; 2 water regimes; and 3 stages or ages of regrowth at harvest. High growth temperatures significantly (P<0.05) increased dry matter yield and accelerated tiller number and the maturation rate of the plants. Significant (P<0.05) increases in leaf area, weight per tiller, and plant height were observed as growth temperatures were increased. Reduction of number of tillers per pot due to water stress reduced dry matter yields approximately 38%. The percent leaf was greater for the water-stressed plants than for the well-watered plants, but the leaf area per plant was less due to reduction of growth and delayed maturation. Dry matter yield of water-stressed plants grown under higher temperatures increased more than corresponding well-watered plants as a result of increased rate of stem elongation and leaf development. Though water-stressed plants were shorter and had less leaf area than well-watered plants, the relative increase in both height and leaf area at higher temperatures of stressed plants was greater than well-watered plants. Apparently supraoptimal temperature (40 degrees C) does not have a negative effect on yield in the presence or absence of moisture stress.
    • The Animal-Unit and Animal-Unit-Equivalent Concepts in Range Science

      Scarnecchia, D. L. (Society for Range Management, 1985-07-01)
      The terms animal-unit and animal-unit-equivalent have evolved as a means of expressing different kinds and classes of livestock in a common form. This paper discusses the evolution of the concepts, analyzes their conceptual boundaries, and discusses their use in the analysis of range livestock systems. Recent efforts to modify these concepts to develop livestock species substitution ratios for specific ranges are discussed. For greater usefulness in describing range livestock systems, animal-unit-equivalents should be calculated based only on animal-related factors. Also, the animal-unit-equivalent concept should not be redefined in the calculation of pasture-specific substitution ratios.
    • The Use of Supplement Blocks for Sheep Grazing Dry, Annual Pastures in California

      DePeters, E. J.; Dally, M. R.; Alwash, A. A.; Therkelsen-Tucker, P. (Society for Range Management, 1985-07-01)
      The objective of this study was to evaluate the use of supplement blocks on body weight change, blood parameters, and lambing performance of ewes grazing dry, annual grasses during the summer prior to and during breeding. Two experiments were conducted in successive years to compare performance of unsupplemented control (C) and supplemented (S) Targhee ewes. In the first season, yearling ewes were used while aged ewes (2 or 4 years) were used during the second season. During the first year (1980), supplemented ewes lost less body weight during the dry grazing season than C ewes. However, no lambing performance difference was found between C and S groups. During the second year (1981), supplemented ewes maintained their body weight over the summer while C ewes lost weight. In addition, lambing performance (multiple births) was higher for S than C ewes. Supplementation of ewes with blocks containing molasses, urea, protein, and minerals required little labor input. However, based on lambing performance, it is unlikely that supplementation would be economically profitable under the range conditions utilized in these trials.