• Botanical Composition of Diet of Steers Grazing a Desert Grassland Range

      Galt, H. D.; Theurer, B.; Ehrenreich, J. H.; Hale, W. H.; Martin, S. C. (Society for Range Management, 1969-01-01)
      Rumen-fistulated steers were employed to study the botanical composition of the diet on a desert grassland range. Botanical composition of the major plant species in the diet was determined on a qualitative and quantitative basis using a microscope point technique. The botanical composition of the diet changed greatly with time of year and was considerably different quantitatively compared to the available forage. Crude protein content of the rumen samples was considerably greater than the protein content of the whole hand-clipped major plant species identified in the rumen samples./Para estudiar la composición botánica de la dieta en un pastizal desértico de gramíneas en Arizona, se emplearon novillos con fistula ruminal. La composición botánica de la dieta de los novillos varió cualitativa y cuantitativamente dentro de los cuatro meses del período de colección. La dieta con el tiempo no solo varió grandemente en la cantidad de ciertas especies de zacates y a fines de otoño y principios de invierno ciertos arbustos y cactus llegaron a ser parte de la dieta. La composición de las especies de las muestras del rumen difirieron marcadamente en forma cuantitativa al compararse con el forraje disponible. Los novillos fueron muy selectivos no solamente en la elección de las especies de plantas disponibles sino también en la parte de la planta que ellos pastoreaban. El contenido de proteína cruda de las muestras del rumen fue marcadamente mas grande que el contenido de proteína cruda estimado basado en un promedio de peso del porciento de composición de las especies de plantas predominantes en la dieta y los valores de proteína para las especies cortadas a mano. El contenido mayor de proteína en las muestras del rumen parece ser debido a la selectividad de los animales a partes específicas de la planta. Estos resultados reflejan la dificultad en estimar el contenido de proteína cruda la dieta de novillos pastoreando por medio de muestras de plantas cortadas a mano. En adición, estimaciones obtenidas por la observación de los novillos cuando pastoreaban proveyó una información cualitativa general acerca de qué especies de plantas fueron seleccionadas, pero tales estimaciones no fueron cuantitativamente confiables.
    • Botanical Composition of Steer Diets on Mesquite and Mesquite-Free Desert Grassland

      Galt, H. D.; Theurer, B.; Martin, S. C. (Society for Range Management, 1982-05-01)
      Botanical composition of cattle diets on mesquite and mesquite-free desert rangeland was determined on a weight basis by a microscope point technique and density constants of species. Pastures consisted primarily of grasses, small amounts of forbs and shrubs, and velvet mesquite (17% crown canopy) on one unit. Dietary composition of plant groups consisted of 67 to 97% grasses, 0 to 4% forbs, and trace to 33% shrubs. Species composition of diets varied by seasons and among animals. Plant preference was not necessarily related to plant availability. Composition of diets was markedly different from composition of pastures. Black grama averaged only 3% of diets, but comprised about one-third of herbage production. Arizona cottontop, which averaged 20% of herbage on pastures, was the most consistently selected species, averaging 34% of the diet. Seasonal preference was shown for certain grasses such as rothrock grama in spring and bush muhly in winter. Highest preference for shrub species was shown in winter and early summer. Overall dietary composition between pastures was much the same, but average herbage production for a 2-year period was 347 kg/ha greater where mesquite had been controlled. Leaves comprised the major plant part of steer diets on both pastures. Leaf content of diets increased from winter to summer while stems decreased for the same periods. Botanical composition of animal diets can be a guide to more efficient use of the range resource by grazing animals.
    • Estimating Botanical Composition of Forage Samples from Fistulated Steers by a Microscope Point Method

      Galt, H. D.; Ogden, P. R.; Ehrenreich, J. H.; Theurer, B.; Martin, S. C. (Society for Range Management, 1968-11-01)
      A microscope point method was used to develop weight prediction equations for plant species in masticated forage samples of known species weights collected at the end of two successive growing seasons. A high correlation was found in regressions of percent weight on percent points for all the masticated plant species. Two observers were consistent in their ability to estimate similar amounts of plant species in a given species mixture. With 400 microscope points, the average weight of a species was estimated within 5% of the mean at a 90% level of probability when the species constituted 30 to 60% of the sample weight.