• Diet selection by sheep and goats on Mediterranean heath-woodland range

      Bartolomé, J.; Franch, J.; Plaixats, J.; Seligman, N. G. (Society for Range Management, 1998-07-01)
      The study determined the species components of the diets of small ruminants grazing mountain ranges of the Montseny Biosphere Reserve (Catalunya, NE Spain). Three mixed flocks of sheep and goats, led by shepherds, were monitored for a year. Animals grazed a mountain rangeland composed of Quercus ilex woodland and Calluna-Erica heathland during the day and were returned to their corrals every night. Diet selection was estimated using fecal analysis. Of the 111 species that were identified, 71 were common to both sheep and goat. Of these, 23 were represented in proportions of more than 1% of the annual diet. Even though goats and sheep grazed together, their diets were significantly different (p < 0.0001), the animal factor accounting for 18% to 60% of the total variation among the main diet components. Variation between seasons was also a major (5% to 56%) highly significant factor, while differences between flocks accounted for a significant, but relatively small part (3 % to 10% ) of the total variation in diet. The outstanding difference was the avoidance of the tree, Quercus ilex, by the sheep while the goats selected it throughout the year. Sheep selected graminoids throughout the year while goats tended to avoid them. For the rest there was substantial overlap in species composition between the diet of sheep and goats, especially when analysed over an entire cycle.
    • Fecal NIRS for predicting percent leafy spurge in diets

      Walker, J. W.; Clark, D. H.; McCoy, S. D. (Society for Range Management, 1998-07-01)
      Research on diet selection is limited by inadequate techniques for determining botanical composition of diets. Our objective was to determine if near infrared reflectance spectroscopy (NIRS) of fecal material could be used to quantify the percentage leafy spurge (Euphorbia esula L.) in the diets of sheep (Ovis aries) and goats (Capra hircus). Fecal material representing diets of known percentage leafy spurge was obtained from feeding trials conducted in 1992 and 1994. In 1992, diets containing 87.5, 75, 60, 45, 30, and 15% leafy spurge were fed to 20 sheep and 20 goats. In 1994 10 sheep and 10 goats were fed alfalfa hay (Medicago sativa L.) at 0.5% of their body weight and ad libitum access to leafy spurge hay. Thus, the percent leafy spurge in the diet varied daily. Microhistological analysis was performed on fecal samples from the 1992 trial for comparison with NIRS predictions. Near infrared reflectance spectroscopy evaluations were performed with a scanning reflectance monochromator. Calibrations were done separately for sheep and goats. Samples were divided into calibration and validation sets. Data from the 1994 feeding trial were analyzed to determine the appropriate lag time between diet consumption and fecal spectral characteristics that provided the best prediction. The average of the diet composition 48 and 72 hours prior to the fecal sample provided the best predictions for the 1994 trial. The effect of spectral outliers on prediction accuracy was also evaluated. Spectral outliers were predicted with equal or better accuracy compared to samples that were spectrally similar to the ones from which calibration equations were derived. The NIRS predictions were more accurate than microhistological estimation of leafy spurge in the diet. The final calibration equation had coefficients of simple correlation for validation samples of 0.91 and 0.93 and standard errors of prediction of 4.6 and 4.8 for goats and sheep, respectively. The results of this study showed that NIRS of fecal material can be used to screen large numbers of animals for phenotypic differences in diet selection and for making treatment comparisons.
    • Soil depth assessment of sagebrush grazing treatments using electromagnetic induction

      Bork, E. W.; West, N. E.; Doolittle, J. A.; Boettinger, J. L. (Society for Range Management, 1998-07-01)
      Depth to a root restricting layer affects both soil moisture and nutrient availability, resources strongly correlated to plant cover and production. We evaluated the potential of 2 electromagnetic induction meters (EM38 and EM31) for non-destructively assessing soil depth to bedrock in 2 long-term seasonal sagebrush steppe sheep grazing treatments with different vegetational compositions. Apparent conductivity readings, measured with the EM38 and EM31 in both the horizontal (H) and vertical (V) dipole orientations, were positively related to soil depth. Apparent conductivity measured with the EM31H (r2 = 0.78) and EM38V (r2 = 0.75) were the best predictors of depth. Soil depth distributions were similar between grazing treatments based on Kolmogorov-Smirnov (K-S) tests of the EM38H apparent conductivity (P = 0.47) and EM38V apparent conductivity (P = 0.56). In constrast, K-S tests for the EM31H apparent conductivity (P = 0.09) and EM31V apparent conductivity (P < 0.01) indicated the fall-grazed treatment had a larger area in which soil depth exceeded 150 cm. Because less than 2% of each grazing treatment was predicted to have soils deeper than 150 cm, however, overall site differences between the 2 treatments appeared to be minor. Therefore, the vegetational differences between the treatments have probably resulted more from differences in the seasonality of grazing rather than ecological site characteristics as reflected in soil depth. Maps of soil depth indicated both treatments consisted of intermittent shallow and deep soils, created by several parallel basalt pressure ridges. Results suggest electromagnetic induction can effectively assess the spatial variability of soil depth and could aid in selecting sites for rangeland monitoring or manipulation.