• Clearcutting Brazilian Semiarid Tropics: Observations on Its Effects on Small Ruminant Nutrition during the Dry Season

      Kirmse, R. D.; Provenza, F. D.; Malechek, J. C. (Society for Range Management, 1987-09-01)
      Small ruminant production in northeast Brazil is limited by prolonged nutritional stress during the dry season. Our study assessed the effects of clearcutting woody vegetation on the nutrition of goats and sheep during the initial dry season following clearing. Dry matter intake g day-1 was higher for animals on cleared than on uncleared areas (818 vs. 627; P<0.05). Extrusa from esophageally fistulated animals grazing cleared, as opposed to uncleared, areas was more digestible (52 vs. 47%; P<0.05), was similar in crude protein (7.1 vs. 7.1%; P<0.05), and was lower in neutral detergent fiber (49 vs. 51%; P<0.05) and lignin (14 vs. 16%; P<0.05). Intake and diet quality declined on both cleared and uncleared areas as forage availability declined. Animals on cleared areas benefitted from increased availability of herbs and of biomass from palatable trees that coppiced and retained green leaves throughout much of the dry season. Animals on uncleared areas relied heavily on leaf litter from trees, which provided a poorer quality, but persistent, source of forage throughout the dry season.
    • Evaluation of the Forage-disk Method in Mixed-grass Rangelands of Kansas

      Karl, M. G.; Nicholson, R. A. (Society for Range Management, 1987-09-01)
      The forage disk meter, a double sampling device used to predict forage biomass, has been used extensively on improved pastures, but its use on rangelands has not been investigated thoroughly. Efficiency of the forage disk meter was investigated in predicting yields of forage biomass on different range sites in western Kansas. Using least squares regression methods, resting heights (forage bulk) and dry matter yields were used to calibrate the disk meter for each site and sampling date. Highly significant regressions (P<0.0001) were obtained on all the shortgrass sites, where several factors that had unfavorable effects on the regression relationship between forage bulk and forage biomass were not apparent. These factors, although not quantified, included accumulation of litter, microrelief, lodged vegetation, and presence of broadleaf species. Regression coefficients (b) and intercepts (a) varied between sites and dates, thus the forage disk meter should be calibrated for every range site. If a forage disk meter is calibrated for a specific range site, regression coefficients and intercepts might not differ from year to year if grazing pressure and species composition are temporally consistent, which implies that recalibration might be unnecessary. The forage disk meter was useful as a double sampling device on range sites dominated by shortgrasses, but its use was limited on areas dominated by annual forbs or midgrasses.
    • Forage Maturity Effects on Rumen Fermentation, Fluid Flow, and Intake in Grazing Steers

      Adams, D. C.; Cochran, R. C.; Currie, P. O. (Society for Range Management, 1987-09-01)
      Eight ruminally fistulated steers were observed on native range from 4 May 1981 to 5 Nov. 1981 to determine effects of advancing forage maturity on rumen fermentation, fluid passage, fluid volume, and forage intake. Effects of these factors are poorly defined for cattle on the Northern Great Plains but are essential for developing management strategies for optimum animal production. On 6 different dates, the steers were given an intraruminal dose of cobalt ethylenediaminetetraacetate (CoEDTA), and samples of rumen fluid were drawn at 4-hour intervals over a 24-hour time period. Rumen fluid samples were analyzed for volatile fatty acid, ammonia-N, cobalt concentration, and pH. CoEDTA was used as a marker to estimate rumen fluid passage and volume. Forage intake was determined by total fecal collection and in vitro digestibility of the forage. Total ruminal volatile fatty acid, molar proportions of individual volatile fatty acid, pH, and ammonia-N concentrations varied (P<0.01) within each of the six 24-hour periods, but the changes were dependent on date. Advancing forage maturity was associated with reduction in individual and total ruminal volatile fatty acid, ammonia-N, pH, and fluid dilution rate. Rumen fluid volume increased with increasing forage maturity. Variation in organic matter intake was small (P>0.05) over the range of forage maturities studied. We concluded that variation in rumen fluid passage, volume, and fermentation depended on forage maturity, and protein supplementation may be beneficial during late summer-early fall to increase or sustain animal production.
    • Influence of Watering Frequency on forage Consumption and Steer Performance in Southeastern Kenya

      Musimba, N. K. R.; Pieper, R. D.; Wallace, J. D.; Galyean, M. L. (Society for Range Management, 1987-09-01)
      Forty-five zebu steers (avg wt 311 kg) were allotted to 3 watering frequency treatments with 15 steers/treatment. The treatments involved watering once every day (1/1), watering once every 2 days (1/2) and watering once every 3 days (1/3) to investigate the effect of watering frequency on forage consumption and steer performance. Three steers/treatment were used to quantify fecal output and estimated forage consumption. All steers were grazed together in a 100-ha paddock for 10 hours daily and confined in a corral overnight. Steers were allowed ad libitum access to water only in the evenings according to the watering schedule. The study was conducted over 6 months, during which time total fecal collections were made in March, April, June, and July. All steers were weighed approximately every 2 weeks. Forage consumption was reduced (P<0.01) for steers watering (1/2) and (1/3), compared with the (1/1) watered group. Forage intake was highest (P<0.01) in April when herbage was green and growing. Steer performance followed a seasonal pattern reflecting changes in forage quality. Watering frequency did not influence steer performance. Reducing watering frequency from daily to once ever 2 or 3 days may enhance utilization of available range and save on cost of providing water for cattle under certain pastoral conditions.
    • Steer and Vegetation Response to Short Duration and Continuous Grazing

      Pitts, J. S.; Bryant, F. C. (Society for Range Management, 1987-09-01)
      Comparisons were made over a 4-year period between 1-herd, 16-pasture short duration grazing (SDG) and continuous grazing (CG) on the Texas High Plains. Animal performance, vegetation response, and diet quality were evaluated. Stocking rate on SDG was equal to that on CG the first year (13.3 ha/AU), double that on CG in the second year, and 1.5 times that on CG the third and fourth years. Average daily gain (ADG) of steers was the same (0.33 kg/day) between SDG and CG the first year. When stocking was doubled on SDG the second year, steers on SDG gained 0.15 kg/day compared to 0.25 kg/day under CG. In the third and fourth years, with stocking under SDG at 1.5 times that on CG, gains were similar. Standing crop biomass on SDG fell below that on CG after 1 year of grazing. In the second year standing crop was greater (P<0.05) on SDG than on CG, but in years 3 and 4, standing crop on the SDG was less than on CG. Changes in species composition were the same on both CG and SDG. Steer diet composition and quality were evaluated during the growing season (May to October) of year 4. Steers on SDG consumed 15% more forbs (39% vs 24%) than steers on CG. No differences (P>0.05) between CG and SDG were observed for dietary crude protein or in vitro digestible organic matter. SDG did not improve animal performance, diet quality, or forage availability over CG when evaluated over 4 years.
    • Ytterbium-Labeled forage as a Marker for Estimation of Cattle Fecal Output

      Musimba, N. K. R.; Galyean, M. L.; Holechek, J. L.; Pieper, R. D. (Society for Range Management, 1987-09-01)
      This study evaluated the accuracy of a once daily dose of ytterbium (Yb)-labeled forage as a marker to estimate fecal output of cattle grazing at the National Range Research Station, Kiboko, Kenya. Ytterbium-labeled forage was administered daily to 15 zebu steers for 10 consecutive days for each of 3 trials. During the last 5 days of each trial, fecal grab samples were collected at 6-h intervals. During this same 5-day period, total fecal output was collected from 9 of the steers. Ytterbium estimates of fecal output were 114%, 104%, and 144% of actual fecal output for March, April, and July trials, respectively. Dry matter and organic matter intake estimates between Yb and total collection procedures differed (P<.05) in the July trial, but not the March and April trials. Compared with total fecal collection, Yb overestimated organic matter intake by 20, 2, and 40%, respectively for March, April and July trials. Based on our results, daily dosing of Yb-labeled forage will provide reasonable estimates of fecal output when relative estimates of intake between range management treatments are needed.