Browsing Journal of Range Management, Volume 42, Number 2 (March 1989) by Authors
Economic consequences of alternative stocking rate adjustment tactics: a simulation approachRiechers, R. K.; Conner, J. R.; Heitschmidt, R. K. (Society for Range Management, 1989-03-01)An economic analysis of alternative stocking rate adjustment tactics is performed using a simulation model which emulates the annual decision-making situation of a rancher. The model includes variation in livestock prices and annual forage production. The manager's decisions are based on the availability of forage at 4 decision points in the year, the expected growth between the current decision point and the next, and the expected portion of the forage that is to be harvested through grazing. Livestock are bought and sold to adjust the stocking rate to equal the expected available forage for grazing. Results are obtained for 3 different stocking tactics based on 4 levels of expected forage production and livestock utilization set at the May decision point. The results reflect the differences in net returns over variable costs and the differences in annual cow investment capital associated with each tactic. The results indicate that the tactics using a maximum stocking rate of 3.6 ha/au offer the most reasonable compromise between mean and variance of net returns. The tactic with no limit on stocking rate provides the possibility of obtaining higher average annual net returns than tactics with limited stocking rates, but the variation in annual returns is considerably greater and the annual cow investments costs are higher.
Some effects of a rotational grazing treatment on cattle preference for plant communitiesWalker, J. W.; Heitschmidt, R. K.; Dowhower, S. L. (Society for Range Management, 1989-03-01)Rotational grazing is commonly assumed to improve livestock distribution compared to continuous grazing, but little evidence supports this contention. Research was conducted on the effects of rotational grazing (RG) compared to continuous grazing (CG) on the preference of cattle for plant communities. Different livestock densities in the RG treatments were created by varying the size of paddocks in a 465-ha, 16-paddock, cell designed RG treatment stocked at a rate of 3.6 ha/cow/yr. Paddock sizes of 30 and 10-ha were used to simulate RG with 14 (RG-14) and 42-paddocks (RG-42), respectively. The CG treatment consisted of a 248-ha pasture stocked at 5.9 ha/cow/yr. Data consisted of hourly daylight observations of cattle location and activity during 8 seasonal trials lasting 6-15 days. These data were expressed as a percent of the time cattle were observed in each of 4 plant communities and the area surrounding permanent water. Relative electivity (RE), a preference index, and a selectivity index (SI) that measures departures from random distribution were calculated from these data. Relative electivity (i.e., preference) for plant communities was not affected by grazing treatment. However, cattle were less selective for plant communities as livestock density decreased from the RG-42 to the CG treatment. In the RG-14 treatment, the cattle were either unaffected or less selective on the last day than on the first day in a paddock. We hypothesize that grazing systems influence cattle preference for plant communities by affecting the availability of forage biomass per unit land area rather than by their effect on grazing pressure.