No abstract

The accuracy of microhiitological techniques for analysis of herbivore diets was evaluated with cattle, sheep, and Angora goats fed grass, forb, and shrub mixtures of known botanical compositions. Two observers performed microhistological analyses on undigested diets as offered and on feces collected. Similarity indices and chi-square tests were used to determine if differences existed among actual diets, estimated diets, and fecal samples. Botanical compositions of diets fed to all 3 anhnal species generally were accurately estimated by fecal analyses. In some other studies, shrubs in ruminant diets have been inaccurately estimated by the microhistological technique. However, in our study, shrubs were accurately estimated with no differences between actual and observed compositions. We attribute this to the fact that shrub materials used in our study had a high proportion of current growth relative to woody materials. Woody plant parts had lower proportions of identifiable epldermal material than leaves and young stems. In grass-forb diets, forbs sometimes were overestimated and differentiation among grasses was difficult. However, In most cases, observers could precisely estimate diets of the 3 herbivore species.

This study evaluated 3 procedures for calculating dry weight composition of forage mixtures when microhistological analysis was used. Dividing the frequency of each species by the total frequencies of all species gave a slightly more accurate representation of dry weight composition than converting frequency to relative density or using actual density. The frequency addition procedure is much quicker than either procedure involving density.

A study simulating herbivore diets was conducted to compare actual and estimated diet constituents as influenced by sample preparation technique and in vitro digestion. Nine plant species, three each representing grass, forb, and shrub forage classes were hand composited into three mixtures so that one forage class dominated each mixture. Samples of each mixture were then allotted to eight treatments involving combinations of grinding through a micro-Wiley mill, soaking in sodium hydroxide and in vitro digestion. Samples were then analyzed for botanical composition using the microhistological technique. In vitro digestion had the greatest impact on the difference between estimated and actual means. In digested samples grasses were overestimated while shrubs and forbs were underestimated. The preferred treatment involved grinding in a micro-Wiley mill and the sodium hydroxide soak.

Our study evaluated the effectiveness of using eight pathways in combination for a complete to transition from fossil fuels to renewable energy by 2050. These pathways included renewable energy development; improving energy efficiency; increasing energy conservation; carbon taxes; more equitable balancing of human wellbeing and per capita energy use; cap and trade systems; carbon capture, utilization, and storage; and nuclear power development. We used the annual ‘British Petroleum statistical review of world energy 2021’ report as our primary database. Globally, fossil fuels, renewable (primarily hydro, wind and solar), nuclear energy accounted for 83%, 12.6%, and 6.3% of the total energy consumption in 2020. To achieve zero fossil fuel use by 2050, we found that renewable energy production will need to be increased by up to 6-fold or 8-fold if energy demand is held constant at, or increased 50% from, the 2020 energy demand level. Constraining 2050 world energy demand to a 25% increase over the 2020 level, improves the probability of achieving independence from fossil fuels. Improvements in energy efficiency need to accelerate beyond the current rate of ~1.5% per year. Aggressive application of energy conservation policies involving land use and taxation could potentially reduce world energy use by 10% or more by 2050. Our meta-analysis shows that the minimum level of per capita energy consumption that would allow 8 billion people to have a ‘Decent Living Standard’ is on average ~70 GJ per capita per year, which is 93% of the 2020 global average. Developed countries in temperate climates with high vehicle-dependency needed ~120 GJ per capita year−1, whereas equatorial countries with low vehicle-dependency needed 30 GJ per capita year−1. Our meta-analyses indicated replacement of fossil fuels with renewable energy by 2050 may be possible but will require aggressive application of all eight pathways, major lifestyle changes in developed countries, and close cooperation among all countries.

A study was conducted to determine the influence of sample preparation procedures on the ratio of identifiable to nonidentifiable fragments in diet samples analyzed by microhistological analysis. The number of identifiable fragments on slides was significantly higher when samples were soakqd in either bleach or sodium hydroxide in conjunction with use of Hertwig's clearing solution compared to the control, which involved the use of only Hertwig's clearing solution. The percentages by weight of grasses, forbs, and shrubs in two prepared diet samples were more accurately estimated when either sodium hydroxide or bleach was applied in comparison with the control. However, some plant species or plant parts may be destroyed by bleach or sodium hydroxide. Therefore, diet materials should also be examined through standard procedures before the decision is made to apply one of these treatments. Microhistological analysis has become the most commonly used method for determining herbivore diets in recent years. A basic problem with this technique, particularly in fecal analyses, is plant pigments that make identification of epidermal material difficult. Sample preparation techniques to reduce this problem have been developed and discussed by Baumgartner and Martin (1939), Dusi

A procedure is described that results in rapid training of observers for microhistological analysis. Observers trained using this procedure were able to evaluate accurately 6 handcompounded diets comprised of semidesert plant species. The accuracy of microhistological analysis was examined by using the 4 trained observers to evaluate 26 additional hand-compounded diets containing various combinations of 30 different grasses, forbs, and shrubs from semidesert range. The relationship between relative density (estimated percent by weight composition) and actual percent by weight composition was close to unity for species in each forage class individually or in combination. However this relationship would probably have been different if the observers had not used known diets to evaluate their accuracy and make corrections. It is recommended that all technicians using microhistological analysis regularly check their accuracy with handcompounded diets.

Increasing world human population, declining reserves of cheaply extracted fossil fuels, scarcity of supplies of fresh water and climatic instability will put tremendous pressure on world rangelands as the 21st century progresses. It is expected that the human population of the world will increase by 40% by 2050 but fossil fuel and reserves of fresh water will be drastically reduced. Avoiding food shortages and famine could be a major world challenge within the next 10 years. Under these conditions, major changes in policies relating to economic growth and use of natural resources seem essential. Stabilisation of the human population, development of clean and renewable energy, enhanced supplies of water and its quality, increased livestock production, and changed land-use policies, that minimise agricultural land losses to development and fragmentation, will all be needed to avoid declining living conditions at the global level. The health and productivity of rangelands will need to receive much more emphasis as they are a primary source of vital ecosystem services and products essential to human life. Changes in tax policies by developed, affluent countries, such as the United States, Australia and Canada, are needed that emphasise saving and conservation as opposed to excessive material consumption and land development. Extreme levels of debt and chronic deficits in trade by the United States and European Union countries need to be moderated to avoid a devastating collision of debt, depletion of natural resources, and environmental degradation. Over the next 10 years, livestock producers of the rangelands will benefit from a major increase in demand and prices for meat. Rapidly increasing demand for meat in China and other Asian countries is driving this trend. Rangeland managers, however, will also likely encounter greater climatic, financial, biological and political risks. Higher interest rates, higher production costs and higher annual variability in forage resources are major challenges that will confront rangeland managers in the years ahead. Under these conditions, a low risk approach to livestock production from rangelands is recommended that involves conservative stocking, use of highly adapted livestock, and application of behavioural knowledge of livestock to efficiently use forage resources.