Equilibrium and non-equilibrium models of livestock population dynamics in pastoral Africa: their relevance to Arctic grazing systems

Equilibrium grazing systems are characterised by climatic stability that results in predictable primary production. Non-equilibrium grazing systems receive low and erratic rainfall that produces unpredictable fluctuations in forage supplies. In semi-arid Africa, these two types of environment present livestock owners with very different management problems. Identifying and maintaining optimal stocking rates is useful in equilibrium systems because livestock reproduce and produce at a rate determined by the availability of feed, which is an inverse function of stock density. The only problem is to determine what stocking rate is optimal. The correct stocking rate for a grazing system will vary depending on the production strategy and the social and economic circumstances of the rangeland user - there is no single, biologically predetermined optimum density. Variable rainfall complicates the picture in non-equilibrium systems. Set stocking rates of any kind have little value if fluctuation in rainfall has a stronger effect than animal numbers on the abundance of forage. More useful in such an environment is the ability to adjust stocking rates rapidly to track sudden changes in feed availability. In semi-arid Africa, the distinction between equilibrium and non-equilibrium systems hinges on the reliability of rainfall. In northern latitudes, at least three primary variables important for plant growth and the survival of herbivores must be considered: rainfall, snow cover and temperature. It is probably not useful to consider arctic grazing systems as equilibrium systems; on the other hand, the non-equilibrium models developed in hot semi-arid environments do not capture the range of complexity which may be an inherent feature of plant-herbivore dynamics on the mountain and tundra pastures where reindeer are herded or hunted

Range-Based Livestock Production in Turkmenistan

Turkmenistan retains a centralized system of livestock production in which many critical assets are owned by the state. Though technically in the temperate zone, the country\u27s climate is harsh and unstable. Groundwater resources are unevenly distributed, leaving many potential grazing areas seasonally inaccessible due to lack of drinking water for livestock. This paper summarizes the results of a three-year study of rangelands, livestock production, flock economics and land tenure at two study sites, one in central and the other in eastern Turkmenistan. The results of this study suggest that pastoral communities in Turkmenistan have coped remarkably well with the institutional changes that followed the demise of the Soviet Union, and with the country\u27s persistently unstable climate and scarce natural resources

Status of the PICASSO Project

The Picasso project is a dark matter search experiment based on the superheated droplet technique. Preliminary runs performed at the Picasso Lab in Montreal have showed the suitability of this detection technique to the search for weakly interacting cold dark matter particles. In July 2002, a new phase of the project started. A batch of six 1-liter detectors with an active mass of approximately 40g was installed in a gallery of the SNO observatory in Sudbury, Ontario, Canada at a depth of 6,800 feet (2,070m). We give a status report on the new experimental setup, data analysis, and preliminary limits on spin-dependent neutralino interaction cross section.Comment: 3 pages, 2 figures. To appear in the Proceedings of the TAUP 2003 conference, 5-9 September, 2003, University of Washington, Seattle, US

A Computer-Assisted Uniqueness Proof for a Semilinear Elliptic Boundary Value Problem

A wide variety of articles, starting with the famous paper (Gidas, Ni and Nirenberg in Commun. Math. Phys. 68, 209-243 (1979)) is devoted to the uniqueness question for the semilinear elliptic boundary value problem -{\Delta}u={\lambda}u+u^p in {\Omega}, u>0 in {\Omega}, u=0 on the boundary of {\Omega}, where {\lambda} ranges between 0 and the first Dirichlet Laplacian eigenvalue. So far, this question was settled in the case of {\Omega} being a ball and, for more general domains, in the case {\lambda}=0. In (McKenna et al. in J. Differ. Equ. 247, 2140-2162 (2009)), we proposed a computer-assisted approach to this uniqueness question, which indeed provided a proof in the case {\Omega}=(0,1)x(0,1), and p=2. Due to the high numerical complexity, we were not able in (McKenna et al. in J. Differ. Equ. 247, 2140-2162 (2009)) to treat higher values of p. Here, by a significant reduction of the complexity, we will prove uniqueness for the case p=3

Cashmere Marketing is a New Income Source for Central Asian Livestock Farmers

Some indigenous goats in the Central Asian republics of Kazakstan, Kyrgyzstan and Tajikistan produce good quality cashmere (Millar 1986). International processors have recently been buying this cashmere. (Kerven et al., 2005), but Central Asian producers are not equipped to take full advantage of these new marketing opportunities. The U.S. AID Global Livestock-Collaborative Research Support Program project, Developing Institutions and capacity for sheep and fiber marketing in Central Asia is working to increase the income of small-scale livestock farmers through improved cashmere marketing

Effects of mill type (hammer vs roller) and particle size uniformity on growth performance, nutrient digestibility, and stomach morphology in finishing pigs

Two experiments were conducted to determine the effects of mill type and particle size uniformity on finishing pigs. In Exp. 1, 120 pigs, with an average initial weight of 105 lb, were fed corn-soybean meal-based diets for 57 d. The corn was milled so that all diets had an average mean particle size of 800 11m (± 20), yet differed in particle size uniformity (Sgw). To obtain the most uniform treatment (1.9 Sgw), corn was milled through a roller mill. The intermediate treatment (2.3 Sgw) was obtained by milling corn through a hammermill. The least uniform treatment (2.7 Sgw) was obtained by blending coarsely and finely ground corn. Growth performance of pigs was not affected by Sgw of the diet. However, digestibilities of DM, N, and GE increased as Sgw was reduced. In Exp. 2, 128 pigs, widl an average initial weight of 150 lb, were fed diets with corn milled to 450 JLm (± 7) in a hammermill or a roller mill. The hammermilled corn had an Sgw of 1.8 and the rollermilled corn had an Sgw of 2.0. The diets were fed in meal or pelleted form. There were no interactions among mill type and diet form. Digestibilities of DM and N were greater for the hammermilled treatments, but no growth performance differences were due to mill type. Pelleting increased ADG 9% and improved efficiency of gain by 5 %. Pelleting also increased the severity of stomach lesions. In conclusion, at 800 and 450 p.m, mill type did not affect growth performance. However, nutrient digestibilities were improved by decreasing variability in particle size, a response that merits further investigation.; Swine Day, Manhattan, KS, November 19, 199