Epidemiology of bovine babesiosis in south-western Angola]

An epidemiological survey on bovine babesiosis was carried out in South-Western Angola. Both parasitological and serological methods were used. Use of the packed cell volume (PCV) technique increased up to five times the detection of infected cattle as compared with the thin blood smear method. Although the PCV method provided better information on the parasitological diagnosis, the indirect fluorescent antibody test represents a better approach for the evaluation of endemic situations. Results obtained by this method proved that in most herds and farms investigated there was an endemic stability. The disease did not present any problem in the traditional sector. Cases of babesiosis were only reported in some commercial farms where the control of ticks was inadequate and responsible for endemic instability.     

A standardized procedure for surveillance and monitoring European habitats and provision of spatial data

Both science and policy require a practical, transmissible, and reproducible procedure for surveillance and monitoring of European habitats, which can produce statistics integrated at the landscape level. Over the last 30 years, landscape ecology has developed rapidly, and many studies now require spatial data on habitats. Without rigorous rules, changes from baseline records cannot be separated reliably from background noise. A procedure is described that satisfies these requirements and can provide consistent data for Europe, to support a range of policy initiatives and scientific projects. The methodology is based on classical plant life forms, used in biogeography since the nineteenth century, and on their statistical correlation with the primary environmental gradient. Further categories can therefore be identified for other continents to assist large scale comparisons and modelling. The model has been validated statistically and the recording procedure tested in the field throughout Europe. A total of 130 General Habitat Categories (GHCs) is defined. These are enhanced by recording environmental, site and management qualifiers to enable flexible database interrogation. The same categories are applied to areal, linear and point features to assist recording and subsequent interpretation at the landscape level. The distribution and change of landscape ecological parameters, such as connectivity and fragmentation, can then be derived and their significance interpreted.     

Via freedom to coercion: the emergence of costly punishment

In human societies, cooperative behavior in joint enterprises is often enforced through institutions that impose sanctions on defectors. Many experiments on so-called public goods games have shown that in the absence of such institutions, individuals are willing to punish defectors, even at a cost to themselves. Theoretical models confirm that social norms prescribing the punishment of uncooperative behavior are stable-once established, they prevent dissident minorities from spreading. But how can such costly punishing behavior gain a foothold in the population? A surprisingly simple model shows that if individuals have the option to stand aside and abstain from the joint endeavor, this paves the way for the emergence and establishment of cooperative behavior based on the punishment of defectors. Paradoxically, the freedom to withdraw from the common enterprise leads to enforcement of social norms. Joint enterprises that are compulsory rather than voluntary are less likely to lead to cooperation.     

Density of the Lunar Atmosphere

The minimum possible density of the lunar atmosphere at the surface is shown to be essentially the value for the interplanetary medium. This value, when combined with the observed maximum, places the particle density between 10(3) and 10(6) per cubic centimeter, while the electron density must be about 10(3) to 10(4) per cubic centimeter. These results are markedly different from those recently obtained by Firsoff.     

Design,rationale and methodological considerations for a long term alternative cropping experiment in the Canadian plain region

An interdisciplinary field experiment was initiated to evaluate sustainability of crop production in the Canadian Prairie region. The objective was to develop a resource that would be used to measure change over time associated with input and cropping diversity strategies. The knowledge generated would serve to provide early indications of potential problems and to guide development of improved systems. The study was located near the geographic center of the region on the transition between the semi-arid prairie and the sub-humid parkland regions. The design of the study is reported here, while later papers will report and discuss treatment responses. The study is based on three levels of inputs; organic, reduced and high combined with three levels of cropping diversity: low, diversified annual grains and diversified annual perennial to give a matrix of nine treatments. The site was uniformly cropped and characterized for one year prior to imposition of the treatments, and results used to validate the experimental design. Systems were defined by general principles that incorporate flexibility and allow systems to be changed so they could function in a near optimal state. Several grassland sites and one native prairie site located nearby were characterized as reference points for examining biodiversity and soil quality attributes of the treatments. To accommodate multidisciplinary use of the data, a central database was developed that allows all collaborating scientists to access the data, yet protects data integrity. Overall results to date provide a clear indication that the study provides a resource that is well suited to meet the objectives.     

Effects of energy intake, implantation, and subcutaneous fat end point on feedlot steer performance and carcass composition

The purpose of this experiment was to evaluate the effects of energy intake, implantation, and fat end point on feedlot performance and carcass composition of steers. Three hundred eighty-four yearling crossbred steers (368 +/- 23.1 kg) were allotted in a completely randomized design. Treatments were arranged in a 2 x 3 x 2 factorial experiment. Main effect factors were two levels of intake, three implant strategies, and two compositional fat end points at slaughter. The levels of intake were ad libitum (AL) and restricted (RS) intake (90% ad libitum). The three implant strategies were Revalor-S (REV) (120 mg trenbolone acetate, 24 mg estradiol), Synovex-Plus (SYN) (200 mg trenbolone acetate, 28 mg estradiol benzoate), and no implant (control). The compositional target end points were 1.0 and 1.4 cm s.c. fat cover over the 12th and 13th rib. Restricted-intake steers consumed 9.2% less (P < .01) DM than AL steers. Ad libitum-intake steers gained weight 15.5% more rapidly (P < .01) than RS-intake steers. Steers implanted with REV tended (P < .07) to gain faster than SYN steers, who in turn gained 15.2% more (P < .01) than control steers. Ad libitum-intake steers were 4.8% more (P < .01) efficient than RS steers. Steers fed to a targeted 1.4 cm s.c. backfat cover were 2.9% less (P < .05) efficient than steers fed to 1.0 cm, and steers implanted with either REV or SYN had similar (P = .47) feed efficiencies, whereas control steers had lower (P < .01) feed efficiencies. Steers fed to a targeted compositional fat end point of 1.4 cm had 1.3% higher (P < .01) dressing percentage (DP) than steers fed to 1.0 cm. Control and SYN steers had similar (P = .13) DP; however, REV steers had 6.1% greater (P < .01) DP than SYN steers. Steers fed to 1.4 cm s.c. fat end point had higher (P < .01) numerical yield grades than steers fed to 1.0 cm (3.34 vs 2.71). There was an interaction (P < .01) for intake level and implant for marbling score. Marbling scores were lower (P < .05) for RS x SYN and AL x REV than in other treatments. Steers on the RS x REV treatment were intermediate in marbling to all treatments except AL control, which was higher (P < .01) than RS x SYN, AL x REV, and RS x REV. No interaction for dry matter intake level and anabolic implants was observed for growth performance. The depression in carcass quality resulting from implanting is reduced as backfat increases from 1.0 to 1.4 cm at slaughter.     

Global-scale similarities in nitrogen release patterns during long-term decomposition

Litter decomposition provides the primary source of mineral nitrogen (N) for biological activity in most terrestrial ecosystems. A 10-year decomposition experiment in 21 sites from seven biomes found that net N release from leaf litter is dominantly driven by the initial tissue N concentration and mass remaining regardless of climate, edaphic conditions, or biota. Arid grasslands exposed to high ultraviolet radiation were an exception, where net N release was insensitive to initial N. Roots released N linearly with decomposition and exhibited little net N immobilization. We suggest that fundamental constraints on decomposer physiologies lead to predictable global-scale patterns in net N release during decomposition.     

Standardised tests in mice and cattle for the detection of drug resistance in tsetse-transmitted trypanosomes of African domestic cattle

Resistance to the drugs used to control African animal trypanosomosis is increasingly recognised as a constraint to livestock production in sub-Saharan Africa. The most commonly used tests for detection of trypanocidal drug resistance are tests using mice or ruminants, but these suffer from lack of standardisation and hence it may be difficult to compare the results of different investigators. Tests in mice are less expensive than tests in ruminants, but while tests in mice they may be useful as a general guide to resistance in a geographic area they should not be extrapolated to cattle on an individual trypanosome level. Moreover, the commonly used protocols are too laborious for their application to large number of trypanosome isolates on an area-wide basis. This paper presents guidelines for standardised testing of trypanocidal drugs in vivo, and introduces a simplified single-dose test for use in mice, which is convenient for use in areas with limited laboratory facilities. The single-dose test is appropriate for characterisation of geographic areas in terms of trypanocidal drug resistance using large numbers of trypanosome isolates, for making comparisons between areas, and for monitoring changes in trypanocidal drug resistance over time. Multiple-dose tests may be used to determine the degree of resistance of individual stabilates to be determined precisely in mice are also described, but for logistical reasons these will rarely be conducted on more than a few stabilates, and testing of a larger number of stabilates in the single-dose test will generally provide more useful information. Finally, we describe tests in cattle that may be used to determine the efficacy of recommended curative doses of trypanocidal drugs for the treatment of infection with individual trypanosome isolates, including Trypanosoma vivax, which is rarely infective for mice.