Identification and control of paratuberculosis in a large goat herd

Mycobacterium paratuberculosis infection was detected in 2 goats in 1974 and in 5 goats in 1975; 5 of which were from a single herd. The magnitude of the subsequent epizootic in the goat herd was not recognized until 1977, when results of bacteriologic culture of fecal and tissue specimens, antibody determinations (agar-gel immuno-diffusion test), and histopathologic studies became available. By 1984, paratuberculosis had been diagnosed in 124 goats. Nearly all the goats were being used in antiserum production and had been given Freund complete adjuvant and human antigens. From 1974 to 1986, herd size varied from 100 to 300. The yearly incidence of paratuberculosis decreased from 13.2% (27 of 204 goats) in 1977 to 0% in 108 goats in 1985. The prevalence was higher in does. In goats that arrived on the farm in 1975 and before, 49 of 121 (40.5%) does developed paratuberculosis vs 41 of 120 (34.2%) wethers. In goats arriving on the farm in 1976 and after, 25 of 274 (8.5%) does and 9 of 216 (4.1%) wethers developed paratuberculosis. The average incubation period was approximately 4 years from arrival on the farm in every year except 1978, regardless of whether the goat was born on the farm or was purchased elsewhere.(ABSTRACT TRUNCATED AT 250 WORDS)     

End-use related physical and mechanical properties of selected fast-growing poplar hybrids (Populus trichocarpa × P. deltoides)

This study focused on physical and mechanical properties of fast-growing poplar clones in relation to potential end uses with high added value. A total of 14 trees from three different clones, all P. trichocarpa × deltoides (T×D) hybrids, were felled in a poplar plantation in Lille (Belgium): six ‘Beaupré’, four ‘Hazendans’ and four ‘Hoogvorst’. Growth rate was found to have no significant influence on the physical mechanical properties. Although the investigated clones are genetically closely related, important variations in physical and mechanical properties were observed. Specific features such as spatial distribution of tension wood and dimensional stability are the main quality factors. It was concluded that ‘Beaupré’ is suitable for a wide range of high value added applications, such as plywood or construction wood. ‘Hazendans’ and ‘Hoogvorst’ will need adapted technology in processing. Further research is needed to characterize clonally induced variation in properties and to assess adequate processing strategies for multiclonal poplar stands.     

Strength properties of thermally modified softwoods and its relation to polymeric structural wood constituents

Thermal modification at relatively high temperatures (ranging from 150 to 260 °C) is an effective method to improve the dimensional stability and resistance against fungal attack. This study was performed to investigate the impact of heat treatment on the mechanical properties of wood. An industrially-used two-stage heat treatment method under relative mild conditions (< 200 °C) was used to treat the boards. Heat treatment revealed a clear effect on the mechanical properties of softwood species. The tensile strength parallel to the grain showed a rather large decrease, whereas the compressive strength parallel to the fibre increased after heat treatment. The bending strength, which is a combination of the tensile stress, compressive stress and shear stress, was lower after heat treatment. This decrease was less than the decrease of only the tensile strength. The impact strength showed a rather large decrease after heat treatment. An increase of the modulus of elasticity during the bending test has been noticed after heat treatment. Changes and/or modifications of the main wood components appear to be involved in the effects of heat treatment on the mechanical properties. The possible effect of degradation and modification of hemicelluloses, degradation and/or crystallization of amorphous cellulose, and polycondensation reactions of lignin on the mechanical properties of heat treated wood have been discussed. The effect of natural defects, such as knots, resin pockets, abnormal slope of grain and reaction wood, on the strength properties of wood appeared to be affected by heat treatment. Nevertheless, heat treated timber shows potential for use in constructions, but it is important to carefully consider the stresses that occur in a construction and some practical consequences when heat treated timber is used.     

Morphologic stages of the equine embryo proper on days 17 to 40 after ovulation

OBJECTIVE: To describe the gross and histologic changes that develop in the equine embryo proper (ie, the portion of the embryo that becomes the fetus) from days 17 to 40 after ovulation and to compare the external features of equine embryos with those of porcine, ovine, and human embryos. SAMPLE POPULATION: 34 embryos collected from mixed-breed pony mares. PROCEDURE: External features for each embryo proper, including length, number of branchial arches, growth of appendages, face and head features, and body features, were examined, using a dissecting microscope, for embryos collected on days 17 to 40. Internal features were histologically examined by serially sectioning embryos collected on days 20 to 35. RESULTS: Number of embryos recovered for each day ranged from 1 to 5. The initial detection of features was not related closely to age; typically, the first attainment of a given body length or characteristic varied over a 3-day period among embryos. Similarly, the period during which individual characteristics for a given Carnegie stage were attained ranged from 3 to 6 days. Age at first appearance of a characteristic was greater for equine embryos than ages reported for ovine and porcine embryos but less than for human embryos. Indicators of age included number of pairs of branchial arches, all limb buds present, retinal pigmentation, and prominence of the pontine flexure. CONCLUSIONS: No embryologic structures or changes were found that could be considered unique to equine embryos on days 17 to 40 after ovulation.     

Exploring life growth patterns in birch (Betula pendula)

The conversion of homogeneous plantations of conifers to mixed or broadleaved forests is part of sustainable forest management strategies in Western Europe. For the conversion of pine plantations on sandy soils, birch seems a convenient choice. Yet, thus far, little is known about the growth of mature birches outside Northern Europe. We sampled 32 birch trees in forests throughout the sandy ecoregion in northern Belgium at sites that varied in soil and local stand conditions. Half of the birches showed the characteristic pattern in growth (expressed as basal area increment) with a sharply increasing growth till around the age of 25 years followed by a steep decrease in growth. The growth was strongly related to tree age and crown dimensions, only weakly related to soil conditions, and not related to the local stand conditions.     

Seed germination response to temperature for a range of international populations of Conyza canadensis

Conyza canadensis is a surface‐germinating ruderal facultative winter annual with recruitment that is highly susceptible to changes in microsite conditions. A key adaptive characteristic for a facultative winter annual species, like C. canadensis, is germination response to temperature. The objective of this study was to determine the germination response to temperature for C. canadensis seed sourced from regions around the world with differing climates and, by doing so, gain insight into the role that seed germination biology plays in the adaptiveness and weediness of facultative winter annual weeds. Seed was sourced from populations in Málaga, Spain, Hertfordshire, UK, Shiraz, Iran and southern Ontario, Canada, and grown out in a common garden under controlled conditions to produce seed for this study. These seeds were then subjected to temperatures from 6.5 to 20°C at 1.5°C increments using a thermogradient plate. Cumulative daily germination counts for 30 days were recorded. Results indicated that temperature and source location had a significant effect on germination response. Estimated base germination temperature ranges were significantly different among the populations [Ontario (8–9.5°C), Iran (9.5–11°C), Spain (12.5–14°C), UK (11–12.5°C)], as were accumulated growing degree days (GDDs; d°C) required to reach 50% germination. For three of the four populations, estimated base germination temperature range values were below those previously reported in the literature. These differences are most likely rapid evolutionary adaptations to local climate and highlight the potential C. canadensis has to be problematic as a native and invasive species.     

Demography of Rumex acetosella in lowbush blueberry (Vaccinium angustifolium)

The demography of Rumex acetosella ramets and seedlings was monitored within and between blueberry clones over the two‐year lowbush blueberry production cycle in Nova Scotia, Canada. Overwintering ramets constituted the majority (>70%) of the flowering ramet population. A small proportion of ramets emerging in May and June flowered, but no ramets emerging between July and November flowered in the year of emergence. Emergence of new ramets was season‐long and ramet populations were regulated by a cycle of birth and death in each production year. Ramet populations in blueberry patches had higher growth rates and lower mortality than ramet populations in bare soil patches in the non‐bearing year, resulting in large net gains to ramet populations in blueberry patches during this production year. Ramet population growth rates and mortality were similar in blueberry and bare soil patches in the bearing year and net ramet populations declined during this production year. Survival rates of overwintering and new ramets varied, but ramets from both the overwintering and monthly cohorts contributed to a distinct ramet age structure at the end of each season. Seedling survival ranged from 6 ± 6 to 51 ± 12% across sites, and no seedlings flowered in the year of emergence. Transition probabilities of ramets and seedlings were used to develop a life‐cycle model of R. acetosella for the 2‐year lowbush blueberry production cycle. This model has utility in developing new management strategies for R. acetosella in lowbush blueberry.     

Potential contribution of organosilicon compounds to reduced leaching of biocides in wood protection

? Leaching of biocide treated wood leads to reduced effectiveness and potential threat to the environment.

? Therefore the effectiveness of organosilicons as protective systems of biocides was evaluated. Scots pine sapwood specimens were impregnated with solely organosilicons and biocides as well as with combinations of both.

? The biocides 3-iodo-2-propynylbutylcarbamate, propiconazole and 3-(trimethoxysilyl)propyldimethyloctadecyl ammonium chloride confirmed their effectiveness regardless the addition of an organosilicon. Low leachate toxicities to the crustacean Daphnia magna were found for the organosilicons, whereas significant leachate toxicities were measured for the biocides. Combining both did not considerably diminish the leachate toxicities.

? It must therefore be concluded that under the circumstances as described in this article, organosilicons do not interfere with the efficacy of the biocides, but they do not contribute to a reduced leaching of the biocides either.

     

竹秆硅含量以及分布

对不同龄级的温带竹种(紫竹)和热带竹种(毛笋竹和马来甜竹)竹秆中硅的总含量及分布进行了分析。不仅径级、高度和年龄,硅占刚竹属干重的0.04%~0.11%,占毛笋竹和马来甜竹干重的0.08%~0.11%,这比早期研究得出的数低很多。硅大量集中在表皮层,,虽然毛笋竹和马来甜竹的硅也存在于真皮细胞内,能量色散X射线图显示硅在刚竹属表皮中分布不均匀,更多的硅集中在表皮细胞壁内。     

The potential of plantations of Terminalia superba Engl. & Diels for wood and biomass production (Mayombe Forest, Democratic Republic of Congo)

? In the 1940s–1950s, large limba (Terminalia superba Engl. & Diels) plantations were established in the Democratic Republic of Congo to reduce the pressure on the natural forests.

? The objective of this study was to evaluate the potential of these long-rotation plantations as production forests (timber) and carbon sinks.

? Five different plantations, between 50 and 58 years old, were sampled. Over a sample surface of more than 73 ha, the diameter above buttresses of 2 680 trees, bole height of 265 trees and tree height of 128 trees was measured.

? To estimate the commercial volume, a nonlinear power law regression was used (R ² = 0.95). A power law variance function was applied to counter heteroscedasticity of the residual plot. Estimates of commercial tree and stand volume at 50 to 58 y were 5.6 ± 4.1 m³ and 183.9 ± 135.0 m³ ha^?1. Stand volumes appear low but are explained by a large decrease in tree density. However, the mean volume increment of 3.2–3.7 m³ ha^?1 y^?1 corresponds well with teak plantations of a similar age. For limba, aboveground biomass and carbon estimates of this study (resp. 108.4 and 54.2 Mg ha^?1) differ significantly from those of existing aboveground biomass models (resp. 135.7–143.9 Mg ha^?1 biomass and 67.9–72.0 Mg ha^?1 C). All aboveground biomass and carbon estimates for T. superba stands were lower than for the estimates of young fast-growing plantations like Tectona grandis L. f., Eucalyptus spp. and Acacia spp. (≤ 30 y).