Diversity in the chemical composition and digestibility of leaves from fifty woody species in temperate areas     

Mahieu  Stéphanie  Novak  Sandra  Barre  Philippe  Delagarde  Rémy  Niderkorn  Vincent  Gastal  François  Emile  Jean-Claude 《Agroforestry Systems》2021,95(7):1295-1308

Agroforestry Systems - In temperate regions, tree leaves could be a source of energy, protein, vitamins and minerals for ruminants. Our objective was to study the diversity in chemical composition...  相似文献   

Cambial activity, wood formation and sapling survival of Pinus halepensis exposed to different irrigation regimes     

Martin de Luis  Klemen Novak  José RaventósJo?ica Gri?ar  Peter PrislanKatarina ?ufar 《Forest Ecology and Management》2011,262(8):1630-1638

Wood formation and the anatomical characteristics of tree-rings play a decisive role in plant performance and survival due to the importance of water transport. Saplings may be especially vulnerable to water stress; however, the level of water stress that they can endure still remains largely unexamined. Thus, the general objective of our research is to determine the plasticity of wood formation in Pinus halepensis saplings. We evaluated cambial activity, xylem growth ring formation and its anatomical characteristics in different experimental irrigation conditions and tested for its influence on the success rate of sapling establishment. Our results demonstrate a high phenological plasticity in wood formation with juvenile P. halepensis saplings in relation to water availability. Dry conditions during spring and summer strongly limit their cambial activity, which is suggested to be linked to sapling survival during summer. Width and anatomical characteristics of tree-rings differ in saplings exposed to different irrigation conditions. Our results suggest that increasing water stress during spring and summer periods, as predicted by future climate change scenarios, may seriously affect the success of both natural regeneration and reforestation of P. halepensis, and this could severely modify potential distribution of the species.  相似文献   

Biological markers of boar fertility     

Dyck MK  Foxcroft GR  Novak S  Ruiz-Sanchez A  Patterson J  Dixon WT 《Reproduction in domestic animals》2011,46(Z2):55-58

The semen evaluation techniques used in most commercial artificial insemination centers, which includes sperm motility and morphology measurements, provides a very conservative estimate of the relative fertility of individual boars. As well, differences in relative boar fertility are masked by the widespread use of pooled semen for commercial artificial insemination (AI) in many countries. Furthermore, the relatively high sperm numbers used in commercial AI practice usually compensate for reduced fertility, as can be seen in some boars when lower numbers of sperm are used for AI. The increased efficiency of pork production should involve enhanced use of boars with strong reproductive efficiency and the highest genetic merit for important production traits. Given that the current measures of semen quality are not always indicative of fertility and reproductive performance in boars, accurate and predictive genetic and protein markers are still needed. Recently, significant efforts have been made to identify reliable markers that allow for the identification and exclusion of sires with reduced reproductive efficiency. This paper reviews the current status of proteomic and genomic markers of fertility in boars in relation to other livestock species.  相似文献   

Seroprevalence of psittacine beak and feather disease in wild psittacine birds in New South Wales     

SR RAIDAL  CL McELNEA  GM CROSS 《Australian veterinary journal》1993,70(4):137-139

SUMMARY A haemagglutination inhibition assay was used to detect antibody to psittacine beak and feather disease virus in sera from wild sulphur crested cockatoos (Cacatua galerita), galahs (Eolophus roseicapillus), short-billed corellas (Cacatua sanguinea), eastern long-billed corellas (Cacatua tenuirostris) and other psittacine birds in New South Wales. The seroprevalence of psittacine beak and feather disease ranged from 41% to 94% in different flocks, indicating infection with the virus is widespread in wild populations.  相似文献   

Identification of toxigenic Pasteurella multocida in atrophic rhinitis of pigs by in vitro characterisation     

GJ EAMENS  PD KIRKLAND  MJ TURNER  JA GARDNER†  MP WHITE‡  CL HORNITZKY 《Australian veterinary journal》1988,65(4):120-123

Toxigenic strains of Pasteurella multocida were readily differentiated from non-toxigenic strains by an agarose overlay method using bovine turbinate cells or bovine lung cells. Cells which were young and densely confluent were best suited to this assay. The incubation period required to distinguish toxigenic strains was dependent on the confluence of the monolayers, which was affected by the seeding rate, cell passage level and growth time prior to overlay. The agarose overlay method correctly identified 11 of 11 reference strains of Pasteurella multocida, and visible cytotoxic changes were present in the monolayers after 48 to 65 h. Outbreaks of the enzootic form of atrophic rhinitis in 2 New South Wales piggeries were associated with the isolation of toxigenic type D strains of P. multocida.  相似文献   

The effects of antigenic competition on the efficacy of multivalent footrot vaccines     

CL SCHWARTZKOFF  JR EGERTON†  DJ STEWART‡  PR LEHRBACH§  TC ELLEMAN¶  PA HOYNE¶ 《Australian veterinary journal》1993,70(4):123-126

SUMMARY A multivalent footrot vaccine has been developed, containing pilus antigens produced in recombinant Pseudomonas aeruginosa and representing all nine serogroups of Dichelobacter (Bacteroides) nodosus commonly recognised in the field. The responses of sheep to the multivalent vaccine have been compared with those to monovalent vaccines representing only a single serogroup. Antigenie competition between serogroups occurred in sheep immunised with the multivalent formulation, but high levels of protection were still achieved. The study showed that in multivalent footrot vaccines, antigenic competition is predominantly due to the presence of a family of immunologically-related pilus antigens rather than to interference by extraneous proteins.  相似文献   

Assessment of the diversity of comfrey (Symphytum officinale L. and S. × uplandicum Nyman)     

Ruzicka  Joana  Berger-Büter  Karin  Esslinger  Nils  Novak  Johannes 《Genetic Resources and Crop Evolution》2021,68(7):2813-2825

Genetic Resources and Crop Evolution - Comfrey Symphytum officinale L. (true comfrey) and S.?×?uplandicum Nyman (a hybrid between S. asperum Lepech?×?S. officinale...  相似文献   

Impact of biodiversity-climate futures on primary production and metabolism in a model benthic estuarine system     

Natalie Hicks  Mark T Bulling  Martin Solan  Dave Raffaelli  Piran CL White  David M Paterson 《BMC ecology》2011,11(1):1-8

Background

A territory as a prerequisite for breeding limits the maximum number of breeders in a given area, and thus lowers the proportion of breeders if population size increases. However, some territorially breeding animals can have dramatic density fluctuations and little is known about the change from density-dependent processes to density-independence of breeding during a population increase or an outbreak. We suggest that territoriality, breeding suppression and its break-down can be understood with an incomplete-control model, developed for social breeders and social suppression.

Results

We studied density dependence in an arvicoline species, the bank vole, known as a territorial breeder with cyclic and non-cyclic density fluctuations and periodically high densities in different parts of its range. Our long-term data base from 38 experimental populations in large enclosures in boreal grassland confirms that breeding rates are density-regulated at moderate densities, probably by social suppression of subordinate potential breeders. We conducted an experiment, were we doubled and tripled this moderate density under otherwise the same conditions and measured space use, mortality, reproduction and faecal stress hormone levels (FGM) of adult females. We found that mortality did not differ among the densities, but the regulation of the breeding rate broke down: at double and triple densities all females were breeding, while at the low density the breeding rate was regulated as observed before. Spatial overlap among females increased with density, while a minimum territory size was maintained. Mean stress hormone levels were higher in double and triple densities than at moderate density.

Conclusions

At low and moderate densities, breeding suppression by the dominant breeders, But above a density-threshold (similar to a competition point), the dominance of breeders could not be sustained (incomplete control). In our experiment, this point was reached after territories could not shrink any further, while the number of intruders continued to increase with increasing density. Probably suppression becomes too costly for the dominants, and increasing number of other breeders reduces the effectiveness of threats. In wild populations, crossing this threshold would allow for a rapid density increase or population outbreaks, enabling territorial species to escape density-dependency.  相似文献   

Relationship between soil CO₂ concentrations and forest-floor CO₂ effluxes   总被引：3，自引：2，他引：3  

Rachhpal Jassal  Andy Black  Mike Novak  Kai Morgenstern  Zoran Nesic  David Gaumont-Guay 《Agricultural and Forest Meteorology》2005,130(3-4):176-192

To better understand the biotic and abiotic factors that control soil CO₂ efflux, we compared seasonal and diurnal variations in simultaneously measured forest-floor CO₂ effluxes and soil CO₂ concentration profiles in a 54-year-old Douglas fir forest on the east coast of Vancouver Island. We used small solid-state infrared CO₂ sensors for long-term continuous real-time measurement of CO₂ concentrations at different depths, and measured half-hourly soil CO₂ effluxes with an automated non-steady-state chamber. We describe a simple steady-state method to measure CO₂ diffusivity in undisturbed soil cores. The method accounts for the CO₂ production in the soil and uses an analytical solution to the diffusion equation. The diffusivity was related to air-filled porosity by a power law function, which was independent of soil depth. CO₂ concentration at all depths increased with increase in soil temperature, likely due to a rise in CO₂ production, and with increase in soil water content due to decreased diffusivity or increased CO₂ production or both. It also increased with soil depth reaching almost 10 mmol mol⁻¹ at the 50-cm depth. Annually, soil CO₂ efflux was best described by an exponential function of soil temperature at the 5-cm depth, with the reference efflux at 10 °C (F₁₀) of 2.6 μmol m⁻² s⁻¹ and the Q₁₀ of 3.7. No evidence of displacement of CO₂-rich soil air with rain was observed.Effluxes calculated from soil CO₂ concentration gradients near the surface closely agreed with the measured effluxes. Calculations indicated that more than 75% of the soil CO₂ efflux originated in the top 20 cm soil. Calculated CO₂ production varied with soil temperature, soil water content and season, and when scaled to 10 °C also showed some diurnal variation. Soil CO₂ efflux and concentrations as well as soil temperature at the 5-cm depth varied in phase. Changes in CO₂ storage in the 0–50 cm soil layer were an order of magnitude smaller than measured effluxes. Soil CO₂ efflux was proportional to CO₂ concentration at the 50-cm depth with the slope determined by soil water content, which was consistent with a simple steady-state analytical model of diffusive transport of CO₂ in the soil. The latter proved successful in calculating effluxes during 2004.  相似文献   

Biodegradation of chlorinated phenols in subsurface soils     

James A. Smith  John T. Novak 《Water, air, and soil pollution》1987,33(1-2):29-42

Microcosm studies were employed to determine the subsurface biodegradation rates of phenol, 2-chlorophenol (2-CP), 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP), and pentachlorophenol (PCP). Soil samples were taken from sites in Pennsylvania and Virginia from depths up to 31 m, and all samples contained significant microbial populations. Soil from both sites readily biodegraded all five compounds. Biodegradation rates increased as initial concentrations increased, and all biodegradation rates appeared to follow first-order kinetics with regard to the initial compound concentrations. Biodegradation rates for the five compounds followed the order: phenol = 2-CP > 2,4,6-TCP > 2,4-DCP. PCP was degraded more slowly than phenol or 2-CP, but similarly to 2,4,6-TCP and 2,4-DCP. Different soils exhibited different degradation rates, and the soil characteristics that may influence the rates are discussed. The data suggest that biological degradation is a significant attenuation mechanism for phenol and its chlorinated derivatives in subsurfaces saturated and unsaturated zones.  相似文献