Non-intertidal habitat use by shorebirds: a reflection of inadequate intertidal resources?

Many species of shorebird typically forage almost exclusively on intertidal habitats. When such strongly maritime species choose to forage on non-intertidal habitats, it may either be a response to deteriorating intertidal conditions or to the discovery of more profitable resources in non-intertidal areas. Methods which allow distinction between these two will clearly be important for identifying problems in intertidal habitats. Since January 1998, turnstone (Arenaria interpres) on the Wash estuary, eastern England have been foraging on the docksides of Port Sutton Bridge (mainly on spilt wheat and fishmeal), fields and river edges, resulting in concern that intertidal food supplies were no longer sufficient to support the population. We quantified the distribution and behaviour of turnstone within the Wash in relation to season, tidal state and weather and used a depletion model to predict the number of turnstone that could be supported by the port, under a range of resource densities and environmental conditions. Numbers of turnstone on non-intertidal habitats increased over the winter and use of the port was significantly greater around high tide and on colder days. The depletion model showed that under virtually all conditions, the port could support a much greater proportion of the turnstone population than current peak numbers. The use of non-intertidal habitats therefore suggests that the preferred intertidal food supplies are not currently capable of supporting the turnstone population throughout the winter. Habitat switches such as this can potentially be important advance warnings of ecological changes for species, which have not yet led to reductions in population size.     

Silencing of host basal defense response-related gene expression increases susceptibility of Nicotiana benthamiana to Clavibacter michiganensis subsp. michiganensis

Clavibacter michiganensis subsp. michiganensis is an actinomycete, causing bacterial wilt and canker disease of tomato (Solanum lycopersicum). We used virus-induced gene silencing (VIGS) to identify genes playing a role in host basal defense response to C. michiganensis subsp. michiganensis infection using Nicotiana benthamiana as a model plant. A preliminary VIGS screen comprising 160 genes from tomato known to be involved in defense-related signaling identified a set of 14 genes whose suppression led to altered host-pathogen interactions. Expression of each of these genes and three additional targets was then suppressed in larger-scale VIGS experiments and the effect of silencing on development of wilt disease symptoms and bacterial growth during an N. benthamiana-C. michiganensis subsp. michiganensis compatible interaction was determined. Disease susceptibility and in planta bacterial population size were enhanced by silencing genes encoding N. benthamiana homologs of ubiquitin activating enzyme, snakin-2, extensin-like protein, divinyl ether synthase, 3-hydroxy-3-methylglutaryl-coenzyme A reductase 2, and Pto-like kinase. The identification of genes having a role in the host basal defense-response to C. michiganensis subsp. michiganensis advances our understanding of the plant responses activated by C. michiganensis subsp. michiganensis and raises possibilities for devising novel and effective molecular strategies to control bacterial canker and wilt in tomato.     

Analysis of Haemophilus parasuis isolates from southern Ontario swine by restriction endonuclease fingerprinting.

To study the occurrence and distribution of various strains of Haemophilus parasuis in southern Ontario swine, organisms isolated from healthy swine, from specific pathogen-free and conventional herds, and from disease cases were examined using restriction endonuclease fingerprinting analysis. In most herds, several strains of H. parasuis could be detected although one or two strains usually predominated. Individual animals were colonized by a single or limited number of strains. In several cases, the same strains were isolated from more than one specific pathogen-free herd. Conventional herds carried a more heterogeneous population of H. parasuis. Only one strain was isolated which was common to more than one conventional herd. No strains were isolated which were common to both specific pathogen-free and conventional herds. None of the strains isolated from disease cases were found in healthy conventional or specific pathogen-free swine examined in this study.     

Type C botulism in intensively farmed turkeys

Type C botulism in turkeys has been confirmed on several production sites by demonstrating the presence of toxin in sera from affected birds. Only male turkeys were affected, mortalities being up to 30 per cent. No source of toxin was found. Possible modes of intoxication are discussed.     

Circulating ghrelin concentrations fluctuate relative to nutritional status and influence feeding behavior in cattle

The objective of these experiments was to establish the relationship of plasma ghrelin concentrations with feed intake and hormones indicative of nutritional state of cattle. In Exp.1, 4 steers (BW 450 +/- 14.3 kg) were used in a crossover design to compare plasma ghrelin concentrations of feed-deprived steers with those of steers allowed to consume feed and to establish the relationship of plasma ghrelin concentrations with those of GH, insulin (INS), glucose (GLU), and NEFA. After adaptation to a once-daily feed offering (0800), 2 steers continued the once-daily feeding schedule (FED), whereas feed was withheld from the other 2 steers (FAST). Serial blood samples were collected via indwelling jugular catheter from times equivalent to 22 h through 48 h of feed deprivation. Average plasma ghrelin concentrations were greater (P < 0.001) in FAST compared with FED (690 and 123 +/- 6.5 pg/mL) steers. Average plasma ghrelin concentrations for FED steers prefeeding were elevated (P < 0.001) when compared with those postfeeding (174 and 102 +/- 4.2 pg/mL, respectively). Average plasma GH concentration was elevated (P < 0.05) for FAST steers compared with FED steers. Plasma GLU concentrations were not different; however, for FAST steers, NEFA concentrations were elevated (P < 0.001) and INS concentrations were decreased (P < 0.001). In Exp. 2, 4 steers (BW 416 +/- 17.2 kg) were used in a crossover design to determine the effects of i.v. injection of bovine ghrelin (bGR) on plasma GH, INS, GLU, and NEFA concentrations; length of time spent eating; and DMI. Steers were offered feed once daily (0800). Serial blood samples were collected from steers via indwelling jugular catheter. Saline or bGR was injected via jugular catheter at 1200 and 1400. A dosage of 0.08 microg/kg of BW bGR was used to achieve a plasma ghrelin concentration similar to the physiological concentration measured in a FAST steer in Exp. 1 (1,000 pg/mL). Injection of bGR resulted in elevated (P < 0.005) plasma GH concentrations after the 1200 but not the 1400 injection. Plasma INS, GLU, and NEFA concentrations were not affected by bGR injection. For the combined 1-h periods postinjection, length of time spent eating was greater (P = 0.02) and DMI tended to be increased (P = 0.06) for bGR steers. These data are consistent with the hypothesis that ghrelin serves as a metabolic signal for feed intake or energy balance in ruminants.     

Pharmacokinetic and pharmacodynamic modelling of intravenous,intramuscular and subcutaneous buprenorphine in conscious cats

ObjectiveTo describe simultaneous pharmacokinetics (PK) and thermal antinociception after intravenous (IV), intramuscular (IM) and subcutaneous (SC) buprenorphine in cats.Study designRandomized, prospective, blinded, three period crossover experiment.AnimalsSix healthy adult cats weighing 4.1 ± 0.5 kg.MethodsBuprenorphine (0.02 mg kg^?1) was administered IV, IM or SC. Thermal threshold (TT) testing and blood collection were conducted simultaneously at baseline and at predetermined time points up to 24 hours after administration. Buprenorphine plasma concentrations were determined by liquid chromatography tandem mass spectrometry. TT was analyzed using anova (p < 0.05). A pharmacokinetic-pharmacodynamic (PK-PD) model of the IV data was described using a model combining biophase equilibration and receptor association-dissociation kinetics.ResultsTT increased above baseline from 15 to 480 minutes and at 30 and 60 minutes after IV and IM administration, respectively (p < 0.05). Maximum increase in TT (mean ± SD) was 9.3 ± 4.9 °C at 60 minutes (IV), 4.6 ± 2.8 °C at 45 minutes (IM) and 1.9 ± 1.9 °C at 60 minutes (SC). TT was significantly higher at 15, 60, 120 and 180 minutes, and at 15, 30, 45, 60 and 120 minutes after IV administration compared to IM and SC, respectively. IV and IM buprenorphine concentration-time data decreased curvilinearly. SC PK could not be modeled due to erratic absorption and disposition. IV buprenorphine disposition was similar to published data. The PK-PD model showed an onset delay mainly attributable to slow biophase equilibration (t_1/2k_e0 = 47.4 minutes) and receptor binding (k_on = 0.011 mL ng^?1 minute^?1). Persistence of thermal antinociception was due to slow receptor dissociation (t_1/2k_off = 18.2 minutes).Conclusions and clinical relevanceIV and IM data followed classical disposition and elimination in most cats. Plasma concentrations after IV administration were associated with antinociceptive effect in a PK-PD model including negative hysteresis. At the doses administered, the IV route should be preferred over the IM and SC routes when buprenorphine is administered to cats.