Retarded growth rate and delayed onset of egg production associated with spirochaete infection in pullets

Retarded growth rates and delayed onset of egg production were recorded in 22-week-old pullets reared on deep litter and with indirect contact with pigs. Birds reared in cages or transferred to cages were unaffected. Spirochaetes were isolated and identified from the intestines of the pullets reared on deep litter but not from those reared in cages. Birds kept solely on deep litter were more severely affected, with 24 per cent immature birds and 10 per cent mortality compared with those transferred from deep litter to cages where no mortality was recorded but 15 to 22 per cent were found to be immature. The histopathological changes are described and the significance of the findings is discussed.     

Microbial characteristics of ectomycorrhizal mat communities in Oregon and California

Summary Specialized ectomycorrhizal fungi form dense mats in forest soils that have different enzyme levels, higher respiration rates, more biomass, different soil fauna, and different soil chemistry compared with adjacent soils not obviously colonized by these mats. In this study, mats formed by two genera of fungi collected in three locations were compared with a wide range of measurements. Per cent moisture, pH, chloroform fumigation-flush C, anaerobic N mineralization, exchangeable ammonium, and respiration, N₂ fixation, and denitrification rates were compared between soils or litter colonized by ectomycorrhizal mat-forming fungi and adjacent non-mat material. Significant differences were observed between the two genera of mat-forming fungi and also between mats formed primarily in mineral soil and those formed in litter. These differences suggest that different mat-forming fungi perform different functions in forest soils and that these fungi function differently in mineral soil compared with litter.Published as Technical Paper 9496, Oregon Agricultural Experiment Station     

Diverse juvenile life‐history behaviours contribute to the spawning stock of an anadromous fish population

Habitat quality often varies substantially across space and time, producing a shifting mosaic of growth and mortality trade‐offs across watersheds. Traditional studies of juvenile habitat use have emphasised the evolution of single optimal strategies that maximise recruitment to adulthood and eventual fitness. However, linking the distribution of individual behaviours that contribute to recruitment at the population level has been elusive, particularly for highly fecund aquatic organisms. We examined juvenile habitat use within a population of sockeye salmon (Oncorhynchus nerka) that spawn in a watershed consisting of two interconnected lakes and a marine lagoon. Otolith microchemical analysis revealed that the productive headwater lake accounted for about half of juvenile growth for those individuals surviving to spawn in a single river in the upper watershed. However, 47% of adults had achieved more than half of their juvenile growth in the downstream less productive lake, and 3% of individuals migrated to the estuarine environment during their first summer and returned to freshwater to overwinter before migrating back to sea. These results describe a diversity of viable habitat‐use strategies by juvenile sockeye salmon that may buffer the population against poor conditions in any single rearing environment, reduce density‐dependent mortality and have implications for the designation of critical habitat for conservation purposes. A network of accessible alternative habitats providing trade‐offs in growth and survival may be important for long‐term viability of populations.     

Forest management impacts on capercaillie (<Emphasis Type="Italic">Tetrao urogallus</Emphasis>) habitat distribution and connectivity in the Carpathians

Context

Distribution and connectivity of suitable habitat for species of conservation concern is critical for effective conservation planning. Capercaillie (Tetrao urogallus), an umbrella species for biodiversity conservation, is increasingly threatened because of habitat loss and fragmentation.

Objective

We assessed the impact of drastic changes in forest management in the Carpathian Mountains, a major stronghold of capercaillie in Europe, on habitat distribution and connectivity.

Methods

We used field data surveys with a forest disturbance dataset for 1985–2010 to map habitat suitability, and we used graph theory to analyse habitat connectivity.

Results

Climate, topography, forest proportion and fragmentation, and the distance to roads and settlements best identified capercaillie presence. Suitable habitat area was 7510 km² in 1985; by 2010, clear-cutting had reduced that area by 1110 km². More suitable habitat was lost inside protected areas (571 km²) than outside (413 km²). Habitat loss of 15 % reduced functional connectivity by 33 % since 1985.

Conclusions

Forest management, particularly large-scale clear-cutting and salvage logging, have substantially diminished and fragmented suitable capercaillie habitat, regardless of the status of forest protection. Consequently, larger areas with suitable habitat are now isolated and many patches are too small to sustain viable populations. Given that protection of capercaillie habitat would benefit many other species, including old-growth specialists and large carnivores, conservation actions to halt the loss of capercaillie habitat is urgently needed. We recommend adopting policies to protect natural forests, limiting large-scale clear-cutting and salvage logging, implementing ecological forestry, and restricting road building to reduce forest fragmentation.

     

CROSS–FERTILIZATION BETWEEN DIPLOID AND TETRAPLOID RYEGRASSES

Preliminary studies have been undertaken to determine the degree to which diploid and tetraploid ryegrass varieties intercross under field conditions. The results obtained through the use of diploid and tetraploid non-red-base tester plants indicate that pollen from tetraploid ryegrasses constitutes little or no danger to the genetic purity of diploid seed crops, even if grown in close proximity. A small proportion of viable triploid hybrids can arise in the progenies of tetraploid plants heavily exposed to diploid pollen, but here again their frequency and incidence are not of practical consequence.     

Detection of radial crossbridge force by lattice spacing changes in intact single muscle fibers

Time-resolved lattice spacing changes were measured (10-millisecond time resolution) by x-ray diffraction of synchrotron radiation in single intact muscle fibers of the frog Rana temporaria undergoing electrically stimulated tension development during application of stretches and releases. Ramp releases, which decreased fiber length at constant speed, caused a lattice expansion. After the ramp, increasing tension during recovery was accompanied by lattice compression. Ramp stretches caused a compression of the lattice. While the fiber was held at a constant length after the stretch, tension decreased and lattice spacing increased. These observations demonstrate the existence of a previously undetected radial component of the force generated by a cycling crossbridge. At sarcomere lengths of 2.05 to 2.2 micrometers, the radial force compresses the myofilament lattice. Hence, the myofilament lattice does not maintain a constant volume during changes in force.     

A Comparison of the Effects of Unilateral Thyroarytenoid Lateralization Versus Cricoarytenoid Laryngoplasty on the Area of the Rima Glottidis and Clinical Outcome in Dogs with Laryngeal Paralysis

OBJECTIVE: To compare the clinical effects of unilateral thyroarytenoid lateralization versus unilateral cricoarytenoid laryngoplasty for the treatment of canine laryngeal paralysis. Study Design-A prospective, clinical trial. ANIMALS: Twenty client-owned dogs admitted to Glasgow University Veterinary Hospital (GUVH) between 1997 and 1999 with a diagnosis of laryngeal paralysis. METHODS: A thorough evaluation of each dog was undertaken that included history, physical and neurologic examinations, complete blood count, serum biochemistry profile, serum thyroxine (T4) level, and thyroid-stimulating hormone (TSH) assay. The exercise tolerance of each dog was investigated by assessing respiratory rate and arterial blood gas analysis at rest and after 5 minutes of mild exercise. Animals were included in the study on the basis of a definitive diagnosis of laryngeal paralysis made by endoscopic observation of the larynx in the lightly anesthetized patient. The animals were randomly assigned to 1 of 2 treatment groups: unilateral thyroarytenoid lateralization or unilateral cricoarytenoid laryngoplasty, with all procedures being performed by the same surgeon. Video images of the rima glottidis were recorded pre- and postoperatively using video endoscopy. Video images were digitized and the area of the rima glottidis measured using image-analysis software. An increase in the area of the rima glottidis was expressed as a percentage of the preoperative area. All animals were reassessed 6 weeks' postoperatively, and exercise tolerance tests were repeated. RESULTS: The mean increase in the area of the rima glottidis postoperatively when compared with the preoperative area was 140% for those animals undergoing unilateral thyroarytenoid lateralization (range, 120%-158%) and 207% for those animals undergoing unilateral cricoarytenoid laryngoplasty (range, 183%-228%). This difference was statistically significant (P < .0001). At the 6-week postoperative examination, there was no significant difference in improvement between the 2 groups when compared on either a clinical basis or exercise tolerance tests. The mean surgical time in the 2 groups was 25 minutes for thyroarytenoid lateralization and 43 minutes for cricoarytenoid laryngoplasty. This was a statistically significant difference (P = .002). CONCLUSION: Although increase in area of the rima glottidis was significantly greater after unilateral cricoarytenoid laryngoplasty compared with unilateral thyroarytenoid lateralization, no difference in clinical outcome could be detected. However, the cricoarytenoid laryngoplasty procedure required significantly more surgical time. CLINICAL RELEVANCE: Both unilateral cricoarytenoid laryngoplasty and unilateral thyroarytenoid lateralization are successful methods for the treatment of laryngeal paralysis; however, thyroarytenoid lateralization requires less surgical time to perform.