The influence of nitrate and ammonium forms of nitrogen fertilizer on the growth and osmoregulation of digitaria eriantha and Chloris gayana grown under saline conditions

Abstract

Digltaria eriantha and Chloris gayana were grown under controlled conditions for three months and were treated with a nutrient solution containing 150 mMol NaCl and the following nitrogen sources: 25 or 200 mg/l NH₄ ⁺‐N or NO₃ ^?‐N or no nitrogen. The application of nitrogen was found to stimulate growth, i.e. leaf area and dry mass in both grasses, with a greatest growth response to both NH₄ ⁺—N treatments in D. eriantha, and NH₄ ⁺‐N and NO₃ ^?—N treatments in C. gayana. Proline accumulated in both grasses, but this accumulation followed different trends in the two grasses. Soluble sugars (non‐structural) accumulated in the above ground component in D. eriantha, while in C. gayana soluble sugars accumulated predominantly in the roots, possibly as osmotica, or for storage and may thus have been available for regrowth.     

Does Kochia prostrata Spread From Seeded Sites? An Evaluation From Southwestern Idaho,USA

Purposeful introductions of exotic species for rehabilitation efforts following wildfire are common on rangelands in the western United States, though ecological impacts of exotic species in novel environments are often poorly understood. One such introduced species, Kochia prostrata (L.) Schrad (forage kochia) has been seeded on over 200 000 ha throughout the Intermountain West to provide fuel breaks and forage, and to compete with invasive plants. Despite its potential benefits, K. prostrata has been reported to spread from some seeded areas, and no studies have addressed its potential interactions with native species. A systematic investigation is needed to increase understanding of the extent to which K. prostrata spreads from seeded areas, the environmental conditions under which it spreads, and its interactions with the associated plant communities. We sampled 28 K. prostrata postfire rehabilitation and greenstrip seedings in southwestern Idaho, which ranged from 3 to 24 yr since seeding. We analyzed cover of K. prostrata and the associated plant community in adjacent seeded and unseeded areas, and quantified extent of spread from seeded areas. Abundance of K. prostrata was negatively associated with that of most plant functional groups, including native species, but was positively associated with abundance of exotic annual forbs. Kochia prostrata spread to unseeded areas on 89% of sampled sites; distances of the farthest individual from the seeding boundary were greater than those previously reported, ranging from 0 to 710 m, with a mean distance of 208 m. Further, although the area covered by K. prostrata increased with time since seeding, we found no evidence that plant community composition affected spread of K. prostrata. Results contribute to current understanding of potential ecological implications of seeding K. prostrata and will enhance the ability of land managers to make scientifically based management decisions about its use.     

Oestrogen,Progesterone and Oxytocin Receptors and COX‐2 Expression in Endometrial Biopsy Samples from the Induction of Ovulation to Luteolysis in Llamas (Lama glama)

Endometrial expression of oestrogen (ERα), progesterone (PR) and oxytocin receptor (OR) and cyclooxygenase‐2 (COX‐2) was evaluated from the induction of ovulation to luteolysis in llamas. Ovarian activity was daily assessed by ultrasonography in five females. Ovulation was induced immediately after the detection of an ovulatory follicle by a GnRH injection (Day 0). Endometrial samples were obtained by transcervical biopsies from the left and right horns on day 0 and days 4, 8, 10 and 12 post‐GnRH. Blood samples were collected daily for progesterone and estradiol‐17β determinations by RIA. An immunohistochemical technique was used to study receptors population and COX‐2 expression which were then evaluated by two independent observers. The expression of ERα and PR was highest on day 0 in the luminal epithelium and stroma in association with high plasma estradiol‐17β concentrations. Thereafter, a decrease in ERα population was registered on day 4 and a new increase of its expression was observed between days 8 and 12 in those cell types. Conversely, PR population was gradually down‐regulated until its lowest expression was reached on day 10 post‐GnRH in the luminal epithelium. Content of OR was similar throughout the study in all cell types. The expression of COX‐2 was highest from day 8 to 12 post‐GnRH in the luminal epithelium, in relation to the time of maximal PGF_2α release. Both steroid receptors populations and COX‐2 expression were similar between horns. Meanwhile, OR expression was higher in the right than in the left uterine horn. In summary, this study showed that the loss of endometrium sensitivity to progesterone by days 8–10 post‐induction of ovulation and the concomitant increase of COX‐2 expression could play a key role in the mechanism of luteolysis and somehow be related to the short corpus luteum lifespan of llamas.     

Multi-attribute evaluation of landscape-level fuel management to reduce wildfire risk

This paper provides an example of the practical application of multi-attribute trade-off analysis (MATA) to wildfire management. The MATA approach supports more informed decision-making because it exposes important trade-offs among competing management objectives (requiring value-based choices), helps guide and structure necessary technical judgements, explicitly represents uncertainty (i.e., not just expected outcomes but risk profiles around outcomes) and addresses temporal trade-offs. MATA promotes critical thinking about what analysis is required for decision-making. A MATA approach can be applied for all types of forest and fire management decisions. In this paper, we provide a sample application of MATA to an evaluation of landscape-level fuel treatments for managing wildfire risk. The study area is located in southeastern British Columbia, Canada where historical fire suppression policies and expanding development in wildland urban interface areas have resulted in an increase in both the probability and the consequences of stand replacement fires. We specify management objectives and develop measurable attributes for fire management costs, timber supply, property damage, landscape-level biodiversity, local air quality and climate change. We then simulate the effects on these attributes of four alternative fuel management strategies that include combinations of mechanical treatments and prescribed burning over a 100-year period. The evaluation illustrates the key features of MATA while highlighting the benefits and challenges of implementing the approach.     

Distribution of Salmonella serovars and phage types on 80 Ontario swine farms in 2004

The objective of this study was to describe the distribution of Salmonella spp. on Ontario grower-finisher pig farms. Eighty swine farms were visited from January through July 2004. On each farm, fecal samples were collected from 5 pens, 2 rectal samples and 1 pooled sample from fresh manure on the floor per pen. Salmonella was isolated from 91 (11%) of the 800 rectal samples and 73 (18%) of the 397 pooled samples. Overall, Salmonella was recovered from 37 (46%) of the 80 farms. On each positive farm, Salmonella was cultured from 1 to 7 pigs or 1 to 5 pens. Of the 37 farms, 18, 13, 5, and 1 yielded 1, 2, 3, and 4 serovars, respectively. The most common serovars were S. Typhimurium var. Copenhagen, S. Infantis, S. Typhimurium, S. Derby, S. Agona, S. Havana, and S. enterica subsp. I:Rough-O. The 3 most frequent phage types were PT 104, PT 104a, and PT 104b. There was a statistically fair agreement between samples collected directly from pigs and pooled pen samples in determining the Salmonella status at the pen and farm level (kappa = 0.6, P < 0.0001). However, in 62 pens, Salmonella status, serovars, or phage types differed between the pig and pooled pen samples. The distribution of Salmonella on the swine farms in this study indicates that, in developing an intervention strategy, priority should be given to farms positive for S. Typhimurium var. Copenhagen. Also, the variation in Salmonella status between pig and pooled pen samples deserves consideration in a sampling strategy.     

Humoral response to Mycobacterium avium subsp. avium in naturally infected ring-neck doves (Streptopelia risoria)

Creation of a reliable and easy to use serologic test would greatly improve ante mortem diagnosis of Mycobacterium avium subsp. avium and aid in the control of avian mycobacteriosis, particularly in captive birds. In order to determine whether serodiagnostics could be of value in testing ring-neck doves (Streptopelia risoria) for M. a. avium infection, Western blot analysis was used to assess the humoral response of ring-neck doves exposed to M. a. avium, and to evaluate whether an association could be made between the humoral response and necropsy findings, histopathology, culture, and PCR testing. Western blot results were examined for reactivity patterns associating humoral response with infection status, severity and type of lesions (diffuse vs. multifocal granulomatous inflammation) and phenotype (white vs. non-white). A sensitivity of 88.24% and a specificity of 100% were achieved utilizing Western blot analysis to detect M. a. avium infection in ring-neck doves, offering a negative predictive value of 93% and a positive predictive value of 100%. While Western blot analysis results did not reflect lesion severity, lesion type did partially correspond with the humoral response. The findings of the present study indicate that serologic testing can be used as a valuable ante mortem screening tool for identifying ring-neck doves infected with M. a. avium.     

Nonsurgical repair of an umbilical hernia in two Asian elephant calves (Elephas maximus)

Umbilical hernias were diagnosed in two captive-born, female Asian elephant (Elephas maximus) calves several weeks after birth. Daily manual reduction of the hernias for 5 wk in the first case and for 5 mo in the second resulted in complete closure of the defects. Nonsurgical repair of uncomplicated, fully reducible umbilical hernias in Asian elephants can be an alternative to surgery.     

Amphibian ocular malformation associated with frog virus 3

During an on-going amphibian ecology study, a free-ranging American bullfrog (Rana catesbeiana) metamorph was captured in a pitfall trap adjacent to a constructed farm pond at the Plateau Research and Education Center (PREC) on the Cumberland Plateau near Crossville, Tennessee, USA. Grossly, the right eye was approximately 50% the size of the left. Stereo and light microscopic examination revealed two granulomas within the orbit. Electron microscopic examination revealed virus particles scattered throughout one structure but mostly aggregated toward the center. Subsequent PCR and sequencing (GenBank accession Number EF175670) confirmed frog virus 3 (FV3). This represents the first report of a malformation in an anuran associated with FV3.     

Unilateral polydactyly in two foals

This case report describes unilateral supernumerary digits of the forelimb in two foals. A diagnosis of polydactyly of the right forelimb in one case and of the left forelimb in the other was made by clinical examination and radiographic interpretation. Surgical excision was performed under general anaesthesia with a good cosmetic and functional outcome in both cases.