SUSTAINABLE NITROGEN MANAGEMENT IN AUSTRALIAN AGROECOSYSTEMS: CHALLENGES AND OPPORTUNITIES

● There is huge potential for improvement of nitrogen management in Australia. ● N management should incorporate environmental, social and economic sustainability. ● Agronomic, ecological and socioeconomic approaches and efforts are needed. Nitrogen is an essential nutrient that supports life, but excess N in the human-environment system causes multiple adverse effects from the local to the global scale. Sustainable N management in agroecosystems, therefore, has become more and more critical to address the increasing concern over food security, environmental quality and climate change. Australia is facing a serious challenge for sustainable N management due to its emission-intensive lifestyle (high level of animal-source foods and fossil fuels consumption) and its diversity of agricultural production systems, from extensive rainfed grain systems with mining of soil N to intensive crop and animal production systems with excessive use of N. This paper reviews the major challenges and future opportunities for making Australian agrifood systems more sustainable, less polluting and more profitable.     

Alternative Solids Removal for Warm Water Recirculating Raft Aquaponic Systems

Aquaponics is an integrated fish and plant recirculating production system. The University of the Virgin Islands' raft aquaponic system uses a cylindro‐conical clarifier as a primary solids removal device; however, a swirl separator may offer advantages. The objectives of the 8‐wk experiment were to compare water quality parameters, Nile tilapia, Oreochromis niloticus, production and water spinach, Ipomoea aquatica, production in a raft aquaponic system using a clarifier or swirl separator for primary treatment of solids in the waste stream . No significant differences (P ≥ 0.05) existed between treatments for temperature, oxygen, pH, total suspended solids, alkalinity, electrical conductivity, total ammonia‐nitrogen, nitrite‐nitrogen, nitrate‐nitrogen, macronutrients, and micronutrients concentrations in the culture water. There were no significant differences (P ≥ 0.05) between treatments for Nile tilapia production, average weight, survival, or feed conversion ratio. There were no significant differences (P ≥ 0.05) between treatments for water spinach production or plant tissue analysis. In conclusion, the swirl separator used in this experiment performed similar to the clarifier and water spinach grew vigorously in the raft aquaponic system .     

Growth and fruit production of Sclerocarya birrea in the South African lowveld

Sclerocarya birrea (A.Rich.) Hochst. subsp. caffra (Sond.) Kokwaro. is a common species throughout the semiarid, deciduous savannas of much of sub-Saharan Africa. It is a favoured species and is frequently maintained in homestead plots and arable fields in an agroforestry situation. Although the abundance and popularity of this species has led to several initiatives to commercialise a number of marula products, the sustainability of the resource base with respect to fruit production has not been considered. This paper reports on a field experiment that monitored growth rates and fruit production of a sample of adult trees from several wild populations. Mean fruit production was 36.8 kg per tree in the first year, and negligible in the second. This was considerably less than previous estimates, which were based largely on small samples or anecdotal reports. The maximum recorded yield was 416.6 kg per tree. Fruit production was positively related to the size of the tree. Growth rates of adult trees were slow. There was a strong positive relationship between mean annual diameter increment and stem diameter. The slow growth rates and low fruit yields indicate that more attention is required regarding the sustainability of there source and its ability to provide sufficient fruit for the growing subsistence and commercial demand at both local and national scales. This revised version was published online in June 2006 with corrections to the Cover Date.     

Egg Water Induced Reaction and Biostain Assay of Sperm from Marine Shrimp Penaeus vannamei: Dietary Effects on Sperm Quality

Reproductive performance was evaluated for sexually mature male Penueus vannamei fed one of four diets: 1) commercial 40% protein shrimp growout diet; 2) 100% squid; 3) 50% squid, 25% bloodworms and 25% Artemia; and 4) starvation. Spermatophores were ejaculated manually from tagged males at stocking and every 12 d thereafter. For each half of the compound spermatophore, weight and sperm count were determined. Four methods were used to assay the sperm quality: 1) gross morphology (GM); 2) trypan blue stain (TB); 3) acridine orange stain (AO); and 4) egg water induced reaction (EW). The reaction induced when P. vannamei sperm are exposed to conspecific egg water is grossly similar to that observed in vivo at the surface of the freshly spawned eggs from naturally mated females. Little correlation was found between spermatophore weight and sperm count. The best correlation was found between GM and AO (r²= 0.859, P < 0.01). Many morphologically abnormal sperm did not stain with TB. For most of the spermatophores evaluated; over 80% of the sperm were morphologically normal, were unstained with TB, and were immediately fluorescing light green when stained with AO. When exposed to egg water, sperm from these apparently good quality spermatophores yielded mixed results. The analysis of dietary effects on spermatophore quality were equivocal. Although a significant decline in body weight, spermatophore weight, and sperm count were observed in the starvation treatment as compared to maturation and squid diets, no significant differences were observed in MY of the sperm quality assays.     

Current and potential carbon stocks of trees in urban parking lots in towns of the Eastern Cape,South Africa

Greening of shopping centre parking lots is a potentially important strategy that can contribute to urban carbon mitigation efforts, improve aesthetics and the shopping experience of consumers, whilst adding to urban biodiversity. Twenty-eight shopping centre parking lots in six Eastern Cape urban centres, South Africa, were sampled to determine tree species composition, density and annual carbon sequestration potential. The best case parking lot found during the study was used as a benchmark to display the difference between current tree density and above-ground carbon stocks relative to the potential optimum. The highest tree density was 66 trees ha^?1, whereas the average density across all sampled parking lots was less than half that (27.2 ± 22.6 trees ha^?1). The average annual carbon sequestration potential per parking lot was 1390 ± 2503 kg ha^?1. Planting density was positively related to annual sequestration rates, whilst parking lot age and the mean annual rainfall of the town had no influence. Mean tree species richness per parking lot was 2.3 ± 1.8 species, with a positive relationship to parking lot size, but not to mean annual rainfall of the site. The majority of trees (62.5%) in parking lots were alien species, although newer parking lots had significantly greater proportions of indigenous species. There was no difference in mean annual carbon sequestration rate per tree between indigenous and alien trees species. Low tree densities and small parking lot areas constrained the potential for earning carbon credits from trees in parking lots. Nonetheless, planners and designers need to be more aware of the potential contribution of trees towards urban sustainability.     

Detection, quantification, metabolism, and behavioral effects of selegiline in horses

Selegiline ([R]-[-]N,alpha-dimethyl-N-2- propynylphenethylamine or l-deprenyl), an irreversible inhibitor of monoamine oxidase, is a classic antidyskinetic and antiparkinsonian agent widely used in human medicine both as monotherapy and as an adjunct to levodopa therapy. Selegiline is classified by the Association of Racing Commissioners International (ARCI) as a class 2 agent, and is considered to have high abuse potential in racing horses. A highly sensitive LC/MS/MS quantitative analytical method has been developed for selegiline and its potential metabolites amphetamine and methamphetamine using commercially available deuterated analogs of these compounds as internal standards. After administering 40 mg of selegiline orally to two horses, relatively low (<60 ng/ml) concentrations of parent selegiline, amphetamine, and methamphetamine were recovered in urine samples. However, relatively high urinary concentrations of another selegiline metabolite were found, tentatively identified as N- desmethylselegiline. This metabolite was synthesized and found to be indistinguishable from the new metabolite recovered from horse urine, thereby confirming the chemical identity of the equine metabolite. Additionally, analysis of urine samples from four horses dosed with 50 mg of selegiline confirmed that N-desmethylselegiline is the major urinary metabolite of selegiline in horses. In related behavior studies, p.o. and i.v. administration of 30 mg of selegiline produced no significant changes in either locomotor activities or heart rates.     

Impact of euthanasia rates, euthanasia practices, and human resource practices on employee turnover in animal shelters

OBJECTIVE: To examine the effects of euthanasia rates, euthanasia practices, and human resource practices on the turnover rate among employees with euthanasia responsibilities at animal shelters. DESIGN: Cross-sectional original study. SAMPLE POPULATION: 36 shelters across the United States that employed at least 5 full-time employees and performed euthanasia on site. PROCEDURES: By mail, 1 survey was sent to each shelter. Surveys were completed by a senior member of management and were returned by mail. Questions assessed characteristics (eg, euthanasia rates) and practices of the animal shelter, along with employee turnover rates. By use of correlation coefficients and stepwise regression analyses, key predictors of turnover rates among employees with euthanasia responsibilities were investigated. RESULTS: Employee turnover rates were positively related to euthanasia rate. Practices that were associated with decreased turnover rates included provision of a designated euthanasia room, exclusion of other live animals from vicinity during euthanasia, and removal of euthanized animals from a room prior to entry of another animal to be euthanized. Making decisions regarding euthanasia of animals on the basis of factors other than behavior and health reasons was related to increased personnel turnover. With regard to human resources practices, shelters that used a systematic personnel selection procedure (eg, standardized testing) had comparatively lower employee turnover. CONCLUSIONS AND CLINICAL RELEVANCE: Data obtained may suggest several specific avenues that can be pursued to mitigate turnover among employees with euthanasia responsibilities at animal shelters and animal control or veterinary medical organizations.     

New production strategy for silver perch (Bidyanus bidyanus); over‐wintering fingerlings in a tank‐based recirculating aquaculture system

Slow growth and losses to bird predation and infectious diseases in winter can compromise the profitability of silver perch farming. To evaluate over‐wintering silver perch (Bidyanus bidyanus) in a recirculating aquaculture system (RAS), fingerlings (38 g) were stocked in either cages in a pond at ambient temperatures (10–21 °C) or tanks in the RAS at elevated temperatures (19–25 °C) and cultured for 125 days. Mean survival (96%), final weight (146 g), specific growth rate (1.07% day^?1) and production rate (28.1 kg m^?3) of fish in the RAS were significantly higher than for fish over‐wintered in cages (77%, 73 g, 0.53% day^?1, 11.1 kg m^?3). Fish from both treatments were then reared in cages for a further 129 days. Final mean weight of fish originally over‐wintered in the RAS was 426 g, while fish over‐wintered in cages were only 273 g. To determine optimal stocking densities, fingerlings (11.8 g) were stocked at 500, 1000 or 1500 fish m^?3 in tanks in the RAS and cultured for 124 days. Survival was not affected, but growth was significantly slower and feed conversion ratio higher at 1500 fish m^?3 compared with 500 or 1000 fish m^?3. Results demonstrate that over‐wintering silver perch in an RAS can produce large fingerlings for grow‐out in early spring. This strategy could eliminate bird predation, reduce losses to diseases and shorten the overall culture period.