AgriFutures Australia

READING the Foreword and Preface of Trees, Water and Salt, I was pleasantly satisfied by the promised content of this, the first publication in a series from CSIRO addressing dryland salinity. This is not a book of "Doom and gloom", all too often associated with salinity, but is a forward thinking attempt to combat a complex problem. The authors suggest that the best way to curtail or stop salinity would involve the re-vegetation of entire catchments with native species. Trees, Water and Salt recognizes the agricultural and economical impracticalities this option proffers, accepting that some salinity will occur as the price of our current consumer demands. Trees, Water and Salt suggests that to help mêlée salinity, land managers must design and implement different agroforestry systems.

OBJECTIVE: To determine the interobserver variability of assessment of exercise-induced pulmonary hemorrhage (EIPH) during tracheobronchoscopic examination in horses. ANIMALS: 747 Thoroughbred racehorses. Procedures-850 tracheobronchoscopic examinations were performed within 2 hours of racing for the horses. Examinations were recorded on videotape, and EIPH and its severity were assessed independently by 3 veterinarians. Concordance was determined by calculation of the Cohen weighted kappa statistic and tabulation of scores assigned by each observer. RESULTS: Weighted kappa statistics ranged from 0.75 to 0.80. In 99.4% of observations, all observers agreed or 2 of 3 agreed and the third differed by < or = 1 grade. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that interobserver reliability of tracheobronchoscopic assessment of EIPH in Thoroughbred racehorses is high when the examination is conducted by experienced veterinarians. Concordance among investigators is sufficient to justify use of this grading system for further studies and clinical descriptions of EIPH.

OBJECTIVE: To determine whether exercise-induced pulmonary hemorrhage (EIPH) was associated with racing performance inThoroughbred horses not medicated with furosemide and not using nasal dilator strips. DESIGN: Observational cross-sectional study. ANIMALS: 744 two- to 10-year-old Thoroughbred horses racing in Melbourne, Australia. PROCEDURE: Horses were enrolled prior to racing, and a tracheobronchoscopic examination was performed after 1 race. Examinations were recorded on videotape, and presence and severity (grade 0 to 4) of EIPH were subsequently determined by 3 observers blinded to the horses' identity. Race records were abstracted for each horse examined. RESULTS: Overall, 52.1% of horses eligible for participation in the study were examined, and horses that were examined did not differ from horses that were not examined in regard to age, sex distribution, or proportion of horses that won or finished in the first 3 positions. Horses with EIPH grades < 1 were 4.0 times as likely to win, 1.8 times as likely to finish in the first 3 positions, and 3.03 times as likely to be in the 90th percentile or higher for race earnings as were horses with grades > 2. Horses with EIPH grades > 1 finished significantly farther behind the winner than did horses without EIPH. However, odds that horses with grade 1 EIPH would win or finish in the first 3 positions were not significantly different from odds for horses without EIPH. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that EIPH is associated with impaired performance in Thoroughbred racehorses not medicated with furosemide and not using nasal dilator strips.

This overview paper presents a description of the National Windbreaks Program (NWP) — its objectives, the main methods used to achieve these objectives and a summary of the key results. It draws these from the individual papers appearing in this special issue, which provide detailed descriptions and discussion about the specific research sites and research methods used, in addition to interpreting and discussing the results. The key findings were the following: (i) Two broad areas of crop and pasture response can be identified downwind of a porous windbreak: a zone of reduced yield associated with competition with the windbreak trees that extended from 1 H to 3 H, where H is the windbreak height, and a zone of unchanged or slightly increased yield stretching downwind to 10 H or 20 H. (ii) Averaged over the paddock, yield gains due to the effect of shelter on microclimate were smaller than expected — especially for cereals. Yield simulations conducted using the APSIM model and 20 years of historical climate data confirmed this result for longer periods and for other crop growing regions in Australia. Larger yield gains were simulated at locations where the latter part of the growing season was characterised by high atmospheric demand and a depleted soil water store. (iii) Economic analyses that account for the costs of establishing windbreaks, losses due to competition and yield gains as a result of shelter found that windbreaks will either lead to a small financial gain or be cost neutral. (iv) Part of the reason for the relatively small changes in yield measured at the field sites was the variable wind climate which meant that the crop was only sheltered for a small proportion of the growing season. In much of southern Australia, where the day-to-day and seasonal variability in wind direction is large, additional windbreaks planted around the paddock perimeter or as closely-spaced rows within the paddock will be needed to provide more consistent levels of shelter. (v) Protection from infrequent, high magnitude wind events that cause plant damage and soil erosion was observed to lead to the largest yield gains. The main forms of direct damage were sandblasting, which either buries or removes seedlings from the soil or damages the leaves and stems, and direct leaf tearing and stripping. (vi) A corollary to these findings is the differing effect that porous windbreaks have on the air temperature and humidity compared to wind. While winds are reduced in strength in a zone that extends from 5 H upwind to at least 25 H downwind of the windbreak, the effects of shelter on temperature and humidity are smaller and restricted mainly to the quiet zone. This means that fewer windbreaks are required to achieve reductions in wind damage than for altering the microclimate. (vii) The wind tunnel experiments illustrate the important aspects of windbreak structure that determine the airflow downwind, and subsequent microclimate changes, in winds oriented both perpendicular and obliquely to porous windbreaks. These results enable a series of guidelines to be forwarded for designing windbreaks for Australian agricultural systems.

OBJECTIVE: To determine pharmacokinetics and plasma steady-state kinetics of metformin after oral or nasogastric administration in insulin-resistant (IR) ponies. ANIMALS: 8 IR ponies. PROCEDURES: Metformin (30 mg/kg) was administered to 8 ponies via nasogastric tube Blood samples were collected at intervals for 24 hours. Plasma concentrations of metformin were measured via liquid chromatography-electrospray tandem mass spectroscopy Pharmacokinetic variables were determined via noncompartmental analysis. Metformin (15 mg/kg, PO, twice daily [8 am and 5 pm]) was administered to 4 ponies for an additional 20 days, and blood samples were obtained every 2 days. Plasma concentration at steady state (Css) was determined. RESULTS: Mean±SD elimination half-life (t1/2) of metformin was 11.7±5.2 hours, maxima plasma concentration was 748±269 ng/mL at 54±32 minutes, mean area under the curve was 355±92 microg.h/mL, and apparent clearance was 90.6±28.1 mL/min/kg. The Css was 122±22 ng/mL. CONCLUSIONS AND CLINICAL RELEVANCE: Metformin reportedly enhances insulin sensitivity of peripheral tissues without stimulating insulin secretion, but bioavailability in horses is low. The t1/2 of metformin in IR ponies was similar to that in humans. Actual clearance of metformin adjusted for bioavailability in IR ponies was similar to that in humans; however, during chronic oral administration at dosages reported in efficacy studies, the Css of metformin was less than values associated with therapeutic efficacy in humans The apparent lack of long-term efficacy of metformin in horses is likely attributable to low bioavailability, rather than to rapid clearance.

OBJECTIVE: To determine whether there is evidence of myocardial injury in horses with acute abdominal disease. DESIGN: Prospective case series. ANIMALS: 18 healthy horses and 69 horses with acute abdominal disease. PROCEDURES: 18 healthy horses had been admitted to the hospital for investigation and were assigned to group 1. Horses examined for acute abdominal disease were assigned to 3 groups: strangulating obstruction, nonstrangulating obstruction, or inflammatory disease (groups 2, 3, and 4, respectively). Heart rate, Hct, and blood lactate and cardiac troponin I (cTnI) concentrations were measured at initial examination. Myocardial function was assessed by echocardiographic measurement of fractional shortening and left ventricular ejection time (LVET). Heart rhythm was evaluated via ECG. RESULTS: The proportion of horses with high (> 0.03 ng/mL) cTnI concentration was significantly greater among horses with strangulating (9/25 [36%]) or inflammatory (9/19 [47%]) lesions, compared with healthy horses (0/18). The proportion of horses with high cTnI concentration was significantly greater among nonsurvivors (12/24 [50%]) than among survivors (10/45 [22%]). Serum cTnI concentration was positively correlated with Hct, heart rate, and blood lactate concentration and negatively correlated with LVET. CONCLUSIONS AND CLINICAL RELEVANCE: Evidence of myocardial injury was observed in horses with acute abdominal disease, and this injury was associated with severity of illness. Recognition of myocardial injury could improve treatment of acute abdominal disease in horses.

Abstract Mortality data for non‐acclimated and acclimated 3rd instar larvae and mid‐term eggs of Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) were obtained after immersing in hot water at 46 °C. Acclimation consisted of holding the larvae and eggs at 35 °C for 20 and 11 h respectively just prior to heat‐treatment. The median lethal time (LT50) for acclimated larvae was found to be 6.9 min compared to 2.5 min for non‐acclimated larvae. LT99.999 for acclimated larvae was 20.9 min compared to 8.7 min for non‐acclimated larvae. LT50 for acclimated eggs was 5.0 min compared to 2.4 min for non‐acclimated eggs. LT99.999 for acclimated eggs was 26.0 min compared to 6.6 min for non‐acclimated eggs. For 3rd instar larvae, most acclimation effect on mortality had occurred by 8 h. A notable residual response was present 20 h after acclimation had occurred, reducing mortality at 46 °C for 4.5 min by roughly 25%. Mortality data at 46 °C were also obtained for non‐acclimated and acclimated late instar larvae of Epiphyas postvittana (Walker) (Lepidoptera: Tortricidae). With this species, LT50 for acclimated larvae was 2.5 min compared to 1.1 min for non‐acclimated larvae. LT99.999 for acclimated larvae was 9.5 min compared to 4.6 min for non‐acclimated larvae.

Summary The challenge for low-rainfall plantation forestry is to develop financially viable plantations using hardy species that produce commercial products as well as delivering environmental benefits. Since 1999, forest research agencies have co-operated on tree improvement for dryland southern Australia through the Australian Low Rainfall Tree Improvement Group (ALRTIG). A small number of key species, including hardwoods (tree-sized eucalypt species), softwoods (Pinus brutia, P. pinaster and P. radiata) and two mallee eucalypt species yielding foliar essential oils were selected for genetic evaluation and improvement. Selection was based on their adaptability, growth rates, yields of potential commercial products, and availability of reliable information and genetic resources. Improvement for the hardwood and softwood species aims to develop breeds that will maximise the net present value (stumpage value less growing costs) of logs produced on rotations of 20–40 y. Breeding will be based on recurrent selection for general combining ability, primarily in open-pollinated breeding populations based on selections from the best natural provenances and planted stands. A total of 29 provenance-progeny trials of the key species have been established across a range of dryland sites. These trials are now yielding information on the genetic control of growth, stem form and branching traits. This will enable production of genetically-improved planting stock through later conversion of some trials to seedling seed orchards and development of clonal seed orchards. Interim seed production areas based on planted stands of known best provenances have been developed for short-term production of somewhat-improved seed, and genetic gain trials to compare these seed sources with unimproved material have been established.