Investigation of the effect of Equivac® HeV Hendra virus vaccination on Thoroughbred racing performance

Objective

To evaluate the effect of Equivac® HeV Hendra virus vaccine on Thoroughbred racing performance.

Design

Retrospective pre‐post intervention study.

Methods

Thoroughbreds with at least one start at one of six major south‐eastern Queensland race tracks between 1 July 2012 and 31 December 2016 and with starts in the 3‐month periods before and after Hendra virus vaccinations were identified. Piecewise linear mixed models compared the trends in ‘Timeform rating’ and ‘margin to winner’ before and after initial Hendra virus vaccination. Generalised linear mixed models similarly compared the odds of ‘winning’, ‘placing’ (1st–3rd) and ‘winning any prize money’. Timeform rating trends were also compared before and after the second and subsequent vaccinations.

Results

Analysis of data from 4208 race starts by 755 horses revealed no significant difference in performance in the 3 months before versus 3 months after initial Hendra vaccination for Timeform rating (P = 0.32), ‘Margin to winner’ (P = 0.45), prize money won (P = 0.25), wins (P = 0.64) or placings (P = 0.77). Further analysis for Timeform rating for 7844 race starts by 928 horses failed to identify any significant change in Timeform rating trends before versus after the second and subsequent vaccinations (P = 0.16) or any evidence of a cumulative effect for the number of vaccines received (P = 0.22).

Conclusion

No evidence of an effect of Hendra virus vaccination on racing performance was found. The findings allow owners, trainers, industry regulators and animal health authorities to make informed decisions about vaccination.     

Long-term base cation mass balances for Swedish forests and the concept of sustainability

Data from the Swedish Forest Inventory was used to calculate mass balances for base cations Ca, Mg and K for Swedish forests. Using lysimeter and forest survey soil analyses to estimate present base cation leaching from the root zone reveals that weathering plus base cation deposition is not sufficient to support both, the present base cation leaching rate and the present rate of uptake caused by stem growth. Calculations suggest that 96% of the productive forested area may have higher rates of removal than supply for one or more base cation. Under a best-case scenario, assuming less pollution, the present growth rate and 100% efficiency in uptake of available nutrients, the area with more removal than supply would still be at least 30% of the total area. Forest soils are being depleted at a rate where the exchangeable reservoirs have high risk of being severely depleted in the next few decades in central and southern Sweden. During 1983–1985 the depletion rate is calculated to be, on the average, 0.33 keq ha⁻¹ year⁻¹. The weathering rate and present base cation deposition can sustain growth at a level where (80–85)×10⁶m³ stemwood year⁻¹ can be harvested. Any harvested growth beyond this volume must be sustained by artificial means.

For whole-tree harvesting without base cation return, the calculations indicate that it would significantly increase the base saturation depletion rate to an average of 0.62 keq ha⁻¹ year⁻¹, and risk depletion of the soil in less than one-to-two rotation periods almost anywhere in Sweden.

The calculations stress the importance that sustainable forest management must include the management of nutrient fluxes and reservoirs.     

Proceedings from the 2012 PAA Symposium: Potato Phosphorus Management and Utilization for Today and Tomorrow

Sustainable management of phosphorus (P) is a critical component of potato production systems because of a comparatively high plant P requirement, soil reactions that create management challenges, and potential environmental degradation from inappropriate P management. Phosphorus affects potato plant growth in many ways including its effects on plant metabolism, cellular structural components, canopy development, tuber set, nutritional quality, and resistance to some diseases.     

Interactive effects of fungicide programs and nitrogen management on potato yield and quality

The use of azoxystrobin (Quadris) for early blight control often results in potato vines remaining greener later in the growing season. This observation has lead to the suggestion that nitrogen (N) fertilizer could be applied at lower rates when azoxystrobin is used in a fungicide program since high N rates are sometimes used to help manage early blight. The objectives of this study were to evaluate the effectiveness of azoxystrobin for control of early blight under various N fertility management regimes and to determine if azoxystrobin affected plant N fertilizer requirements. Plots were established in 1999 and 2000 at Becker, MN, on a Hubbard loamy sand as a complete factorial, split-plot arrangement using a randomized complete block design with four replications. Fungicide treatments were used as the whole plot factor and included an untreated control, chlorothalonil, and azoxystrobin rotated with chlorothalonil. Fertility treatments were used as the sub-plot factor and included N applied at three levels (170, 250, and 340 kg ha^?1) and two timings (all prehilling or pre- and post-hilling). Early blight was problematic in 1999 and both early and late blight were severe in 2000. Significant interactions were observed between fungicide and fertility treatments for disease control. Control of diseases with fungicides was generally more effective at higher N rates regardless of N application timing. When azoxystrobin was used in the fungicide program, N rate was not as critical in managing foliar disease. In 1999, an interaction was not observed between N rate and fungicide treatment for yield. Yields increased with increasing N rate regardless of fungicide program. However, a significant interaction did occur between N rate and fungicide treatment in 2000 where yields decreased linearly in the control with increasing N rate, increased linearly with N rate using chlorothalonil, and did not respond significantly to N rate using azoxystrobin/chlorothalonil. Results of this study indicate that interactions between the incidence of early/late blight disease and N requirement for potato may depend on the rate of vine death and conditions affecting tuber maturity. At equivalent N rates, post-hilling N tended to depress yield regardless of fungicide program, suggesting that under the conditions of this study late season N is not an effective practice for managing foliar diseases such as early or late blight.     

Effect of region on the uncertainty in crop variety trial programs with a reduced number of trials

Results from crop variety trials may vary between geographical regions because of differences in climate and soil types. Results are usually presented at regional level. To evaluate the importance of the regions used in the Swedish variety trial programs, we examined which regions produced similar levels of yield and similar ratios in yield between cultivars; the amount by which variance could be reduced by division into regions or clusters of regions; and the amount of trials per region and year, replicates per trial, and trials per year required in order to fulfill specifications on the precision of results. Yield data from spring barley and winter wheat trials performed during 1997–2006 were studied using cluster analysis and variance component estimation. The objectives were (1) to discuss the effects of regions on precision when the number of trials has decreased; (2) to demonstrate the method; and (3) to report the results obtained. In spring barley, clusters of regions produced different levels of yield, but similar yield ratios between cultivars. In winter wheat, clusters of regions giving different yield ratios were identified. When the option of a single analysis was compared with that of region-wise analysis, the reduction in variance with the former, due to the larger number of trials, outweighed the reduction in variance with the latter due to decreased random interaction between trials and cultivars.