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Testing virtual fencing for the sustainable management of north Australian rangelands: Impacts on beef cattle grazing behaviour, pasture resource, and cattle production.
No full textThe selective grazing behaviours of cattle frequently lead to degradation of selected areas. Virtual fencing (VF) will be tested to control cattle spatial grazing distributions in extensively managed herds in northern Australia. If VF can successfully be used to change spatial grazing pressure, this would allow for increased rest for preferred areas and improved utilisation of less preferred areas that would otherwise have limited productive value. This will likely improve land condition, carrying capacity, and drought resilience. If successful, VF could be an important tool for management of grazing impacts to increase production and achieve a variety of environmental goals in the extensive systems of northern Australia
Using the Australian tropical forages collection to develop new pasture legumes for Australian rangelands
No full textBeef cattle production is the key agricultural industry in the seasonally-dry and moderate rainfall zones of northern Australia. Uncleared natural woodlands are the key feed resource in the northern monsoonal zone, whereas sown pastures dominate the moderate rainfall zone further south. In additional to seasonal feed gaps, beef producers face emerging challenges from declining land condition, a warming and more variable climate and pasture dieback associated with mealy bugs. Sown deep-rooted legumes (Desmanthus, Leucaena, Macroptilium, Stylosanthes) can improve productivity on these pastures by improving nitrogen cycling and improving diet quality. The development of tropical pasture cultivars in Australia is underpinned by the Australian Tropical Forages Collection (ATFC), now held in the Australian Pastures Genebank supported by state and federal governments and primary industry research and development corporations. The ATFC comprises ~10100 warm season grasses and 7300 legumes sourced from other tropical countries and within Australia over 40+ years, including over 4000 legumes from genera with potential in permanent or semi-permanent pastures in the dry zone. Comprehensive plant evaluation and release activities by federal and state governments saw the development of a network of on-property plant evaluation sites and the release of useful legume cultivars for key beef production land-types. However, some environments have no well-adapted pasture legumes. The evaluation site network has recently been exploited to develop legumes for frost-prone areas on light-textured soils and clay soils in the monsoonal zone. A Queensland government regeneration and characterisation program has also prioritised the development of legumes for the seasonally dry and moderate rainfall zones to enable access to seeds and plant traits to breeders both in Australia and overseas
Spelling strategies for recovery of poor land condition
No full textPasture condition has declined across many pasture communities across northern Australia. Pasture spelling is a key recommendation for the recovery of land condition but there is limited information on the optimum length and frequency of spelling or the recovery rates possible under different spelling and stocking rate combinations. This 12-year study examined the effects of early and full wet season spelling applied annually or biennially, on the recovery of poor condition land and the demography of the key perennial grass, Bothriochloa ewartiana, under heavy and moderate stocking rates. The study period was characterised by low rainfall and extreme drought conditions in some years. Average basal cover of perennial species declined with the onset of dry years with the effects of drought amplified under heavy stocking. Basal cover later increased as conditions improved but cover under heavy stocking never recovered to that under moderate stocking. Annual early and full wet season spelling under moderate stocking had a positive effect on the basal cover of B. ewartiana but this effect was only significant (P < 0.03) after 12 years. Spelling had no effect on basal cover under heavy stocking, emphasising the overriding effect of stocking rate on recovery. Basal cover through the drought was largely maintained through the persistence of original tussocks, emphasising the importance of maintaining established plants through good management. In later years, an increasing number of recruits also increased basal cover. Land condition can be improved with annual wet season spelling provided stocking rates are appropriate, but recovery can initially be slow, particularly through dry years. These results emphasise the key role that spelling has in maintaining and improving pasture condition
Effect of natural and synthetic antioxidants in poultry feed during different storage temperatures
No full textResponsible consumption and production are one of the sustainable development goals. Antioxidant plays a crucial role in the prevention of oxidative deterioration of poultry and farm animal feed. This study examined the physical (moisture content, ash content, flow ability) and antioxidant properties of commercially available natural (Ozox A and Ozox B) and synthetic (Oxistat) antioxidant additives in Australia. Also, their effectiveness in poultry feed (mashed and cooked) during different storage temperatures (25, 30, and 45 °C) was investigated. The results indicated the ash content was higher in Oxistat (95.69%) compared to Ozox A (3.77%) and Ozox B (3.71%) (P < 0.05). Flow ability results suggested that Ozox A and Ozox B are cohesive powders, whereas Oxistat was an easy-flowing powder. Antioxidant activities of additives were determined by DPPH radical scavenging activity and oxidative preventive effect in poultry feed was measured by peroxidation value (PV) and thiobarbituric acid reactive substances (TBARS) method. The percentage of DPPH radical inhibition of Ozox A (90.37%) was higher followed by Ozox B (71.02%) and Oxistat (67.88%) (P < 0.05). Furthermore, mashed and cooked feed treated with Ozox A and Ozox B show lowered free fatty acid (FFA) content during storage at 45 °C. A lower PV and TBARS values were noted in Ozox A treated samples compared to Ozox B and Oxistat at higher temperatures (30 and 45 °C). Overall, results suggested that Ozox A and Ozox B had higher antioxidant activity and could prevent oxidative changes in poultry feed during storage at 25, 30, and 45 °C. Therefore, natural blend antioxidants (Ozox A and Ozox B) are more promising additives to poultry feed than synthetic additives, addressing sustainable development goals
Pathways to Recovery: Genomics and Resistance Assays for Tree Species Devastated by the Myrtle Rust Pathogen
No full textMyrtle rust is a plant disease caused by the invasive fungal pathogen Austropuccinia psidii (G. Winter) Beenken, which has a global host list of 480 species. It was detected in Australia in 2010 and has caused the rapid decline of native Myrtaceae species, including rainforest trees Rhodamnia rubescens (Benth.) Miq. (scrub turpentine) and Rhodomyrtus psidioides (G.Don) Benth. (native guava). Ex situ collections of these species have been established, with the goal of preserving remaining genetic variation. Analysis of reduced representation sequencing (DArTseq; n = 444 for R. rubescens and n = 301 for R . psidioides ) showed genetic diversity is distributed along a latitudinal gradient across the range of each species. A panel of samples of each species ( n = 27 for R. rubescens and n = 37 for R . psidioides ) was resequenced at genome scale, revealing large historical effective population sizes, and little variation among individuals in inferred levels of deleterious load. In Rhodamnia rubescens , experimental assays ( n = 297) identified individuals that are putatively resistant to myrtle rust. This highlights two important points: there are tangible pathways to recovery for species that are highly susceptible to rust via a genetically informed breeding programme, and there is a critical need to act quickly before more standing diversity is lost
Predicted foot and mouth disease virus and African swine fever virus inactivation within carcases undergoing field decomposition in three Australian climate zones
No full textAustralia's large populations of feral and extensively farmed livestock pose challenges to implementing response plans in the event of an Emergency Animal Disease outbreak. This study aimed to determine if a “Destroy and Let Lie” approach to carcase disposal (leaving carcases in situ to decompose naturally after field euthanasia) would reliably inactivate Foot and Mouth Disease virus (FMDV) and African Swine Fever virus (ASFV) under Australian conditions. Ninety‐five animals (24 each of cattle, sheep, goats and 23 pigs) were used across six trials, conducted in winter and summer, in three locations in Eastern Australia. After euthanasia, temperature and pH were measured at six internal anatomical sites hourly for 24 h, then less frequently for a further 24 h. Data were compared with published FMDV and ASFV inactivation thresholds to assess the likely effectiveness of field decomposition in reducing viral infectivity. Tissue pH levels generally declined for the first 6–12 h postmortem. Based on a pH threshold of <6, FMDV would be reliably inactivated in the thoracic and abdominal cavities and deep and superficial muscle sites. In contrast, no porcine tissues at any location in any season would provide inactivation of ASFV, based on a pH threshold of <3.9. “Destroy and Let Lie” appears to be a suitable approach to reduce risk of FMDV transmission from carcases that cannot be disposed of using conventional means under Australian field conditions. This would not be the case for an ASF outbreak, where expected viral inactivation would be minimal
Threats, risk assessment and recovery action planning for rare and threatened freshwater fish in Queensland’s Wet Tropics region
No full textThis report presents a comprehensive desktop review, risk assessment and list of potential recovery actions for 22 rare and threatened freshwater fish species in Queensland’s Wet Tropics region. Threats to these species in the Wet Tropics include climate change, land use alteration, invasive species, fire regimes, natural disasters, water resource management and infrastructure, residential development and recreational use, hybridization with sister species, and overharvesting and illicit collection. The risk assessment was conducted during a workshop attended by experts from a range of organisations including government, universities, consultancies and local management.
The risk assessment identified several species at very high risk to some threats. Changes in the flow regime and occurrence of extreme events such as cyclones, drought and landslides were rated as very high risk to Daintree and Cairns rainbowfishes and cling gobies (except Sicyopterus spp.). Remaining populations of Melanotaenia rainbowfishes (Malanda, Utchee Creek and Lake Eacham) are at very high risk of hybridization with eastern rainbowfish, the spread of which is accelerated by habitat degradation that leads to warmer water temperatures. Bloomfield River cod are at very high risk of impacts associated with invasive and translocated fish due to their restricted range and overlapping diet and habitat preferences with introduced species
Clonal Expansion from Standing Genetic Variation Underpins the Evolution of Curtobacterium flaccumfaciens pv. flaccumfaciens in Australia
No full textPathogens can evolve rapidly, leading to the emergence of novel strains that can overcome commercially deployed host plant resistance. Understanding the genetic and phenotypic diversity and population dynamics of plant pathogens is crucial to inform breeding programs targeting resistance. Tan spot, otherwise known as bacterial wilt, caused by Curtobacterium flaccumfaciens pv. flaccumfaciens, is an increasingly significant pathogen affecting beans and mungbean worldwide. Since the 1990s, several mungbean cultivars with partial resistance to tan spot have been released in Australia; however, cultivars initially rated as moderately resistant were later rated as moderately susceptible to tan spot. This study investigated the genetic and phenotypic diversity and temporal evolutionary dynamics of C. flaccumfaciens pv. flaccumfaciens in Australian mungbean fields. Whole-genome sequencing of 119 isolates collected from mungbean and other legumes (1986 to 2019) enabled analyses of pathogen evolution in Australia and in a global context. Results revealed that clonal expansion from standing genetic variation, rather than introduction of novel genotypes, has driven the evolution of this pathogen in Australia since the 1980s. Glasshouse trials confirmed the role of a plasmid in pathogenicity of C. flaccumfaciens pv. flaccumfaciens but found no significant differences in aggressiveness between clonal lineages. Our research provides insights into genetic and phenotypic diversity of this important plant pathogen and temporal changes in its population structure in Australia and highlights the need for further studies on the competitive fitness of isolates and characterisation of private alleles linked to dominant clonal lineages
Mass rearing and releasing biological control agents for weed species. What’s it all about?
No full textThe process of mass rearing and releasing biological control agents involves mass producing and releasing approved post-risk analysis introduced agents, at facilities such as Queensland’s Department of Primary Industries (QDPI) Tropical Weeds Research Centre (TWRC) in Charters Towers. The purpose of a program is to disseminate these agents, achieve establishment and spread, whilst impacting invasive weed species. This involves a web of interconnecting factors.
This paper will discuss the processes, challenges and considerations used at TWRC to mass rear and release biological control agents for the management of targeted invasive weed species for northern Australia over the last 20 years