Effect of seasonal conditions on fleece weight and its components in merino sheep grazing Mitchell grass pasture in North West Queensland

SUMMARY Seasonal conditions in the pre to post natal period and selected periods before and during wool growth were described using climatic measures and estimates of the quality and quantity of pasture on offer derived from a validated pasture production model (GRASP). The variation in greasy and clean fleece weight, yield, staple length, fibre diameter, neck and side wrinkle score of Merinos grazing Mitchell grass in north west Queensland was explained in terms of these pasture and climatic measures and animal characteristics such as reproductive status, age and skin area. Multiple regression equations predicting clean and greasy fleece weight from the proportion of days in the wool growth period that the green pool in the pasture was less than one kg/ha, the percentage utilisation of the pasture, age, reproductive status and skin area of the ewes explained 87% and 79% of the variation respectively. Equations with similar predictors explained 58-85% of the variation of the other components. The inclusion of pasture conditions in the pre to post natal period did not significantly improve the predictions of the animal’s later performance. 22nd Biennial Conference.

Genetic Parameters for Staple Length and Staple Strength of Merino Wool Produced in Central and North West Queensland

Estimates of genetic parameters are presented for staple length and staple strength for 15 month old, medium Peppin sheep at Longreach and Julia Creek Queensland. The effects of birth type, sex and year of birth are shown. There were significant interactions for sex by site and for sex by year of birth. Heritability of staple length and strength were respectively 0.75 and 0.37 for the Longreach flock and 0.70 and 0.23 for the Julia Creek flock. The heritability of staple strength agrees with other published data however the estimate for staple length is very high. Phenotypic and genetic correlations with greasy fleece weight, yield, clean fleece weight, average fibre diameter and liveweight are in general agreement with other published estimates. Animal production for a consuming world : proceedings of 9th Congress of the Asian-Australasian Association of Animal Production Societies [AAAP] and 23rd Biennial Conference of the Australian Society of Animal Production [ASAP] and 17th Annual Symposium of the University of Sydney, Dairy Research Foundation, [DRF]. 2-7 July 2000 University of New South Wales, Sydney, Australia.

Low-density koala (Phascolarctos cinereus) populations in the mulgalands of south-west Queensland. II. Distribution and diet

This study used faecal pellets to investigate the broadscale distribution and diet of koalas in the mulgalands biogeographic region of south-west Queensland. Koala distribution was determined by conducting faecal pellet searches within a 30-cm radius of the base of eucalypts on 149 belt transects, located using a multi-scaled stratified sampling design. Cuticular analysis of pellets collected ffom 22 of these sites was conducted to identify the dietary composition of koalas within the region. Our data suggest that koala distribution is concentrated in the northern and more easterly regions of the study area, and appears to be strongly linked with annual rainfall. Over 50% of our koala records were obtained from non-riverine communities, indicating that koalas in the study area are not primarily restricted to riverine communities, as bas frequently been suggested. Cuticular analysis indicates that more than 90% of koala diet within the region consists of five eucalypt species. Our data highlights the importance of residual Tertiary landforms to koala conservation in the region.

Low-density koala (Phascolarctos cinereus) populations in the mulgalands of south-west Queensland. IV. Abundance and conservation status

Urban encroachment on dense, coastal koala populations has ensured that their management has received increasing government and public attention. The recently developed National Koala Conservation Strategy calls for maintenance of viable populations in the wild. Yet the success of this, and other, conservation initiatives is hampered by lack of reliable and generally accepted national and regional population estimates. In this paper we address this problem in a potentially large, but poorly studied, regional population in the State that is likely to have the largest wild populations. We draw on findings from previous reports in this series and apply the faecal standing-crop method (FSCM) to derive a regional estimate of more than 59 000 individuals. Validation trials in riverine communities showed that estimates of animal density obtained from the FSCM and direct observation were in close agreement. Bootstrapping and Monte Carlo simulations were used to obtain variance estimates for our population estimates in different vegetation associations across the region. The most favoured habitat was riverine vegetation, which covered only 0.9% of the region but supported 45% of the koalas. We also estimated that between 1969 and 1995 -30% of the native vegetation associations that are considered as potential koala habitat were cleared, leading to a decline of perhaps 10% in koala numbers. Management of this large regional population has significant implications for the national conservation of the species: the continued viability of this population is critically dependent on the retention and management of riverine and residual vegetation communities, and future vegetation-management guidelines should be cognisant of the potential impacts of clearing even small areas of critical habitat. We also highlight eight management implications.

Supply capability of sheep on the Mitchell grass downs of North and Central West Queensland

While, in the past, sheep have been predominantly reared and grazed in western Queensland for wool, interest in the sheep meat industry increased when wool prices became depressed. For north west and central west Queensland producers, opportunities may exist to participate in live sheep and meat export to Asia. The capability of the Mitchell grass downs to provide sufficient numbers of export quality sheep under the variable climatic conditions while sustaining the land resources has been simulated. Sheep numbers were found to be insufficient to maintain a consistent supply for live export. However, raising marking rates and lowering mortalities effectively increased reproductive performance to a level at which a surplus for export could be sustainable. Other practices might be required for the liveweight specifications to be met. 24th Biennial Conference. Adelaide, South Australia.

Genetic Parameters for Physiological Characters in Merino Rams in Central and North West Queensland

Genetic and phenotypic parameters for respiration rate (RR) and rectal temperature (RT) are presented for weaner and hogget Merino rams, at Longreach and Julia Creek, Queensland. Heritability estimates for RT and RR at both sites and at both ages ranged from moderate to very high. Phenotypic and genetic correlations between these characters are also reported. AAABG 14th Conference; Proceedings of the Association for the Advancement of Animal Breeding and Genetics. AAABG

Simulation of the supply capability of sheep on the Mitchell grass downs of north west Queensland

Sheep in western Queensland have been predominantly reared for wool. When wool prices became depressed interest in the sheep meat industry, increased. For north west Queensland producers, opportunities may exist to participate in live sheep and meat export to Asia. A simulation model was developed to determine whether this sheep producing area has the capability to provide sufficient numbers of sheep under variable climatic conditions while sustaining the land resources. Maximum capacity for sustainability of resources (as described by stock numbers) was derived from an in-depth study of the agricultural and pastoral potential of Queensland. Decades of sheep production and climatic data spanning differing seasonal conditions were collated for analysis. A ruminant biology model adapted from Grazplan was used to simulate pregnancy rate. Empirical equations predict mortalities, marking rates, and weight characteristics of sheep of various ages from simple climatic measures, stocking rate and reproductive status. The initial age structure of flocks was determined by running the model for several years with historical climatic conditions. Drought management strategies such as selling a proportion of wethers progressively down to two-tooth and oldest ewes were incorporated. Management decisions such as time of joining, age at which ewes were cast-for-age, wether turn-off age and turning-off rate of lambs vary with geographical area and can be specified at run time. The model is run for sequences of climatic conditions generated stochastically from distributions based on historical climatic data correlated in some instances. The model highlights the difficulties of sustaining a consistent supply of sheep under variable climatic conditions.

Melaleuca densispicata in Currawinya National Park, South-West Queensland: Ecology and preliminary implications for management of a rare plant species

Melaleuca densispicata Byrnes is an uncommon species with a limited distribution, comprising disjunct populations in inland southern Queensland and northern New South Wales, Australia. It is a dense, woody shrub, 2–4 m in height, which exhibits a marked 'clumping' growth habit. It has thick, papery bark and displays many white flowers during spring or early summer. Although it has long been known to exist, M. densispicata was only formally described in 1984, and very little is currently known about its ecology or specific management requirements. There are only seven known subpopulations of the species across its range. A major population at the western limit of its distribution occurs on Currawinya National Park (28°52'S, 144°30'E). Here, it is locally abundant and listed as a noteworthy plant species under the Management Plan (Queensland Parks & Wildlife Service 2001). This study aimed to identify patterns in the distribution of M. densispicata in Currawinya National Park, describe its ecological niche and role, and provide management recommendations for the species within the study area. Recent anecdotal observations of recruitment failure in south-western Queensland (Peter McRae, QPWS, October 2004, pers. comm.; Dick O'Connell, local grazier, July 2005 pers. comm.) caused additional emphasis to be placed on the examination of recruitment and recruitment factors.

A PCR assay for gender assignment in dugong (Dugong dugon) and West Indian manatee (Trichechus manatus)

Gender assignment for some aquatic mammals in the field is difficult. Molecular sexing from tissue biopsies is possible as males are heterogametic. Here we describe a multiplex PCR assay that amplifies the male specific SRY gene and differentiates ZFX and ZFY gametologues in two sirenian species, dugong (Dugong dugon) and West Indian manatee (Trichechus manatus). The assay was validated with animals of known gender and proved accurate and robust to experimental failure.

Impact of subsoil constraints on wheat yield and gross margin on fine-textured soils of the southern Victorian Mallee

The APSIM-Wheat module was used to investigate our present capacity to simulate wheat yields in a semi-arid region of eastern Australia (the Victorian Mallee), where hostile subsoils associated with salinity, sodicity, and boron toxicity are known to limit grain yield. In this study we tested whether the effects of subsoil constraints on wheat growth and production could be modelled with APSIM-Wheat by assuming that either: (a) root exploration within a particular soil layer was reduced by the presence of toxic concentrations of salts, or (b) soil water uptake from a particular soil layer was reduced by high concentration of salts through osmotic effects. After evaluating the improved predictive capacity of the model we applied it to study the interactions between subsoil constraints and seasonal conditions, and to estimate the economic effect that subsoil constraints have on wheat farming in the Victorian Mallee under different climatic scenarios. Although the soils had high levels of salinity, sodicity, and boron, the observed variability in root abundance at different soil layers was mainly related to soil salinity. We concluded that: (i) whether the effect of subsoil limitations on growth and yield of wheat in the Victorian Mallee is driven by toxic, osmotic, or both effects acting simultaneously still requires further research, (ii) at present, the performance of APSIM-Wheat in the region can be improved either by assuming increased values of lower limit for soil water extraction, or by modifying the pattern of root exploration in the soil pro. le, both as a function of soil salinity. The effect of subsoil constraints on wheat yield and gross margin can be expected to be higher during drier than wetter seasons. In this region the interaction between climate and soil properties makes rainfall information alone, of little use for risk management and farm planning when not integrated with cropping systems models.

Zero tillage and nitrogen fertiliser application in wheat and barley on a Vertosol in a marginal cropping area of south-west Queensland

Winter cereal cropping is marginal in south-west Queensland because of low and variable rainfall and declining soil fertility. Increasing the soil water storage and the efficiency of water and nitrogen (N) use is essential for sustainable cereal production. The effect of zero tillage and N fertiliser application on these factors was evaluated in wheat and barley from 1996 to 2001 on a grey Vertosol. Annual rainfall was above average in 1996, 1997, 1998 and 1999 and below average in 2000 and 2001. Due to drought, no crop was grown in the 2000 winter cropping season. Zero tillage improved fallow soil water storage by a mean value of 20 mm over 4 years, compared with conventional tillage. However, mean grain yield and gross margin of wheat were similar under conventional and zero tillage. Wheat grain yield and/or grain protein increased with N fertiliser application in all years, resulting in an increase in mean gross margin over 5 years from $86/ha, with no N fertiliser applied, to $250/ha, with N applied to target ≥13% grain protein. A similar increase in gross margin occurred in barley where N fertiliser was applied to target malting grade. The highest N fertiliser application rate in wheat resulted in a residual benefit to soil N supply for the following crop. This study has shown that profitable responses to N fertiliser addition in wheat and barley can be obtained on long-term cultivated Vertosols in south-west Queensland when soil water reserves at sowing are at least 60% of plant available water capacity, or rainfall during the growing season is above average. An integrative benchmark for improved N fertiliser management appears to be the gross margin/water use of ~$1/ha.mm. Greater fallow soil water storage or crop water use efficiency under zero tillage has the potential to improve winter cereal production in drier growing seasons than experienced during the period of this study.

Validating economic and environmental sustainability of a short-term summer forage legume in dryland wheat cropping systems in south-west Queensland.

The present study set out to test the hypothesis through field and simulation studies that the incorporation of short-term summer legumes, particularly annual legume lablab (Lablab purpureus cv. Highworth), in a fallow-wheat cropping system will improve the overall economic and environmental benefits in south-west Queensland. Replicated, large plot experiments were established at five commercial properties by using their machineries, and two smaller plot experiments were established at two intensively researched sites (Roma and St George). A detailed study on various other biennial and perennial summer forage legumes in rotation with wheat and influenced by phosphorus (P) supply (10 and 40 kg P/ha) was also carried out at the two research sites. The other legumes were lucerne (Medicago sativa), butterfly pea (Clitoria ternatea) and burgundy bean (Macroptilium bracteatum). After legumes, spring wheat (Triticum aestivum) was sown into the legume stubble. The annual lablab produced the highest forage yield, whereas germination, establishment and production of other biennial and perennial legumes were poor, particularly in the red soil at St George. At the commercial sites, only lablab-wheat rotations were experimented, with an increased supply of P in subsurface soil (20 kg P/ha). The lablab grown at the commercial sites yielded between 3 and 6 t/ha forage yield over 2-3 month periods, whereas the following wheat crop with no applied fertiliser yielded between 0.5 to 2.5 t/ha. The wheat following lablab yielded 30% less, on average, than the wheat in a fallow plot, and the profitability of wheat following lablab was slightly higher than that of the wheat following fallow because of greater costs associated with fallow management. The profitability of the lablab-wheat phase was determined after accounting for the input costs and additional costs associated with the management of fallow and in-crop herbicide applications for a fallow-wheat system. The economic and environmental benefits of forage lablab and wheat cropping were also assessed through simulations over a long-term climatic pattern by using economic (PreCAPS) and biophysical (Agricultural Production Systems Simulation, APSIM) decision support models. Analysis of the long-term rainfall pattern (70% in summer and 30% in winter) and simulation studies indicated that ~50% time a wheat crop would not be planted or would fail to produce a profitable crop (grain yield less than 1 t/ha) because of less and unreliable rainfall in winter. Whereas forage lablab in summer would produce a profitable crop, with a forage yield of more than 3 t/ha, ~90% times. Only 14 wheat crops (of 26 growing seasons, i.e. 54%) were profitable, compared with 22 forage lablab (of 25 seasons, i.e. 90%). An opportunistic double-cropping of lablab in summer and wheat in winter is also viable and profitable in 50% of the years. Simulation studies also indicated that an opportunistic lablab-wheat cropping can reduce the potential runoff+drainage by more than 40% in the Roma region, leading to improved economic and environmental benefits.

Poor adoption of ley-pastures in south-west Queensland: biophysical, economic and social constraints.

The present review identifies various constraints relating to poor adoption of ley-pastures in south-west Queensland, and suggests changes in research, development and extension efforts for improved adoption. The constraints include biophysical, economic and social constraints. In terms of biophysical constraints, first, shallower soil profiles with subsoil constraints (salt and sodicity), unpredictable rainfall, drier conditions with higher soil temperature and evaporative demand in summer, and frost and subzero temperature in winter, frequently result in a failure of established, or establishing, pastures. Second, there are limited options for legumes in a ley-pasture, with the legumes currently being mostly winter-active legumes such as lucerne and medics. Winter-active legumes are ineffective in improving soil conditions in a region with summer-dominant rainfall. Third, most grain growers are reluctant to include grasses in their ley-pasture mix, which can be uneconomical for various reasons, including nitrogen immobilisation, carryover of cereal diseases and depressed yields of the following cereal crops. Fourth, a severe depletion of soil water following perennial ley-pastures (grass + legumes or lucerne) can reduce the yields of subsequent crops for several seasons, and the practice of longer fallows to increase soil water storage may be uneconomical and damaging to the environment. Economic assessments of integrating medium- to long-term ley-pastures into cropping regions are generally less attractive because of reduced capital flow, increased capital investment, economic loss associated with establishment and termination phases of ley-pastures, and lost opportunities for cropping in a favourable season. Income from livestock on ley-pastures and soil productivity gains to subsequent crops in rotation may not be comparable to cropping when grain prices are high. However, the economic benefits of ley-pastures may be underestimated, because of unaccounted environmental benefits such as enhanced water use, and reduced soil erosion from summer-dominant rainfall, and therefore, this requires further investigation. In terms of social constraints, the risk of poor and unreliable establishment and persistence, uncertainties in economic and environmental benefits, the complicated process of changing from crop to ley-pastures and vice versa, and the additional labour and management requirements of livestock, present growers socially unattractive and complex decision-making processes for considering adoption of an existing medium- to long-term ley-pasture technology. It is essential that research, development and extension efforts should consider that new ley-pasture options, such as incorporation of a short-term summer forage legume, need to be less risky in establishment, productive in a region with prevailing biophysical constraints, economically viable, less complex and highly flexible in the change-over processes, and socially attractive to growers for adoption in south-west Queensland.

Resistance to the root-lesion nematode Pratylenchus thornei in wheat landraces and cultivars from the West Asia and North Africa (WANA) region.

Resistance to the root-lesion nematode Pratylenchus thornei was sought in wheat from the West Asia and North Africa (WANA) region in the Watkins Collection (148 bread and 139 durum wheat accessions) and the McIntosh Collection (59 bread and 43 durum wheat accessions). It was considered that landraces from this region, encompassing the centres of origin of wheat and where P. thornei also occurs, could be valuable sources of resistance for use in wheat breeding. Resistance was determined by number of P. thornei/kg soil after the growth of the plants in replicated glasshouse experiments. On average, durum accessions produced significantly lower numbers of P. thornei than bread wheat accessions in both the Watkins and McIntosh Collections. Selected accessions with low P. thornei numbers were re-tested and 13 bread wheat and 10 durum accessions were identified with nematode numbers not significantly different from GS50a, a partially resistant bread wheat line used as a reference standard. These resistant accessions, which originated in Iran, Iraq, Syria, Egypt, Sudan, Morocco, and Tunisia, represent a resource of resistance genes in the primary wheat gene pool, which could be used in Australian wheat breeding programs to reduce the economic loss from P. thornei.

Inheritance of resistance to root-lesion nematode (Pratylenchus thornei) in wheat landraces and cultivars from the West Asia and North Africa (WANA) region.

The root-lesion nematode Pratylenchus thornei causes substantial loss to bread wheat production in the northern grain region of Australia and other parts of the world. West Asia and North Africa (WANA) wheat accessions with partial resistance to P. thornei were analysed for mode of inheritance in a half-diallel crossing design of F1 hybrids (10 parents) and F2 populations (7 parents). General combining ability was more important than specific combining ability as indicated by components of variance ratios of 0.93 and 0.95 in diallel ANOVA of the F1 and F2 generations, respectively. General combining ability values of the 'resistant' parents were predictive of the mean nematode numbers of their progeny in crosses with the susceptible Australian cv. Janz at the F1 (R populations showed relatively continuous distributions. Heritability was 0.68 for F2 populations in the half-diallel of resistant parents and 0.82-0.92 for 5 'resistant' parent/Janz doubled-haploid populations (narrow-sense heritability on a line mean basis). The results indicate polygenic inheritance of P. thornei resistance with a minimum of from 2 to 6 genes involved in individual F populations of 5 resistant parents crossed with Janz. Morocco 426 and Iraq 43 appear to be the best of the parents tested for breeding for resistance to P. thornei. None of the P. thornei-resistant WANA accessions was resistant to Pratylenchus neglectus.