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Packer E.L.,Charles Sturt University | Clayton E.H.,Australian Department of Primary Industries and Fisheries | Clayton E.H.,Graham Center for Agricultural Innovation | Cusack P.M.V.,Australian Livestock Production Services
Australian Veterinary Journal | Year: 2011

Objective To determine the prevalence of subacute rumen acidosis (SARA) in beef cattle grazing lush pasture and the effect of monensin on reducing SARA and improving animal performance. Design Commercial Angus and Murray Grey steers received a monensin slow-release capsule (n = 19) or remained untreated (n = 19). Cattle grazed an oats crop or tetraploid ryegrass pasture for a total of 91 days. Rumen fluid pH, volatile fatty acids (VFA) and lactic acid concentrations and body weight data were collected prior to treatment and again 28, 56 and 91 days after treatment. Changes in measures over time were analysed using mixed model repeated measures analysis. Differences in average daily gain between treatment groups were determined. Results The prevalence of SARA was low during the study, with only one animal satisfying criteria for SARA at one time point. Cattle treated with monensin capsules were 11.9kg heavier at the completion of the study compared with untreated controls (414.5 ± 3.88kg vs 402.6 ± 4.03kg, P = 0.04). Rumen VFA and L- and D-lactate levels did not differ between cattle treated with monensin and untreated cattle. However, the ratio of propionate to acetate plus two times butyrate was higher (P < 0.001) when cattle were treated with monensin. Conclusions Subacute rumen acidosis was not consistently detected under the conditions of the study. The higher body weight of cattle treated with monensin may have been due to improved energy utilisation of the pasture, indicated by increased propionate proportions in the rumen, rather than prevention of SARA. © 2011 The Authors. Australian Veterinary Journal © 2011 Australian Veterinary Association. Source

Moody P.W.,Science Delivery | Speirs S.D.,Graham Center for Agricultural Innovation | Scott B.J.,Charles Sturt University | Mason S.D.,University of Adelaide
Crop and Pasture Science | Year: 2013

The phosphorus (P) status of 535 surface soils from all states of Australia was assessed using the following soil P tests: Colwell-P (0.5m NaHCO3), Olsen-P (0.5m NaHCO3), BSES-P (0.005m H2SO4), and Mehlich 3-P (0.2m CH3COOH+0.25m NH4NO3+0.015m NH4F+0.013m HNO3+0.001m EDTA). Results were correlated with soil P assays selected to estimate the following: soil solution P concentration (i.e. 0.01m CaCl2 extractable P; Colwell-P/P buffer index); rate of P supply to the soil solution (i.e. P released to FeO-impregnated filter paper); sorbed P (i.e. Colwell-P); mineral P (i.e. fertiliser reaction products and/or soil P minerals estimated as BSES-P minus Colwell-P); the diffusive supply of P (i.e. P diffusing through a thin gel film, DGT-P); and P buffer capacity (i.e. single-point P buffer index corrected for Colwell-P, PBICol). Across all soils, Colwell-P and BSES-P were highly correlated with FeO-P (r≤0.76 and 0.58, respectively). Colwell-P was moderately correlated with mineral P (r≤0.24), but not solution P. Olsen-P and Mehlich-P were both highly correlated with FeO-P (r≤0.80 and 0.78, respectively) but, in contrast to Colwell-P and BSES-P, also showed moderate correlations with soil solution P (r≤0.29 and 0.34, respectively) and diffusive P supply (r≤0.31 and 0.49, respectively). Correlation coefficients with mineral P were r≤0.29 for Olsen-P and r≤0.17 for Mehlich-P. Soils were categorised according to their pH, clay activity ratio, content of mineral P and CaCO3 content, and the relationships between the empirical soil P tests examined for each soil category. Olsen-P and Colwell-P were correlated across all soil categories (r range 0.66-0.90), and a widely applicable linear equation was obtained for converting one soil test to the other. However, the correlations between other soil tests varied markedly between soil categories and it was not possible to develop such widely applicable conversion equations. Multiple step-up linear regressions were used to identify the key soil properties affecting soil solution P, P buffer capacity, and diffusive P supply, respectively. For all soil categories, solution P concentration (measured by CaCl2-P) increased as rate of P supply (measured as FeO-P) increased and P buffer capacity decreased. As an assay of sorbed P, Colwell-P alone did not significantly (P>0.05) explain any of the variability in soil solution P, but when used in the index (Colwell-P/P buffer index), it was highly correlated (r≤0.74) with CaCl2-P. Soil P buffer capacity was dependent on different properties in different soil categories, with 45-65% of the variation in PBI accounted for by various combinations of Mehlich-Al, Mehlich-Fe, total organic C, clay content, clay activity ratio, and CaCO3 content, depending on soil category. The diffusive supply of P was primarily determined by rate of P supply (measured as FeO-P; r range 0.34-0.49), with significant (P<0.05) small improvements due to the inclusion of PBICol and/or clay content, depending on soil category. For these surface soil samples, key properties of pH, clay activity ratio, clay content, and P buffer capacity varied so widely within individual Australian Soil Orders that soil classification was not useful for inferring intrinsic surface soil P properties such as P buffer capacity or the relationships between soil P tests. © CSIRO 2013. Source

Bellis G.A.,Fisheries and Forestry | Dyce A.L.,CSIRO | Gopurenko D.,Australian Department of Primary Industries and Fisheries | Gopurenko D.,Graham Center for Agricultural Innovation | Mitchell A.,College Street
Zootaxa | Year: 2013

The Immaculatus Group of Culicoides encompassing four species from Australia, New Caledonia, Fiji, Solomon Islands, New Guinea and the Malay archipelago is revised. A diagnosis for the group, descriptions of males and females of C. shivasi sp. n. and C. collessi sp. n., a description of the male of C. immaculatus Lee & Reye, a redescription of the female of C. immaculatus and a diagnosis of C. agas Wirth & Hubert together with keys for their specific determination are presented. Specific separation of the morphologically similar C. shivasi and C. immaculatus is supported by DNA barcodes (mitochondrial cytochrome oxidase I or COI) and nuclear carbomoylphosphate synthetase (CAD) sequence data. Copyright © 2013 Magnolia Press. Source

Mulki M.A.,Max Planck Institute for Plant Breeding Research | Jighly A.,International Center for Agricultural Research in the Dry Areas | Ye G.,International Rice Research Institute | Emebiri L.C.,Graham Center for Agricultural Innovation | And 3 more authors.
Molecular Breeding | Year: 2013

Soilborne pathogens such as cereal cyst nematode (CCN; Heterodera avenae) and root lesion nematode (Pratylenchus neglectus; PN) cause substantial yield losses in the major cereal-growing regions of the world. Incorporating resistance into wheat cultivars and breeding lines is considered the most cost-effective control measure for reducing nematode populations. To identify loci with molecular markers linked to genes conferring resistance to these pathogens, we employed a genome-wide association approach in which 332 synthetic hexaploid wheat lines previously screened for resistance to CCN and PN were genotyped with 660 Diversity Arrays Technology (DArT) markers. Two sequence-tagged site markers reportedly linked to genes known to confer resistance to CCN were also included in the analysis. Using the mixed linear model corrected for population structure and familial relatedness (Q+K matrices), we were able to confirm previously reported quantitative trait loci (QTL) for resistance to CCN and PN in bi-parental crosses. In addition, we identified other significant markers located in chromosome regions where no CCN and PN resistance genes have been reported. Seventeen DArT marker loci were found to be significantly associated with CCN and twelve to PN resistance. The novel QTL on chromosomes 1D, 4D, 5B, 5D and 7D for resistance to CCN and 4A, 5B and 7B for resistance to PN are suggested to represent new sources of genes which could be deployed in further wheat improvement against these two important root diseases of wheat. © 2012 Springer Science+Business Media B.V. Source

Bell R.,Murdoch University | Reuter D.,Reuter and Associates | Scott B.,Graham Center for Agricultural Innovation | Sparrow L.,University of Tasmania | And 2 more authors.
Crop and Pasture Science | Year: 2013

Soil testing is the most widely used tool to predict the need for fertiliser phosphorus (P) application to crops. This study examined factors affecting critical soil P concentrations and confidence intervals for wheat and barley grown in Australian soils by interrogating validated data from 1777 wheat and 150 barley field treatment series now held in the BFDC National Database. To narrow confidence intervals associated with estimated critical P concentrations, filters for yield, crop stress, or low pH were applied. Once treatment series with low yield (<1t/ha), severe crop stress, or pHCaCl2 <4.3 were screened out, critical concentrations were relatively insensitive to wheat yield (>1t/ha). There was a clear increase in critical P concentration from early trials when full tillage was common compared with those conducted in 1995-2011, which corresponds to a period of rapid shift towards adoption of minimum tillage. For wheat, critical Colwell-P concentrations associated with 90 or 95% of maximum yield varied among Australian Soil Classification (ASC) Orders and Sub-orders: Calcarosol, Chromosol, Kandosol, Sodosol, Tenosol and Vertosol. Soil type, based on ASC Orders and Sub-orders, produced critical Colwell-P concentrations at 90% of maximum relative yield from 15mg/kg (Grey Vertosol) to 47mg/kg (Supracalcic Calcarosols), with other soils having values in the range 19-27mg/kg. Distinctive differences in critical P concentrations were evident among Sub-orders of Calcarosols, Chromosols, Sodosols, Tenosols, and Vertosols, possibly due to differences in soil properties related to P sorption. However, insufficient data were available to develop a relationship between P buffering index (PBI) and critical P concentration. In general, there was no evidence that critical concentrations for barley would be different from those for wheat on the same soils. Significant knowledge gaps to fill to improve the relevance and reliability of soil P testing for winter cereals were: lack of data for oats; the paucity of treatment series reflecting current cropping practices, especially minimum tillage; and inadequate metadata on soil texture, pH, growing season rainfall, gravel content, and PBI. The critical concentrations determined illustrate the importance of recent experimental data and of soil type, but also provide examples of interrogation pathways into the BFDC National Database to extract locally relevant critical P concentrations for guiding P fertiliser decision-making in wheat and barley. © CSIRO 2013. Source

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