Molar absorbance of cyanmethemoglobin from blood of different animals.

The molar absorbance of cyanmethemoglobin at 540 nm was measured in 35 species of mammals, birds, and reptiles. Values obtained were compared with those measured on human cyanmethemoglobin by the same procedure. There was no significant difference (P greater than or equal to 0.1) between the human and animal blood values observed in 29 samples. In six cases (4 mammals, 1 reptile, and 1 bird), the significant difference (P greater than or equal to 0.05) did not exceed 5% of the human value. The practice of applying the accepted absorbance of 1.10 x 10(4) M-1 cm-1 per mole of iron in human cyanmethemeglobin for the analysis of animal blood will not cause more than 5% uncertainty. Such results are satisfactory for use in clinical veterinary medicine except for those research projects concerned with animal hemoglobin function and structure.     

Sheep-farm risk factors for ivermectin resistance in Ostertagia circumcincta in Western Australia

On-farm risk factors associated with ivermectin resistance on sheep farms in Western Australia were identified from data derived from a postal survey of 235 farmers who had conducted a fecal egg-count-reduction test in 1999, 2000, or both years. A response of 54% was achieved. We developed a logistic-regression model. Contributory main effects in the final model were selling 10% more sheep in 2000 than is the usual policy (OR=4.00), farm purchased since 1975 (OR=2.34), and number of winter flock anthelmintic treatments in the previous 5 years (OR=1.04). A secondary logistic-regression model assessed risk factors for farms selling 10% more sheep than usual in 2000; these farmers appeared less committed to their sheep enterprises than other farmers. These results are discussed in relation to current hypotheses of anthelmintic resistance. This is the first time that the farmer’s management of the flock has been implicated in the development of anthelmintic resistance.     

A new look at an old practice: Benefits from soil water accumulation in long fallows under Mediterranean conditions

The practice of long fallowing, by omitting a year of cropping, is gaining renewed focus in the low rainfall zone of the northern agriculture region of Western Australia. The impetus behind this practice change has been a reduced use of pasture breaks in cereal crop rotations, and the belief that a fallow can improve soil water accumulation and thus buffer the negative effects of dry seasons on crop yields. We evaluated the benefits of long fallowing (full stubble retention, no weed growth allowed) in a continuous wheat sequence via simulation modelling with APSIM at two rainfall locations and five soil types. The simulated benefits to long fallowing were attributable to soil water accumulation only, as the effects on soil nitrogen, diseases or weeds were not evaluated.The long-term (100 years) mean wheat yield benefit to fallowing was 0.36-0.43 t/ha in clay, 0.20-0.23 t/ha in sand and loam, and 0-0.03 t/ha in shallow sand and shallow loams. Over the range of seasons simulated the response varied from −0.20 to 3.87 t/ha in the clay and −0.48 to 2.0 t/ha for the other soils. The accumulation of soil water and associated yield benefits occurred in 30-40% of years on better soils and only 10-20% on poorer soils. For the loam soil, the majority of the yield increases occurred when the growing-season (May-September) rainfall following the fallow was low (<210 mm) and the difference in plant available soil water at sowing between fallowed and continuously cropped soil was high (>30 mm), although yield increase did occur with other combinations of growing-season rainfall and soil water. Over several years of a crop sequence involving fallow and wheat, the benefits from long fallowing due to greater soil water accumulation did not offset yield lost from omitting years from crop production, although the coefficient of variation for inter-annual farm grain production was reduced, particularly on clay soils during the 1998-2007 decade of below-average rainfall. We conclude that under future drying climates in Western Australia, fallowing may have a role to play in buffering the effects of enhanced inter-annual variability in rainfall. Investigations are required on the management of fallows, and management of subsequent crops (i.e. sowing earlier and crop density) so as to maximise yield benefits to subsequent crops while maintaining groundcover to prevent soil erosion.     

Modelling soil nitrogen levels under acacia/sorghum rotations

A mathematical model is formulated and implemented for the nitrogen (N) cycle, on a yearly time scale, in an arid-zone fallow system. The model is generally applicable to such systems; by combining data from a number of sources, its behaviour is investigated for a genericsorghum bicolor — Acacia senegal system. The model reproduces such observed effects as the initial fall in soil N early in theAcacia rotation, and provides support for the hypothesis that the N fixing potential ofAcacia roots is less important than their ability to take up otherwise inaccessible mineral N through deep roots.     

How farming systems simulation can aid the development of more sustainable smallholder farming systems in southern Africa

Over the past 20 years, farming systems modelling has become an accessible tool for developing intervention strategies targeted at smallholder farmers in southern Africa. Applying the Agricultural Productions Systems sIMulator (APSIM) to credibly simulate key soil and crop processes in highly constrained, low yielding maize/legume systems has led to four distinct modes of use: (i) to add value to field experimentation and demonstration; (ii) in direct engagement with farmers; (iii) to explore key system constraints and opportunities with researchers and extension agencies; and (iv) in the generation of information for policy makers, bankers and insurance institutions. Examples of application in each of these modes are presented. Despite being demonstrated as an excellent tool for developing intervention strategies and extension material, the use of simulation is limited by a lack of competent local users. Better co-operation within the simulation community, sharing of climate, soil and crop parameterisation and validation datasets, and focussing of efforts on using models to benefit smallholder farmers are suggested as ways of increasing the use and relevance of simulation. Substantial investment in the training of agriculturalists and the further science development of systems simulation is required to tackle the enormous challenges facing agricultural development in the region.     

Development of best practices for ex situ conservation of radish germplasm in the context of the crop genebank knowledge base

Information about crop-specific best practices for ex situ conservation of plant genetic resources has been difficult to find until recently. The CGIAR, together with national and regional partners, started to fill that gap by publishing best practices on the crop genebank knowledge base (CGKB -http://cropgenebank.sgrp.cgiar.org/), a website specifically developed and officially launched in 2010 to provide easy access to knowledge about all aspects of ex situ conservation of specific crops to genebank managers and ex situ conservation researchers. A collaborative study, undertaken by Bioversity International with eight national and international genebanks, utilized the framework provided by the CGKB to develop and publish radish conservation best practices. This paper focuses on two aspects of this study: (1) Differences in procedures and practices in radish conservation currently applied in five key genebank activities, namely, acquisition of germplasm, viability testing and monitoring, seed drying, seed storage, and regeneration. While in a few cases genebanks agreed on a specific best practice to recommend, in others it was not desirable to identify one practice as superior to another, therefore a range of existing practices is described as a variety of equivalent options. The results highlight the importance of proactive genebank management aimed at meeting the standards within the specific context in which a genebank operates. (2) The framework and template provided by the CGKB in guiding the development of genebank best practices, and the CGKB as an excellent resource to widely and freely share best practices with the global community to support the effective management of crop genebanks.     

Application of electron spin resonance spectroscopy and spin probes to investigate the effect of ingredients on changes in wheat dough during heating

The change in microviscosity of the aqueous and lipid phases of wheat flour dough, during heating and subsequent cooling, has been measured using novel spin probes based on the isoindolin-yloxyl structure. The spin probes, water and/or lipid soluble, were used with combinations of dough ingredients: diacetyl tartaric acid ester of monoglycerides (DATEM), salt, yeast, and sodium ascorbate. The lipid soluble probe showed that DATEM does not produce a homogeneous phase with endogenous lipids but is found in a separate, less mobile phase. Also, the lipids were shown not to be involved in the baking process, although DATEM may be incorporated into the gelled starch matrix. The water soluble probe enabled starch gelatinization to be investigated in detail and showed that gelatinization produces a reduction of dielectric constant. The technique is appropriate for the detailed examination of the behavior of different ingredients during baking and also potentially to examine interactions between ingredients and flour components in dough.     

A new multistep Ca2+-induced cold gelation process for beta-lactoglobulin

The objective of this study was to obtain beta-lactoglobulin (beta-lg) gels at very low protein concentrations using a new multistep Ca(2+)-induced cold gelation process. In the conventional cold gelation process, salt free beta-lg solutions were heated at neutral pH, cooled, and cross-linked by adding salts. In our new process, first, long linear beta-lg fibrils were formed at pH 2. Solutions of these fibrils were cooled, and subsequently, the pH was adjusted to 7 or 8. Transmission electron microscopy studies showed that the long linear fibrils formed at pH 2 were stable when the pH was adjusted to 7 or 8. In the final step, the fibrils were cross-linked using CaCl(2). Using rheological measurements, the critical percolation concentration was determined. In the new multistep cold gelation process, the critical percolation concentration was an order of magnitude lower than in the conventional cold gelation method.