Growth and carcass characteristics of cast-for-age Merino ewes fed sorghum-based feedlot diets

Grain feeding low bodyweight, cast-for-age (CFA) sheep from pastoral areas of eastern Australia at the end of the growing season can enable critical carcass weight grades to be achieved and thus yield better economic returns. The aim of this work was to compare growth and carcass characteristics for CFA Merino ewes consuming either simple diets based on whole sorghum grain or commercial feed pellets. The experiment also compared various sources of additional nitrogen (N) for inclusion in sorghum diets and evaluated several introductory regimes. Seventeen ewes were killed initially to provide baseline carcass data and the remaining 301 ewes were gradually introduced to the concentrate diets over 14 days before being fed concentrates and wheaten hay ad libitum for 33 or 68 days. Concentrate treatments were: (i) commercial feed pellets, (ii) sorghum mix (SM; whole sorghum grain, limestone, salt and molasses) + urea and ammonium sulfate (SMU), (iii) SMU + whole cottonseed at 286 g/kg of concentrate dry matter (DM), (iv) SM + cottonseed meal at 139 g/kg of concentrate DM, (v) SMU + virginiamycin (20 mg/kg of concentrate) for the first 21 days of feeding, and (vi) whole cottonseed gradually replaced by SMU over the first 14 days of feeding. The target carcass weight of 18 kg was achieved after only 33 days on feed for the pellets and the SM + cottonseed meal diet. All other whole grain sorghum diets required between 33 and 68 days on feed to achieve the target carcass weight. Concentrates based on whole sorghum grain generally produced significantly (P < 0.05) lower carcass weight and fat score than pellets and this may have been linked to the significantly (P < 0.05) higher faecal starch concentrations for ewes consuming sorghum-based diets (270 v. 72 g/kg DM on day 51 of feeding for sorghum-based diets and pellets, respectively). Source of N in whole grain sorghum rations and special introductory regimes had no significant (P > 0.05) effects on carcass weight or fat score of ewes with the exception of carcass weight for SMU + whole cottonseed being significantly lower than SM + cottonseed meal at day 33. Ewes finished on all diets produced acceptable carcasses although muscle pH was high in all ewe carcasses (average 5.8 and 5.7 at 33 and 68 days, respectively). There were no significant (P > 0.05) differences between diets in concentrate DM intake, rumen fluid pH, meat colour score, fat colour score, eye muscle area, meat pH or meat temperature.

Concentrates based on sorghum grain provide a basis for a finishing system for crossbred lambs

In parts of Australia, sorghum grain is a cheaper alternative to other cereal grains but its use and nutritive value in sheep feeding systems is not well understood. The aim of this work was to compare growth and carcass characteristics for crossbred lambs consuming several simple, sorghum-based diets. The treatments were: (1) whole sorghum grain, (2) whole sorghum grain + urea and ammonium sulfate, (3) cracked sorghum grain + urea and ammonium sulfate, (4) expanded sorghum grain + urea and ammonium sulfate, (5) whole sorghum grain + cottonseed meal, and (6) whole sorghum grain + whole cottonseed. Nine lambs were slaughtered initially to provide baseline carcass data and the remaining 339 lambs were gradually introduced to the concentrate diets over 14 days before being fed concentrates and wheaten hay ad libitum for 41, 56 or 76 days. Neither cracking nor expanding whole sorghum grain with added non-protein nitrogen (N) resulted in significantly (P > 0.05) increased final liveweight, growth rates or carcass weights for lambs, or in decreased days on feed to reach 18-kg carcass weight, although carcass fat depth was significantly (P < 0.05) increased compared with the whole sorghum plus non-protein N diet. However, expanding sorghum grain significantly (P < 0.05) reduced faecal starch concentrations compared with whole or cracked sorghum diets with added non-protein N (79 v. 189 g/kg DM after 59 days on feed). Lambs fed whole sorghum grain without an additional N source had significantly (P < 0.05) lower concentrate intake and required significantly (P < 0.05) more days on feed to reach a carcass weight of 18 kg than for all diets containing added N. These lambs also had significantly (P < 0.05) lower carcass weight and fat depth than for lambs consuming whole sorghum plus true protein diets. Substituting sources of true protein (cottonseed meal and whole cottonseed) for non-protein N (urea and ammonium sulfate) did not significantly (P > 0.05) affect concentrate intakes or carcass weights of lambs although carcass fat depth was significantly (P < 0.05) increased and the days to reach 18-kg carcass weight were significantly (P < 0.05) decreased for the whole sorghum plus cottonseed meal diet. In conclusion, processing sorghum grain by cracking or expanding did not significantly improve lamb performance. While providing an additional N source with sorghum grain significantly increased lamb performance, there was no benefit in final carcass weight of lambs from substituting sources of true protein for non-protein N.

Maize kernel hardness classification by near infrared (NIR) hyperspectral imaging and multivariate data analysis.

The use of near infrared (NIR) hyperspectral imaging and hyperspectral image analysis for distinguishing between hard, intermediate and soft maize kernels from inbred lines was evaluated. NIR hyperspectral images of two sets (12 and 24 kernels) of whole maize kernels were acquired using a Spectral Dimensions MatrixNIR camera with a spectral range of 960-1662 nm and a sisuChema SWIR (short wave infrared) hyperspectral pushbroom imaging system with a spectral range of 1000-2498 nm. Exploratory principal component analysis (PCA) was used on absorbance images to remove background, bad pixels and shading. On the cleaned images. PCA could be used effectively to find histological classes including glassy (hard) and floury (soft) endosperm. PCA illustrated a distinct difference between glassy and floury endosperm along principal component (PC) three on the MatrixNIR and PC two on the sisuChema with two distinguishable clusters. Subsequently partial least squares discriminant analysis (PLS-DA) was applied to build a classification model. The PLS-DA model from the MatrixNIR image (12 kernels) resulted in root mean square error of prediction (RMSEP) value of 0.18. This was repeated on the MatrixNIR image of the 24 kernels which resulted in RMSEP of 0.18. The sisuChema image yielded RMSEP value of 0.29. The reproducible results obtained with the different data sets indicate that the method proposed in this paper has a real potential for future classification uses.

Functional dynamics of the nitrogen balance of sorghum: I. N demand of vegetative plant parts.

Stay-green, an important trait for grain yield of sorghum grown under water limitation, has been associated with a high leaf nitrogen content at the start of grain filling. This study quantifies the N demand of leaves and stems and explores effects of N stress on the N balance of vegetative plant parts of three sorghum hybrids differing in potential crop height. The hybrids were grown under well-watered conditions at three levels of N supply. Vertical profiles of biomass and N% of leaves and stems, together with leaf size and number, and specific leaf nitrogen (SLN), were measured at regular intervals. The hybrids had similar minimum but different critical and maximum SLN, associated with differences in leaf size and N partitioning, the latter associated with differences in plant height. N demand of expanding new leaves was represented by critical SLN, and structural stem N demand by minimum stem N%. The fraction of N partitioned to leaf blades increased under N stress. A framework for N dynamics of leaves and stems is developed that captures effects of N stress and genotype on N partitioning and on critical and maximum SLN.

Simulating the evolution of glyphosate resistance in grains farming in northern Australia.

Background and Aims: The evolution of resistance to herbicides is a substantial problem in contemporary agriculture. Solutions to this problem generally consist of the use of practices to control the resistant population once it evolves, and/or to institute preventative measures before populations become resistant. Herbicide resistance evolves in populations over years or decades, so predicting the effectiveness of preventative strategies in particular relies on computational modelling approaches. While models of herbicide resistance already exist, none deals with the complex regional variability in the northern Australian sub-tropical grains farming region. For this reason, a new computer model was developed. Methods: The model consists of an age- and stage-structured population model of weeds, with an existing crop model used to simulate plant growth and competition, and extensions to the crop model added to simulate seed bank ecology and population genetics factors. Using awnless barnyard grass (Echinochloa colona) as a test case, the model was used to investigate the likely rate of evolution under conditions expected to produce high selection pressure. Key Results: Simulating continuous summer fallows with glyphosate used as the only means of weed control resulted in predicted resistant weed populations after approx. 15 years. Validation of the model against the paddock history for the first real-world glyphosate-resistant awnless barnyard grass population shows that the model predicted resistance evolution to within a few years of the real situation. Conclusions: This validation work shows that empirical validation of herbicide resistance models is problematic. However, the model simulates the complexities of sub-tropical grains farming in Australia well, and can be used to investigate, generate and improve glyphosate resistance prevention strategies.

Potential of piperonyl butoxide-synergised pyrethrins against psocids (Psocoptera: Liposcelididae) for stored-grain protection.

BACKGROUND: Piperonyl butoxide (PB)-synergised natural pyrethrins (pyrethrin:PB ratio 1:4) were evaluated both as a grain protectant and a disinfestant against four Liposcelidid psocids: Liposcelis bostrychophila Badonnel, L. entomophila (Enderlein), L. decolor (Pearman) and L. paeta Pearman. These are key storage pests in Australia that are difficult to control with the registered grain protectants and are increasingly being reported as pests of stored products in other countries. Firstly, mortality and reproduction of adults were determined in wheat freshly treated at 0.0, 0.75, 1.5, 3 and 6 mg kg-1 of pyrethrins + PB (1:4) at 301C and 702% RH. Next, wheat treated at 0.0, 1.5, 3 and 6 mg kg-1 of pyrethrins + PB (1:4) was stored at 301C and 702% RH and mortality and reproduction of psocids were assessed after 0, 1.5, 3 and 4.5 months of storage. Finally, the potential of synergised pyrethrins as a disinfestant was assessed by establishing time to endpoint mortality for adult psocids exposed to wheat treated at 3 and 6 mg kg-1 of synergised pyrethrins after 0, 3, 6, 9 and 12 h of exposure. RESULTS: Synergised pyrethrins at 6 mg kg-1 provided 3 months of protection against all four Liposcelis spp., and at this rate complete adult mortality of these psocids can be achieved within 6 h of exposure. CONCLUSION: Piperonyl butoxide-synergised pyrethrins have excellent potential both as a grain protectant and as a disinfestant against Liposcelidid.

Analysis and Modelling of the Effects of Water Stress on Maize Growth and Yield in Dryland Conditions.

It is essential to provide experimental evidence and reliable predictions of the effects of water stress on crop production in the drier, less predictable environments. A field experiment undertaken in southeast Queensland, Australia with three water regimes (fully irrigated, rainfed and irrigated until late canopy expansion followed by rainfed) was used to compare effects of water stress on crop production in two maize (Zea mays L.) cultivars (Pioneer 34N43 and Pioneer 31H50). Water stress affected growth and yield more in Pioneer 34N43 than in Pioneer 31H50. A crop model APSIM-Maize, after having been calibrated for the two cultivars, was used to simulate maize growth and development under water stress. The predictions on leaf area index (LAI) dynamics, biomass growth and grain yield under rain fed and irrigated followed by rain fed treatments was reasonable, indicating that stress indices used by APSIM-Maize produced appropriate adjustments to crop growth and development in response to water stress. This study shows that Pioneer 31H50 is less sensitive to water stress and thus a preferred cultivar in dryland conditions, and that it is feasible to provide sound predictions and risk assessment for crop production in drier, more variable conditions using the APSIM-Maize model.

Net radiation dynamics: performance of 20 daily net radiation models as related to model structure and intricacy in two climates.

We compared daily net radiation (Rn) estimates from 19 methods with the ASCE-EWRI Rn estimates in two climates: Clay Center, Nebraska (sub-humid) and Davis, California (semi-arid) for the calendar year. The performances of all 20 methods, including the ASCE-EWRI Rn method, were then evaluated against Rn data measured over a non-stressed maize canopy during two growing seasons in 2005 and 2006 at Clay Center. Methods differ in terms of inputs, structure, and equation intricacy. Most methods differ in estimating the cloudiness factor, emissivity (e), and calculating net longwave radiation (Rnl). All methods use albedo (a) of 0.23 for a reference grass/alfalfa surface. When comparing the performance of all 20 Rn methods with measured Rn, we hypothesized that the a values for grass/alfalfa and non-stressed maize canopy were similar enough to only cause minor differences in Rn and grass- and alfalfa-reference evapotranspiration (ETo and ETr) estimates. The measured seasonal average a for the maize canopy was 0.19 in both years. Using a = 0.19 instead of a = 0.23 resulted in 6% overestimation of Rn. Using a = 0.19 instead of a = 0.23 for ETo and ETr estimations, the 6% difference in Rn translated to only 4% and 3% differences in ETo and ETr, respectively, supporting the validity of our hypothesis. Most methods had good correlations with the ASCE-EWRI Rn (r2 > 0.95). The root mean square difference (RMSD) was less than 2 MJ m-2 d-1 between 12 methods and the ASCE-EWRI Rn at Clay Center and between 14 methods and the ASCE-EWRI Rn at Davis. The performance of some methods showed variations between the two climates. In general, r2 values were higher for the semi-arid climate than for the sub-humid climate. Methods that use dynamic e as a function of mean air temperature performed better in both climates than those that calculate e using actual vapor pressure. The ASCE-EWRI-estimated Rn values had one of the best agreements with the measured Rn (r2 = 0.93, RMSD = 1.44 MJ m-2 d-1), and estimates were within 7% of the measured Rn. The Rn estimates from six methods, including the ASCE-EWRI, were not significantly different from measured Rn. Most methods underestimated measured Rn by 6% to 23%. Some of the differences between measured and estimated Rn were attributed to the poor estimation of Rnl. We conducted sensitivity analyses to evaluate the effect of Rnl on Rn, ETo, and ETr. The Rnl effect on Rn was linear and strong, but its effect on ETo and ETr was subsidiary. Results suggest that the Rn data measured over green vegetation (e.g., irrigated maize canopy) can be an alternative Rn data source for ET estimations when measured Rn data over the reference surface are not available. In the absence of measured Rn, another alternative would be using one of the Rn models that we analyzed when all the input variables are not available to solve the ASCE-EWRI Rn equation. Our results can be used to provide practical information on which method to select based on data availability for reliable estimates of daily Rn in climates similar to Clay Center and Davis.

Temporal genetic structure patterns in tropical maize populations under reciprocal recurrent selection.

In order to investigate the effect of long term recurrent selection on the pattern of gene diversity, thirty randomly-selected individuals from the progenitors (p) and four selection cycles (C0, C3, C6 and C11) were sampled for DNA analysis from the tropical maize (Zea mays L.) breeding populations, Atherton 1 (AT1) and Atherton 2 (AT2). Fifteen polymorphic Simple Sequence Repeat markers amplified a total of 284 and 257 alleles in AT1 and AT2 populations, respectively. Reductions in the number of alleles were observed at advanced selection cycles. About 11 and 12% of the alleles in AT1 and AT2 populations respectively, were near to fixation. However, a higher number of alleles (37% in AT1 and 33% in AT2) were close to extinction. Fisher's exact test and analysis of molecular variance (AMOVA) showed significant population differentiations. Gene diversity estimates and AMOVA revealed increased genetic differentiations at the expense of loss of heterozygosity. Population differentiations were mainly due to fixation of complementary alleles at a locus in the two breeding populations. The estimates of effective population at an advanced selection cycle were close to the population size predicted by the breeding method.

Nutritional constraints on displacement of Fusarium pseudograminearum from cereal straw by antagonists.

Displacement of the fungus Fusarium pseudograminearum from stubble by antagonists is a potential means of biocontrol of crown rot in cereals. The role of carbon and nitrogen nutrition in interactions between the pathogen and the antagonists Fusarium equiseti, Fusarium nygamai, Trichoderma harzianum and the non-antagonistic straw fungus Alternaria infectoria was investigated. Sole carbon source utilization patterns on Biolog plates were similar among the three Fusarium species, suggesting a possible role for competition. However, carbon niche overlap was unlikely to be important in antagonism by T. harzianum. Straw medium supplemented with sugars generally reduced the inhibitory effect of antagonists on growth of F. pseudograminearum in dual culture, indicating that availability of simple carbon sources does not limit antagonism. Adding nitrogen as urea, nitrate or ammonium to straw medium had little effect on antagonism by F. equiseti and F. nygamai, but ammonium addition removed the inhibitory effect of T. harzianum on growth of F. pseudograminearum. Displacement of F. pseudograminearum from straw by all fungi in a Petri dish assay was greater when urea or nitrate was used as a nitrogen source than with ammonium. All forms of nitrogen significantly increased displacement of F. pseudograminearum from straw under simulated field conditions when straws were either inoculated with T. harzianum or exposed to resident soil microbes. However, in 2 out of 3 experiments urea and nitrate were more effective than ammonium. The results suggest that availability of nitrogen, but not carbon, is limiting the activities of antagonists of F. pseudograminearum in straw, and the way nitrogen is applied can influence the rate of displacement and mortality of the pathogen in host residues.

Characterisation of sweetpotato from Papua New Guinea and Australia: Physicochemical, pasting and gelatinisation properties.

The physicochemical and functional properties of flours from 25 Papua New Guinean and Australian sweetpotato cultivars were evaluated. The cultivars (white-, orange-, cream-, and purple-fleshed, and with dry matter, from 15 to 28 g/100 g), were obovate, oblong, elliptic, curved, irregular in shape, and essentially thin-cortexed (1-2 mm). Flour yield was less than 90 g/100 g solids, while starch, protein, amylose, water absorption and solubility indices, as well as total sugars, varied significantly (p < 0.05). Potassium, sodium, calcium, and phosphorus were the major minerals measured, and there were differences in the pasting properties, which showed four classes of shear-thinning and shear-thickening behaviours. Differential scanning calorimetry showed single-stage gelatinisation behaviour, with cultivar-dependent temperatures (61-84 degrees C) and enthalpies (12-27 J/g dry starch). Oval-, round- and angular-shaped granules were observed with a scanning electron microscope, while X-ray diffraction revealed an A-type diffraction pattern in the cultivars, with about 30% crystallinity. This study shows a wide range of sweetpotato properties, reported for the first time.

Utilisation of local ingredients in commercial pig feeds

The long-term competitiveness of the both the Vietnamese feed and pig production industries are constrained and under pressure whilst the industry is dependent on the use of imported feed ingredients in diets for animal production. These cost pressures are a result of import taxes, transport costs, currency fluctuations and feed supply limitations. By undertaking studies on available resources which are currently under-utilised and with potential as local feeds, we can prove their suitability for use as feedstuffs in pig diets and as replacements for imported feed ingredients. In undertaking this process we can lower feeding costs for pig production in Vietnam by the use of local feeds which are cheaper, generate new industries in Vietnam harvesting or processing these feeds and increase the incomes of Vietnamese workers who are involved in producing these by-products. Our project has shown that rubber seed, when processed correctly to lower the hydrogen cyanide content, is a safe and suitable protein meal feedstuff for use in pig diets with the potential to replace significant quantities of imported soybean and fishmeal in Vietnamese pig diets as long as diets are balanced for any amino acid shortfalls. Our peanut studies have shown that use of binders can help alleviate pig production problems with aflatoxin content in peanut meals. Further work is needed to characterise the fate of the bound aflatoxin to see if there is any meat residue risk. Cassava residue is a resultant by-product from starch extraction in both large and small cassava processing factories. Sub-samples from these two mill types were collected and evaluated for residue HCN. Analyses has shown that the processing and sun drying results in a product with relatively consistent low HCN content. Chemical analyses also reveal that significant residual starch also remains in this by-product. Digestibility studies and pig performance feeding studies have shown that cassava residue can be included in diets at 30% with no adverse effect, although the higher fibre content of this product means that strategically, cassava residue is more suitably used in finisher and sow diets. Research has examined the digestible energy content of a number of sunflower meal types available in Australia and identified major differences in their energy value based on processing, additionally, amino acid analysis has shown a significantly lower lysine content than previous reported. We also examined the digestible energy content of a number of Australian stylo forage legume harvest batches and identified the differences in their energy value based on age/harvest time of the forage legume. Analysis results of various stylo cuts showed that the early cut stylo has a higher starch content and lower fibre fraction content than observed in late and recut stylo which were allowed to grow longer. As a result the faecal digestible energy content was higher for the early cut stylo than for the subsequent cut stylo material which had been allowed to become woody. The results have shown that feeding of stylo meal does provide some nutritive value to the pig with increased energy and nitrogen supply, with a portion of the nitrogen presented which the pig is able to retain. Based on nutrient and fibre content stylo could have a useful role in sow feeding and satiety under non-stall housing situations. With increasing Vietnamese investment in rubber production seen with larger areas under plantations the amounts of rubber seed available for animal feeding will grow significantly over the next 15 years and the importance of the by-product ie rubber seed meal as a protein source in diets for Vietnamese pigs.

Screening of new lines of cereal grains for inclusion in Near Infra Red Scan calibrations

The project will provide enough data for a reliable and robust NIRs. It will more fully develop the in vitro method to enable less costly assessment of grains in the future. It will also provide a reliable assessment for DE which is the most expensive component of pig feed.

Improved Post Entry Quarantine Diagnostics

Develop a new diagnostic platform for Post Entry Plant Quarantine to support the detection of Emergency Plant Pests in the Australian Grains and Nursery Industries.

Flotation of calcareous Mussorie phosphate ore

Separation of Mussorie rock phosphate (P2O5 = 20%) from Uttar Pradesh, India, containing pyrite, calcite and other carbonaceous impurities by flotation has been successfully attempted to upgrade the phosphate values. Based on Hallimond cell flotation results of single and synthetic mineral mixtures of calcite and apatite using oleic acid and potassium phosphate, conditions were obtained for the separation of calcite from apatite which is considered to be the most difficult step in the beneficiation of calcareous phosphates. Further studies using 250 g of the mineral (−60 +150 and −150 mesh fractions, deslimed) in laboratory size Fagergren subaeration machine employed a stagewise flotation viz. carbonaceous materials using terpineol, pyrite using potassium-ethyl xanthate and calcite using oleic acid respectively. Separation was, however, found to be unsatisfactory in the absence of a depressant. Among starch, hydrofluosilicic acid and dipotassium hydrogen phosphate, which were tried as depressants for apatite in the final flotation stage, dipotassium hydrogen phosphate proved to be superior to others. However, the tests with the above fractions did not yield the required grade. This was possibly due to insufficient liberation of the phosphate mineral from the ore body and different experimental conditions due to scale up operations. Experiments conducted using −200 mesh deslimed fractions has yielded an acceptable grade of 27.6% P2O5 with a recovery of about 60%. The results have been explained in terms of the specific adsorption characteristics of phosphate ions on apatite and the liberation size of the mineral.