Showing papers in "Australian Journal of Experimental Agriculture in 2008"

Nutritional management for enteric methane abatement: A review

Abstract: A variety of nutritional management strategies that reduce enteric methane (CH4) production are discussed. Strategies such as increasing the level of grain in the diet, inclusion of lipids and supplementation with ionophores (>24 ppm) are most likely to be implemented by farmers because there is a high probability that they reduce CH4 emissions in addition to improving production efficiency. Improved pasture management, replacing grass silage with maize silage and using legumes hold some promise for CH4 mitigation but as yet their impact is not sufficiently documented. Several new strategies including dietary supplementation with saponins and tannins, selection of yeast cultures and use of fibre-digesting enzymes may mitigate CH4, but these still require extensive research. Most of the studies on reductions in CH4 from ruminants due to diet management are short-term and focussed only on changes in enteric emissions. Future research must examine long-term sustainability of reductions in CH4 production and impacts on the entire farm greenhouse gas budget.

Redirecting rumen fermentation to reduce methanogenesis

Abstract: McAllister, T. A., Newbold, C. J. (2008). Redirecting rumen fermentation to reduce methanogenesis. Australian Journal of Experimental Agriculture, 48, (1-2), 7-13.

Targeted technologies for nitrous oxide abatement from animal agriculture

Abstract: Nitrous oxide (N2O) emissions account for ~10% of global greenhouse gas (GHG) emissions, with most of these emissions (~90%) deriving from agricultural practices. Animal agriculture potentially contributes up to 50% of total agricultural N2O emissions. In intensive animal agriculture, high N2O emission rates generally coincide with anaerobic soil conditions and high soil NO3–, primarily from animal urine patches. This paper provides an overview of animal, feed-based and soil or management abatement technologies for ruminant animal agriculture targeted at reducing the size of the soil NO3– pool or improving soil aeration. Direct measurements of N2O emissions from potential animal and feed-based intervention technologies are scarce. However, studies have shown that they have the potential to reduce urinary N excretion by 3–60% and thus reduce associated N2O emissions. Research on the effect of soil and water management interventions is generally further advanced and N2O reduction potentials of up to 90% have been measured in some instances. Of the currently available technologies, nitrification inhibitors, managing animal diets and fertiliser management show the best potential for reducing emissions in the short-term. However, strategies should always be evaluated in a whole-system context, to ensure that reductions in one part of the system do not stimulate higher emissions elsewhere. Current technologies reviewed here could deliver up to 50% reduction from an animal housing system, but only up to 15% from a grazing-based system. However, given that enteric methane emissions form the majority of emissions from grazing systems, a 15% abatement of N2O is likely to translate to a 2–4% decrease in total GHG emissions at a farm scale. Clearly, further research is needed to develop technologies for improving N cycling and reducing N2O emissions from grazing-based animal production systems.

DairyMod and EcoMod: biophysical pasture-simulation models for Australia and New Zealand

Abstract: DairyMod and EcoMod, which are biophysical pasture-simulation models for Australian and New Zealand grazing systems, are described. Each model has a common underlying biophysical structure, with the main differences being in their available management options. The third model in this group is the SGS Pasture Model, which has been previously described, and these models are referred to collectively as ‘the model’. The model includes modules for pasture growth and utilisation by grazing animals, water and nutrient dynamics, animal physiology and production and a range of options for pasture management, irrigation and fertiliser application. Up to 100 independent paddocks can be defined to represent spatial variation within a notional farm. Paddocks can have different soil types, nutrient status, pasture species, fertiliser and irrigation management, but are subject to the same weather. Management options include commonly used rotational grazing management strategies and continuous grazing with fixed or variable stock numbers. A cutting regime simulates calculation of seasonal pasture growth rates. The focus of the present paper is on recent developments to the management routines and nutrient dynamics, including organic matter, inorganic nutrients, leaching and gaseous nitrogen losses, and greenhouse gases. Some model applications are presented and the role of the model in research projects is discussed.

Consumer assessment of eating quality – development of protocols for Meat Standards Australia (MSA) testing

Abstract: Meat Standards Australia sought a consistent measure of the beef eating experience to the consumer. Rather than objective measurements or trained panel sensory assessment, it was decided to proceed with direct consumer assessment. Consumer-based assessment has much greater variation, but it has the decided advantage of validity. This paper summarises the path taken to obtain consistent consumer assessment. What meat samples to present to consumers? What responses to ask for? What to do with these responses when they were obtained? The answers to these questions have led to the MQ4 measure of consumer assessment of meat eating quality, which now forms the basis of the MSA predictive model.

Climate change and Australian livestock systems: impacts, research and policy issues

Abstract: The recent changes in Australia’s climate, the likelihood of further changes over the next decades to centuries, and the likely significant impacts of these changes on the Australian livestock industries, provide increasing urgency to explore adaptation options more effectively. Climate and atmospheric changes are likely to impact on the quantity and reliability of forage production; forage quality; thermal stress on livestock; water demands for both animal needs and for growing forage; pest, disease and weed challenges; land degradation processes; and various social and economic aspects including trade. Potential adaptation options are available for moderate climate changes, with these often being variations of existing climate risk management strategies. However, to date there are few Australian examples where these adaptations have been assessed systematically on any scale (e.g. enterprise, regional, whole of industry or national). Nor have many studies been undertaken in a way that (i) effectively harness industry knowledge, (ii) undertake climate change analyses in the framework of existing operational systems, or (iii) assess climate change in the context of other socioeconomic or technical changes. It is likely that there are limits to the effectiveness of existing adaptations under more severe climate changes. In such cases more systemic changes in resource allocation need considering, such as targeted diversification of production systems and livelihoods. Dealing with the many barriers to effective adaptation will require ‘mainstreaming’ climate change into policies covering a range of scales, responsibilities and issues. This mainstreaming will facilitate the development of comprehensive, dynamic and long lasting policy solutions. The integrative nature of climate change problems requires science to include integrative elements in the search for solutions: a willingness to apply integrated rather than disciplinary science and a strengthening of the interface with decision-makers.

The search for new pasture plants to achieve more sustainable production systems in southern Australia

Abstract: Increasing the proportion of the landscape planted to deep-rooted perennial pasture species is recognised as one of several remedial actions required for the control of dryland salinity in southern Australia. The widespread use of perennials in farming systems is limited at present by the lack of well-adapted perennials that can be grown to reduce recharge in a landscape where drought, soil acidity, temporary waterlogging, infertile soils and unrestricted grazing prohibit the use of many species. The range of plants adapted to salinity also needs to be expanded to stabilise and ameliorate soils already degraded by rising watertables and to increase the profitability of grazing discharge regions within the landscape. This paper describes the steps involved in a national forage screening and breeding program initiated by the Cooperative Research Centre (CRC) for Plant-based Management of Dryland Salinity1, seeking to expand the range of perennial and or salt-tolerant forage plants that can be incorporated into farming systems of southern Australia. It describes the target environments, soil constraints, farming systems and the criteria being considered when assessing the potential of new plants, including assessment of the weed risk posed by introducing new species. This paper forms an introduction to a special issue which presents the outcomes of the pasture species field evaluation and plant breeding program conducted by the CRC.

Livestock methane emission and its perspective in the global methane cycle

Abstract: Over the past three centuries, the atmospheric methane burden has grown 2.5-fold, reaching levels unprecedented in at least 650 000 years. Agricultural expansion has played a large part in this anthropogenic signal, with enterically fermented methane emitted by farmed ruminant livestock accounting for about one quarter of all anthropogenic emissions. This paper summarises the range of measurements that give confidence in estimates of the emission per animal and per unit feed intake and in their extrapolation to national and global emission inventories, while noting also some of the inherent uncertainties. Global emissions are discussed in the context of the evolving global methane cycle.

Managing ecosystem services in broadacre landscapes: what are the appropriate spatial scales?

Abstract: Over the past 200 years agriculture has expanded throughout Australia. The culmination of clearing and cultivating land at the farm scale has resulted in highly modified landscapes and a perceived loss of ecosystem services from pest control and pollination. We examine the literature: (i) to identify the appropriate spatial scale for managing pests, natural enemies and pollinators; and (ii) for evidence that farm-scale changes (due to agricultural intensification) across a landscape have resulted in a tipping point favouring pests and hindering pollinators. Although there is limited information to draw firm conclusions, the evidence suggests that actions undertaken on individual farms have an impact both on their neighbours and regionally, and that the culmination of these actions can lead to changes in population dynamics of pests, natural enemies and pollinators. For major pest species, there is reasonable evidence that grain growers may benefit from improved management and higher yields by implementing area-wide pest management strategies on a landscape scale in collaboration with growers of other crops that also share these pests. As yet, for natural enemies and pollinators there is little direct evidence that similar area-wide initiatives will have a greater effect than management strategies aimed at the field and farm level. Managing pests, natural enemies and pollinators beyond the scale of the field or farm is technically and socially challenging and will required a well defined research agenda, as well as compromise, balance and trading among stakeholders. We highlight critical knowledge gaps and suggest approaches for designing and managing landscapes for ecosystem services.

Effect of plant extracts on methanogenesis and microbial profile of the rumen of buffalo: a brief overview

Abstract: Plants rich in secondary metabolites (saponins, tannins, essential oils, etc) have antimicrobial activity which can be exploited for selective inhibition of a particular group of microbes in the rumen We have screened a large number of plant extracts for their potential to inhibit methanogenesis and ciliate protozoa in an in vitro gas production test using buffalo rumen liquor as the inoculum Out of 93 plant extracts tested, 11 inhibited in vitro methanogenesis to the extent of 25–50% and nine plant extracts inhibited methanogenesis more than 50% Among 20 extracts exhibiting antimethanogenic activity, nine were ethanol extracts, 10 were methanol extracts and only one was a water extract Some of these plant extracts inhibited ciliate protozoa as tested by microscopic examination and 14C-labelled radioisotopic technique, but the protozoa inhibition was not correlated with methane inhibition, indicating that the methanogens sensitive to plant secondary metabolites may or may not be having any symbiotic relationship with ciliate protozoa Methane inhibition was accompanied by a drastic fall in the number of methanogens as determined by real time PCR Plants that appeared to have some potential as feed additives to control methanogenesis by the ruminants are: (i) seed pulp of Sapindus mukorossi (rich in saponins) and Terminalia chebula (rich in tannins); (ii) leaves of Populus deltoides, Mangifera indica and Psidium guajava (rich in tannins and essential oils); and (iii) flower buds of Syzygium aromaticum and bulb of Allium sativum (rich in essential oils) Some of the plants reported in literature exhibiting antimethanogenic activity include Equisetum arvense, Lotus corniculatus, Rheum palmatum, Salvia officinalis, Sapindus saponaria, Uncaria gambir and Yucca schidigera

Insecticide resistance and implications for future aphid management in Australian grains and pastures: a review

Abstract: Aphids can cause substantial damage to cereals, oilseeds and legumes through direct feeding and through the transmission of plant pathogenic viruses. Aphid-resistant varieties are only available for a limited number of crops. In Australia, growers often use prophylactic sprays to control aphids, but this strategy can lead to non-target effects and the development of insecticide resistance. Insecticide resistance is a problem in one aphid pest of Australian grains in Australia, the green peach aphid (Myzus persicae). Molecular analyses of field-collected samples demonstrate that amplified E4 esterase resistance to organophosphate insecticides is widespread in Australian grains across Australia. Knockdown resistance to pyrethroids is less abundant, but has an increased frequency in areas with known frequent use of these insecticides. Modified acetylcholinesterase resistance to dimethyl carbamates, such as pirimicarb, has not been found in Australia, nor has resistance to imidacloprid. Australian grain growers should consider control options that are less likely to promote insecticide resistance, and have reduced impacts on natural enemies. Research is ongoing in Australia and overseas to provide new strategies for aphid management in the future.

Methanogen genomics to discover targets for methane mitigation technologies and options for alternative H2 utilisation in the rumen

Abstract: Reducing ruminant methane emissions is an important objective for ensuring the sustainability of ruminant-based agriculture. Methane is formed in the rumen by methanogens (part of the domain Archaea), mainly from H2 and CO2. Methanogens from a wide range of habitats are being genome-sequenced to gain a better understanding of their biology and, in particular, to identify targets for inhibition technologies for gut-associated methanogens. Genome comparisons are identifying common genes that define a methanogen, while gene differences are providing an insight into adaptations that allow methanogen survival and persistence under different environmental conditions. Within the rumen microbial food web, methanogens perform the beneficial task of removing H2, which allows reduced cofactors to be reoxidised and recycled, thereby enhancing the breakdown and fermentation of plant material. Therefore, rumen methane mitigation strategies need to consider alternative routes of H2 utilisation in the absence (or decreased levels) of methanogenesis to maintain rumen function. Two main alternatives are possible: enhancing rumen microorganisms that carry out reductive acetogenesis (combining CO2 and H2 to form acetate) or promotion of organisms that consume reducing equivalents during the conversion of metabolic intermediates (malate, fumarate and crotonate) into propionate and butyrate. A better understanding of the role and scale of methane oxidation in the rumen may also lead to future options for methane mitigation.

Modelling climatic risks of aflatoxin contamination in maize

Abstract: Aflatoxins are highly carcinogenic mycotoxins produced by two fungi, Aspergillus flavus and A. parasiticus, under specific moisture and temperature conditions before harvest and/or during storage of a wide range of crops including maize. Modelling of interactions between host plant and environment during the season can enable quantification of preharvest aflatoxin risk and its potential management. A model was developed to quantify climatic risks of aflatoxin contamination in maize using principles previously used for peanuts. The model outputs an aflatoxin risk index in response to seasonal temperature and soil moisture during the maize grain filling period using the APSIM’s maize module. The model performed well in simulating climatic risk of aflatoxin contamination in maize as indicated by a significant R2 (P ≤ 0.01) between aflatoxin risk index and the measured aflatoxin B1 in crop samples, which was 0.69 for a range of rainfed Australian locations and 0.62 when irrigated locations were also included in the analysis. The model was further applied to determine probabilities of exceeding a given aflatoxin risk in four non-irrigated maize growing locations of Queensland using 106 years of historical climatic data. Locations with both dry and hot climates had a much higher probability of higher aflatoxin risk compared with locations having either dry or hot conditions alone. Scenario analysis suggested that under non-irrigated conditions the risk of aflatoxin contamination could be minimised by adjusting sowing time or selecting an appropriate hybrid to better match the grain filling period to coincide with lower temperature and water stress conditions.

Reliability of the sulfur hexafluoride tracer technique for methane emission measurement from individual animals: an overview

Abstract: Measurements of enteric methane (CH4) emissions from individual animals have traditionally been made with indirect calorimetry techniques, which are both accurate and reliable. However, the expense and need for animal training and the extent to which calorimetric results can be extrapolated to free-ranging animals have been questioned and stimulated the development of the sulfur hexafluoride (SF6) tracer technique. The tracer technique is now widely used in New Zealand and many other countries for CH4 emission measurements on grazing and pen-fed cattle, sheep, deer and alpacas. Few studies with cattle and sheep have examined the validity of the SF6 tracer technique. Most of these studies have concluded that estimations of CH4 emission by this technique do not differ from those of calorimetric techniques, though some exceptions have been reported. There is general agreement that the tracer technique is associated with large between-animal variability in the CH4 emission estimates from animals on the same diet, but it remains unknown whether this is due to the environment, housing conditions or the technique itself. High within-animal variability has also been reported from tracer CH4 measurements. There is growing evidence that CH4 emission estimates by the tracer technique are positively influenced by the permeation rate (PR) of the SF6 gas from permeation tubes and it has been suggested that fate of the tracer in the rumen rather than unrepresentative breath sample collection is the likely reason for the latter. It is concluded that although some issues related to the tracer technique need to be clarified, using a narrow range in PR and balancing of PR between treatments should be practised in order to overcome the relationship between PR and CH4 emission estimates.

Measurement of greenhouse gas emissions from Australian feedlot beef production using open-path spectroscopy and atmospheric dispersion modelling

Abstract: Feedlot production of beef cattle results in concentrated sources of gas emissions to the atmosphere. Reported here are the preliminary results of a micrometeorological study using open-path concentration measurements to determine whole-of-feedlot emissions of methane (CH4) and ammonia (NH3). Tunable near-infrared diode lasers were used to measure line-averaged (150–400 m) open-path concentrations of CH4 and NH3. A backward Lagrangian stochastic model of atmospheric dispersion and the software package WindTrax were used to estimate greenhouse gas fluxes from the measured concentrations. We studied typical Australian beef feedlots in the north (Queensland) and south (Victoria) of the continent. The data from a campaign during summer show a range of CH4 emissions from 146 g/animal.day in Victoria to 166 g/animal.day in Queensland and NH3 emissions from 125 g/animal.day in Victoria to 253 g/animal.day Queensland.

Changes in methane emission and rumen fermentation parameters induced by refaunation in sheep.

Abstract: Elimination of protozoa or defaunation is known to reduce methane emission by ruminants. However, the long-term efficacy of this practice is not well documented. In this work methane and other end products of fermentation were monitored in five adult, rumen-cannulated wethers that had been kept defaunated for two years (Def1) and successively refaunated (Fau, 12 weeks) and defaunated (Def2) during a 6-month-long experiment. Methane was measured for periods of 4 days at about 4-weekly intervals using the SF6 tracer technique, and rumen content samples were taken regularly throughout the experiment. Refaunation was performed by single administration of a mixed protozoal inoculum (103 cells). A noticeable protozoal population was observed at 12 days after inoculation, which was followed by an exponential increase that peaked at 12 ± 3 × 105 cells/mL rumen fluid at 4 weeks and decreased thereafter to 8 ± 4 × 105 cells/mL at the end of the 12-week Fau period. Production of methane, which was 33 ± 8 L/animal.day in Def1, increased (P 0.05). Even though protozoal numbers were comparable to conventional animals 20 days after inoculation, the increase in methane production was observed later, at 8 weeks, suggesting that protozoa are not the only microbial factor favouring methanogenesis and that the ecosystem needs a relatively long adaptation time following protozoal introduction to optimise this function. The presence of protozoa did not affect total volatile fatty acids and acetate concentration in the rumen but increased butyrate, while decreasing propionate concentration (Fau v. Def1, Def2, P < 0.05). These results show that the decrease in methane emissions induced by defaunation in sheep was stable for a period of up to 2 years. In the absence of protozoa, methane decreased by ~20% in both short- and long-term defaunated animals.

Methane emissions from beef cattle – a comparison of paddock- and animal-scale measurements

Abstract: Methane (CH4) emissions from a herd of 58 grazing cattle were determined in a field experiment using paddock-scale (micrometeorological) methods. The emissions were also measured daily from each animal, using the sulfur hexafluoride tracer method. The paddock-scale methods exploit how the gas, once emitted from the cattle, is transported and dispersed by the wind. Hence, the emission rate may be calculated from measurements of windspeed, wind direction and turbulence statistics, as well as CH4 concentration upwind and downwind of the herd. The paddock-scale methods include a mass-budget approach, flux-gradient method and gas dispersion model. Accuracy can be assessed in unprecedented detail because the animal-scale (reference) method included all individuals in the herd, and the measurement site was ideal for micrometeorological methods (flat, usually windy and free of obstructions that alter the turbulent airflow). The cattle were hand-reared steers of average weight 325 ± 20 kg. Based on the animal-scale method, the average CH4 emission rate over 9 days was 161 ± 20 g/steer.day. The gas dispersion model, when utilising vertical concentration profiles, yielded on average 27% greater emissions. The other paddock-scale methods agreed with the animal-scale method, provided the cattle were at least 22 m away from the location of the downwind concentration measurements. When the cattle were allowed to graze as closely as 5 m from the instruments, the paddock-scale methods gave greater emissions than the animal-scale method; reasons for this are discussed.

Field evaluation of perennial grasses and herbs in southern Australia. 1. Establishment and herbage production

Abstract: To review pasture species for regions with 465–680 mm average annual rainfall, 22 perennial grasses and herbs were evaluated for pasture establishment and productivity in four states at seven locations where the arrest of groundwater recharge is considered necessary to ameliorate dryland salinity. Species represented introduced and native, temperate and subtropical grasses, chicory (Cichorium intybus L.) and plantain (Plantago lanceolata L.). This report describes establishment and yield; the following paper describes persistence and root characteristics. Yields were measured over 2–3 years except at one site, which suffered severe drought. Perennial ryegrass (Lolium perenne L., cv. Avalon) and tall fescue (Festuca arundinacea Schreb. = syn. Lolium arundinaceum. (Schreb.) Darbysh., cvv. AU Triumph and Resolute MaxP), cocksfoot (Dactylis glomerata L., cv. Porto) and phalaris (Phalaris aquatica L., cv. Holdfast and Australian) were the most productive species, with dry matter (DM) yields of 13.6–15.1 t/ha. For summer growth, Porto and Rhodes grass (Chloris gayana Kunth, cv. Katambora) were the most productive species; relative to Australian in summer, Porto and Katambora produced 41% and 26% more DM, respectively (95% confidence). Perennial ryegrass (cv. Avalon), tall fescue (cv. Resolute MaxP) and chicory (cv. Grouse) were particularly valuable for autumn growth; Avalon was 30% more productive than Australian. Tall fescue (cv. Resolute MaxP) was 32% more productive than Australian in winter. Avalon and AU Triumph were the most productive grasses and herbs in spring. Based on natural rainfall over the 2–3 years of measurement, the mean water use productivity, ignoring any runoff, was 10.5 kg DM/ha.mm for the three most productive species. Apart from kangaroo grass (Themeda triandra Forssk), native grasses gradually established, but over a prolonged period weeping grass (Microlaena stipoides (Labill.) R.Br., cv. Wakefield) was the most rapid. Perennial ryegrass, tall fescue, cocksfoot and phalaris maintained productive yields across a diverse range of soils and climates. Exploration of the diversity within these species in a nationally coordinated program of genetic improvement appears warranted for improving reliability and expanding the zone of adaptation.

Supplementation with whole cottonseed reduces methane emissions and can profitably increase milk production of dairy cows offered a forage and cereal grain diet

Abstract: The experimental objective was to determine if whole cottonseed (WCS) could be used as a dietary supplement to reduce enteric methane emissions and profitably increase milk production from dairy cattle over the summer period when pasture is limited in quantity and has a low nutritive value. Fifty lactating cows, ~200 days in milk, were randomly allocated to one of two groups (control or WCS). Cows were offered lucerne hay (in the morning) and pasture silage (in the afternoon) made from a predominantly ryegrass sward in one group for 5 weeks. The hay and silage were placed on the ground in a bare paddock. Cows in each group were also individually offered cracked grain in a feed trough at 3 kg DM/cow.day at milking times. In addition, at milking times, cows in the WCS group were individually offered 2.7 kg DM/cow.day of untreated WCS with their grain supplement. Measurements of methane emissions (n = 12), using the SF6 tracer technique, were made in weeks 3 and 5 after the commencement of feeding treatments. Supplementation with WCS significantly reduced methane emissions by 12% (g/cow.day) and by 21% (g/cow.kg milk solids) and significantly increased yield of milk (n = 25) by 15%, milk fat by 19% and milk protein by 16%. WCS had no effect on concentration of milk fat or lactose, but resulted in a significant 3% decrease in protein concentration. WCS appears to be a promising supplement for reducing methane emissions and increasing milk production from dairy cattle when pasture is limited in quantity and has a low nutritive value.

Metabolic profile and oxidative status in goats during the peripartum period

Abstract: The aim of this study was to monitor the metabolic profile and oxidative status in goats during the peripartum period. A blood sample was taken from 10 Red Syrian goats on days −21, −3, +1, +14, and +28 from delivery. Samples were assayed for glutathione peroxidase and superoxide dismutase activities, and reactive oxygen metabolites, insulin, insulin-like growth factor-I, free triiodothyronine (fT3), free thyroxine (fT4), leptin, urea, non-esterified fatty acids, triglycerides, cholesterol, total protein, albumin, globulin, calcium and inorganic phosphorus concentrations. Blood glutathione peroxidase activity decreased during the postpartum period and its values were significantly (P < 0.05) lower on days 14 and 28 postpartum. Albumin levels were significantly (P < 0.05) lower on days −3, 1 and 28 from delivery compared with day −21. Plasma urea levels significantly (P < 0.001) decreased starting from day −3 from delivery. No effect of time from delivery was noted on reactive oxygen metabolites, non-esterified fatty acids, triglycerides, cholesterol, total protein, calcium and inorganic phosphorus, insulin and leptin concentrations and superoxide dismutase activity. Plasma concentrations of fT3 were significantly (P < 0.01) higher on days 14 and 28 compared with days −21, −3 and 1 from delivery. Plasma levels of fT4 were significantly (P < 0.01) lower on days −3 and 1 from delivery. Plasma insulin-like growth factor-I values slowly decreased during the postpartum period and its values were significantly (P < 0.05) lower on day 28. This study indicates that goats experienced moderate oxidative stress during the peripartum period.

Comparison of the antioxidant properties of emu oil with other avian oils

Abstract: The antioxidant properties of emu oil were compared with oils derived from the fat of other avian species. We first examined their free radical scavenging activity against the 2,2-diphenyl-1-picryl hydracyl radical. The concentration of emu oil in the test solution that caused 50% neutralisation (IC50) was variable (24.5 ± 5.9 mg/mL, range 5.3–55.4 mg/mL), but similar to values obtained for other ratites (10.7 ± 5.9 mg/mL). In contrast, the IC50 values for duck and chicken oil were much higher (118.0 ± 8.1 mg/mL). The variability in the radical scavenging activity of emu oil preparations may reflect variations in the diets of the birds, the processing protocol and/or the storage age of the oil. We also evaluated some of the ratite oils for their inhibitory capacity on human erythrocyte membrane oxidation, by measuring the reduction of the thiobarbituric acid-reactive substance (TBAR) production. Emu oil had a greater effect in decreasing TBAR production than either the ostrich or rhea oil, suggesting that it offers more protection than the other ratite oils against oxidative damage. In conclusion, we demonstrated that emu oil has both antioxidant properties in vitro and a protective role against oxidative damage in a model biological membrane system. The antioxidant or radical scavenging properties of emu oil appear to be due to minor constituents in the non-triglyceride fraction of the oil, while its high ratio of unsaturated to saturated fatty acids (UFA : SFA) offers protection against oxidative damage.

Methane emissions from anaerobic ponds on a piggery and a dairy farm in New Zealand

Abstract: Over 1000 anaerobic ponds are used in the treatment of wastewater from farms and industry in New Zealand. These anaerobic ponds were typically designed as wastewater solids holding ponds rather than for treatment of the wastewater. However, visual observation of these uncovered ponds indicates year-round anaerobic digestion and release of biogas to the atmosphere. The release of biogas may be associated with odour nuisance, contributes to greenhouse gas (GHG) emissions and is a waste of potentially useful energy. The aim of this study was to measure the seasonal variation in quantity and quality of biogas produced by an anaerobic pond at a piggery (8000 pigs) and a dairy farm (700 cows). Biogas was captured on the surface of each anaerobic pond using a floating 25 m2 polypropylene cover. Biogas production was continually monitored and composition was analysed monthly. Annual average biogas (methane) production rates from the piggery and dairy farm anaerobic ponds were 0.84 (0.62) m3/m2.day and 0.032 (0.026) m3/m2.day, respectively. Average CH4 content of the piggery and dairy farm biogas was high (74% and 82%, respectively) due to partial scrubbing of CO2 within the pond water. The average daily volume of methane gas that could potentially be captured by completely covering the surface of the piggery and dairy farm anaerobic ponds was calculated as ~550 m3/day and ~45 m3/day, respectively (assuming that the areal methane production rate was uniform across the pond surface). Conversion of this methane to electricity would generate 1650 kWh/day and 135 kWh/day, respectively (with potentially 1.5 times these values co-generated as heat) and reduce GHG emissions by 8.27 t CO2 equivalents/day and 0.68 t CO2 equivalents/day, respectively. These preliminary results suggest that conventional anaerobic ponds in New Zealand may release considerable amounts of methane and could be a more significant point source of GHG emissions than previously estimated. Further studies of pond GHG emissions are required to accurately assess the contribution of wastewater treatment ponds to New Zealand’s total GHG emissions.

The changing status of invertebrate pests and the future of pest management in the Australian grains industry

Abstract: The Australian grains industry is dealing with a shifting complex of invertebrate pests due to evolving management practices and climate change as indicated by an assessment of pest reports over the last 20-30 years. Acomparisonofpestoutbreakreportsfromtheearly1980sto2006-07fromsouth-easternAustraliahighlightsadecreasein the importance of pea weevils and armyworms, while the lucerne flea, Balaustium mites, blue oat mites and Bryobia mites have increased in prominence. In Western Australia, where detailed outbreak records are available from the mid 1990s, the relative incidence of armyworms, aphids and vegetable weevils has recently decreased, while the incidence of pasture cockchafers,Balaustiummites,blueoatmites,redleggedearthmites,thelucerne fleaandsnailshasincreased.Thesechanges are the result of several possible drivers. Patterns of pesticide use, farm management responses and changing cropping patterns are likely to have contributed to these shifts. Drier conditions, exacerbated by climate change, have potentially reduced the build-up of migratory species from inland Australia and increased the adoption rate of minimum and no-tillage systems in order to retain soil moisture. The latter has been accompanied by increased pesticide use, accelerating selection pressures for resistance. Other control options will become available once there is an understanding of interactions between pests and beneficial species within a landscape context and a wider choice of 'softer' chemicals. Future climate change will directly and indirectly influence pest distributions and outbreaks as well as the potential effectiveness of endemic natural enemies.Geneticallymodifiedcropsprovidenewoptionsforcontrolbutalsopresentchallengesasnewpestspeciesarelikely to emerge.

Predicting livestock productivity and methane emissions in northern Australia: development of a bio-economic modelling approach

Abstract: Enteric fermentation from livestock is a large source of methane, which has a global warming potential 23 times that of carbon dioxide. In Australia, enteric emissions from the livestock sector contribute 10% of Australia’s greenhouse gases. The northern Australian beef industry about 16 million animals is a major contributor to these emissions. However, relative to temperate systems, comparatively little research has been conducted on enteric methane emissions from tropical feeding systems. This paper describes a modelling approach that estimates cattle methane emissions for various bioregions of northern Australia. The approach incorporates a metabolisable energy based model of animal production linked to a property herd economic model. This provides a flexible tool to evaluate animal and property herd dynamics on regional methane yields and liveweight productivity, as well as to assess financial impacts. The model predicts that an important determinant of methane output per unit of product is reduced days to market. Reduced days to market may be achieved through a range of energy supplementation and marketing strategies.

Short- and long-range dispersal of the Queensland fruit fly, Bactrocera tryoni and its relevance to invasive potential, sterile insect technique and surveillance trapping

Abstract: Dispersal of immature and sexually mature Queensland fruit fly, Bactrocera tryoni (Froggatt) from releases made at a single point was assessed from recapture rates obtained by using arrays of traps. The recapture data (pertaining to distances up to 480 m) fitted both logarithmic and Cauchy models although the fits for the releases of immature flies were inferior because of high variability in catches at certain distances. When combined with data previously published for longer distances, a Cauchy model fitted data for releases of immature flies well and indicated that the median distance dispersed after emerging from the puparium was ~120 m and that 90% of flies would displace less than 800 m despite the fact that a consistent trend in declining catch rates can be obtained up to at least 85 km. This is consistent with the tail of the Cauchy distribution having a slope congruent with a negative power curve and thus being scale invariant for longer distances. The distribution of recaptured flies that were released as adults also fitted a Cauchy model with a tail of the same slope, suggesting that the spatial distribution of long-distance dispersers is not only scale invariant but also age invariant. This has significance to the ability of surveillance trapping arrays to detect infestations and also to methods of distributing insects for the sterile insect technique. Whereas the spread of invading propagules in the first generation is likely to be limited by a decline to non-viable density within 1 km or less of the incursion point, the influence of larger infestations on nearby uninfested regions would be limited by the longevity of the dispersers.

The effect of level of intake and forage quality on methane production by sheep

Abstract: In an experiment to determine the effect of level and quality of forage intake on methane (CH4) emissions, 16 wether lambs were allocated over two periods to two dietary treatments consisting of ryegrass at two stages of physiological maturity: an advanced stage of flowering and seeding (reproductive phase) and before flowering (vegetative phase). Additionally, in each period the lambs were divided into four groups and fed differing levels of food, from three-quarters maintenance to twice maintenance, to ensure a range of dry matter intakes amongst lambs. Apparent in vivo digestibility was measured and the mean values were 62.5% and 75.3% (s.e.d. = 0.84) for reproductive and vegetative ryegrass, respectively. Methane emissions were measured with the sulfur hexafluoride tracer technique. Daily methane emission was highly correlated with the amount of dry matter intake (DMI) (R2 = 0.83) and the regression was similar for both types of feed. Mean CH4 emissions per unit of DMI were 23.7 and 22.9 g/kg DMI (s.e.d. = 0.59) for reproductive and vegetative phases of ryegrass, respectively. The CH4 emissions per unit of DMI were not related to either level of DMI or diet quality.

Absence of persistent methane emission differences in three breeds of dairy cows

Abstract: In the present study, data from an experiment with 10 purebred Holstein, Simmental and Jersey cows each were analysed to test the assumption that there are genetically low methane-producing animals. Methane emission of cows offered forage ad libitum and some concentrate was measured for 3 days in open-circuit respiration chambers in weeks 8, 15, 23, 33 and 41 of lactation. Individual cow data were analysed in five different ways: (i) plotting the trend of methane per unit of dry matter intake (DMI) and milk yield over time; relating measured methane production to estimates derived from equations based on either; (ii) DMI or (iii) nutrient intake; (iv) relating residual feed intake (RFI) to methane emission; and (v) analysis of variance of cow × measurement interactions. The Holstein, Simmental and Jersey cows emitted on average 25, 25 and 26 g methane/kg DMI, respectively. There was no indication of individual cows with persistently low or high methane yield per kg DMI and per kg milk. Measured methane emissions differed from estimated values without a clear pattern, and the relationship between RFI and methane emission of the cows was weak. Finally, analysis of variance failed to show distinct patterns of methane per unit of DMI and milk for individual animals. The apparent lack of persistence of individual animal differences in methane yields suggests that genetic determination of this trait is of minor importance in dairy cows.

International perspective: characterisation of United States Department of Agriculture and Meat Standards Australia systems for assessing beef quality

Abstract: The intent, in this manuscript, is to characterise the United States Department of Agriculture (USDA) and Meat Standards Australia (MSA) systems for assessing beef quality and to describe the research evidence that supports the principles involved in grade application. USDA beef quality grading standards rely on carcass-trait-only assessments of approximate age of the animal at harvest and amount of intramuscular fat (as marbling) inside the muscles. USDA beef quality grading started 82 years ago. Then, as now, because no traceability system was in place, each animal’s history (exact age, feeding regimen, management practices, etc.) was incomplete; those who assigned quality grades used indicators of age (physiological maturity) and plane of nutrition (amount of marbling), and they do so still. Since 1926, research studies have identified a multitude of palatability-determining live-animal factors (e.g. genetics, use of hormonal growth promotants, high-energy diet finishing) and carcass-treatment factors (e.g. electrical stimulation, tenderstretch carcass suspension, postmortem aging) that cannot be incorporated into a carcass-trait-only quality assessment system. The USA beef industry has depended on development of more than 100 beef brands – some using palatability assurance critical control point plans, total quality management (TQM) philosophies, USDA certification and process verification programs, or combinations of live-animal factors, carcass-treatment factors and carcass-trait constraints – to further differentiate fresh beef products. The MSA grading system is a TQM grading approach that incorporates animal-specific traits (e.g. genetics, sex, age), control of certain pre-harvest and post-harvest processes in the beef chain, cut-specific quality differences and consumer preferences, into a beef pricing system. A unique aspect of the MSA grading system is that the grades are assigned to cuts or muscles, not carcasses; cuts or muscles from the same carcass are assigned individual (and in many cases, different) grades that reflect differences in expected eating quality performance among the various cuts of beef further adjusted to reflect the influence of cut or muscle aging and alternative cooking methods. The MSA grading system is still being modified and refined (using results of an extensive, ongoing consumer testing program), but it represents the best existing example of a TQM grading approach for improving beef quality and palatability. Research studies have shown that the accuracy of palatability-level prediction by use of the two systems – USDA quality grades for US customers and consumers and MSA grades for Australian customers and consumers – is sufficient to justify their continued use for beef quality assessment.

Within- and between-animal variance in methane emissions in non-lactating dairy cows

Abstract: Several studies on methane (CH4) emissions have focussed on selecting high and low CH4-emitting animals. One challenge faced by this work is the lack of consistency, or repeatability, in animal rankings over time. Repeatability for individual animals over time needs to be high to reliably detect high and low CH4-emitting animals. A possible explanation for the lack of repeatability is a relatively high within-animal variation in daily CH4 emissions, meaning that animals could then change their ranking when compared at different points in time. An experiment was undertaken with four non-lactating dairy cattle to assess the within- and between-animal variation in CH4 emissions over time when measured using the sulfur hexafluoride (SF6) tracer technique. Two contrasting diets were fed to the cattle at maintenance energy levels: lucerne silage (diet 1) and a cereal + lucerne + straw mixed ration diet (diet 2). Daily CH4 measurements were undertaken for 23 days on diet 1 and 30 days on diet 2. There was a significant (P < 0.001) difference between diet 1 and diet 2 in daily CH4 production, with mean (±s.e.) production of 124.3 (11.1) g CH4/day from diet 1 and 169.8 (±11.0) g CH4/day from diet 2. Lower CH4 yield (g CH4/kg dry matter intake) was recorded on diet 1 (22.8 ± 2.0) than diet 2 (32.0 ± 2.0). Cows differed significantly (P < 0.05) from one another in daily CH4 yield (diet 1: cow 1 = 19.4 ± 0.6, cow 2 = 22.2 ± 0.8, cow 3 = 23.2 ± 0.7, cow 4 = 25.4 ± 0.6; diet 2: cow 1 = 26.0 ± 0.7, cow 2 = 36.4 ± 0.7, cow 3 = 29.3 ± 0.7, cow 4 = 36.6 ± 0.7). Variances for daily CH4 yield were smaller for diet 1 (within animal = 6.91, between animals = 6.23) than for diet 2 (within animal = 10.09, between animals = 27.79). Estimates of repeatability (variation between animals/total variation) for daily CH4 yield were 47 and 73% in diet 1 and 2, respectively. Coefficients of variation in average daily CH4 emissions in this experiment ranged from 8 to 18% despite the fact that each animal received the same quantity and quality of feed each day. While further research is required, the high within-animal variability in CH4 emissions measured using the SF6 tracer technique may explain why there has been difficulty in obtaining consistent rankings in CH4 yields when animals are measured on multiple occasions. The results also suggest that the SF6 tracer technique may exaggerate apparent between animal differences in CH4 emissions.

Artificial insemination technology for ratites: a review

Abstract: In ratite farming, the low male to female ratio in the mating system restricts genetic improvement and prevents reduction of the number of males kept on-farm for fertilisation of the female flock. These issues can be overcome and the industry can better realise its potential by using artificial insemination (AI) technology. It is the only practical method for intensive genetic improvement of reproduction and the production of eggs, chicks, oil, meat and leather. For AI to be feasible, we need reliable methods for semen collection, artificial insemination, prolonged storage of spermatozoa in the female tract, high rates of lay, efficient protocols for semen storage, and a panel of quantitative methods for measuring true fertility and hatchability, sperm supply rates in vivo and sperm viability in vitro. For both emus and ostriches, prolonged sperm storage in females has already been demonstrated. Methods for semen collection and artificial insemination, using animal-friendly techniques, have also been developed. Semen storage and cryopreservation protocols are yet to be optimised and we still need to overcome the male-dependent rate of lay, but adoption of AI technology by the ratite industries is now feasible. It also seems likely that these technologies will be relevant to wild ratites that need intensive conservation efforts, such as cassowaries, rheas and ostrich subspecies.