The influence of feeds containing varying dietary cation-anion differences (DCADs) with and without supplements of 25-hydroxyvitamin D (25(OH)D) on urine pH and excretion of macro minerals was determined in fistulated crossbred steers (mean live weight 315 ± 45 kg). A basal forage diet comprising lucerne hay and wheat chaff was used, to which varying quantities of MgCl2 or K₂CO₃ were added to achieve four levels of DCAD: -300, 50, 150 or 250 mEq/kg dry matter (DM). Steers were allocated to one of six treatments, one treatment for each diet and a further treatment for both the 50 and 150 mEq/kg DCAD diets, which were supplemented with 25(OH)D at a rate of 3 mg/steer per day. Urine pH from steers offered the diets comprising DCADs of 50, 150 and 250 mEq/kg ranging from 8.3 to 8.8. In treatments not containing 25(OH)D with DCADs of 50 to 250 mEq/kg, there were no significant differences in urine pH or Ca excretion. However, steers offered the diet with a DCAD of 2300 mEq/kg DM produced urine with a significantly lower pH (6.5 to 7.5). Daily output of Ca in urine was also significantly higher from steers given this diet. Supplementation with 25(OH)D significantly increased urinary Ca excretion from steers offered diets of DCADs 50 and 150 mEq/kg DM. Estimates of daily urinary Ca excretion, calculated using the ratio of creatinine to Ca in 'spot' urine samples, were less variable than those based on total collection (residual mean square of 0.54 and 0.63, respectively).

Australian sheep grazing environments are currently classified into 3 very broad zones (High Rainfall, Wheat/Sheep and Pastoral) that do not differentiate sheep grazing environments to a level allowing sheep producers to assess the impact grazing environments may have on sire progeny performance. If a genotype by environment interaction (GEI) is expressed more as environments diverge then a finer classification of environments may help breeders when selecting stud rams. A sheep grazing environment classification system has been developed in this study using readily obtainable monthly Normalised Difference Vegetation Index (NDVI), from satellite data, and monthly maximum temperature for a 10 year period. Cluster analysis was used on the NVDI and temperature data to create 25 sheep grazing environment classes (SGEclass) around Australia. Two-way analysis of variance revealed a significant interaction between sire progeny performance and SGEclass for hogget weight, fibre diameter and greasy fleece weight. Further ASReml analysis of Merino data from Sheep Genetics illustrated that sire by SGEclass explained similar amounts of variation as sire by flock. Recording the geographic location of the flock would improve the ability to account for environmental differences between flocks.

Stocking rate is often the most important and manageable factor influencing the profitability and environmental sustainability of pastoral properties. Methods for determining carrying capacity, and therefore stocking rate, include subjective approaches based on land manager experience, long-term 'benchmark' stocking rates and techniques using computer-aided predictions of pasture growth. This paper presents a new approach for objectively calculating short-term livestock carrying capacities of pastoral properties by integrating remotely sensed ground cover assessments as a proxy for land condition. The study region was three commercial pastoral properties in the north Australian pastoral region (above 26°S). Two properties were situated in the Victoria River District of the Northern Territory and a third in the Kimberley region of Western Australia. Annual pasture growth was estimated using GRASP, a deterministic, point-based, native pasture model developed for semiarid and tropical grasslands, which was calibrated for the different land types in the study region. Carrying capacity estimates were further refined by investigating trends in landscape cover change between years using data from satellite imagery assessment. These tools have been shown to be useful for inferring land condition and pasture growth within these regions of northern Australia but had not been integrated before this study. This study developed an approach for inferring rangeland pasture condition and applying it to refine short-term carrying capacities, thus aiding decision making. The approach developed in this study is considered to be more applicable for commercial land management than currently available methods for determining carrying capacities on pastoral properties in northern Australia.

An experiment was conducted to develop and optimize a chicken bioassay to detect the presence of infective viral pathogens in poultry litter from a variety of sources. The experiment also aimed to determine the effect of type of chickens and age of exposure to litter on the level of viral infectivity. The bioassay detected chicken anaemia virus, infectious bursal disease virus and fowl adenovirus from chicken litters. SPF chickens showed higher sensitivity than commercial broiler chickens without any effect of age of exposure, however, the assay was more sensitive in broiler chickens when exposed at day 8. We conclude that the bioassay based on exposure of day-old SPF chickens is a viable assay of viral infectivity of poultry litter.

Objective: To develop a chicken bioassay to detect infective viral pathogens in poultry litter and to determine the effects of type of chicken and age of exposure, as well as the effect of simulated litter transportation, on the level of viral infectivity detected. Design: A 5 x 2 x 2 factorial design, plus negative controls. Five chicken litters, including two with deliberate contamination (one transported and one not), two chicken types (specific-pathogen-free (SPF) Leghorns and Cobb broilers) and two ages at initial exposure (days 1 and 8). Two replicates of each treatment combination. Methods: The 10 chickens in each of 22 isolators were either exposed (20 isolators) or not (2 isolators) to 8 L of previously used or deliberately contaminated poultry litter in two deep scratch trays. At day 35 post-exposure, sera were assayed for antibodies against chicken anaemia virus (CAV), infectious bronchitis virus (IBV), infectious bursal disease virus (IBDV), Newcastle disease virus (NDV) and fowl adenovirus (FAV). Spleen samples were tested for Marek's disease virus (MDV) using real-time polymerase chain reaction. Results: The bioassay detected CAV, IBDV and FAV, but not NDV, IBV or MDV, in chickens exposed to infected litters. Infection in SPF chickens was detected with greater sensitivity than in the broiler chickens. Sensitivity increased with age at exposure in broiler but not SPF chickens. Simulated transportation for 24 h had little effect on pathogen detection. Conclusion: A bioassay based on the exposure of day-old SPF chickens to poultry litter and measurement of seroconversion at day 35 post-exposure is a useful semi-quantitative assay for viral infectivity in poultry litter, with overnight transportation of litter having little effect on the level of viral infectivity detected. This bioassay has applications in research on litter treatment protocols.

We investigated the development of standardised methods of extraction and quantitation of viral nucleic acids from broiler litter. To detect and quantify virus we used fully quantitative Taqman® qPCR assays with plasmid-based standard curves to quantify Marek's disease virus (MDV, dsDNA), infectious laryngotracheitis virus (ILTV, dsDNA), Fowl adenovirus (FadV, dsDNA), chicken anaemia virus (CAV, ssDNA) and infectious bursal disease virus (IBDV, dsRNA). A series of experiments examined the effects of litter washing, blending, bead beating, and removal of inhibitors using polyvinylpolypyrrolidone (PVPP). To evaluate the qPCR assays and the DNA extraction techniques we monitored the recovery of fixed amounts of virus added to litter samples. The three litter types used were hardwood shavings, softwood (pine) shavings and rice hulls. Hardwood shavings were shown to contain high levels of PCR inhibitors but these could be neutralised by PVPP. Detectable virus recovery was good for IBDV and CAV, but low for the dsDNA viruses ILTV and MDV. The third dsDNA virus, FAdv, was unable to be detected. The four detectable viruses were detectable in all fractions of material (retentate after filtration, and in both the pellet and supernatant fractions following centrifugation of the filtrate) with highest concentrations in the pellet. The results indicate that a method based on washing samples with buffer containing 0.15% Tween-80 followed by bead beating and PVPP treatment would enable detection of most DNA and RNA viruses from litter with the greatest concentration of virus found in the pellet fraction after centrifugation. Work is ongoing to resolve the low recovery rate of dsDNA viruses and to simplify the litter processing and DNA extraction further.

Excessive nitrogen volatilization from poultry litter as ammonia (NH₃) is harmful for chickens and poultry workers' health. Litter amendments such as bentonite and zeolite can reduce NH₃ and improve air quality in the poultry shed. Inclusion of these materials in poultry litter can reduce nitrogen volatilization and the solubility of phosphorus thus increasing the fertilizer value of the spent litter. To determine the extent to which the latter could be optimised we investigated the effect of high level inclusion of bentonite and zeolite in fresh pine shavings on broiler chicken live weight and welfare and a range of litter measurements including NH₃ production using the chamber acid trap method. The experiment ran for 42 days and had 5 treatments each replicated in two 2.25 m² pens with 25 chickens per pen. Treatments were nil amendment and 33% and 50% by weight addition of each of bentonite and zeolite. Inclusion of bentonite but not zeolite at these levels increased mortality of chickens during brooding, but did not adversely affect chicken live weight, footpad dermatitis, hock burn, breast blister and breast feathering of chickens up to day 42. Both amendments significantly reduced NH₃ in litter up to day 28. The effects of these amendments on the fertilizer value of the end of batch litter are under investigation.

Broiler chickens in Australia are traditionally reared on new litter. To increase resource utilization and improve production efficiency, industry is moving towards reusing litter in the shed for multiple batches. A study was conducted to compare the ammonia and dust production by meat chickens reared in new and reuse litter. Although Australian meat chicken industry increasingly establishing modern tunnel ventilated sheds, a vast majority of growers still using conventional sheds. Therefore, the study also investigated the dust and ammonia level in conventional and tunnel ventilated shed. To investigate the effect of shed type, ammonia concentration in ppm and particulate matter (dust) in mg/m³ of air was measured at various heights from the floor level and ages of chickens up week 7. Ammonia and dust levels were compared in new and reused litter in a separate experiment. The ammonia concentration was rapidly increasing with the age of chickens up to 3 weeks and then relatively steady up to week 5 without significant effect of shed type. The dust level was higher in conventional than tunnel shed. Overall, the dust level was increasing with the age of chickens up to week 5 and then steady or lower. The ammonia concentration in the reused litter was higher all along, whereas, dust level was higher in reused litter from week 3 and 4 but lower in week 2 and 5. Ammonia concentration always remained below the industry set limit of 25ppm.

We investigated the effects of adding alum, sodium bisulphate, bentonite, zeolite and NaturClean CSM® at 3.2, 3.2, 13, 13 and 0.9 % by weight respectively to reused litter on moisture content, pH, ammonia production, bird liveweight and conditions linked to welfare including scores for footpad dermatitis, hock burn, breast burn and breast feathering. Treatments, including no amendment, were applied to four pens each 2.25 m² with half the pens having 20% additional water added. Nineteen broiler chicks were reared in each pen up to day 42 with sampling of the litter and birds at various intervals. Litter moisture content of 31% on day 0, reduced to approximately 21% on days 7 and 14 before increasing to a value of 53% on day 42. All litter amendments except NaturClean CSM® reduced ammonia production with the greatest reductions seen with alum and sodium bisulphite on days 7 and 14. Amendments worked similarly in litter with or without water addition. There were no significant effects of litter amendment on bird weights or measures of welfare with welfare measures generally worsening with time and with initial addition of water. Ranking of reused litter treatments from 1 to 6 (best to worst) for each welfare measure, followed by the averaging of those rankings, provided mean rankings of 1.75, 2.25, 3, 3.75, 4.75 and 5.5 respectively for reused litter without amendment, bentonite, alum, sodium bisulphite, NaturClean CSM® and zeolite treatments. Both acidifying and adsorbent litter additives have potential to significantly reduce ammonia concentrations on reused litter. Further work is required to determine optimum inclusion rates and more clearly identify effects on welfare and performance.

The potential impact of Australia's proposed carbon pollution reduction scheme (CPRS) on the Australian sheep industry was modelled. The model assumes that there will be a considerable delay before overseas nations adopt similar emissions policies. Even if agriculture were exempt from the CPRS and did not incur any liability for emissions, the indirect effects of the CPRS on farm input costs would be significant by 2016. Even if 90% of required emission permits were allocated to sheep farmers at no cost, farm cash margins would decrease by 6–30% by 2016 and by 12–31% by 2030. With the exception of improved feeding management, current technologies for controlling methane emissions from ruminants are not cost effective and may result in under-utilisation of low-cost fibrous feed resources. Farm systems models such as GrassGro3 and SGS Pasture have a limited ability to automatically model the effects of changes in flock nutritional management on methane production. Australian sheep breeders are unlikely to have a financial incentive to include methane production and feed intake as selection criteria in Merino breeding programs. This is not surprising considering that the annual worth of a fleece is about $36 per ewe, whereas the annual methane production of a ewe would only be valued at –$3.50 if carbon were valued at $28/t of carbon dioxide equivalent. Research is needed to quantify genetic associations between methane emission and production traits and to develop strategies for reducing sheep methane emission without affecting productivity and profitability.

Reusing poultry litter for multiple batches of broiler chickens risks transfer of pathogens between batches. On two commercial farms we investigated the effects of various litter heaping treatments for 9-10 days between batches of chickens (heaping or windrowing, with or without turning at day 3-4, or litter turning only) on temperature profiles and loss of infectivity of litter for key viral pathogens and coccidia. Treatments within farm were replicated in two sheds. Temperature was monitored continuously at depths of 0, 25, 50 and 75-100 cm. On days 0, 3-4, 6-7, and 9-10, representative litter from these depths was collected, pooled and infectivity tested using a published chick bioassay measuring seroconversion or oocyst production in chicks exposed to litter in isolators. Temperature varied markedly with depth and time. Mean below surface maxima of 65-68 °C (Farm 1) and 55-63 °C (Farm 2) were reached more rapidly at 25 cm (3-4 days) than 50-100cm (7-10 days) with the highest peak temperatures recorded at 50cm. Temperatures were higher in heaps than windrows and turning did not increase temperature. Coccidial infectivity was undetectable by day 3. Fowl adenovirus infectivity was mostly undetectable by days 6-7 while chicken infectious anaemia virus and infectious bursal disease virus infectivity were undetectable by days 6-10. Marek's disease virus showed reduction in infectivity with significant infectivity remaining at days 9-10. This work confirmed litter transmission of several viral pathogens and showed that heaping of litter between batches will markedly reduce the infective load of most pathogens evaluated, and potentially eliminate some.

The growth of the poultry industry in Australia has placed strains on the availability of litter materials, driving costs up. A survey of poultry companies in 2007 (Islam and Walkden-Brown, 2010) revealed that they spent $12-21 per m³ for new litter material, if it was available at all. Transportation of these bulky materials is also expensive. Runge (2007), using earlier lower input prices, estimated that the meat chicken industry spent $10.78 million annually on bedding material and received about $0.71 million in return for the used litter. This left a cost of $10.07 million annually for bedding material. They reported that about 1.17 million m³ of bedding material was used by the industry each year with approximately 1.60 million m³ of used chicken litter produced. Coufal et al. (2006) working in the USA reported production of between 1.2 and 1.5 tons of used litter per 1,000 broiler chickens, when reared on a single-batch litter. In the USA and increasingly in Australia, the disposal of spent litter is also under increasing regulatory control. Thus there are potential economic and environmental advantages if litter can be safely reused for chicken production.

Because of seasonal variability between years, it is difficult to determine the most appropriate time to supplement breeding beef cattle in northern Australia. As the sampling, storage and transportation of pasture samples is relatively easy, analysis of pasture samples has been suggested as a management tool. We used the indicator species method (Ash and McIvor, 1995) to evaluate associations between faecal and pasture nitrogen levels and to determine if pasture samples are as useful a management tool as faecal nitrogen samples for determining the quality of the diet consumed by grazing animals.

Reducing fragmentation and habitat loss by restoring or maintaining connectivity has been promoted as a way to mitigate the negative impacts of human activities on biodiversity. This study is an example of collaboration between spatial researchers and on-ground practitioners, to deliver better informed management options for investment in connectivity and biodiversity outcomes. Using the Border Rivers-Gwydir catchment revegetation programmes in New South Wales, Australia, we describe a fit-for-purpose, cross-scale methodology consisting of multiple-component models, where each component reflected varying spatial scales. The methodology was based on the concepts of metapopulation ecology and landscape ecology and used least-cost paths analyses. At the wider scale, native vegetation extent and condition were used as a surrogate for all biodiversity; at the finer scale, landscape structure and generalised movement parameters related to a focal woodland species group were used to derive least-cost paths. The output from the analyses provided spatially explicit management action zones that were used to prioritise areas for revegetation investment. Combining local priority zones for linking habitat with regional-scale and broad-scale zones should increase access to resources for biota, increase dispersal potential and thereby enhance biodiversity persistence. Promoting connectivity is a global concern. Our approach could be relevant in other geographical settings where the implementation needs of NRM practitioners can be assisted through the application of scientific knowledge.

Effective university level education in animal nutrition requires both research-led teaching and motivated students (Brew, 1999). With the aim of providing both of these requirements, we established the "State of Origin Chicken Challenge" competition. This annual event capitalises on Australian students' love of sporting competition (albeit linked to sport in name only) and incorporates this into the teaching of animal nutrition. Practical activities involving diet formulation and the effects of different diets on chicken growth have been part of the traditional animal nutrition curriculum at most universities. The basis of the current competition was that students at the University of New England, Armidale (UNE) and The University of Queensland, Gatton (UQ) would formulate diets and subsequently feed these diets to chickens at both campuses. The competition winner is the university that grows the greatest weight of chicken per dollar of feedstuff.

Meat chickens in Australia are mostly reared on fresh litter materials such as wood shavings. Such materials are becoming increasingly unavailable and expensive. Reuse of litter for raising multiple batches of chickens is an option used in many countries despite the risk of pathogen carryover and compromised productivity. The small number of Australian growers who reuse litter (East 2007) use composting by heaping or windrowing of litter in sheds between batches of chickens to of inactivating pathogens and improving the physical condition due to the heat generated. As part of a larger study investigating pathogen inactivation following heaping and windrowing of broiler litter we measured the temperature profile at various depths in heaps and windrows over 9-10 days and also assessed changes in litter dry matter, pH and chemical content in two experiments on commercial broiler farms. Expt. 1, on a Sydney farm, compared windrowed (Win), heaped (H) and heaped litter with mechanical turning on day 3 (HT) over 9 days. Expt. 2, on a Brisbane farm, compared windrowed litter (Win) and the same mechanically turned at day 4 (WT) with no heaping (NH) in which litter was undisturbed "in situ" apart from mechanical ripping at day 4, over 10 days. Temperature was recorded at 15-minute intervals using iButton data loggers at the various depths. Representative litter samples were collected at 4 times for determination of pH, dry matter, nitrogen, potassium and carbon contents. In expt. 1 H had higher mean temp than Win (P<0.05) due to more sustained heating (Fig. 1a). In expt. 2 the NH treatment did not result in any heating with temperatures below 30°C throughout, while the Win produced similar temperature profiles to that seen in Expt. 1. In Expt. 2 turning had no effect on temperature while in Expt. 1 it increased after turning by 2-4°C. Depth within the heap had profound effects on the temperature profile (Fig. 1b) with surface temperatures remaining around 30°C and unlikely to induce significant pathogen inactivation. Litter dry matter increased with time post heaping/windrowing from ~74% to ~77%. Litter had an alkaline pH (~8.6) which declined with time in heaped/windrowed litter (by 0.2-0.4) over 9-10 days. There was a significant positive association between the dry matter content and litter pH (R²=0.33, P<0.001). ... Sustained temperatures above 50°C were achieved during litter heaping and windrowing with high temperatures persisting for the duration of measurement. These temperatures are likely to induced significant inactivation of poultry pathogens, and indeed this was observed in these experiments (Islam et al., 2010).

In Australia, enteric methane from ruminants represents 11% of total agricultural GH emissions. Practical ways of reducing methane emissions from ruminants in Australia are required to enable the livestock industries to reduce their carbon footprint. When rumen microorganisms ferment feed organic matter, they generate the reduced cofactor NADH which is in equilibrium with rumen H₂. In ruminants, the H₂ is normally removed by the reduction of CO₂ to form methane. However, NO₃⁻ (present in some fresh pasture forage) has a higher affinity for H₂ than CO₂ and, when it is present, H₂ is first used in the reduction of NO₃⁻ to NO₂⁻ and NO₂⁻ to NH₃ thereby reducing the production of methane from CO₂. After reviewing the literature and considering the potential for NO₂⁻ poisoning, Leng (2008) concluded that supplementation of ruminants with NO₃⁻ (as an alternative to urea) is entirely feasible. This study therefore examined digestion, microbial growth and methane production in sheep given a diet of chaffed oaten hay supplemented with isonitrogenous amounts of KNO₃, urea, or both N sources. Eight Merino wethers (38.6 kg, SE 2.4; aged 3 years with long-established rumen fistulas) were housed in metabolism cages in 2 rooms (15-20°C, continuous lighting) and allocated to 2 treatment groups. Two isonitrogenous diets based on chaffed oat hay were prepared. A diet with 4% added KNO3 was prepared by sprinkling a solution of KNO₃ onto the hay while it was stirred in a rotary feed mixer. Another diet (0% KNO₃) was similarly prepared using a urea solution so that 5.54 g N was added per kg hay for both diets. The sheep were gradually acclimated to the NO₃⁻ containing diet over 18 days. The daily ration (1 kg/d air-dry feed) was delivered to both groups of sheep in equal portions each hour by automatic feeders during a 4-day digestibility trial, and every 2 h while the sheep were in respiration chambers to determine their methane output.

This workshop has its origins in two successful Australian Centre for International Agricultural Research (ACIAR) projects on meat sheep development in Maharashtra, India, that ran between 1998 and 2008. These projects aimed to increase sheep meat production by traditional smallholder sheep owners in an environment where the coarse wool produced by local sheep had lost most or all of its value. Smallholders are a socially and economically disadvantaged group in rural India and boosting their income and status was an important goal. The Indian partners on these projects had established that the low reproductive rate of sheep on the Deccan Plateau was a major limitation on productivity for meat production. They had identified the highly fecund Garole sheep from West Bengal, which regularly produce twins and some triplets, as a potential means of genetically improving the reproductive component of productivity. Under the ACIAR projects, it was established that the basis of fecundity in the Garole is the FecB (Booroola) gene mutation. This was originally described in Australia by Helen Newton Turner, in whose honour this workshop is named, and attributed by her to early importation of Bengal sheep. Using direct DNA tests for the presence of the mutation, the project team set about introducing (introgressing) the gene into an experimental flock comprising local Deccani sheep and their crosses with promising local meat breeds. This work suggested that the mutation conferred useful increases in fecundity and meat production efficiency. During 2003–08 this was confirmed in 26 collaborating smallholder sheep owners' flocks in which the biological and economic impact of introduction of the mutation was assessed. Use of the FecB gene is one of the few examples where DNA technologies have been shown to clearly benefit practical breeding programs. ACIAR is therefore pleased to be a major sponsor of this, only the second, international workshop dedicated to the FecB (Booroola) gene. The first workshop on 'The Booroola Merino' was held in Armidale (New South Wales, Australia) in 1980. The first paper in those proceedings was written by Dr Helen Newton Turner on the 'Origins of the CSIRO Booroola' and included the postulate about the Bengali origin of the gene. Between these two workshops dedicated to FecB, another two workshops on major genes in sheep were held in Toulouse, France, in 1990 and 2003, at which advances in understanding of FecB were also presented. Major developments over the 28 years since the first workshop include the discovery of the single gene origin of the fecundity effect, improved understanding of the physiological basis of the effect and the reproductive and economic consequences of this, and the development of methods for accurate genotyping of animals at the FecB locus, which culminated in the development of a direct DNA test. The FecB gene has spread from the Booroola Merino to some 40 4 breeds of sheep worldwide. It is now also spreading from the Garole, Hu and Han breeds in India and China, from one of which it probably originated. The workshop was attended by approximately 100 delegates and speakers from 13 countries and 9 Indian states. Invited speakers were largely drawn from researchers from around the world involved in major projects on the introgression of the FecB gene. The aim was that these proceedings would summarise our current understanding of the FecB mutation, with special emphasis on the biological and economic consequences of its use in new breeds for commercial reasons. These proceedings are testament to the achievement of this goal. They also include a summary of a panel discussion on recommendations and strategies for a wider introgression of the FecB gene into the Indian sheep population. These proceedings will be an invaluable resource for those involved in commercial use of the FecB mutation in any country. ACIAR is proud to have been centrally involved in much of the research reported at the workshop, and in its sponsorship and publication. The ACIAR Indian projects have provided some of the clearest evidence of successful commercial use of the FecB gene, and it can be expected that this will contribute to a substantial improvement in sheep productivity and smallholder sheep owners’ incomes in India.

This publication is a collection of research and review papers presented at the Helen Newton Turner Memorial International Workshop held in India, November 2008. The workshop was the conclusion of ACIAR projects that entailed more than a decade of research in India on improved meat sheep production.

This research was designed to determine if divergent selection for resistance to 'Haemonchus contortus' had produced correlated changes in voluntary feed intake and diet selection. Voluntary feed intake, diet selection and production were determined in 54 Merino weaner rams from the CSIRO 'Haemonchus' selection flock, increased resistance to 'Haemonchus' (IRH), decreased resistance to 'Haemonchus' (DRH) and random bred control (C) selection lines. Weaner rams were fed ad libitum either a high (9.2 MJ ME/kg DM, 90 g MP/kg DM) or moderate (6.3 MJ ME/kg DM, 30 g MP/kg DM) quality diet and given the choice between the two diets, when uninfected (NIL) or infected with 'H. contortus' (INF). Symmetrical response to divergent selection for worm egg count (WEC) was not matched by a symmetrical change in feed intake and there was no difference in diet selection between selection lines. Feed intake, growth and wool production of DRH animals remained the same as that of IRH, yet DRH animals had five times greater WEC than IRH. This study begins to explain the mechanisms that allow resistant animals to effectively prevent establishment and/or development of 'H. contortus', by maintaining a greater immune response to infection through higher circulating eosinophils, plasma globulin and IgG₁ antibody titres. Susceptible animals have displayed resilience by improving feed conversion efficiency and increasing protein synthesis.

Worms continue to be the most costly animal health issue for the Australian sheep industry. The WormBoss worm control program applied in the summer rainfall tablelands region of NSW has been demonstrated to reduce the annual cost (and its between year variation) of worms by over $5.00 per ewe. Adoption of the WormBoss control program provides a financial and risk management advantage for sheep producers though history suggests that achieving on-farm adoption of management programs requires a concerted and long-term approach. As part of this approach, a Worm Boss regional worm control program, Drench Decision Guide and worm control workshop have been developed, through the CRC for Sheep Industry Innovation, for the summer rainfall region of the tablelands and slopes of north-eastern NSW and south-eastern QLD. This approach will be used as a template in other regions to establish regionally-relevant WormBoss services.