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High-field 1H-n.m.r.-spectroscopic studies supported by chemical carbohydrate analyses show that skeletal keratan sulphates (KS-II) of bovine origin may be sub-classified into two groups. Keratan sulphate chains from articular and intervertebral-disc cartilage (KS-II-A) contain two structural features, namely alpha(1----3)-fucose and alpha(2----6)-linked N-acetyl-neuraminic acid residues, that are absent from keratan sulphates from tracheal or nasal-septum cartilage (KS-II-B).

High-field 1H-n.m.r.-spectroscopic studies supported by chemical carbohydrate analyses show that skeletal keratan sulphates (KS-II) of bovine origin may be sub-classified into two groups. Keratan sulphate chains from articular and intervertebral-disc cartilage (KS-II-A) contain two structural features, namely alpha(1----3)-fucose and alpha(2----6)-linked N-acetyl-neuraminic acid residues, that are absent from keratan sulphates from tracheal or nasal-septum cartilage (KS-II-B).

Incidence of visual signs of bacterial infection and mortality, from causes related to bacterial infection, were recorded on a weekly basis in growing meat rabbits from 5 to 10 weeks of age. Heritability of Weekly Incidence of disease was highest in weeks 9 and 10 (0.05 ± 0.02 and 0.06 ± 0.02, respectively with linear model, and 0.10 ± 0.06 and 0.12 ± 0.05, respectively with a threshold model). Common litter effects accounted for 5–20% of the variance of disease incidence, while maternal genetic variance was small (0–3%). Individuals from small litters at weaning had higher disease incidence, and disease incidence reduced as litter parity of the doe increased (P < 0.05), when the disease trait was measured at week 9 and 10, but not for earlier weeks. Genetic correlations between disease incidence and mortality were imprecise and not different from zero. Phenotypic correlations were low to moderate, and positive. Although the mechanism at this stage is unknown, these findings suggest that there are common/shared immunological responses to bacterial challenge that are under genetic control. This study demonstrates that observed signs of bacterial infection in rabbits can be used as an indicator trait for resistance to bacterial infection, and the heritability of the trait is high enough to warrant further evaluation of the merit of including it in a breeding program. From one week to the next, rabbits exhibiting disease symptoms were more likely (10 to 50 times depending on week of measurement) to die than those that were healthy. The relative economic value of resistance to bacterial infection could be based on the relationship between disease incidence and survival, as well as the direct costs of effective disease control and treatment.

This paper considers the development, plant implementation and application of X-ray diffraction (XRD) analysis and near infrared (NIR) analysis for reliable quantitative mineralogical ore profiling at several copper mines. This allows ore routing to be optimised, ore-type profiling improved, swelling clay identified so that permeability losses in heap leaching can be rectified, conveyor chute plugging prevented, flotation problems avoided and tailings thickening controlled., This paper considers the development, plant implementation and application of X-ray diffraction (XRD) analysis and near infrared (NIR) analysis for reliable quantitative mineralogical ore profiling at several copper mines. This allows ore routing to be optimised, ore-type profiling improved, swelling clay identified so that permeability losses in heap leaching can be rectified, conveyor chute plugging prevented, flotation problems avoided and tailings thickening controlled.

This CSIRO report provides an in-depth assessment of the greenhouse gas (GHG) sequestration/mitigation potential likely to be achieved through change in rural land use and management, based on a review of current knowledge and consultation with a cross-section of scientists and land management experts. The focus is on Queensland but in most instances national potential is also estimated. The report revisits the Garnaut Review (2008) estimates1 for terrestrial greenhouse gas sequestration – in more detail, with a discussion of implementation issues, risks and interactions between options. The review was requested by the Queensland Premier’s Council on Climate Change – as a technical input to policy development. The report confi rms that there are a wide variety of options for sequestering or mitigating GHG emissions through changed land use and management; the options studied were based on the Garnaut Review categories with some changes in defi nition and emphasis. This report demonstrates that Australia has the opportunity to offset a signifi cant proportion of our GHG emissions, by storing carbon in the landscape and changing the emissions profile from rural land use. Thus, the broad thrust of the Garnaut Review is supported – within Queensland an overall technical potential of 293Mt CO2-e/yr for GHG abatement was estimated, with 140 Mt of this potential being assessed as attainable with concerted efforts in technical and management changes, policy adjustment and shifts in current land management priorities. It must be recognised that these estimates contain a combination of biological, technical and implementation uncertainty.

This CSIRO report provides an in-depth assessment of the greenhouse gas (GHG) sequestration/mitigation potential likely to be achieved through change in rural land use and management, based on a review of current knowledge and consultation with a cross-section of scientists and land management experts. The focus is on Queensland but in most instances national potential is also estimated. The report revisits the Garnaut Review (2008) estimates1 for terrestrial greenhouse gas sequestration – in more detail, with a discussion of implementation issues, risks and interactions between options. The review was requested by the Queensland Premier’s Council on Climate Change – as a technical input to policy development. The report confi rms that there are a wide variety of options for sequestering or mitigating GHG emissions through changed land use and management; the options studied were based on the Garnaut Review categories with some changes in defi nition and emphasis. This report demonstrates that Australia has the opportunity to offset a signifi cant proportion of our GHG emissions, by storing carbon in the landscape and changing the emissions profile from rural land use. Thus, the broad thrust of the Garnaut Review is supported – within Queensland an overall technical potential of 293Mt CO2-e/yr for GHG abatement was estimated, with 140 Mt of this potential being assessed as attainable with concerted efforts in technical and management changes, policy adjustment and shifts in current land management priorities. It must be recognised that these estimates contain a combination of biological, technical and implementation uncertainty.

This CSIRO report provides an in-depth assessment of the greenhouse gas (GHG) sequestration/mitigation potential likely to be achieved through change in rural land use and management, based on a review of current knowledge and consultation with a cross-section of scientists and land management experts. The focus is on Queensland but in most instances national potential is also estimated. The report revisits the Garnaut Review (2008) estimates1 for terrestrial greenhouse gas sequestration – in more detail, with a discussion of implementation issues, risks and interactions between options. The review was requested by the Queensland Premier’s Council on Climate Change – as a technical input to policy development. The report confi rms that there are a wide variety of options for sequestering or mitigating GHG emissions through changed land use and management; the options studied were based on the Garnaut Review categories with some changes in defi nition and emphasis. This report demonstrates that Australia has the opportunity to offset a signifi cant proportion of our GHG emissions, by storing carbon in the landscape and changing the emissions profile from rural land use. Thus, the broad thrust of the Garnaut Review is supported – within Queensland an overall technical potential of 293Mt CO2-e/yr for GHG abatement was estimated, with 140 Mt of this potential being assessed as attainable with concerted efforts in technical and management changes, policy adjustment and shifts in current land management priorities. It must be recognised that these estimates contain a combination of biological, technical and implementation uncertainty.

This CSIRO report provides an in-depth assessment of the greenhouse gas (GHG) sequestration/mitigation potential likely to be achieved through change in rural land use and management, based on a review of current knowledge and consultation with a cross-section of scientists and land management experts. The focus is on Queensland but in most instances national potential is also estimated. The report revisits the Garnaut Review (2008) estimates1 for terrestrial greenhouse gas sequestration – in more detail, with a discussion of implementation issues, risks and interactions between options. The review was requested by the Queensland Premier’s Council on Climate Change – as a technical input to policy development. The report confi rms that there are a wide variety of options for sequestering or mitigating GHG emissions through changed land use and management; the options studied were based on the Garnaut Review categories with some changes in defi nition and emphasis. This report demonstrates that Australia has the opportunity to offset a signifi cant proportion of our GHG emissions, by storing carbon in the landscape and changing the emissions profile from rural land use. Thus, the broad thrust of the Garnaut Review is supported – within Queensland an overall technical potential of 293Mt CO2-e/yr for GHG abatement was estimated, with 140 Mt of this potential being assessed as attainable with concerted efforts in technical and management changes, policy adjustment and shifts in current land management priorities. It must be recognised that these estimates contain a combination of biological, technical and implementation uncertainty.

This CSIRO report provides an in-depth assessment of the greenhouse gas (GHG) sequestration/mitigation potential likely to be achieved through change in rural land use and management, based on a review of current knowledge and consultation with a cross-section of scientists and land management experts. The focus is on Queensland but in most instances national potential is also estimated. The report revisits the Garnaut Review (2008) estimates1 for terrestrial greenhouse gas sequestration – in more detail, with a discussion of implementation issues, risks and interactions between options. The review was requested by the Queensland Premier’s Council on Climate Change – as a technical input to policy development. The report confi rms that there are a wide variety of options for sequestering or mitigating GHG emissions through changed land use and management; the options studied were based on the Garnaut Review categories with some changes in defi nition and emphasis. This report demonstrates that Australia has the opportunity to offset a signifi cant proportion of our GHG emissions, by storing carbon in the landscape and changing the emissions profile from rural land use. Thus, the broad thrust of the Garnaut Review is supported – within Queensland an overall technical potential of 293Mt CO2-e/yr for GHG abatement was estimated, with 140 Mt of this potential being assessed as attainable with concerted efforts in technical and management changes, policy adjustment and shifts in current land management priorities. It must be recognised that these estimates contain a combination of biological, technical and implementation uncertainty.

This CSIRO report provides an in-depth assessment of the greenhouse gas (GHG) sequestration/mitigation potential likely to be achieved through change in rural land use and management, based on a review of current knowledge and consultation with a cross-section of scientists and land management experts. The focus is on Queensland but in most instances national potential is also estimated. The report revisits the Garnaut Review (2008) estimates1 for terrestrial greenhouse gas sequestration – in more detail, with a discussion of implementation issues, risks and interactions between options. The review was requested by the Queensland Premier’s Council on Climate Change – as a technical input to policy development. The report confi rms that there are a wide variety of options for sequestering or mitigating GHG emissions through changed land use and management; the options studied were based on the Garnaut Review categories with some changes in defi nition and emphasis. This report demonstrates that Australia has the opportunity to offset a signifi cant proportion of our GHG emissions, by storing carbon in the landscape and changing the emissions profile from rural land use. Thus, the broad thrust of the Garnaut Review is supported – within Queensland an overall technical potential of 293Mt CO2-e/yr for GHG abatement was estimated, with 140 Mt of this potential being assessed as attainable with concerted efforts in technical and management changes, policy adjustment and shifts in current land management priorities. It must be recognised that these estimates contain a combination of biological, technical and implementation uncertainty.

Merino sheep representing a range of bloodlines in resource flocks located across Australia were tested for resistance to gastro-intestinal nematodes. These flocks included the JB Pye Flock (Camden, NSW), Katanning Base Flock (Katanning, WA), Turretfield Merino Resource Flock (Rosedale, SA), and the CSIRO Finewool Flock (Armidale, NSW) and included a total of 328 sire groups. Resistance to nematodes was measured by faecal egg count (FEC). Data were also available for greasy and clean fleece weight (GFW and CFW, respectively), fibre diameter (FD), and body weight (BW) at a range of ages from weaning to 21 months. Variance components were estimated by restricted maximum likelihood, fitting an animal model and estimating covariances in a series of bivariate analyses. Phenotypic correlations between FEC0·33 and production traits were all close to zero ( –0·09–0·02). Genetic correlations between FEC0·33 and production traits were –0·20, –0·18, and –0·26 for weaning weight, 10-month BW, and 16-month BW, respectively; 0·21, –0·06, and 0·21 for 10-month GFW, 16-month GFW, and 21-month GFW; 0·21, –0·05, and 0·07 for 10-month CFW, 16-month CFW, and 21-month CFW; and –0·09, –0·12, and 0·04 for 10-month FD, 16-month FD, and 21-month FD. When estimates were pooled for all fleece traits and all BW traits, the genetic correlations between FEC0·33 and GFW, CFW, FD, and BW were 0·15, 0·10, –0·06, and –0·21, respectively. Using pooled estimates for CFW, FD, and BW, selection for a breeding objective based on production traits alone would lead to an unfavourable correlated response in FEC0·33 of approximately 1% per year.

Merino sheep representing a range of bloodlines in resource flocks located across Australia were tested for resistance to gastro-intestinal nematodes. These flocks included the JB Pye Flock (Camden, NSW), Katanning Base Flock (Katanning, WA), Turretfield Merino Resource Flock (Rosedale, SA), and the CSIRO Finewool Flock (Armidale, NSW) and included a total of 328 sire groups. Resistance to nematodes was measured by faecal egg count (FEC). Data were also available for greasy and clean fleece weight (GFW and CFW, respectively), fibre diameter (FD), and body weight (BW) at a range of ages from weaning to 21 months. Variance components were estimated by restricted maximum likelihood, fitting an animal model and estimating covariances in a series of bivariate analyses. Phenotypic correlations between FEC0·33 and production traits were all close to zero ( –0·09–0·02). Genetic correlations between FEC0·33 and production traits were –0·20, –0·18, and –0·26 for weaning weight, 10-month BW, and 16-month BW, respectively; 0·21, –0·06, and 0·21 for 10-month GFW, 16-month GFW, and 21-month GFW; 0·21, –0·05, and 0·07 for 10-month CFW, 16-month CFW, and 21-month CFW; and –0·09, –0·12, and 0·04 for 10-month FD, 16-month FD, and 21-month FD. When estimates were pooled for all fleece traits and all BW traits, the genetic correlations between FEC0·33 and GFW, CFW, FD, and BW were 0·15, 0·10, –0·06, and –0·21, respectively. Using pooled estimates for CFW, FD, and BW, selection for a breeding objective based on production traits alone would lead to an unfavourable correlated response in FEC0·33 of approximately 1% per year.

Merino sheep representing a range of bloodlines in resource flocks located across Australia were tested for resistance to gastro-intestinal nematodes. These flocks included the JB Pye Flock (Camden, NSW), Katanning Base Flock (Katanning, WA), Turretfield Merino Resource Flock (Rosedale, SA), and the CSIRO Finewool Flock (Armidale, NSW) and included a total of 328 sire groups. Resistance to nematodes was measured by faecal egg count (FEC). Data were also available for greasy and clean fleece weight (GFW and CFW, respectively), fibre diameter (FD), and body weight (BW) at a range of ages from weaning to 21 months. Variance components were estimated by restricted maximum likelihood, fitting an animal model and estimating covariances in a series of bivariate analyses. Phenotypic correlations between FEC0·33 and production traits were all close to zero ( –0·09–0·02). Genetic correlations between FEC0·33 and production traits were –0·20, –0·18, and –0·26 for weaning weight, 10-month BW, and 16-month BW, respectively; 0·21, –0·06, and 0·21 for 10-month GFW, 16-month GFW, and 21-month GFW; 0·21, –0·05, and 0·07 for 10-month CFW, 16-month CFW, and 21-month CFW; and –0·09, –0·12, and 0·04 for 10-month FD, 16-month FD, and 21-month FD. When estimates were pooled for all fleece traits and all BW traits, the genetic correlations between FEC0·33 and GFW, CFW, FD, and BW were 0·15, 0·10, –0·06, and –0·21, respectively. Using pooled estimates for CFW, FD, and BW, selection for a breeding objective based on production traits alone would lead to an unfavourable correlated response in FEC0·33 of approximately 1% per year.

Merino sheep representing a range of bloodlines in resource flocks located across Australia were tested for resistance to gastro-intestinal nematodes. These flocks included the JB Pye Flock (Camden, NSW), Katanning Base Flock (Katanning, WA), Turretfield Merino Resource Flock (Rosedale, SA), and the CSIRO Finewool Flock (Armidale, NSW) and included a total of 328 sire groups. Resistance to nematodes was measured by faecal egg count (FEC). Data were also available for greasy and clean fleece weight (GFW and CFW, respectively), fibre diameter (FD), and body weight (BW) at a range of ages from weaning to 21 months. Variance components were estimated by restricted maximum likelihood, fitting an animal model and estimating covariances in a series of bivariate analyses. Phenotypic correlations between FEC0·33 and production traits were all close to zero ( –0·09–0·02). Genetic correlations between FEC0·33 and production traits were –0·20, –0·18, and –0·26 for weaning weight, 10-month BW, and 16-month BW, respectively; 0·21, –0·06, and 0·21 for 10-month GFW, 16-month GFW, and 21-month GFW; 0·21, –0·05, and 0·07 for 10-month CFW, 16-month CFW, and 21-month CFW; and –0·09, –0·12, and 0·04 for 10-month FD, 16-month FD, and 21-month FD. When estimates were pooled for all fleece traits and all BW traits, the genetic correlations between FEC0·33 and GFW, CFW, FD, and BW were 0·15, 0·10, –0·06, and –0·21, respectively. Using pooled estimates for CFW, FD, and BW, selection for a breeding objective based on production traits alone would lead to an unfavourable correlated response in FEC0·33 of approximately 1% per year.

Merino sheep representing a range of bloodlines in resource flocks located across Australia were tested for resistance to gastro-intestinal nematodes. These flocks included the JB Pye Flock (Camden, NSW), Katanning Base Flock (Katanning, WA), Turretfield Merino Resource Flock (Rosedale, SA), and the CSIRO Finewool Flock (Armidale, NSW) and included a total of 328 sire groups. Resistance to nematodes was measured by faecal egg count (FEC). Data were also available for greasy and clean fleece weight (GFW and CFW, respectively), fibre diameter (FD), and body weight (BW) at a range of ages from weaning to 21 months. Variance components were estimated by restricted maximum likelihood, fitting an animal model and estimating covariances in a series of bivariate analyses. Phenotypic correlations between FEC0·33 and production traits were all close to zero ( –0·09–0·02). Genetic correlations between FEC0·33 and production traits were –0·20, –0·18, and –0·26 for weaning weight, 10-month BW, and 16-month BW, respectively; 0·21, –0·06, and 0·21 for 10-month GFW, 16-month GFW, and 21-month GFW; 0·21, –0·05, and 0·07 for 10-month CFW, 16-month CFW, and 21-month CFW; and –0·09, –0·12, and 0·04 for 10-month FD, 16-month FD, and 21-month FD. When estimates were pooled for all fleece traits and all BW traits, the genetic correlations between FEC0·33 and GFW, CFW, FD, and BW were 0·15, 0·10, –0·06, and –0·21, respectively. Using pooled estimates for CFW, FD, and BW, selection for a breeding objective based on production traits alone would lead to an unfavourable correlated response in FEC0·33 of approximately 1% per year.

Merino sheep representing a range of bloodlines in resource flocks located across Australia were tested for resistance to gastro-intestinal nematodes. These flocks included the JB Pye Flock (Camden, NSW), Katanning Base Flock (Katanning, WA), Turretfield Merino Resource Flock (Rosedale, SA), and the CSIRO Finewool Flock (Armidale, NSW) and included a total of 328 sire groups. Resistance to nematodes was measured by faecal egg count (FEC). Data were also available for greasy and clean fleece weight (GFW and CFW, respectively), fibre diameter (FD), and body weight (BW) at a range of ages from weaning to 21 months. Variance components were estimated by restricted maximum likelihood, fitting an animal model and estimating covariances in a series of bivariate analyses. Phenotypic correlations between FEC0·33 and production traits were all close to zero ( –0·09–0·02). Genetic correlations between FEC0·33 and production traits were –0·20, –0·18, and –0·26 for weaning weight, 10-month BW, and 16-month BW, respectively; 0·21, –0·06, and 0·21 for 10-month GFW, 16-month GFW, and 21-month GFW; 0·21, –0·05, and 0·07 for 10-month CFW, 16-month CFW, and 21-month CFW; and –0·09, –0·12, and 0·04 for 10-month FD, 16-month FD, and 21-month FD. When estimates were pooled for all fleece traits and all BW traits, the genetic correlations between FEC0·33 and GFW, CFW, FD, and BW were 0·15, 0·10, –0·06, and –0·21, respectively. Using pooled estimates for CFW, FD, and BW, selection for a breeding objective based on production traits alone would lead to an unfavourable correlated response in FEC0·33 of approximately 1% per year.

Merino sheep representing a range of bloodlines in resource flocks located across Australia were tested for resistance to gastro-intestinal nematodes. These flocks included the JB Pye Flock (Camden, NSW), Katanning Base Flock (Katanning, WA), Turretfield Merino Resource Flock (Rosedale, SA), CSIRO Finewool Flock (Armidale, NSW), and the Trangie D Flock (Trangie, NSW). Faecal egg count (FEC) was used to measure relative resistance of sheep to nematode parasites after either natural or artificial infection with Haemonchus contortus and Trichostrongylus colubriformis. Differences in FEC 0' 33 between strains and between and within bloodlines were examined and the heritability of this trait was estimated. A low proportion of the total variation in parasite resistance could be attributed to strain and bloodline effects (1 and 3.5%, respectively) after either natural or artificial infection. The major source of genetic variation was found within bloodlines (22.2% of total variation), with individual sires showing a wide range in parasite resistance. Paternal half-sib heritability estimates for FEC 0' 33 were significant (P < 0.05) in 9 of the 11 analyses and ranged from 0.07 to 0.42, with a weighted average of 0.22. The influence of the environmental effects of sex, age of dam, birth-rearing rank, and day of birth were also investigated, and were found to be only occasionally significant, accounting for a small proportion (0.3-2.2%) of variation. Management group effects both prior to and at the time of measurement were often significant, and accounted for 2.2-19.4% of variation in FEC. Correction of FEC for effects other than management group would seem to add little to precision of selection. These results have demonstrated that significant genetic variation for nematode parasite resistance exists within a wide range of Merino bloodlines, and within-flock selection of resistant sires appears to be an effective method of improving this trait in Merino sheep.

Merino sheep representing a range of bloodlines in resource flocks located across Australia were tested for resistance to gastro-intestinal nematodes. These flocks included the JB Pye Flock (Camden, NSW), Katanning Base Flock (Katanning, WA), Turretfield Merino Resource Flock (Rosedale, SA), CSIRO Finewool Flock (Armidale, NSW), and the Trangie D Flock (Trangie, NSW). Faecal egg count (FEC) was used to measure relative resistance of sheep to nematode parasites after either natural or artificial infection with Haemonchus contortus and Trichostrongylus colubriformis. Differences in FEC 0' 33 between strains and between and within bloodlines were examined and the heritability of this trait was estimated. A low proportion of the total variation in parasite resistance could be attributed to strain and bloodline effects (1 and 3.5%, respectively) after either natural or artificial infection. The major source of genetic variation was found within bloodlines (22.2% of total variation), with individual sires showing a wide range in parasite resistance. Paternal half-sib heritability estimates for FEC 0' 33 were significant (P < 0.05) in 9 of the 11 analyses and ranged from 0.07 to 0.42, with a weighted average of 0.22. The influence of the environmental effects of sex, age of dam, birth-rearing rank, and day of birth were also investigated, and were found to be only occasionally significant, accounting for a small proportion (0.3-2.2%) of variation. Management group effects both prior to and at the time of measurement were often significant, and accounted for 2.2-19.4% of variation in FEC. Correction of FEC for effects other than management group would seem to add little to precision of selection. These results have demonstrated that significant genetic variation for nematode parasite resistance exists within a wide range of Merino bloodlines, and within-flock selection of resistant sires appears to be an effective method of improving this trait in Merino sheep.

Merino sheep representing a range of bloodlines in resource flocks located across Australia were tested for resistance to gastro-intestinal nematodes. These flocks included the JB Pye Flock (Camden, NSW), Katanning Base Flock (Katanning, WA), Turretfield Merino Resource Flock (Rosedale, SA), CSIRO Finewool Flock (Armidale, NSW), and the Trangie D Flock (Trangie, NSW). Faecal egg count (FEC) was used to measure relative resistance of sheep to nematode parasites after either natural or artificial infection with Haemonchus contortus and Trichostrongylus colubriformis. Differences in FEC 0' 33 between strains and between and within bloodlines were examined and the heritability of this trait was estimated. A low proportion of the total variation in parasite resistance could be attributed to strain and bloodline effects (1 and 3.5%, respectively) after either natural or artificial infection. The major source of genetic variation was found within bloodlines (22.2% of total variation), with individual sires showing a wide range in parasite resistance. Paternal half-sib heritability estimates for FEC 0' 33 were significant (P < 0.05) in 9 of the 11 analyses and ranged from 0.07 to 0.42, with a weighted average of 0.22. The influence of the environmental effects of sex, age of dam, birth-rearing rank, and day of birth were also investigated, and were found to be only occasionally significant, accounting for a small proportion (0.3-2.2%) of variation. Management group effects both prior to and at the time of measurement were often significant, and accounted for 2.2-19.4% of variation in FEC. Correction of FEC for effects other than management group would seem to add little to precision of selection. These results have demonstrated that significant genetic variation for nematode parasite resistance exists within a wide range of Merino bloodlines, and within-flock selection of resistant sires appears to be an effective method of improving this trait in Merino sheep.

Merino sheep representing a range of bloodlines in resource flocks located across Australia were tested for resistance to gastro-intestinal nematodes. These flocks included the JB Pye Flock (Camden, NSW), Katanning Base Flock (Katanning, WA), Turretfield Merino Resource Flock (Rosedale, SA), CSIRO Finewool Flock (Armidale, NSW), and the Trangie D Flock (Trangie, NSW). Faecal egg count (FEC) was used to measure relative resistance of sheep to nematode parasites after either natural or artificial infection with Haemonchus contortus and Trichostrongylus colubriformis. Differences in FEC 0' 33 between strains and between and within bloodlines were examined and the heritability of this trait was estimated. A low proportion of the total variation in parasite resistance could be attributed to strain and bloodline effects (1 and 3.5%, respectively) after either natural or artificial infection. The major source of genetic variation was found within bloodlines (22.2% of total variation), with individual sires showing a wide range in parasite resistance. Paternal half-sib heritability estimates for FEC 0' 33 were significant (P < 0.05) in 9 of the 11 analyses and ranged from 0.07 to 0.42, with a weighted average of 0.22. The influence of the environmental effects of sex, age of dam, birth-rearing rank, and day of birth were also investigated, and were found to be only occasionally significant, accounting for a small proportion (0.3-2.2%) of variation. Management group effects both prior to and at the time of measurement were often significant, and accounted for 2.2-19.4% of variation in FEC. Correction of FEC for effects other than management group would seem to add little to precision of selection. These results have demonstrated that significant genetic variation for nematode parasite resistance exists within a wide range of Merino bloodlines, and within-flock selection of resistant sires appears to be an effective method of improving this trait in Merino sheep.

Merino sheep representing a range of bloodlines in resource flocks located across Australia were tested for resistance to gastro-intestinal nematodes. These flocks included the JB Pye Flock (Camden, NSW), Katanning Base Flock (Katanning, WA), Turretfield Merino Resource Flock (Rosedale, SA), CSIRO Finewool Flock (Armidale, NSW), and the Trangie D Flock (Trangie, NSW). Faecal egg count (FEC) was used to measure relative resistance of sheep to nematode parasites after either natural or artificial infection with Haemonchus contortus and Trichostrongylus colubriformis. Differences in FEC 0' 33 between strains and between and within bloodlines were examined and the heritability of this trait was estimated. A low proportion of the total variation in parasite resistance could be attributed to strain and bloodline effects (1 and 3.5%, respectively) after either natural or artificial infection. The major source of genetic variation was found within bloodlines (22.2% of total variation), with individual sires showing a wide range in parasite resistance. Paternal half-sib heritability estimates for FEC 0' 33 were significant (P < 0.05) in 9 of the 11 analyses and ranged from 0.07 to 0.42, with a weighted average of 0.22. The influence of the environmental effects of sex, age of dam, birth-rearing rank, and day of birth were also investigated, and were found to be only occasionally significant, accounting for a small proportion (0.3-2.2%) of variation. Management group effects both prior to and at the time of measurement were often significant, and accounted for 2.2-19.4% of variation in FEC. Correction of FEC for effects other than management group would seem to add little to precision of selection. These results have demonstrated that significant genetic variation for nematode parasite resistance exists within a wide range of Merino bloodlines, and within-flock selection of resistant sires appears to be an effective method of improving this trait in Merino sheep.