Who is the report targeted at?
The report is targeted primarily at geneticists and animal breeders in the fibre goat industry. It is also targeted at policy makers within the industry. Parasitologists servicing the goat industry will also find the information in this report useful.

Background
At the time this project commenced there was emerging evidence from overseas studies of genetic variation in resistance to GIN in goats that could be exploited to select for resistance to infection. No such information was present for Australian goats. At that point the sheep industry had made considerable progress in describing the genetic component of resistance to infection and incorporating this trait in breeding programs. The goat industry has lagged behind in this, both because of less use of industry-wide performance recording schemes (eg. Sheep Genetics Australia) and also because the genetic parameters for resistance traits, and their association with production traits had not been defined in Australian goat breeds. Successful incorporation of genetic resistance to gastro-intestinal helminth infection in goats could result in reduced anthelmintic (drench) usage and concurrent reduction in the selection pressure for anthelmintic resistance, and improved efficiency of fibre production.

Aims/Objectives
The major aims of the project were as follows:

• to obtain genetic parameter estimates for worm resistance traits and production traits in Australian Cashmere and Angora goats, and phenotypic and genetic correlations amongst them;
• to develop a DNA marker set for parentage analysis and to have the quantitative genetic analysis based on DNA verified pedigrees;
• to provide an evaluation of potential markers for worm infection or resistance in goats other than faecal worm egg count (WEC);
• to evaluate the use of irradiated larval vaccines for control of worm infections in goats; and
• to obtain new information on the effects of worm infections in goats of the two breeds in the New England environment.

The beneficiaries of the project are likely to be geneticists, parasitologists and animal breeders in the fibre goat industry who have a new and comprehensive set of genetic parameter estimates for Angora and Cashmere goats under commercial Australian conditions. Ultimately goat producers themselves should be the beneficiaries as decision-making regarding breeding programs and parasite control is put on a more scientific footing.

Methods used
The project utilised one commercial Angora and one commercial Cashmere resource herd, both near Barraba in Northern NSW (Latitude 30.38° S; Longitude 150.61° E). In both herds does were mated in single sire groups in March/April. In the Angora herd does were regrouped into a single mob after joining and they kidded down as one mob. In the Cashmere herd, does were allocated to different “management groups” after joining and kidded down in these groups, each containing does mated to each of the sires used. Link sires were used across years to account for year effects. Both male and female kids were included in the analysis for Angora goats, but only female kids were included for cashmere goats. Kids were weighed, and had blood and faecal samples collected at 3 and 5 months of age after exposure to natural worm challenge from the pastures they were grazing. At the 5-month sampling the kids were treated with anthelmintic and a week later each kid was orally dosed with 10,000 infective larvae of Trichostrongylus colubriformis (black scour worm). Four weeks later the animals were again weighed, and had blood and faecal samples collected. A week after this, another faecal sample was collected and the animals were treated with anthelmintic to terminate the artificial challenge. Bodyweight and fleece data were collected at the first two annual shearings for Cashmere goats, and for the first 3 6-monthly shearings for Angora goats. For cashmere goats the project dataset included kids from the 2000, 2001, 2002 and 2003 kid drops, while for the Angora goats only the first 3 of these kid drops were included.

WEC was estimated using a modification of the standard McMaster technique, and fleece samples were tested for a range of fibre variables using the OFDA 100 after calibration with AWTO mohair tops. Blood samples were assessed for a wide range of haematological variables using a Cell Dyn® 3500 automated haematology analyser.

Pedigree assignment was tested using DNA tests (PCR) developed and validated by the project, using a set of 14 microsatellite markers. In total, 18 production and parasite associated traits were analysed to estimate (co) variance components, heritabilities and correlations. Where necessary data were transformed prior to analysis. Fixed effects were estimated using a sire model with sire fitted as a random effect. Estimation of variance components for the estimation of genetic parameters utilised four single-trait models fitting the animal as a random effect. Model 1 included significant fixed effects only; Model 2 added the direct additive effect of the animal; Model 3 added the with permanent environment effect of the dam and model 4 added the additive and permanent environmental effect of the animal itself. Genetic parameters were estimated from the model giving the best fit beyond which no further improvement occurred (mostly model 2).

Results and key findings
The project was successfully implemented but drought conditions in 2002, carrying over into 2003 resulted in very low levels of natural worm challenge of kids in these years. The main findings of the project are as follows:

• Both Angora and Cashmere goats are able to mount significant effective immune responses to worm infection by 5 months of age that are capable of limiting subsequent infections.
• Despite this, early vaccination at 1 and 2 months of age with bolus challenges of radiationattenuated infective worm larvae failed to induce a protective immune response.
• A DNA test for parentage analysis was developed and validated. The panel of microsatellite markers used provided a very high level of power (99.7%) of exclusion of non-true parents. The overall pedigree error rate of 12.7% was within the range reported for other species. As expected ascertaining the dam by mothering up at marking reduced dam pedigree accuracy only relative to mothering up at birth (14.6% and 9.8% error rate respectively).
• Heritability estimates for faecal worm egg count (WEC) were within the range of published estimates for other goat populations and were generally low (range 0.2-0.22), indicating that genetic progress for selection on this trait is likely to be low to moderate and somewhat lower than may be seen in sheep. This is particularly true if selection is based on phenotypic evaluation of sires (as is the case in much of the Cashmere industry). If however, progeny and other relative data is captured in industry performance recoding schemes such as MOPLAN, accurate EBVs can be calculated, even for traits of low heritability.
• Although the heritability estimates of some parasite-associated traits measure in blood were high or very high insufficient information is available to recommend selection based on these variables in the place of WEC. This is mainly due to the lack of estimable genetic correlations. For several of these variables this report contains the first estimates of heritability made for these variables in goats.
• The heritability estimates for liveweight and fleece traits for cashmere goats were mostly within the range of other published estimates, with moderate to high heritability for most traits. This indicates that rapid genetic progress can be made by genetic selection for these traits although a strong unfavourable genetic correlation between cashmere down weight and diameter requires that both traits be measured for optimum genetic progress.
• The heritability estimates for liveweight and fleece traits for Angora goats tended to be higher than most other published estimates. Once again this indicates that rapid genetic progress can be made by genetic selection for these traits although a strong unfavourable genetic correlation between fleece weight and mean fibre diameter requires that both traits be measured for optimum genetic progress.
• The project has produced the first genetic parameter estimates for the trait of fibre curvature in goats. The trait is moderately heritable in both breeds of goats and has a strong negative genetic correlation with fibre diameter suggesting that crimp frequency can be used as a marker for fibre diameter in both breeds of goat.
• Genetic associations between parasite-associated traits and production traits were non-estimable.

Phenotypic associations were in the expected directions for both breeds, and did not suggest that selection for parasite-associated traits would lead to negative effects on production traits.

Implications for relevant stakeholders
The major implications of this project are that it has provided an additional set of genetic parameter estimates for Australian Cashmere and Angora goats to complement those of Pattie and Restall (1991) and Gifford et al (1991) for cashmere goats, and Gifford et al (1989) for Angora goats. The parameter estimates were obtained in current commercial animals in commercial herds in typical goat production areas. For the first time, traits associated with worm infection and resistance to it were included in the analysis and the trait of fibre curvature was also included. Also for the first time the analysis was based up pedigree data validated by DNA testing. The findings support other studies in showing that rapid genetic progress can be made in selection for fleece traits and moderate progress for bodyweight.

Selection for resistance to worm infection is likely to result in slow genetic progress with no evidence of negative correlated responses in production traits.

The project has also developed and validated a panel of microsatellite markers that can be used for parentage analysis in goats. An attempt to control worm infections using early oral vaccination with radiation-attenuated larvae was unsuccessful and should not be pursued further.

Recommendations

• The inclusion of selection for resistance to worm infection on the basis of individual WEC measurements will result in slow genetic gains in this trait. Inclusion of the trait should only be considered where additional information from relatives would allow accurate estimates of EBV (eg. within MOPLAN). Selection for this trait based on sire measurements alone is unlikely to be worthwhile due to the low heritability. Inclusion of WEC in the selection index requires careful evaluation as not only will the response to selection be relatively slow, but applying significant selection differential to WEC will reduce the selection differential able to put on traits of high heritability and economic value such as fleece traits.
• Given the lack of estimable genetic correlations between WEC and production traits in this dataset, published values from overseas studies will need to be used. Based on such studies the genetic correlation between WEC and liveweight is not different from 0 but tending towards positive, that between WEC and fleece variables is weakly positive and that between WEC and PCV is moderately to strongly negative.
• Given environmental variation in the level of parasite challenge, individual tests of WEC should always be preceded by a bulk WEC test indicating significant worm burdens in the herd (eg. at least 500 epg in regions with Haemonchus contortus present).
• Given the moderate to very high heritabilities of some parasite-associated blood traits and the increasing availability of automated haematology analysis, support should be given to determining genetic correlations between these traits and WEC to more fully evaluate whether they are viable alternative measures of resistance and/or resilience to GIN. The physiological consequences of extreme values for blood constituents also need to be determined.
• Given the difficulty of using selection for genetic resistance to control worms, research emphasis should be applied to other control measures suitable for inclusion in an integrated worm control program in goats. Two approaches supported by the findings of this project are detailed below.
• The evidence in this study that immune regulation of worm burdens is related to the level of prior worm challenge indicates that parasite control methods that rely on maintaining some parasite burden in the host are more likely to be successful than those that totally suppress worm infections intermittently. Tactical worm control based upon close monitoring of WEC and treatment intervention only when the WEC exceeds a given threshold based on worm species involved, animal condition, feed availability and climatic conditions is likely to maintain immunity in the population and help regulate infections. Such an approach has been successfully used in sheep (Kahn et al., 2006; Scrivener et al., 2006).
• The marked year to year variation in worm burdens associated with drought conditions reinforces the susceptibility of the free-living stages of gastro-intestinal nematodes to adverse environmental conditions (Review: O’Connor et al., 2006) and our ability to exploit this weakness using grazing management practices such as alternate grazing with cattle (Southcott and Barger, 1975) and intensive rotational grazing (Colvin et al., 2007).
• Early oral vaccination of kids with bolus doses of irradiated worm larvae cannot be recommended as a practical worm control method and there is little evidence that it is likely to ever be so.
• The findings of this project would support the use of an on-farm measure of fibre curvature (eg.= “crimp” frequency) as an indirect measure of fibre fineness in both Angora and Cashmere goats.However full objective measurement in a laboratory will maximise genetic progress.
• The project results should be published in the scientific literature and be made widely available to industry.