Kurzbeschreibung
(Englisch)
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Gastrointestinal nematodes (GIN) substantially impact on the health of sheep and goats. The control of these parasites is based on treatment with synthetic drugs (anthelmintics). In recent years the development of GIN resistant to anthelmintics has given a strong impetus on the development of alternative control strategies. Breeding for animals with enhanced resis-tance to GIN has been one of the intensively followed strategies, particularly in Australia and New Zealand. In these coun-tries large selection programs in sheep successfully managed to select animals with increased genetic resistance to GIN and have led to the formulation of breeding values for GIN resistance. Compared to sheep, the progress with respect to breeding for GIN resistance for various reasons has been much slower in goats. Data on heritabilities of potential traits for selection and their genetic correlation to production traits is limited. However, recent studies with goats have reported promising results with respect to the feasibility of breeding GIN resistant goats. The proposed research aims at generating (i) high quality heritability estimates of different phenotypic traits for GIN resis-tance in Swiss goat breeds, (ii) data on the genetic correlation between selection and production traits (milk) and (iii) will propose an efficient way to incorporate selection against GIN infection into the breeding scheme of the goat breeds con-sidered.
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Partner und Internationale Organisationen
(Englisch)
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BE, CH, DE, DK, ES, FR, GR, HR, HU, IL, IT, LT, MK, NO, PT, RO, RS, SE, SK UK
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Abstract
(Englisch)
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Based on the average genetic relationship between animals, their exposure to gastro-intestinal nematodes and the geographical location of the farms, 20 herds of Saanen and Swiss Alpine Goats were ascertained to the present study comprising 2974 phenotypes for faecal egg count per gram of faeces (FEC), 2961 FAMACHA scores and 2937 phenotypes for packed cell volume (PCV) recorded on 1585 animals. Lactation and test day yields of all animals were available for milk, fat and protein. Birth and litter dates, breed and number of lactation were available from the Swiss Goat Breeding Association. The pedigree consisted of 10043 animals. FEC was power-transformed using FECtrans = (FEC+1)^0.36. The dependent variables FECtrans, FAMACHA, PCV and milk yield were modeled using multivariate linear models with fixed effects of breed, season, sex, type of anthelmintic, efficacy of anthelmintic and age. Breed was fitted as genetic group, i.e. each animal got its appropriate breed proportion included in the model. Random effects fitted in all models were animal, herd and permanent environment. In some models milk yield of the lactation was considered as an additional fixed effect divided into classes of <200 kg, 200-300kg, …, >500kg. Lactation stage was used as month in milk. All models consistently revealed an estimated heritability for FECtrans, FAMACHA and PCV of 0.08, 0.24 and 0.23 with genetic correlations between FECtrans and FAMACHA close to zero, FECtrans and PCV of -0.3 and FAMACHA and PCV of -0.6. When milk yield was considered as dependent variable, genetic correlation of FECtrans to test day milk yield was 0.4 and dropped to 0.1, when lactation milk yield was considered. Genetic correlations of Milk yield with FAMACHA score were low, irrespective whether lactation or test day yield was considered whereas correlation to PCV where -0.3 for test day milk yield and even slightly higher when lactation yield was considered. Results imply that selection for resistance to gastrointestinal nematodes is possible. However, from the findings in this study, FAMACHA and PCV are not suitable as proxy traits for FECtrans. This implies that a selection program for resistance to gastro-intestinal nematodes will have to rely on relatively expensive measurements of FEC. Thus, emphasis should be put on progeny testing of sires, where additionally sires get their own FEC recorded on testing stations plus that of some of their daughters. It seems advantageous if those measurements would be to initiated on the males through predefined challenging schemes at the testing station.
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