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Genetic parameters of tick-infestation on lambs of the Norwegian White Sheep breed
Sheep farmers in Norway experience an increase in lamb loss on range pasture during the last decades. It is proposed that one reason for this increase in lamb loss in coastal areas is due to tick-borne fever (TBF) caused by A. phagocytophilum infection transmitted by the tick Ixodes ricinus. Within breed variation in response to an A. phagocytophilum infection suggest that genetic variation is present. Here genetic parameters of tick-count on lambs are estimated using data on 555 lambs of the Norwegian White Sheep breed from 6 different farms and a 10-generation pedigree. Results suggest that heritability for tick-count among Norwegian White Sheep was moderate to high and that tick-load may be reduced by selective breeding. The heritability estimates presented in this study may however be inflated. Further, the relationship between tick-count and robustness to TBF need further investigation and verification.
Keywords:
sheep
ticks
robustness
