The Genetic resistence to Coccidia in Appenninica sheep

The research confirms that differences between young and adult animals exist; adult subjects appear more resistant to Coccidia but more susceptible to the other parasites: adult females of the resistant group are more resistant to Coccidia and to Dicrocoelium compared with the subject of the not resistant group, though less resistant to Strongylids. Sheep selection may be based on OPG in adult animals, as it appears to be an indicator of sheep resistance to Coccidia. This may be used as a long-term parasite control method especially under production system where the use of drugs is not allowed or limited. Before incorporating the parameter into breeding programmes, however it is necessary to better appraise the degree of infestation of the other parasites as it may be difficult to select simultaneously for resistance to Coccidia and Strongylids unless the genetic correlation between these two traits is calculated and a selection index approach is used.