A method for studying interbreeding of nematodes of the subfamily Ostertagiinae in sheep with abomasal fistulae.

Interbreeding in two nematode species, Teladorsagia circumcincta and Ostertagia leptospicularis, was studied in lambs using small populations. Offspring from a single mated female were investigated for T. circumcincta. The following protocol was found to be satisfactory for small populations: virgin females and adult males were obtained from donor lambs infected artificially and transferred into the abomasa of fistulated sheep or lambs being treated with a long-acting corticosteroid. Infective larvae obtained from cultures of faeces of fistulated sheep were given to a recipient lamb and when this animal was slaughtered it was possible to examine the adult nematodes resulting from the interbreeding. Interbreeding between one male and one female was not successful while there was limited recovery of infective larvae from the implantation of a single mated female.