The study investigated the effect of gastrointestinal passage in pigs on free-living stages of bovine nematodes. Two Landrace x Yorkshire pigs, A and B, were fed fresh eggs of Ostertagia ostertagi and Cooperia oncophora while two other pigs, C and D, were fed third stage larvae (L3) of the same parasites. Faeces from the pigs were collected for 48 h after ingestion. In pigs A and B, 15 and 66% of the eggs were recovered after passage, respectively. However, only 0.003 and 0.002% of the ingested eggs developed into third stage larvae (L3) after subsequent culturing. In pigs C and D, 0.01 and 0.02% of the L3 survived the passage of the gastrointestinal tract. Fresh O. ostertagi and C. oncophora eggs were cultured in parasite free porcine and bovine faeces. Only 0.05% L3 developed in porcine faeces, whereas 21% of the eggs developed into L3 in the bovine culture. Our results demonstrate an extremely poor rate of development and survival of both bovine nematode eggs and infective larvae after passage in pigs. It may imply that pigs can play an important role in reducing transmission of cattle nematodes if the two species are grazed together or alternately.