title: On the development of gastrointestinal parasitism in bovine yearlings.
abstract: A comparative study on the development of Osteragia Ostertagi, Cooperia oncophora and Nematodirus helvetianus in 15-month-old yearlings and three-month-old calves demonstrated that yearlings have considerably greater resistance to gastrointestinal parasitism than calves. This was manifested by the establishment of smaller worm burdens, marked stunting of worms and a markedly lower worm egg output in the yearlings. The characteristic marked rise in egg counts observed in calves a few weeks after exposure to a heavy gastro-intestinal parasite infection did not occur in the yearlings. It was concluded that fecal examinations have a limited usefulness as a reliable aid to diagnosis of gastrointestinal parasitism in older cattle.
mesh_terms: D000367:Age Factors; D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000175:diagnosis / Q000276:immunology; D005243:Feces / Q000382:microbiology; D005767:Gastrointestinal Diseases / Q000276:immunology / Q000662:veterinary*; D007410:Intestinal Diseases / Q000276:immunology; D007411:Intestinal Diseases, Parasitic / Q000662:veterinary; D009349:Nematode Infections / Q000175:diagnosis / Q000662:veterinary*; D014252:Trichostrongyloidiasis / Q000175:diagnosis / Q000662:veterinary*