Notes on necropsy and herbage processing techniques for gastrointestinal nematodes of ruminants

Abstract

Necropsy techniques for the digestive tract of ruminants used at the University of Utrecht differ from those used elsewhere in three respects: (1) the abomasum is opened immediately after slaughter and the "contents" are treated separately from the "washings"; (2) the first 10 m of the small intestine are treated separately from the remainder of the intestine; (3) the aliquots are coloured with iodine before being examined for worms. The majority of the worms are found in the washings of the abomasum and the first part of the small intestine, whereas the contents of the abomasum and the remainder of the small intestine contain the bulk of the digesta. Because inhibited stages of Ostertagia, Haemonchus and, particularly, the very small third stage larvae (L3) of Trichostrongylus can be overlooked easily in digesta, these methods imply a more rapid and accurate enumeration of worms. This is more important in small ruminants than in cattle because a much higher proportion of the inhibited larvae will be washed out of the mucosa and because Trichostrongylus is more important in small ruminants. Herbage sampling methods for monitoring gastrointestinal nematode infections on cattle pastures in northwest Europe should also be suitable for lungworm. The agar-bile technique of Jørgensen is an elegant method, but disadvantages are that many gastrointestinal nematode larvae exsheath, resulting in identification difficulties, and recovery of lungworm larvae decreases as a result of ageing. A simple sucrose flotation method, based on the principle that a sucrose solution does not mix easily with water containing nematodes, has been tested at our laboratory.(ABSTRACT TRUNCATED AT 250 WORDS)