A Durable Esophageal Cannula for Sheep and Goats

The esophageal fistula fitted with various types of cannulae provides a popular technique for estimating dietary constituents of range animals. Cannulae are continually being modified to minimize cost, weight, and animal stress, while maximizing efficiency and durability. Types of cannulae have been adequately described by Van Dyne and Ton-e11 (1964). Construction materials mentioned included latex, stainless steel, and lucite. Acrylic resin tubing and butyrate plastic also have been used, but these were easily broken (Veteto et al. 1972). Thus, stronger materials are desirable. Lesperance et al. ( 1974) reported a permanent cannula is neither necessary nor desirable due to reduced recovery of ingesta. Further, a permanent cannula may cause the development of a “pouch” anterior to the fistula (Van Dyne and Ton-e11 1964). However, the permanent cannula is advantageous because it minimizes animal stress, reduces the chances of the fistula closing upon removing the cannula for extended time periods, and increases the ease and efficiency in obtaining diet samples. Two construction materials for permanent cannulae are described in this paper and their advantages are enumerated.