Rumen and Abomasal Cannulation of Sheep with Specially Designed Cannulas and a Cannula Insertion Instrument

Abstract

Rumen and abomasal cannulas for sheep and an instrument that facilitates rapid insertion of the cannulas were developed. The cannulas were made from epoxy-filled polyurethane and were supported by outer support rings held in place by nuts screwed onto the threaded tops of the cannula barrels. The insertion device was used to pull the cannula through a separately made incision in the abdominal wall and to stretch the skin and other tissues over a cone and onto the barrel of the cannula, thus ensuring a tight fit and the formation of a ring of scar tissue that virtually eliminated digesta leakage. Expansion plugs, used to seal the cannulas, were designed to eliminate a twisting force that could be transferred to the cannula when the plugs were secured or released. The plugs were also designed to protrude minimally from the side of the animal. More than 75 sheep were cannulated, and the preparations proved to be relatively maintenance free and resistant to mechanical disturbance by the animal. The cannulas had a long functional life and permitted convenient sampling of digesta and introduction of liquid and solid materials, including digestion bags.