Effects of gastrointestinal cannulation and jugular vein catheterization on the metabolism of sheep.

1. Certain digestive and metabolic criteria were examined in mature wethers before and following (1) a simple exploratory laporotomy (two sheep), (2) establishment of a rumen cannula plus simple ('T'-shaped) cannulas in the duodenum and ileum (six sheep), (3) establishment of a rumen cannula plus two cannulas in the caecum (four sheep), (4) establishment of a rumen cannula plus re-entrant cannulas in the duodenum and ileum (four sheep) and (5) insertion of catheters into both external jugular veins (four sheep). 2. Metabolizability of a standard ration and nitrogen balance and rumen retention time of the sheep were not significantly changed by any of the surgical procedures carried out. 3. The amount of heat produced per unit metabolic weight of the sheep prepared with re-entrant cannulas increased significantly (21 +/- 5.6%; P less than 0.001). 4. The use of the different preparations in digestive and metabolic studies is discussed.