The intestinal and hepatic contributions to the flow and composition of thoracic duct lymph in young milk-fed calves.

Abstract

The establishment of recirculating lymphatico‐venous shunts permitted the repeated collection of lymph from either the thoracic or intestinal duct in healthy calves. Hepatic lymph was also collected from calves with lymphatic fistulæ. The operations were carried out on calves in the first week of life.The mean flow of thoracic duct lymph from four calves was 9·73 ml./kg./hr., of intestinal lymph from three calves 8·25 ml./kg./hr. and of hepatic lymph from two calves 0·64 ml./kg./hr. During the experiment the calves were fed 2·27 litres (0·5 gal.) of cow's milk twice daily. The mean protein concentration of lymph from the thoracic, intestinal and hepatic ducts was 56·5, 56·7 and 80·6 per cent, respectively, of the plasma levels. Thus the intestinal lymph contributed most of the volume of lymph and output of protein from the thoracic duct. It was estimated that 275 and 330 per cent of the volume and 155 and 190 per cent of the total protein of the blood plasma compartment passed through the intestinal and thoracic ducts, respectively, in a 24‐hr. period.There was a rapid transfer of T‐1824‐labelled albumin from plasma into intestinal and hepatic lymph in the young calf. Equilibration of the specific activity curves for plasma and for intestinal and hepatic lymph occurred within 100 min. after the injection of the T‐1824.The lipid composition of intestinal lymph was found to be very similar to that of thoracic duct lymph. The concentrations of triglyceride and free fatty acid in hepatic lymph were 350 and 170 per cent, respectively, of those in plasma. It is suggested that a triglyceride‐rich component and free fatty acid were released from the liver into the hepatic lymph.The high flow and output of protein from the intestinal duct may be related to the absorption of large quantities of fat in young milk‐fed calves.