1. Emulsions with egg phosphatides of nine synthetic triglycerides (tributyrin, tricaprylin, tripelargonin, tricaprin, trilaurin, trimyristin, tripahitin, triisostearin, triolein) and of rapeseed oil and a proprietary emulsion of cottonseed oil were given as continuous infusions into the jugular vein of lactating sows. The effects of the infusions on the concentration and composition of blood plasma lipids and on the composition of milk fat were determined.
2. The infusions did not affect the concentrations in blood plasma of cholesterol, phospholipid or cholesterol esters, but there was a tendency for the concentration of plasma triglycerides to be increased which was most pronounced for the infusions of longer-chain triglycerides. The fatty acid composition of the plasma triglycerides was not altered by the infusion of tributyrin, except that there was an increase in the content of oleic and a decrease in that of linoleic acid. With other infusions the composition of the plasma triglycerides was altered towards that of the infused material and the effect was more marked for the longer-chain triglycerides, with the exception of triisostearin.
3. The changes in the composition of the milk fat reflected those in the composition of plasma triglycerides, with two exceptions. The infusion of tripalmitin was associated with an increase not only in the palmitic acid content of milk fat but also in the palmitoleic acid content. Also, the changes in the content in milk fat of eicosenoic acid and, more especially of erucic acid during the infusion of rapeseed oil were much less than the corresponding changes in the plasma triglycerides.