The effects of intravenous infusions of triglycerides on the composition of milk fat in the sow

Abstract

I .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.Studies of arteriovenous differences across the mammary glands of lactating sows (Linzell, Mepham, Annison & West, 1969; Spincer, Rook & Towers, 1969) have demonstrated an uptake of triglyceride fatty acids, which are incorporated largely into the triglycerides of milk fat (J. Spincer & J. A. F. Rook, unpublished). The fatty acids principally involved are palmitic, stearic and oleic, the major fatty acids of the plasma triglycerides. The present experiments were undertaken to study the extent to which these and other fatty acids are transferred to milk fat when infused as triglycerides into the blood plasma.Pharmacological and toxicological side-effects have been reported in a number of animal species following the infusion of vegetable oils in combination with a range of emulsifiers, but Schuberth & Wretlind (1961) found emulsions of soya-bean oil with egg phosphatides to be free of such effects. Emulsions with egg phosphatides of tripropionin, tricaproin, tricaprylin, tripelargonin, tricaprin, trilaurin and triolein (Storry, Tuckley & Hall, 1969) Animals and their management. Lactating Wessex/Landrace/Large White sows with piglets were taken as required from the University herd. Sows were confined in a holding crate and piglets to a separate pen. Suckling was permitted at 1.5 h intervals. Meal (5.5 kg/head per day) was offered to the sows twice daily and there was free access to water. ...

The influence of the amount and nature of dietary fat on milk fat composition in the sow

“…A similar, limited response in milk fat to changes in plasma triglyceride composition was apparent for myristic and capric acids during the feeding of coconut oil. As in the experiments in which artificial emulsions were infused intravenously (Witter et al 1970), an increase in the plasma triglycerides of palmitic acid was associated with an increased output in milk triglycerides not only of palmitic acid but also of palmitoleic acid, owing to the presence in sow mammary tissue of a desaturase system (Bickerstaffe & Annison, 1968).…”

“…The changes in the plasma triglyceride fatty acids were not, however, accompanied by similar changes in the plasma free fatty acids, through which the changes would be expected to be mediated. The observed effects of dietary fat composition on milk fat composition can be explained largely in terms of the associated changes in the fatty acid make-up of the plasma triglycerides and the responses to such changes observed in experiments in which artificial emulsions were infused intravenously (Witter et al 1970); of the major added acids, the main exception was lauric acid during the feeding of coconut oil when an increase of lauric acid in the plasma triglycerides of 12% was associated with an increase of that acid in milk fat of 4 %, a proportionately much smaller response than that observed following the intravenous infusion of trilaurin (Witter et al 1970). A similar, limited response in milk fat to changes in plasma triglyceride composition was apparent for myristic and capric acids during the feeding of coconut oil.…”