Utilization Of Volatile Fatty Acids Research Articles

Metabolism of volatile fatty acids by liver and portal-drained viscera in sheep.

Metabolism of volatile fatty acids by liver and portal-drained viscera in sheep.

Utilization of volatile fatty acids in ruminants II. Comparison of the metabolism of acetate, propionate and butyrate when injected into the jugular vein, portal vein or the rumen

[1- 14C]Acetate, [1- 14C]propionate and [1- 14C]butyrate were administered to sheep and goats via the jugular vein, portal vein or added directly into the rumen in order to study the effect of route of administration on transfer of 14C to liver glycogen and various blood substrates. The data show that the extent to which 14C from [1- 14C]-acetate, [1- 14C]propionate or [1- 14C]butyrate is incorporated into blood glucose or liver glycogen depends on whether the acids are injected into the jugular vein or portal vein or added to the rumen. The work demonstrates that a tracer dose of [ 14C]butyrate injected into the jugular vein labels blood glucose more than [ 14C]acetate because of the higher specific activity of blood butyrate. When unlabeled butyrate is administered along with a tracer dose of [1- 14C]butyrate the specific activity of blood glucose is similar to that observed when acetate is administered. This glucogenic effect of butyrate that has been observed many times is an anomaly and is explained by the fact that a tracer dose of [1- 14C]butyrate injected into the jugular vein is not diluted with unlabeled butyrate because butyrate is not normally present in peripheral blood.

Utilization of volatile fatty acids in ruminants. 3. Comparison of mitochondrial acyl coenzyme A synthetase activity and substrate specificity in different tissues.

Utilization of volatile fatty acids in ruminants. 3. Comparison of mitochondrial acyl coenzyme A synthetase activity and substrate specificity in different tissues.

Use of radioactive microspheres to assess distribution of cardiac output in rabbits.

Use of radioactive microspheres to assess distribution of cardiac output in rabbits.

Absorption and Utilization of Volatile Fatty Acids by the Young Calf

Absorption and utilization of volatile fatty acids (VFA) by young milk-fed calves were studied using sodium salts of 14C-labeled acids. In two trials acetate was administered orally; in four later trials, either acetate, propionate, or n-butyrate was administered into the extreme terminal portion of the ileum via a re-entrant fistula, followed several hours later by the same acid administered orally. Radioactivity was measured in expired CO2, ileal digesta, feces and, in one experiment, blood.Radioactivity in blood of a week-old calf peaked 90min after acetate feeding. In two other acetate trials radioactivity in expired CO2, peaked 3 hr after feeding. Peak activity in expired CO2 appeared in 2 hr or less after ileal administration. Large amounts of the 14C were eliminated as 14CO2, primarily during the first 8 hr.Separate trials with propionate and butyrate indicated they also were efficiently absorbed and used.In all trials, only small amounts of 14C appeared in feces, urine, or ileal digesta. These data indicate that the very young calf can absorb and metabolize VFA, whether the acids are produced in the forestomach or large intestine.

Utilization of Volatile Fatty Acids in Ruminants. I. Removal of Them from Portal Blood by the Liver

Removal of volatile fatty acids from portal blood by the liver was studied in 20 ewes and 5 goats. When animals were fed hay, practically all of the propionate but only a small part of the acetate present in portal blood was removed by the liver. However, on a molar basis more acetate than propionate was taken up by the liver. In animals fed grain for extended periods, or grain plus fish oil, the proportion of propionate in the rumen fluid increased markedly and more propionate than acetate was taken up by the liver.The liver showed a greater capacity for removing acetate than either propionate or butyrate from the portal blood when these acids were added to the rumen. Butyrate was not present in significant amounts in right rumen vein blood or portal blood. Only acetate and propionate are absorbed from the rumen as such and presented to extraruminal tissues for metabolism.This work confirms the conclusion by others (4, 6) that propionate is metabolized mainly by the liver and acetate by extrahepatic tissues. The manner in which butyrate is utilized by ruminant tissues under normal conditions remains to be elucidated.