The absorption of acetate, propionate and butyrate from the rumen of sheep

Abstract

When solutions of sodium acetate, propionate and butyrate are placed separately in the empty rumen of sheep anaesthetized with nembutal, analysis of the blood leaving the rumen shows that absorption of the acids occurs and that the rate of absorption appears to decrease as the molecular size increases (Barcroft, McAnally & Phillipson, 1944).. Recently this was reinvestigated by Gray (1948), who concluded that no absorption at all occurred from the rumen of sheep when the pH was slightly alkaline as would be expected when solutions of the sodium salts are introduced. Gray's method consisted of introducing solutions of sodium acetate and propionate into the empty washed rumen of an unanaesthetized sheep through a rumen cannula. Pectin was included in the solution as a marker. The solution was allowed to remain in the rumen for 5 hr. or more and was then removed and the interior of the organ was washed with water. The loss of pectin from the rumen was taken as indicative of the quantity of solution that had passed on to the abomasum; on this basis the quantity of acetate and propionate absorbed from the rumen was calculated and found to vary between -10 and + 22 m.equiv. during 5 or 6 hr. In addition, Gray (1948) introduced solutions of pectin or sodium acetate into the empty rumen of anaesthetized sheep from which the exits were blocked by ligature, and found a loss of less than 5 % of either substance over an experimental period of 4 hr.Acetic, propionic and butyric acids are absorbed more rapidly than the corresponding anions, and the rate at which free acid disappears from the rumen increases with the length of the hydrocarbon chain (Danielli, Hitchcock, Marshall & Phillipson, 1945;Gray, 1947). If the epithelium of the rumen is impermeable to the anion, as Gray (1948) contends, then the ratio propionic/ acetic and butyric/acetic should be greater in the blood leaving the rumen than in the rumen contents, but this is not so (Kiddle, Marshall & Phillipson, 1951); in fact, the mixture of acids in the blood leaving the rumen is much the same as that in the rumen except that it contains less butyrate. 190 M. J. MASSON AND A. T. PHILLIPSON On account of these contradictions a further series of experiments on the absorption of acetate, propionate and butyrate from the rumen has been conducted, and the results are recorded in this paper. METHODSChemical. Acetic, propionic and butyric acids were determined by steam distillation, after acidifying with sulphuric acid, using a 'Markham' still. The distillates were titrated with carbonfree 0-02 or 0-05N-potassium hydroxide under carbon-dioxide-free conditions using phenol red as indicator. In one experiment in which rumen liquor was used total volatile acid was determined in the same way after precipitation of protein by McAnally's reagent .Volatile acid in blood was determined by a modification of the method of McClendon (1944), the details and accuracy of which are described elsewhere (Kiddle et al. 1951).Chloride was determined in earlier experiments by the Volhard meth...

The Absorption of Lactic Acid from the Reticulo-Rumen of the Sheep

“…The marked reduction in volatile fatty acid absorption rate due to a decrease in the acidity of the solution from acid to alkaline (Table 7) was expected from the results of other workers (Danielli et al 1945;Masson and Phillipson 1951).…”

“…This was done to show any consistent differences in the rate of absorption occurring during period 1 compared with period 2 due to deterioration in the preparations with time. Masson and Phillipson (1951) found that the rate of absorption of volatile fatty acids from the washed-out rumen decreased with time.…”

Functional development of epithelial tissue of the reticulo-rumen in calves

“…One probable explanation of some of these differences was provided by the work of Masson and Phillipson (1951). When they deter mined absorption by measuring the disappearance of the VFA from the rumen contents, they found butyrate to be absorbed faster than the other two acids.…”

“…Gray (1948) could measure no appreciable absorption at an alkaline pH and suggested that the results of Danlelll _et al ( 1945) were not outside the range of experimental error. However, Masson and Phillipson (1951) demonstrated conclusively that absorption could occur from rumen contents at a pH greater than 7.0. More limited results by and Armstrong et al (1961) supported the contention of Danlelll .et al ( 1945) that absorption is reduced as the pH rises.…”

“…More limited results by and Armstrong et al (1961) supported the contention of Danlelll .et al ( 1945) that absorption is reduced as the pH rises. Changes in the rumen concentrations of the individual VFA measured by Masson and Phillipson (1951) suggested that specific absorption rates were In the order butyrate > propionate > acetate. Danlelll et al (1945) had concluded that the order of absorption at alkaline pH was the reverse of this; measurements of blood changes by Masson and Phillipson (1951) and of rumen changes by Pfander and Phillipson (1953) and Armstrong et al (1957) tended to support this belief.…”