The rates of absorption of acetic, propionic and n‐butyric acids

Abstract

Numerous experiments on the absorption of acetic, propionic and n-butyric acids have provided considerable information on the rates at which individual acids disappear from the rumen under the conditions of the experiment and of the concentrations appearing in the blood stream, but none of these experiments simulates normal conditions sufficiently to allow deductions to be made of the quantities of these acids normally absorbed.Recently, Johnson (1951) studied the concentrations of these acids in the rumen of fasting goats and sheep after the administration of large quantities of propionic and n-butyric acids, and came to the conclusion that butyric acid was absorbed in greater quantity than propionic acid. It is known that more butyrate can be absorbed from the rumen than can be accounted for by the butyrate entering the blood stream (Masson & Phillipson, 1951), and this is due to metabolism of butyrate by the rumen epithelium (Pennington, 1952) which in vitro is more pronounced than metabolism of propionate or acetate. The experiments described here were designed to study (a) the absorption of these three acids quantitatively by introducing a steady inflow of a solution of these acids at a suitable pH and in amounts that would maintain the concentrations in the rumen at physiological levels, and (b) to see whether the information so gained could be used to determine the rates of absorption in unanaesthetized sheep that were fasting or feeding. METHODS ExperimenkaZOne-year-old Scottish Blackface sheep, with the rumen previously cannulated, were used. The sheep were starved for 18 hr prior to the experiment to facilitate the removal of food from the rumen. The rumen was emptied and washed clean with warm saline. The sheep were anaesthetized by the intravenous injection of pentobarbitone, and the rumen was isolated in the manner described by Danielli, Hitchcock, Marshall & Phillipson (1945 ABSORPTION OF FATTY ACIDS FROM RUMEN 103The solution introduced into the rumen was Krebs's bicarbonate Ringer in which NaCl was substituted by sodium acetate, propionate and n-butyrate to give concentrations of 63 ±9, 21 i 3, and 15 ± 3 m.equiv/l. These concentrations are within the range usually found in the rumen. A similar solution, except that it contained different proportions of the three acids, was introduced into the rumen from a burette at the rate of 1 ml./min. The concentrations of acids in this solution were adjusted as the experimental series progressed until the concentrations in the rumen were steady throughout the experimental period. In this way the rate of introduction of acid served as an index to the rate of absorption. The solution in the rumen was gassed with carbon dioxide at 15 min intervals throughout the experimental period.In later experiments comparisons were made between solutions at neutral and acid pH values, and between the presence or absence of inorganic ions and carbon dioxide.Experiments on two unanaesthetized sheep were conducted in a metabolism cage. Both were accustomed to standing in th...

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

“…Danlelll et al (1945), using the change in the concentration of VFA in the rumen contents as the criterion of absorption, found that the order of absorption of the three principal VFA was as suggested by Barcroft et al (1944a) when the rumen con tents were alkaline (pH 7.5)• However from rumen contents at a more acid reaction (pH 5.8) the higher homologues of the VFA were absorbed faster. Kiddle et al (1951) concluded that the higher homologues of the VFA were not absorbed prefer entially from rumen contents at an acid pH, but Gray et al (1951), Gray and Pilgrim (1951), Hungate et al (1961), Johnson (1951) and Pfander and Phillipson (1953) confirmed the conclusions of Danlelll et al (1945) and Gray (1947Gray ( , 1948.…”

“…1951;Pfander and Phillipson, 1953). However, the work of Gray et al (1951) and Gray and Pilgrim (1951) indicated that ^-The absorption rate relative to the concentration in the rumen (Hungate et al, 1961), on diets of wheaten hay or lucerne hay, the production of propionate in the rumen exceeded that of acetate end their belief as to the specific absorption rates of VFA was based partially on these rates of production.…”

Absorption of Volatile Fatty Acids, Tritiated Water and Antipyrine From the Abomasum of Goats

“…Re-entrant cannulae. -One goat was provided with re-entrant cannulae both at the duodenum [Phillipson, 1952] and at the anterior end of the abomasum [Ash, 1962]. This preparation proved difficult to maintain and only one goat out of three prepared could be used for experiments; even in this goat, blockage of the abomasal cannulae often occurred and affected the condition of the animal adversely.…”

“…It is well known that the absorption of VFA in the rumen occurs faster from acid than from alkaline contents [Danielli et al, 1945;Pfander and Phillipson, 1953;Sutton et al, 1963;Aafjes, 1967]. Danielli et al [1945] assumed from their measurements that in an alkaline environment the absorption of VFA takes place as a passage of anions through water-filled pores; but at a pH of 5-8 already part is absorbed through the lipid layers.…”

Interconversions and production of volatile fatty acids in the sheep rumen

“…The quantitative importance of the individual volatile fatty acids as contributors to the total metabolism of the whole animal has therefore been the subject of considerable interest and investigation (Pfander & Phillipson, 1953;Schambye, 1955;Armstrong, Blaxter & Graham, 1957;Annison & Lindsay, 1961, 1962Bensadoun, Paladines & Reid, 1962;Bergman & Kon, 1964b;Lindsay & Ford, 1964).…”