Production, absorption, distribution and excretion of vitamin B₁₂in sheep

Abstract

I. The efficiency of production and utilization of vitamin BIZ was studied with sheep given a cobalt-deficient diet with and without supplementary Co (I mg/d). Vitamin B,, to lignin ratios in rumen contents were used to estimate minimum rates of production and these were related to faecal and urinary excretion. Tissue distribution and excretion of vitamin Blz were studied with [58Co]cyanocobalamin and ~'-deoxyadenosyl[60Co]cobalamin.2. Labelled Co was rapidly sequestered by particulate material in the rumen and was largely excreted in the faeces. Most of the vitamin Blz in whole rumen contents was contained in micro-organisms, but was released on incubation at pH 2. Added cyanocobalamin was partly degraded in the rumen. 3.The vitamin B,, to lignin ratio in rumen contents began to decline 1-3 d after cessation of a daily Co drench. Estimated ruminal production of vitamin B,, on full feed was not less than 400-700 pg/d with supplementary Co and 50-1 10 pg/d from the Co ( O O I -O .~~ pg/g dry weight) in the basal diet. Production of vitamin B,, appeared to be limited by food intake with or without additional Co. 4.At full feed the efficiency of production of vitamin Blz from Co in the basal diet was about 13 yo while that from added Co was about 3 yo. Part of the vitamin B,, produced in the rumen was degraded before reaching the faeces and about 5 % was absorbed. The minimum total requirements of sheep for vitamin B,, are assessed at about I I ,ug/d. 5.Injected 5'-deoxyadenosylcobalamin was better retained than injected cyanocobalamin, faecal excretion exceeded urinary excretion with both. Labelled cobalamin was selectively retained by liver (particularly by the mitochondria), kidneys and the walls of parts of the alimentary tract. Vitamin B,, was secreted into the duodenum and reabsorbed in the ileum, but little secretion occurred above the duodenum and little absorption below the small intestine.Production of vitamin B,, in rumen contents of sheep depends on the presence of cobalt (Hale, Pope, Phillips & Bohstedt, 1950;Hoekstra, Pope & Phillips, 1952; Hine & Dawbarn, 1954;Kercher & Smith, 1956) and this is reflected in faecal excretion (Hale et al. 1950; Dawbarn, Hine & Hughes, 1952;Dawbarn & Hine, 1955). Little is known, however, either of the quantities produced or of the efficiency of absorption.Kercher & Smith (1955) The quantities of vitamin B,, in rumen contents of sheep given Co-deficient diets are not negligible, and it is not necessarily true that the efficiency of absorption is the same as that when additional Co is supplied or the same as that when crystalline cyanocobalamin is given orally. The work now described was aimed at estimating these rates and efficiencies and in addition at determining the tissue distribution and excretory pattern of injected cobalamins. The total requirements of sheep for vitamin B,, are assessed at about I I pg/d and, although the arguments leading to this estimate are not entirely rigorous, the results permit a reasonable description of the production, absorption a...

Macromineral and trace element supply in sheep and goats in Austria

“…Mo levels are least tolerated by cattle, followed by sheep, but are tolerated by goats (Haenlein and Anke 2011). Concentrations of vitamin B12 rise in times of Co supply and fall during periods of dietary deficiency, because Co is needed for the production of vitamin B12 by ruminant bacteria (Smith and Marston 1970;Suttle 2005). Beside all these factors, which have an impact on the concentration macrominerals and trace elements in body tissues, the reliability of reference values is another variable which warrants discussion.…”

Net flux of folates and vitamin B12 through the gastrointestinal tract of sheep

“…After perfusing the rumen and the small intestine of fed sheep with blood from other sheep and measuring changes in concentrations of vitamin B 12 in blood after 2 h of perfusion, Rérat et al (1958a) did not demonstrate absorption of vitamin B 12 through the rumen wall, but showed absorption in the distal small intestine. Similarly, from the distribution of a radioactive dose of vitamin B 12 , Smith and Marston (1970) concluded that in sheep, the site of absorption of vitamin B 12 is the small intestine although they measured an important accumulation of vitamin B 12 in the rumen wall. However, using measurements of blood enrichment in the vitamin, Rérat et al (1958b) showed some absorption of vitamin B 12 through the rumen wall when the vitamin solution was placed in the empty rumen of sheep.…”

“…Moreover, the rumen wall could retain the vitamin and release it later into the blood or the rumen cavity (Rérat et al 1958b). Similarly, Smith and Marston (1970) failed to detect vitamin B 12 absorption from the rumen of sheep, but they also observed an accumulation of vitamin B 12 in the rumen wall. To our knowledge, there is no information in the literature on the fate of folic acid in the gastrointestinal tract of sheep.…”

Supplementing lactating dairy cows with a vitamin B12 precursor, 5,6-dimethylbenzimidazole, increases the apparent ruminal synthesis of vitamin B12

“…However, the proportion of dietary cobalt used for these synthetic processes is relatively low in sheep and cows, varying from 3% to 15% (Smith and Marston, 1970;Stemme et al, 2008;Girard et al, 2009b). In vitro studies demonstrated that addition of different bases to the culture media enhanced the synthesis of the corresponding cobamides at the expense of the other forms (Ford et al, 1955;Gawthorne, 1970b).…”

“…Efficiency of cobalt utilization in the present study was lower than expected. Indeed, in sheep, efficiency of cobalt utilization decreased as the dietary concentration of cobalt increased (Smith and Marston, 1970). In cows fed different diets, efficiency of cobalt utilization for CBL synthesis in the rumen has been reported to be 7.1%, 9.5% and 4.4% for diets providing 0.17, 0.29 and 2.5 mg of Co/kg of DM, respectively (Stemme et al, 2008;Girard et al, 2009a).…”