Production within the rumen and removal from the blood-stream of volatile fatty acids in sheep given a diet deficient in cobalt

Abstract

I . The production and metabolism of volatile fatty acids were stndied in sheep offered a cobalt-deficient diet.2. The molai proportions of acetic (60 "/o), propionic (zh x) and butyric (14 ?(, ) acids in the rumen fluids of' sheep giccn thc Co-deficient diet, but whose stores of vitamin B,, were adequate, were similar before arid after administration of an oral supplement of Co.3. In pair-fed sheep, one member of which was vitamin BIZ-deficient and the other (control) trcatcd with vitamin B,, parenterally, the concentrations after feeding of both totill and individual volatile fatty acids in the blood tended to be higher in deficient than in contro! sheep.1. Following injection of thc respective salts of individual volatile fatty acids into the blood-stream, formate clearance was apparently not affected, whereas that of acetate was slightly, and that of propionate very significantIy, delayed in vitamin B,,-dcficient sheep compared with pair-fed control animals.5 . Acetate metabolism was retarded in the prescncc of propionate; the effect was greater in deficient than in pair-fed control sheep.6 . The hypothesis is advanced that it is the failure to metabolize propionate at the normal rate that leads to the progressive loss of appetite in vitamin BIZ-deficient sheep.LOSS of appetite, the first sign of vitamin B,, deficiency seen in sheep that consume a cobalt-deficient diet, occurs when the concentration of vitamin R,, in the liver is reduced to about 0.1 pgig h e r tissue (Marston, 1970).Observation of pair-fed animals showed that, whereas the animal whose stores of vitamin B,, were adequate ate the whole of its ration in 1-2 h, the deficient member of the pair might take 24 h to consume the same amount of food. Following a 24 h fast, a deficient sheep sometimes ate ravenously for a short time and then left the remainder of its ration untouched for several hours.The :issociation, in deficient sheep. between consumption of small quantities of food a i d impairment of appetite led to a search for a metabolite(s) which accumulated in the blood-stream after feeding. As the ruminant derives the major portion of its cncrgy from volatile fatty acids produced by fermentation, a study was made of some aspects of the production, absorption and utilization of these acids in shecp given the Co-deficient diet. Lack of Co in the diet had no apparent influence on production or absorption of the volatile fatty acids produced by micro-organisms mithin the rumen. In those animals in which there was a lack of vitamin BIZ in the tissues, homever,

The influence of an increased cobalt supply on ruminal parameters and microbial vitamin B12synthesis in the rumen of dairy cows

“…bacteria and in the type of bacteria strains in the rumen of cobalt deficient sheep, Singh and Chhabra (1995) found significant higher bacterial counts in supplemented animals. Changes in ruminal microbial species might result in changes in molar proportions of short chain fatty acids, but Marston et al (1972) and Kisˇidayova´et al (2001) did not find any effect of cobalt supply on molar portions of short chain fatty acids in ruminal fluid. These results correspond to the present investigation, in which the cobalt content in the ration did not affect ruminal parameters.…”

Analysis of corrinoids in ovine tissues

“…These differences in the distribution as well as vitamin B 12 content of ado-cbl may have been due to it being the most active metabolic pool and possibly the form in which surplus vitamin B 12 is excreted. This may also point towards the primary metabolic defect in vitamin B 12 deficiency originating from impairment in the propionate-succinate pathway, as has been suggested by some researchers (Marston et al, 1961(Marston et al, , 1972Smith and Marston, 1971), rather than from a deficiency of me-cbl as Kennedy et al (1991) thought. On the other hand, these reflections will need to be taken with care since no deficiency state was seen in the animals and it is therefore not possible to associate any particular corrinoid concentration with any particular state of deficiency.…”

Abnormal fermentations in continuous cultures of rumen microorganisms given cobalt-deficient hay or barley as the food substrate

“…Eventually, however, the functional vitamin B L 2 deficiency in the host tissues, believed to involve an impaired ability to metabolize Pr due to a co-enzyme (adenosyl cbl) deficiency (Marston et al 1961), might be exacerbated. Marston et al (1972) concluded from studies of VFA concentrations in the rumen of two sheep on a Co-deficient hay, with and without Co supplements, that the proportions of Ac and Pr present were not influenced by Co supply. However, it is noteworthy that both animals began the experiment with low Ac : Pr (2 : 1).…”