Changes in Ruminal Oxalate Degradation Rates Associated with Adaptation to Oxalate Ingestion

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Abstract
Two sheep and 1 cow were changed gradually from diets of alfalfa hay to diets that contained Halogeton glomeratus (halogeton). The halogeton used contained 12% (w/w) oxalic acid, and transitions to the halogeton diet were accompanied by marked (10-fold and greater) increases in the in vitro rate of oxalate metabolism by ruminal microbes. A transition period of 3 to 4 days appeared to be required for selection of a microbial population that rapidly degraded oxalate. Adapted animals tolerated the oxalate (.45 moles/day per sheep) and signs of toxicity were not observed. Increased rates of oxalate degradation were also observed in response to infusion of gradually increasing amounts of sodium oxalate into the rumens of two other sheep. These sheep however, died because they were unable to tolerate the .43 to .46 moles of oxalate infused per day. Oxalate degrading capacity was negligible in cell-free ruminal fluid from adapted sheep but was associated with fractions that contained bacterial cells. Degradation was inhibited by several antibiotics and by exposure of the incubation mixtures to oxygen. None of 99 pure cultures of bacteria isolated from an oxalate adapted sheep degraded oxalate. Copyright © 1977. American Society of Animal Science . Copyright 1977 by American Society of Animal Science.