On the insensitivity of sheep to the almost complete microbial destruction of dietary choline before alimentary-tract absorption

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Abstract
Injection of [Me-14C]choline into sheep indicated that the small amount of phosphatidylcholine present in abomasal digesta was largely (69%) of nondietary or ruminal origin. Long-term feeding of [Me-3H]choline to sheep produced insignificant labeling of plasma phosphatidylcholine, indicating that > 99% of the choline body pool was of nondietary origin. When rats were fed with [Me-3H]choline for similar periods, 18-54% of the tissue phosphatidylcholine was derived from dietary choline. The loss of [14C]choline and 32P from the plasma phosphatidylcholine after a single injection of these isotopes indicated a markedly slower turnover of choline in the sheep compared with the rat. This observation, coupled with a lack of liver glycerophosphocholine diesterase, provides an explanation for the insensitivity of the sheep to an amost complete microbial destruction of dietary choline before alimentary tract absorption.