Urinary methylmalonic acid as an indicator of the vitamin B₁₂ status of grazing sheep

Abstract

Lambs grazing cobalt-deficient pastures and injected with hydroxocobalamine gained significantly more weight and excreted significantly less methylmalonic acid in the urine than untreated controls. Lambs with liver vitamin B₁₂ levels in the range 0.1–0.2ώg/g excreted less than 25 ώg of methylmalonic acid per ml of urine, whereas lambs with liver vitamin B₁₂ concentrations of less than 0.1 ώg/g excreted greater amounts. Lambs in both groups had serum vitamin B₁₂ concentrations less than 500 pg/ml.

No consistent diurnal variation in urinary methylmalonic acid concentrations was found for four lambs studied.

There was a decrease in the methylmalonic acid levels of urine after storage for more than 24 hours which could be prevented by acidification of the urine.

A mean urinary methylmalonic acid concentration greater than 30 ώg/ml for 10 animals randomly selected from a flock would indicate a cobalt deficiency in the flock as a whole.