Analysis of serum methylmalonic acid for the determination of cobalt deficiency in cattle.

An improved method has been developed and validated for the determination of methylmalonic acid (MMA) in serum to determine cobalt deficiency in cattle. Serum samples were extracted with ethyl acetate and derivatised to form the propyl esters using 14% boron trifluoride-propanol derivatising reagent. Derivatised samples were analysed by capillary gas chromatography using split injection, a DB-17 30 m x 0.25 mm I.D. capillary column and flame ionisation detection. The detection limit for the method was 0.5 mumol/l and precision, determined by replicate analyses of spiked serum samples, was less than 2% relative standard deviation. When cobalt deficiency is defined as a MMA serum concentration of more than 2 mumol/l, the method was able to detect clinical deficiency of cobalt in animals with symptoms such as "coasty" coats and low weight gain.