The determination of the choline content of feed ingredients using choline kinase
1998
Menten, J.F.M. | Pesti, G.M.
This study was conducted to establish a methodology for a more accurate and less laborious determination of the choline content of feed ingredients, compared to the available procedures. The methodology involved an extraction-hydrolysis step, in which the feed sample was heated in a methanolic KOH solution using a Goldfisch apparatus, followed by an enzymatic assay, involving a series of coupled reactions started by choline kinase, which allowed the quantitation of the extracted choline. The enzymatic assay was very accurate over the range of choline concentrations from 1 to 20 mg l-1, with a lower detection limit in feeds of 50 mg kg-1, The hot extraction procedure was more efficient than the conventional thimble cool extraction for maize, soybean meal and canola meal, especially for maize. Extraction for 2 h gave choline values similar to those obtained with 4 or 6 h extraction. The recovery of added choline to maize, soybean meal or canola meal samples averaged 97.4%, indicating very little loss of choline in the procedure. This methodology provided more realistic values of the choline content of feed ingredients than previous methods.
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