[Studies on lysine availability with Tetrahymena pyriformis as the test organism]

A series of experiments was performed to verify the suitability of the protozoon Tetrahymena pyriformis (T.P.) for determining the lysine availability of feeds. The multiplication rate was estimated with the aid of organism counting, turbidimetry and reduction of triphenyltetrazolium chloride. The volume of T.P. was calculated on the basis of length and breadth measurements, Within higher rates of multiplication, there was connected a tendency towards larger organism volumes. A comparison of the growth tests showed that only turbidimetry is able to reflect, under certain conditions, the efficiency of the test organism in protein synthesis. The values for lysine availability varied widely according to the kind and pretreatment of the feedstuff, but did in no case attain those obtained with animal experiments. T.P. is, therefore, scarcely suited as a test organism for determining the protein quality and amino-acid availability of feedstuffs.