Chick bioassay of Lysine

Synopsis

A series of experiments have been conducted with young chicks to develop a valid bioassay for the available lysine content of protein concentrates. The greatest problem to overcome was that of the secondary effects of adding test protein to a well‐defined basal diet. The solution to such a “ protein effect” was based upon the development of a reference standard diet with specifications (except for lysine) to be maintained in all test diets irrespective of supplementary levels of test proteins and amino acids.

A reference standard diet was established in which a mixture of maize meal, sesame meal and dried whey provided 20 per cent crude protein. This diet was shown to be deficient in no dietary factors other than lysine and, when adequately supplemented with lysine, it supported excellent chick growth. The adaptation of the diet for assay purposes is described; it involves the replacement of part of the dietary protein by an amino acid mixture simulating the composition of the basal protein. The potential assay range lies between 0.05 and o‐8 per cent of L‐lysine hydrochloride supplementation.

Notes

Present address: Department of Agricultural Chemistry and Soil Science, University of Ibadan, Ibadan, Nigeria.