Biological Assay of Lactoflavin with Chicks

Abstract

A diet similar to that used in ‘vitamin G’ assays (Norris and co-workers, '36) was found to be deficient in both lactoflavin and the filtrate factor. Addition of crystalline lactoflavin to the diet appeared to provoke dermatitis in chicks. A basal diet for chicks is described which was used in the biological assay of lactoflavin by growth. Maximal growth under the conditions of assay required the addition of about 0.60 mg. of a crystalline preparation of lactoflavin to 100 gm. of the diet. The exact purity of the lactoflavin used was not known. The growth response to lower levels was roughly proportional to the amount of lactoflavin which was fed. Symptoms of prolonged lactoflavin deficiency in chicks are described. The lactoflavin content of some feeding stuffs is reported in terms of a chick unit which was based on chick growth, and was equivalent to one-tenth of the daily amount which will just provide for maximal growth under the conditions described. The unit was approximately equivalent to a modified Bourquin and Sherman unit of ‘vitamin G.’ Under the conditions of the assay, the requirement of the chick for maximal growth was about 100 units per 100 gm. of diet. Attention is drawn to the differences in distribution of lactoflavin and the filtrate factor is certain feeding stuffs.