252 PYRIDOXINE AND RELATED COMPOUNDS 



daily supplements to the ration or when injected interperitoneally. How- 

 ever, pyridoxal and pyridoxamine were approximately 25 % less active than 

 pyridoxine when the three compounds were mixed with the ration; this 

 may be due to the increased destruction or utilization of pyridoxal and 

 pyridoxamine by intestinal bacteria. 



Biological materials to be assayed are mixed in the diet at two levels so 

 that they supply between 25 and 75 7 of vitamin Be per 100 g. of ration. 

 Weight gain is recorded weekly; after four weeks, the average weight gain 

 per week is calculated. This value is then compared to a standard curve. 

 In most cases, higher results were obtained at the lower level of assay. 

 The values obtained by this method are somewhat lower than values ob- 

 tained by the yeast growth method, presumably because of the decreased 

 activity of pyridoxal and pyridoxamine when mixed in the diet. 



3. Chick GroW'Th Test 



Prophylactic** and curative^" techniques have been employed. In the 

 prophylactic test, day-old white Leghorn chicks were fed the following 

 vitamin Be-deficient diet: Cerelose 61 g., blood fibrin 18 g., gelatin 10 g., 

 salts IV 5 g., CaHP()4,2H20 1 g., L-cystine 0.3 g., thiamine hydrochloride 

 0.3 mg., riboflavin 0.0 mg., calcium pantothenate 2.0 mg., choline chloride 

 150 mg., nicotinic acid 5.0 mg., biotin 0.02 mg., inositol 100.0 mg., folic 

 acid 0.125 mg., vitamin D3 0.004 mg., a-tocopherol 0.03 mg., 2-methyl- 

 1 , 4-naphthoquinone 0.05 mg., and vitamin A 1700 I.U. Chicks on this diet 

 died in two weeks without gaining any weight. Those chicks receiving 

 vitamin Be , either as a standard dose or a test food, were allowed to grow 

 on their respective diets for three weeks. The response was recorded in 

 terms of body weight. There is no depletion period in this procediu'e; the 

 test dose of vitamin Be is given at the beginning of the assay. Pyridoxal 

 and pyridoxamine exhibited lower activity than pyridoxine when fed in the 

 ration, just as in the rat growth test. Growth response was equal for all 

 three forms of the Be complex when the vitamins were fed by dropper or 

 injected interperitoneally. 



In the curative test^*^ chicks are placed on the basal vitamin Be-delicient 

 ration for a six-day depletion period. They are then divided into groups of 

 seven, of equal average w^eight, and continued on the depletion diet for an 

 additional five days. The test substance or standard is given in a single 

 oral dose to each chick and repeated on the following three alternate days. 

 Basal diet and water are given ad libitum. The chicks are weighed before 

 each dose and on the second day after the last dose is given. The basal 

 vitamin Be-deficient diet used in this test has the following composition: 

 Cerelose 46.5 g., casein (vitamin free) 25.0 g., gelatin 10.0 g., salts IV 5.0 g., 



W. II. Ott, PiQc. Soc. Exptl. Biol. M('<l. 61, 125 (l'.)4G). 



