VII. KSTIMA'IIOX 453 



The following procedure may i)e used in the l)iological assay with chicks. 

 The breeding flock are placed on diet 1 (Table IX) at 6 months of age. The 

 l>irds are kept in a laying house on a sugar-cane litter which is changed 

 weekly, and the eggs laid by these pullets are incubated to serve as a source 



TABLE IX 

 Composition of Basal Diets 



" The salt mixture is composed of the following in grams: bone ash 1000; KjHPOi 200, KH2PO4 225, MgSOi 

 125, MnS04 (anhydrous) 40, ferric citrate 25, CuSOi-SHiO 1.0. KI 0.3, Zn acetate 0.7, Ah(S04).-18H.O 0.8, 

 cobalt acetate 0.2, Ni carbonate 0.1. 



* Vitamin A acetate, 1500 U.S.P. units; vitamin Dj (DeLsterol) 200 A.O..\.C. units; mixed tocopherols, 34 

 mg. dissolved in 1 g. of corn oil (Mazula). 



of chicks, no eggs being used until after the hens have been on diet 1 for 

 at least 2 weeks. If the hatchability of the eggs drops below 60%, 0.5% 

 fish meal is added to diet 1. The chicks are placed in electrically-heated 

 battery brooders with ^^-in. mesh wire floors in an air-conditioned room 

 at 28° and are fed the experimental diets immediately. Diet 2 (Table IX) 

 is used as the deficient l)asal diet, and duplicate groups of eight to twelve 

 chicks are usually used for each experimental diet. The assay period is 25 

 days, and the average weights obtained at the end of this period are used 



