Newton G L, Tucker R E, Mitchell G E, Schelling G T, Alderson N E, Knight W M
Int J Vitam Nutr Res. 1979;49(3):240-5.
Vitamin A bioassay techniques based on liver storage in the chick were adapted for the assay of vitamin A in molasses based liquid supplements for cattle. Methods of administering the assayed supplement to the chicks were: 1) direct dosing of the supplement via four crop infusions at hourly intervals and 2) ether extraction, suspension in cottonseed oil with solvent removal in vacuo followed by direct crop dosing. The last method allowed a larger dosage with fewer analytical problems. Five sequential extractions were required for 97% recovery of the vitamin A from the molasses supplement. With the higher dosage range, the variance of response was a function of dose level. Transformation to a log dose - log response curve allowed a linear plot with homogeneity of variance. Detection of a 10% loss of vitamin A potency (P less than .10) was estimated to require 27 chicks per treatment by the slope ratio bioassay procedure.
基于雏鸡肝脏储存的维生素A生物测定技术被应用于牛用糖蜜基液体补充剂中维生素A的测定。给雏鸡施用待测补充剂的方法有：1）通过每小时一次的四次嗉囊灌注直接给药；2）乙醚萃取，悬浮于棉籽油中并真空除去溶剂，然后直接嗉囊给药。最后一种方法允许使用更大剂量且分析问题更少。从糖蜜补充剂中回收97%的维生素A需要进行五次连续萃取。在较高剂量范围内，反应的方差是剂量水平的函数。转换为对数剂量-对数反应曲线可得到方差齐性的线性图。通过斜率比生物测定法估计，检测到维生素A效价损失10%（P<0.10）时，每种处理需要27只雏鸡。
