16 CONTROL BULLETIN NO. 148 



MEDICATED FEEDS 



It will be noted that a considerable number of samples are below guarantee 

 in the drugs for which guarantees are made. This is not due, always, to the 

 fact that an insufficient amount of drug was used when the feed was mixed. 



It has been found that it is impossible with the present methods of analysis 

 to recover all the added drugs after the feed has been in storage only a relatively 

 short period of time. This does not mean necessarily that there is an attendant 

 loss of the drug's effectiveness in preventing disease. It may mean that the drug 

 is incompletely extracted during analysis. Further, it is difficult to obtain uni- 

 form mixtures when as little as one-quarter of one pound of a drug is used per 

 ton of feed. Therefore this Control Service considers at present that the drug 

 guarantees are met if analysis shows the content to be within 20 per cent of that 

 guaranteed. 



