Sentence:  Our standard wheat flour contains only the endosperm and represents practically a 75 per cent. extraction. The remaining 25 per cent. is known in the trade as grain <WSD>offal</WSD> or mill-feed, and is used largely as a concentrated food for live stock, being prized in the feeding of dairy cattle. 
Meaning of the word marked with <WSD> tags:  A by-product of the grain milling process, which may include bran, husks, etc.