Hi Tracy,
Crude fiber is a measure of the total cellulose, hemicellulose, xylans,
lignin and any other components associated with fibrous carbohydrates.
Acid-detergent fiber just refers to a more specific analysis of fiber
content, because some fibrous carbohydrates can be utilized better than
others, which is usually of more interest to people feeding
"high-performance" ruminants, like dairy cows, rather than horse
people. Crude fiber analysis involves boiling in a weakly acidic
solution and then filtering and drying a feed sample to simulate
digestion. The disadvantage is that some of the fibrous carbohydrates
remain protein-bound or otherwise still tied up in the cell wall. Acid
detergent fiber analysis further extracts the components, specifically
the hemicellulose, which is only partially utilized by horses and only
moderately utilized by ruminants like cows.
Bottom line, if the crude fiber content is 20% and the acid-detergent
fiber content is 25%, it means there's a 5% content of hemicellulose.
No big deal. Just an analysis thing, doesn't mean the feed contains
either acid or detergent. Hope this helps.
Susan Evans Garlinghouse