ANSC Feeds Practice Exam

What is the typical range of ADF percentage in forage hay that indicates a lower consumption by cows?

1. Under 30%

2. 30% to 40%

3. 40% to 50%

4. Above 50%

The correct answer is: Above 50%

The typical range of Acid Detergent Fiber (ADF) percentage in forage hay that indicates lower consumption by cows is indeed above 50%. ADF is a measure of the plant cell wall components that are more difficult for ruminants to digest, including lignin, cellulose, and some hemicellulose. When ADF levels exceed 50%, it signifies that a considerable portion of the forage is composed of these tougher, less digestible components, making it less palatable and reducing intake by the animals. Cows tend to consume less forage that has high ADF levels, as it requires more effort to digest and provides less energy compared to forages with lower ADF percentages. For forages with ADF levels below 30%, cows generally find these to be more palatable and digestible, encouraging higher intake. The range of 30% to 40% also generally supports reasonable consumption, but as values approach and exceed 50%, the likelihood of reduced intake becomes significant. Therefore, understanding ADF levels is crucial for formulating rations that meet the energy requirements and encourage adequate feed consumption in dairy cattle or beef cows.