Fiber is a cornerstone of dairy cow diets, yet it’s often misunderstood. Knowing the types of fiber and their roles in digestion and milk production can help farmers balance rations more effectively for healthier cows and higher-quality milk.

Why Fiber Matters

Fiber is a carbohydrate that makes up the structural part of plants. While it breaks down more slowly than starch or sugars, fiber provides several essential benefits:

• Stimulates chewing and cud regurgitation, which increases saliva production to buffer the rumen.

• Supports rumen microbes, which are key to digesting feed.

• Helps prevent digestive issues like bloat and displaced abomasum (DA).

• Fuels acetate production, an energy source that also boosts milk fat.

Types of Fiber

1. Effective Fiber

• Refers to fiber that stimulates chewing and saliva production.

• Particle size matters:

  • Too small → fast passage, higher risk of acidosis.

  • Too large → gut fill slows energy intake and milk yield.

• Tools like the Penn State Particle Separator can help farmers evaluate rations.

2. Lab-Measured Fiber Fractions

• Neutral Detergent Fiber (NDF): Measures total cell wall (cellulose, hemicellulose, lignin). High NDF = slower digestion and less intake.

• Acid Detergent Fiber (ADF): Measures cellulose and lignin. High ADF = lower digestibility and energy.

• Lignin: Totally indigestible. Levels increase as plants mature, lowering feed value. Selecting low-lignin forages (like BMR corn or low-lignin alfalfa) can improve digestibility.

3. Soluble vs Insoluble Fiber

• Insoluble Fiber: Cellulose, hemicellulose, lignin — harder to digest.

• Soluble Fiber: Includes pectins, fructans, and beta-glucans — easier to digest and a valuable energy source.

Forage Maturity and Harvest Timing

• Less mature forages: Thinner cell walls, lower NDF/ADF, higher energy and intake.

• More mature forages: Higher lignin, thicker walls, less digestible.

• Proper harvest timing is key for balancing yield and nutritional value.

Takeaway

Fiber isn’t just “filler” in the diet — it’s the foundation of rumen health, digestion, and milk fat production. By balancing effective fiber, monitoring NDF/ADF levels, and harvesting forages at the right maturity, farmers can keep cows healthy and productive.

How do you check whether your ration has the right balance of effective fiber — by cow behavior (chewing, cud), lab tests, or both?

By Manuel Peña & Liz Gartman, UW–Madison Division of Extension
Adapted from: “What are the different types of fiber and how do they support milk production?”