How to Read Forage Test Results Correctly

By Scout Nelson

Forage testing is one of the most useful tools available for livestock and forage producers. It helps measure feed quality, so animals receive the right amount of nutrients while reducing unnecessary feed costs. Testing also helps producers compare hay lots, improve feeding plans, and make better management decisions throughout the year.

Kim Ricardo, SDSU Extension Forage Field Specialist, encourages producers to use forage testing as part of their regular feeding program. Understanding forage quality allows farmers to match feed with the nutritional needs of different classes of livestock while improving animal health, productivity, and overall farm efficiency.

A forage test measures several important nutrients. These include Dry Matter (DM), Crude Protein (CP), Acid Detergent Fiber (ADF), Neutral Detergent Fiber (NDF), Relative Feed Value (RFV), Relative Forage Quality (RFQ), and Total Digestible Nutrients (TDN). Each value provides different information about forage quality, digestibility, and energy content.

Crude Protein and Total Digestible Nutrients are often the first values producers should review because they show whether the forage provides enough protein and energy. Fiber measurements such as ADF and NDF help estimate digestibility and the amount of forage livestock are likely to consume. Lower fiber levels usually mean better-quality forage and greater feed intake.

RFV and RFQ combine several measurements into one quality score. RFQ is generally more accurate for mixed-grass forages because it considers fiber digestibility, while RFV works best for legume-rich forages such as alfalfa. However, these values should support, not replace, the review of individual nutrient levels.

Producers should evaluate all test results together instead of focusing on a single number. Two hay samples may contain the same protein level but differ greatly in digestibility and energy. Looking at the complete forage analysis provides a better understanding of overall feed value.

Forage test results also help producers decide which animals receive the highest-quality hay. Lactating cows, growing calves, and replacement heifers usually need higher-quality forage than mature dry cows. Testing also helps determine whether protein or energy supplements are actually needed.

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