AgEBB-MU CAFNR Extension
and University of Missouri Extension
The Value of a Forage Analysis
Forage makes up the major portion of livestock diets. A livestock producer maximizes the value of a forage when the diet is properly balanced considering the nutritional value of the forage. A forage sample needs to be analysed for moisture, protein fiber,(ADF and NDF which allows us to calculate TDN or net Energy) and minerals.
An analysis of a forage is the only positive means of knowing the nutrient content.Book values or guesses can be very misleading in balancing a ration.Underestimating the protein content of alfalfa hay by 2% in a diet fed to dairy cows at 25 lbs./ day could result in the excess feeding of 100 lbs. soybean meal/day to a 100 cow herd.
A hay test should include to following items:
| Moisture: | Forage sample is fully dried in an oven to determine the % water.Hay will usually have 7-20% moisture. |
| Crude Protein: | A calculated value based on N x 6.25. Made up of true protein and non protein nitrogen. Early cut ,leafy forages are highest in crude protein. |
| Acid Detergent Fiber: | ADF is the % of the highly indigestible portion of the plant.The lower the ADF value , the higher the digestibility and energy value of a hay. |
| Neutral Detergent Fiber: | NDF is the % of the cell wall of a plant. Directly related to fill or intake.The lower the NDF, more the animal can eat. |
| Relative Feed Value: | RFV is an over all indicator of forage quality Calculated from ADF and NDF. Comparing alfalfa, a RFV of 100 equals full bloom mature alfalfa. Grasses at similar stages of maturity will have a lower RFV because of a higher %NDF. |
Comparison of forage Quality of a Legume and a Grass
High Quality Low quality
Analysis Alfalfa Orchard Grass Alfalfa Orchard Grass
CP 20 18 15 8
ADF 29 31 37 45
NDF 40 55 50 72
RFV 160 110 100 80
NE lac. Mcal/lb. 0.65 0.75 0.56 0.55
TDN % 63 72 55 54
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