How To Calculate TDN

TDN stands for total digestible nutrients. It is a number that indicates the amount of energy provided to cattle from feed. TDN can be expressed as either a percentage of the ration or of the weight. Although other methods can calculate the energy in feed, TDN is still the most widely used method in the United States.

Difficulty: Moderate

Instructions

Things You'll Need:

• Percentage of digestible protein
• Percentage of digestible carbohydrates
• Percentage of digestible fat
• Palculator

1. Add the percentage of digestible protein to the percentage of digestible carbohydrates.

2. Multiply the percentage of digestible fat by 2.25.

3. Add the sum of the digestible protein and the digestible carbohydrates from Step 1 to the number obtained in Step 2.

Tips & Warnings

• A quality feed will consist of approximately 65 percent TDN.
• A major criticism of this standard formula for calculating TDN is that it doesn't take into consideration any energy losses such as those due to urination. Some methods for calculating TDN seperate digestible carbohydrates into digestible fiber and digestible non-fat extract. If this is the case simply add the two together and treat the sum as digestible carbohydrates.

References

• Golden Plains Area Extension Website
• Jn.nutrition.org

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