total digestible nutrient
Quick Summary
Total Digestible Nutrients (TDN) is a measure of the energy content in animal feed. It represents the sum of digestible protein, digestible fat (ether extract multiplied by 2.25), digestible carbohydrates (nitrogen-free extract), and digestible crude fiber.1
TDN is one of several ways to express the energy value of feed, alongside digestible energy (DE), metabolizable energy (ME), and net energy (NE). While historically significant, the use of TDN has declined because it does not account for energy lost through digestion and metabolism, nor does it differentiate the efficiency of energy utilization for different purposes like maintenance, milk production, or growth.1
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