Total digestible nutrients (TDN)

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The sum of the digestible crude protein, digestible nitrogen-free extract, digestible crude fiber, and 2.25 times the digestible ether extract (fat). This value is often calculated from ADF. It is less accurate than NE for formulating diets containing both forage and grain. Most rations are now formulated using NE; however, TDN is still used to calculate beef cow rations where the diet is primarily forage. [Source: USDA National Plant Materials Manual]

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