Raw material and nutrient lexicon

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Ruminal N balance (RNB)

RNB means "ruminal N balance" and indicates for a feed whether there is a nitrogen (N) surplus or a N deficiency in the rumen due to the corresponding feed in dairy cow feeding.

The determination is based on the following equation: RNB = (crude protein-usable crude protein)/6.25. A lack of rumen-available nitrogen in the total ration leads to an impairment of rumen fermentation including microbial protein synthesis.

The RNB values of a feed can be positive (e.g. with grass silage as the basic feed component, with soybean meal as the protein component) or negative (e.g. with maize silage as the basic feed component, with wheat as the energycomponent). When calculating the ration, care should be taken to balance the overall balance of the ration as much as possible by combining feeds with positive and negative RNB. However, the "fine tuning" of a dairy ration should also be done by checking the urea content in the milk.