Adviser Jens Møller, Danish Cattle Federation

The NorFor protein evaluation in is based on the former AAT/PBV system developed 20 years ago. In 2002 the AAT/PBV system was further developed with the inclusion of single amino acid. In NorFor the feed values are not additive for single feedstuffs. It means that the AAT and PBV value is calculated for the total ration at a given feeding level. For energy (NEL MJ/ kg dry matter) and AAT / PBV there are calculated Standard feeding values for each feedstuff. For the single amino acids i.e. AAT lysine and AAT methionine the values has to be evaluated for the total ration.

NorFor calculates the microbial protein synthesis based on the amount of digested organic matter in the rumen. In the former system it was calculated based on digested carbohydrate i the rumen. In the calculations the results depend on: Feeding level, amount of sugar and starch in the ration and energy from carbohydrate, protein and glycerol.

For rations with high proportions roughage the microbial protein synthesis gives a high content of AAT methionine and AAT lysine in % of AAT. The content is higher than in the former system.

We do not have norms for the content of AAT methionine and AAT lysine, but both "Bedriftsløsning" and the NorFor system can be used to calculate the content of single amino acids in the rations.

The actual high price for the milk/ milk protein means that use of the single amino acids has become more actually.