PREDICTION OF DUODENAL FLOW OF UTILIZABLE CRUDE PROTEIN IN DAIRY-COWS

The amount of utilizable crude protein (nXP) at the duodenum is substa nial for protein supply of ruminants. To estimate the duodenal flow of utilizable crude protein from dietary parameters, the results of 532 individual experiments conducted with fistulated cows in Braunschweig- Volkenrode and Dummerstorf-Rostock were used to formulate equations fo r prediction, Most of the variation in nXP could be explained by diffe rences in metabolizable energy (ME) or digestible organic matter (DOS) and non-urea feed protein (XP), Some improvement in predicted values was obtained when taking into account the flow of undegraded feed crud e protein (UDP), which was measured in 335 experiments. The best appro ach could be achieved Lv considering the relationship between microbia l protein synthesis and crude protein degradation in the rumen. The fo llowing equations showed the highest coefficient of determination (tau (3) = 0.91) and the lowest coefficient of variation (cv = 8.9): g nXP = [11,93 - (6,82 (UDP/XP))]ME + 1,03 UDP, and g nXP = [187,7 - (115,4 (UDP/XP))]DOS + 1,03 UDP.