In this study, the 10 kinds of concentrates (including 5 kinds of protein supplements and 5 kinds of energy feed) and 7 kinds of roughages are selected, and these feed have characteristics of almost all the feed in China, such as the class of protein characteristics, high (protein supplements), media (energy feeds) and low (roughages), which may influence the method used for analyzing DRUP values.
On average, the determined DRUP value of SBM was 98.
The 16 hours of incubation in the rumen may reflect the process of rumen degradation for all types of the concentrates, but for the roughages, varieties may be greatly affected by the cultivation time greatly, which may result in different DRUP values.
A series of findings has been published concerning the determined DRUP values, and their estimations are influenced greatly by the methods being used (such as MNB, OTS, MTS, and ADIN).
In the concentrates, there were no significant differences between the determined DRUP values of the CSM, RSM, SFM, and CGM using the MTS method and those using the MNB method, which showed that the MNB method can be replaced by the MTS method to determine the DRUP values for these four feeds.
Comparative analysis of the DRUP values between MNB and ADIN estimated methods
Although the use of neutral detergent insoluble nitrogen to measure DRUP and the total tract digestibility of forage protein has been violated (Haugen et al.
Regression relation analysis between routine nutrient contents and the DRUP values
The mobile nylon bag method has many disadvantages such as high price, long time period, and the use of a duodenal T-fistula, therefore, accurate methods for predicting DRUP values need to be explored.
i) The mobile nylon bag method can be replaced by the OTS and MTS methods to determine the DRUP values of feeds, and the determined DRUP values using the MTS method were closer to those obtained using MNB, compared with the OTS method.
ii) The use of the ADIN method to predict the DRUP values of the feeds is limited, but routine nutrient contents are available.
iii) Estimates of the DRUP values may be influenced by the rumen incubation time, and further efforts should be aimed at methods to determine the rate of passage rapidly and accurately in cows.