The in sacco protein degradability vs. protein solubility of concentrate ingredients1

Protein degradation in different feedstuffs labelled with 15N by using the nylon bag technique

The nylon bag technique was used to determine the Nitrogen (N) and 15N degradation of 15N labelled feedstuffs in the rumen. The N and 15N degradation values were calculated according to Orskov and McDonald (1979) and ranged from 46.8 to 92.0 and from 61.8 to 93.6%, respectively. The differences between N and 15N degradation values of high fibre content feedstuffs are the highest, thus the measuring errors were greatest here. But differences also existed in concentrates. This study indicated that especially barley had a higher proportion of microbial N in the bag residues after the washing than the other concentrates. Therefore it is necessary to correct the N degradation values not only in cases of high fibre content but also in cases of low nitrogen content of feedstuffs. The calculation of the N degradation values could be possible on the basis of crude fibre and crude protein contents of feedstuffs. But experiments with a much larger number of 15N labelled feedstuffs have to be realized to give an accurate prediction of N degradation.

Effect of grain processing on in sacco digestibility and degradability in the rumen

Effect on nylon-bag digestibility of rolling and steam-flaking as such or followed by grinding through a 1-mm screen was studied in wheat, barley and maize grains. Digestibilities of ground grains were not different, irrespective of rolling or steam-flaking, except flaked and ground barley, which was less digestible than ground barley. Rolled and flaked grains were less digestible than ground grains, except for rolled wheat which was not different from ground wheat. These results suggest that particle size due to grinding is more important than other methods of processing. Dry matter and protein degradabilities of steam-flaked grains were investigated by in sacco technique and compared with unprocessed grains. Dry matter degradability during incubation periods up to 24 h was reduced for steam-flaked wheat and barley, but increased for flaked maize. Protein degradability was lower for flaked grains.