Studies on the evaluation of feed protein for ruminants. 1. Passage of nitrogen fractions to the duodenum of dairy cows fed different protein and carbohydrate sources.

The duodenal passages of non-ammonia nitrogen (NAN), amino acid N (AA-N) and microbial N (MN) were measured in seven duodenal fistulated dairy cows (6130 kg FCM/305 d) during lactation receiving 30 different rations similar to those used in dairy practice. The rations consisted of roughage (protein-rich silages, hay) and concentrate mixture (corn, barley, oat) in a ratio of 60:40 on a DM basis or roughage/concentrate mixture/fodder beets in the proportions 60:20:20 or 60:0:40 respectively. N supplements consisted of soya bean meal and peas meal (untreated or treated with formaldehyde in each case), rapeseed meal, fish meal and urea.

[The effect of different centrifugation conditions in the isolation of mixed rumen bacteria on their content of nitrogen and diaminopimelic acid: use of duodenal content as raw material].

The objective of the present study was, to investigate the effect of varying conditions of differential centrifugation of duodenal content on the isolation of bacteria (B-fraction) and feed particles + protozoa (FP-fraction). The treatments at low-speed centrifugation were as follows: 100 x g/5 min, 400 x g/10 min, 1000 x g/10 min and 2000 x g/10 min, high speed conditions were 30,000 x g/30 min/4 degrees C. The results of three experiments are given.

[The effect of different centrifugation conditions for the isolation of mixed rumen bacteria, on their nitrogen and diaminopimelic acid content].

Three cows were given two rations, a silage diet (3 animals) and a green forage diet (2 animals). Samples of rumen content were collected and aliquots of these were separated in a fraction of feed particles and protozoa (FP-fraction) and a fraction of mixed bacteria, varying the conditions of differential centrifugation. The low speed centrifugation was practised at 100 X g/5 min, 400 X g/10 min, 1000 X g/10 min, and 2000 X g/10 min.

[Effect of the content of crude plant protein in the ration on the utilization of urea in dairy cattle. 2. 15N-urea metabolism].

The metabolism of 15N-urea in the rations of dairy cows was investigated in dependence on the crude protein content of the rations. With energy concentration remaining unchanged, the rations contained 10.7 (I), 13.

[Protein digestion in ruminant calves].

The influence of various protein sources on N-digestion in forestomachs was investigated with 10 calves of the average age of 12 weeks which were supplied with duodenal re-entrant cannulae. 50 and 100% resp. of the soybean coarse meal-N in the standard ration (A) were replaced by urea-N (B) and lucerne-N (C).