Over a period of 7 days, 38 experimental rats were fed a casein diet with a supplementation of 6.6 mg 15N-excess (15N') in the form of ammonium acetate. From the 5th experimental day, groups of 4 or 5 rats each were fed, over 5 days, different protein carriers to meet the meintenance requirement (115 kcal/kg body weight 0.75). The 15N-excretion via the urine, in terms of % of N absorbed from the food protein, served as yardstick of protein quality under maintenance conditions. The least 15N-excretion rates were reciprocally relativated for this maximum value (reciprocal 15N excretion biological value). The least 15N-excretion values from the 2nd to the 5th experimental days allowed to establish the following order for protein quality under maintenance conditions: fish meal, casein, wheat, whole egg, soybean (assayprotein), yeast peas, gelatin. The very good quality of the wheat protein for the maintenance state is seen in relation with the high content of glutamic acid (33.5 g/16 g N) and aspartic acid (5.7 g/16 gN). The found lysine content of the wheat protein (3.1 g/16 g N) proved sufficient for maintenance conditions.
Four male castrated pigs (55-65 kg) either received a wheat--fish meal diet (1 and 2) or a wheat--horse bean diet (3 and 4) without straw meal supplement (1 and 3) or with a supplement of 20% DM partly hydrolysed straw meal to the DM of the ration (2 and 4). In order to investigate whether a 15N-labelling of the pigs is also possible with a protein excess in the ration, the animals 1 and 2 received 24.8 g and the animals 3 and 4 = 11.6 g crude protein/kg0,75 live weight. During a 10-day 15N-labelling 385 mg 15N-excess (15N') per kg0,75 were applied in a mixture of ammonia acetate and ammonia chloride in the feed. During the period of 15N-labelling the following quotas of the applied 15N-amount were incorporated: 1 = 10.2%, 2 = 7.2%, 3 = 18.7%, 4 = 14.4%. 15N-excretion in both TCA fractions of faeces showed a highly significant positive correlation to the increasing content of crude fibre in the 4 diets. The immediate 15N-incorporation into the TCA-precipitable fraction of faeces (from the 2nd of the beginning of the 15N-application onwards) proves that 15N enters the large intestine endogenously (probably as 15N-urea) and serves bacterial protein synthesis. Three days after the last 15N-application the pigs were killed. The following values of atom-% 15N' could be determined in the TCA-precipitable blood plasma and in the TCA-precipitable fraction of the liver: 1 = 0.18 and 0.19 resp., 2 = 0.22 and 0.27 resp., 3 = 0.22 and 0.23 resp. and 4 = 0.24 and 0.26 resp. The other examined organs and tissues showed smaller differences between the test animals. The following atom-% 15N' were measured in the TCA-precipitable fractions on an average of the 4 test pigs: kidney = 0.20, pancreas = 0.18, intestinal wall tissue, duodenum = 0.18, jejunum (beginning) = 0.17, jejunum (end) = 0.15, ileum = 0.15, caecum = 0.16, colon (beginning) = 0.15, colon (middle) = 0.14, colon (end) = 0.13, stomach (cardia) = 0.11, stomach (fundus) = 0.12, spleen = 0.13, heart = 0.12, skin = 0.07 and skeleton muscles = 0.06. The results show that the 15N-labelling of tissues and organs of pigs is also possible at a high level of protein supply by means of an oral application of 15N ammonia salts.
4 different groups of experimental animals (rats) were injected 14C leucine at 4 different levels of specific 14C activity. Groups A and B received a dosis of leucine corresponding to the daily leucine requirements of the animals. The specific 14C activity was high in group A and low in group B. Groups C and D were injected a leucine dosis at a level of 10% from the groups A and B. the specific 14C activity being again high (group C) or low (group D). The results showed that a true evalution of the experiment could lnly be achieved if the values were related to the true rate of labeling (DPM/mg N or specific 14C leucine activity). The "percentage of the injected dosis" proved to be unsuitable for the analysis of the experimental results when taken as reference frame. The levels of specific 14leucine activity in free plasma leucine were in the same order as the specific activities of the injected solutions (C greater than A greater than D greater than B) whereas the order of specific 14C leucine activities in the TCE-soluble fraction of the pancreatic gland (TCE-trichloroacetic acid) was found to be A greater than C greater than B greater than D. This was due to the higher rate of 14C-leucine transfer into the protein fraction in the animals of group C and D receiving a normal supply of leucine. In these groups an equilibrium in specific 14C-leucine activity between the TCE-soluble and TCE-precipitable fractions was achieved 20-30 mins after injection. A relatively high degree of labelling of the pancreatic protein was noted as early as about 2 minutes after the injection of 14C-leucine. This indicates that in studies on amino acid absorption the secretion of those amino acids that are first absorbed and then resecreted via the pancreatic gland should always be taken into account.
Four pigs (59-65 kg live weight) were labelled over a period of 10 days with 15N in the feeding of a fishmeal diet (1), a fishmeal diet + partly hydrolysed straw meal (2), a horse bean diet (3) and a horse bean diet + partly hydrolysed straw meal (4). After a 24-hour fasting the animals were provided with simple cannulae in the upper part of the small intestines. After a fasting period of 24 h all four pigs received a 14C-leucine injection and the cannula secretion was collected in the subsequent 24 h. After the feeding of the diets without straw meal supplement (1 and 3) there were distinct differences in the secretion in comparison with the feeding with straw meal supplements (2 and 4) despite the long fasting period (48-72 h). 14C-activity could already be detected in the TCA-precipitable fraction of the secretion after 3-6 min of the injection in 1 and 3 but only 20 to 25 min after the 14C-leucine injection in 2 and 4. The specific 14C-leucine activity of the TCA-soluble fraction of the secretion was, after the straw meal supplementation to the fish meal diet, 15 times higher 25 min after the 14C-leu-injection, 25 times higher after 70 min, 36 times after 2 h and 1.8 times after 4 h than without straw meal supplementation. For all four diets a specific correlation (r = 0.96) could be ascertained between the increase of 14C-activity/mg N in the TCA-soluble fraction and the increasing crude fibre content in the diet between 25 and 180 min after the injection. Furthermore, a distinctly decreased N-secretion/h could be ascertained (correlation coefficient r = 0.84) with the increasing crude fibre content in the diet. The influence of the crude fibre on the parameters mentioned is seen in the changed osmotic conditions in the secretion, which may be caused by the changed regulation by hormones of the gastro-intestinal tract. The atom-% 15N' in both TCA-fractions of the secretion underwent big rhythmic variations, which is explained by different ratios of the components pancreatic juice, bile, and intestinal juice.
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