[Physiological nutrition studies of swine for the evaluation of modified proteins. 3. Relationship between the true and apparent N digestibility and amino acid absorption of the small intestines and the parameters of N metabolism]

[Evaluation of the protein quality of silaged corn ear products with different crude fiber contents]

The assessment of the protein quality of silaged maize ear products was carried out on the basis of crude protein and amino acid analyses and of N balance measurings with growing pigs including comparative studies with maize corns and cereals. The differences found in the amino acid concentrations between the individual maize ear products could be verified on the basis of the analysed values of husks, cobs and corns. There were no significant differences in the parameters of total protein utilization (PNu, b-value) between the studied silages. The differing crude fibre content resulted, however, in reverse shifts in N excretion in faeces and urine, i.e. diminished protein digestibility was compensated by improved intermediary utilization.

[Nitrogen and amino acid absorption in the small intestine of growing pigs. 2. Apparent and true crude protein digestibility and amino acid absorption to the end of the small intestine]

Studies of the apparent and true ileal digestibility of crude protein and the apparent and true amino acid (AA) absorption were carried out with 7 female pigs in the live weight range between 22 and 34 kg after ileorectostomy. Protein sources of varied quality with regard to the method of treatment (toasted) and untoasted soybean oilmeal) and to the AA composition (vital gluten or vital gluten + L-lysine X HCl) were used. Distinct differences regarding the apparent ileal digestibility of crude protein and the apparent absorption of amino acids were discovered between the protein sources, the cause of which is to be seen in the different amounts of endogenous N. The true ileal digestibility of crude protein and amino acid absorption were partly distinctly higher than the values of the apparent ileal digestibility of crude protein and AA absorption. On the whole one can say that the results of the investigation gained by means of ileorectostomy can be compared to the values gained from cannulated animals. Thus the experimental method used is suitable for studying the absorption process to the end of the small intestine of pigs.

[The influence of cellulose and various starches in feed on nitrogen metabolism in growing swine]

In N-balance experiments with a total of 49 female fattening pigs with a live weight between 33 and 47 kg the influence of cellulose supplements (exchanger principle) and changing quotas of maize starch and maize soak starch in semisynthetic feed mixtures on parameters of N-utilization was studied. The results show that there may be a positive influence of the supplement of cellulose on total N utilization (b-value, Gebhardt, 1963). One can conclude that, apart from a shift of the ways of N-excretion through faeces and urine, the utilization of products of microbial protein synthesis for N-retention is possible to a nutrition-physiologically relevant degree. The influence of the kind of starch on N-utilization was small.

[Nitrogen and amino acid resorption in the small intestine of growing swine. 1. Animal study method, nitrogen content and amino acid composition of the small intestine chyme by administration of various proteins]

The amount of endogenous N in the chyme at the end of the small intestine and the amino acid composition of the ileum chyme were ascertained with growing pigs with ileorectostomy after feeding qualitatively differentiated protein sources. In dependence on the protein used, distinct differences turned out for some amino acids with regard to their content in the ileum chyme. Bacteriologic and histologic investigations subsequent to the dissection of the test animals showed that - in comparison to the control animals-the functions of the small intestine remained the same during the time of the experiment. The experiment method described appears to be suitable for absorption investigations up to the end of the small intestine of growing pigs.

[Exocrine pancreas secretion in swine after feeding soybean extract meal]

Exogenous N-secretion of the pancreas was investigated with growing pigs with fistulae in the pancreas. For this purpose the two protein sources toasted and untoasted soybean oilmeal were used. After the feeding of untoasted soybean oilmeal a significant increase of the secretion volume and of protein outpour could be observed in contrast to toasted soybean oilmeal within 24 h. The heat-labile soybean trypsin inhibitor also caused an activity increase of the pancreatic enzymes.

[Absorption and use of differently structured protein isolates by rats]

Differently structured isolated proteins with the same amino acid composition were tested with growing albino rats in an N-balance and absorption experiment. The following items were tested: --isolated horse bean protein --hydrolysed isolated horse bean protein with an amino acid supplement to make up for losses due to hydrolysis --horse bean protein-casein (1:1) fibres --isolated horse bean protein with an amino acid supplement to achieve the same amino acid concentrations as in the horse bean protein-casein fibres. The lowest digestibility and utilisation values were ascertained for the hydrolysed protein. Endogenous N-excretion calculated according to the isotope dilution method was higher than for intact proteins, the transport of the chyme in the digestive tract and the true absorption of N in the small intestine had significantly diminished. In comparison with horse bean protein supplemented with amino acids, the horse bean protein-casein fibres showed decreased protein utilisation and increased endogenous N-excretion. Independent of the protein fed and of the time after feeding a relatively constant endogenous N-quota of approximately 70% could be ascertained in the chyme in the small intestine. In contrast to this, the relation between exogenous and endogenous N determined from the contents of the large intestine proved to be dependent on the intermediary utilisation of the protein fed.

[Determination of amino acid balance in the gastrointestinal tract of chickens]

11 different feedstuffs (barley, wheat, rye, oat, wheat bran, soybean meal, peanut meal, cottonseed meal, rapeseed meal, horse bean, fish meal) were tested with adult colostomized broiler hens in digestion experiments; the digestibility of the crude protein and the amino acid (AA) balance of the gastro-intestinal tract were ascertained. The results achieved can be summarised as follows: The AA-composition in faecal protein is relatively independent of the AA-composition of the feedstuffs, it is not constant, however. The NPN-quota in faecal crude protein rises with the increasing crude fibre content in the feed. AA-digestibility calculated from the balance of the gastro-intestinal tract is, with the exception of some AA, in particularly the limiting ones, higher than the digestibility of the crude protein. As the AA-balance of the gastro-intestinal tract does not give a realistic picture of the digestibility of the AA, we recommend to ascertain the AA-balance up to the end of the small intestines in order to gain more profound knowledge with the help of such basic investigations with selected feedstuffs.