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In the series of experiments with labelled urea three colostomized laying hybrids were butchered after a six-day application of 1% urea with 96.06 atom-% 15N excess (15N') in the ration and another 2 days with a supplement of 1% unlabelled urea. Out of the individual samples from crop, gizzard, small intestine, caecum and rectum, the content of the small intestine and the caecum showed the highest labelling with greater than 1 atom-% 15N'. The TCA soluble fraction of the content of the gizzard was more highly and that of the intestines less labelled than the total nitrogen. The tissue of the gizzard is distinctly less labelled than the "omasum system" and the small intestine. The atom-% 15N' of the oesophagus with crop and glandular stomach largely showed agreement in the individual hens with that of intestinal tissue and ranged between 0.71 and 0.89 atom-%. 2% of the 15N' supplemented with the urea could be recovered in the content and the tissue of the gastro-intestinal tract.

Four Friesian steers (103-150 kg) each equipped with simple abomasal and re-entrant ileal cannulas were used. Different amounts of glucose, maltose or one of several isolated starches or ground cereal grains, ranging from 80-400 g/8 h, together with polyethylene glycol were infused into the abomasums and absorption up to the ileum examined. The efficiency of removal of glucose remained high at all levels of infusion (greater than 80%) and at the highest level, 26.4 g glucose/kg body weight 0.75/d were calculated to be removed in the small intestines. At low levels of infusions, maltose was removed almost as efficiently as glucose, but the capacity of the small intestines to remove maltose was exceeded with infusions above 15 g/kg body weight 0.75/d. Soluble and isolated wheat starch were removed to similar extents and almost identically to maltose. Isolated maize starch, whilst being removed in the small intestines almost as rapidly as maltose at the lowest level of infusion, was less efficiently removed at higher levels. Rice and potato starches were poorly removed in the small intestines. Intestinal capacities for the removal of related wheat, soluble starch, maize, rice and potato starches were 102, 99, 80, 77 and 55% that of equivalent amounts of maltose. Starch in ground cereal grains (maize and wheat) were removed in the small intestines slightly less efficiently (75-90%) than the corresponding isolated starches.

Forty-two samples were taken from the contents of the proximal small intestine of two lactating dairy cows fitted with re-entrant duodenal cannula. Most samples were free of detectable amylase activity. The (chymo)trypsinogen present was only partially activated to (chymo)trypsin. The activation was continued in vitro: slowly at the original pH of the samples (between pH 2.8 and 4.2), and faster after neutralization or a slight alkalinization. The effect of Ca, EDTA and soybean inhibitor on the activation of trypsinogen was also studied. The pancreatic enzymes were inactive in the acid pH range of the samples, but pepsin was markedly active. At pH 3.8 casein was digested rapidly by purified pepsin and slowly by the samples (agar-plate experiments). In model experiments performed with purified enzymes, pepsin digested (chymo)trypsin rapidly at pH 1-2 and slowly at pH 3.8. In the intestinal juice (chymo)trypsin and their zymogens seemed to be unaffected by pepsin under the conditions of the samples. It is concluded that the conditions prevailing in the duodenum/upper jejunum of the experimental cows account for a gastric-type digestion, despite the presence of pancreatic enzymes. In vivo the intestinal contents pass in distal direction. Meanwhile the pH of the chyme gradually increases and gives rise to first an increase of enterokinase activity accounting for a faster activation of the zymogens; second a start of function of activated pancreatic proteases and third a gradual decrease of pepsin activity and finally to its irreversible denaturation. Thus the development of intestinal type digestion is delayed in ruminants.

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.

Young bulls of average live weight 130 kg, with rumen cannulae and re-entrant cannulae of the proximal duodenum, were fed on a diet of maize meal from whole plants, potato starch and a mineral mixture, containing 7.6% crude protein in DM (group IV). For three groups the diet was supplemented to contain about 17.5% crude protein with groundnut oilmeal (group I), grundnut oilmeal and urea, 27 and 31.2% of dietary N (group II) or urea alone (group III). The content of gross energy was similar in all diets. The amount of total N entering the duodenum in groups I to IV was 61.6, 59.2, 49.9 and 38.0 g/day and apparent digestibility of N in the stomachs was -0.4, 5.8, 21.6 and -44.4%. Total amount of amino acids in the duodenal digesta was, in the same order, 257, 261, 215 and 170 g/day, equivalent to 80, 116, 165 and 127% of intake. The ratio of the amounts of essential to nonessential amino acids was in feed 0.84 and in duodenal digesta in all groups 0.98. The amount of lysine in duodenal digesta was 1.5, 2.0, 3.5 and 2.5 times its intake in the same order of the groups.

The crude protein and lysine digestibility values available in literature and ascertained in comparative investigations at the end of the small intestine (distal ileum) and in the complete digestive tract (faeces analysis method) of pigs were subjected to a correlation calculation in order to find out whether and to what degree there are relations between apparent 'ileal' and apparent 'faecal' digestibility. For both crude protein and lysine the relation between ileal and faecal digestibility is so close (r = 0.73 resp. 0.85 ... 0.98) so that for practical purposes it is not necessary to determine the apparent ileal digestibility for each feedstuff by means of the complicated cannula method. This can be calculated with great reliability from the experimentally ascertained apparent faecal digestibility. The differences between faecal and ileal digestibility are smaller for lysine (conversion factors 0.92 ... 0.99) than for crude protein (conversion factors 0.89 ... 0.93).

Concentrations of amines were analysed in the digesta of piglets and fattening pigs after refining using an aminoacid-analyser. Feed contained only small amounts of putrescine. In the stomach histamine, tyramine, putrescine and cadaverine were nearly equally distributed, whereas in the colon cadaverine presented the main part. Piglets with 24% CP had in stomach/small intestine/hindgut 4.2/10.2/9.6 mmol, with 18% CP-/5.5/4.9 mmol amines/kg DM digesta. Fattering pigs showed in jejunal digesta from 2.1 to 8.7 mmol, in the caecum 1 to 4.8 mmol and in the colon 0.2 to 2.2 mmol amines/kg DM. Increasing CF-contents and bactericide supplements in the diet lowered amine concentration in all gut sections not significantly.

In an experiment with 10 colostomized broiler breeding hens the digestibility of wheat straw meal labelled with 15N and the incorporation of heavy nitrogen into individual body fractions were studied. The straw meal contained a 15N excess (15N') of 14.88 atom-%. Before the experiment part of the straw meal was treated with gamma-rays (2.0 MGy). 5 animals each received in addition to the basic ration 30 g untreated (group I) and irradiated 15N labelled straw meal (group II). The apparent 15N' digestibility amounted for untreated straw meal to 49% and for irradiated straw meal to 46% (p less than 0.05). The labelling of uric acid amounted to 0.25 atom-% 15N', urine with 0.30 atom-% 15N' was more highly labelled (p less than 0.05). On an average of both groups the same labelling of 0.18 atom-% could be detected in the follicles and the liver, whereas 0.17 were ascertained in the blood plasma and 0.16 atom-% 15N' in the oviduct. 18% of the digested 15N' were incorporated in the muscles. There were only insignificant differences between the two groups with regard to the incorporation of 15N'. In conclusion one can say that the apparent digestibility of straw protein is 47.5% and that the utilization of the absorbed N is about the same as that of wheat protein.

The flow of the individual amino acids (AA) into the duodenum was determined after the feeding of 28 different rations to young bulls supplied with duodenal re-entrant cannulae in the live weight range between 140 and 460 kg. The distribution of AA into AA of bacterial origin and AA from the feed was made by difference calculation between the AA at the duodenum (corrected by the endogenous AA quota) and the AA from the bacteria crude protein, with our own results based on a constant AA composition of the bacteria crude protein; by the regression analysis from relative values according to AAD/app. dig. org. m. = a + b AAF/app. dig. org. m. and by the regression analysis of the absolute values according to AAD = b1 app. dig. org. m. + b2 AAF showed the same results from the regression methods but deviating ones from the difference method. The calculation of the flow of the individual AA into the duodenum from the AA content of the ration and the content of app. dig. org. m. of the ration is possible. The equations derived for this purpose of the individual AA are given.

Friesian steers, virtually protozoa free, were equipped with simple rumen and abomasal cannulas. They were given diets consisting of approximately equal proportions of ground, pelleted alkali treated straw and a rolled barley, tapioca mixture supplemented with urea + casein (UC), soybean meal (SBM), 'normal' white fishmeal (NDF) or white fishmeal designated as being of 'low' rumen degradability (LDF). The diets were isoenergetic (the protein sources replacing part of the tapioca) and they were given in amounts to supply sufficient metabolizable energy (ME) to support an average growth rate of 0.5 kg/d. Rumen degradable nitrogen (RDN): ME values were estimated to be 2.08, 1.40, 1.90 and 1.66 for diets UC, SBM, NDF and LDF respectively. RNA, alpha-epsilon-diaminopimelic acid and 35S (added as sulphate) were used as bacterial markers. Chromic oxide and polyethylene glycol (PEG) were given as flow markers and flows (g/24 h) at the abomasum of organic matter (OM) and nitrogenous constituents were calculated. Rumen volumes and ruminal liquid fractional outflow rates were measured using PEG. Samples of mixed rumen bacteria separated from strained rumen digesta from animals receiving diet UC contained significantly less DAP-N (0.322 g/kg DM) than those from animals receiving diets SBM, NDF or LDF (0.530 g/kg DM). Mean rumen volume (approximately 15 l) and liquid fractional outflow rates (approximately 0.105/h) were similar on all diets but there was appreciable variation between animals. The proportion of OM intake digested in the rumen was similar on all diets. The proportional contribution of bacterial-N to the total non-ammonia-N passing the abomasum based on mean values derived from DAP and 35S as markers was 0.57, 0.47, 0.39 and 0.31 for diets UC, SBM, NDF and LDF respectively. Corresponding values based on RNA were 0.71, 0.50, 0.48 and 0.35 respectively. Bacterial-N (RNA) flows at the abomasum were 31, 25, 26 and 20 g/d for diets UC, SBM, NDF and LDF respectively. Corresponding values for 35S and DAP were 26, 24, 21 and 18 g/d respectively. Values derived from RNA flows were consistently and significantly higher (P less than 0.01) than those based on DAP or 35S. Mean estimated efficiencies of bacterial protein synthesis (g bacterial-N/kg OM truly digested) were 15, 15, 14 and 12 for diets UC, SBM, NDF and LDF respectively.(ABSTRACT TRUNCATED AT 400 WORDS)

Isobutylidene diurea (IBDU) was tested against urea with regard to the ammonia release in the rumen, the amount and composition of the nitrogen fraction reaching the intestine, the nitrogen and energy balances and the performance of lactating cows. Maize silage was the basal feed in all experiments. The ammonia concentration in the rumen liquor was measured in two dry cows fitted with a permanent rumen cannula. The ammonia release was clearly restrained when IBDU was substituted for urea, and the peak values were of the same order as those found with soybean meal. Two dry cows fitted with a re-entrant cannula at 10 cm from the pylorus were fed with maize silage supplemented with increasing amounts of either urea or IBDU. The duodenal flow levelled off with urea, but it continued to rise with IBDU even when high amounts were added to the silage. However, a large fraction of this increase was in the form of ammonia, corresponding to 60% of the dietary nitrogen supplied by IBDU. The amount of non-ammonia nitrogen was also higher with IBDU. The nitrogen balance of lactating cows was not noticeably affected when IBDU instead of urea was added to the maize silage. In the same manner, the digestibility of the rations and their metabolizable energy supply were not significantly modified, and the milk productions were quite similar with the two N compounds, apart from the tendency to lower milk fat and milk protein productions.

Four groups of four colostomized laying hens each received rations only consisting of wheat, vitamins plus a mineral mixture and a graded daily feed supply of 110 g, 88 g, 66 g and 44 g. The determination of amino acids from faeces was carried out after hydrolysis from a 6-day sampling period from the 16 laying hybrids. At the end of the experiment the animals were slaughtered. The corpuscular fractions of the blood, the contents of crop and stomach as well as of the intestines were also hydrolysed and the amino acid content in the crude protein was determined. In addition, the content of free amino acids in the blood plasma was determined. The content of amino acids in the protein of the corpuscular blood fractions remained uninfluenced by the decreasing amino acid and energy supply. The content of free basic amino acids in the blood plasma decreased with the decreasing supply with amino acids and energy, whereas the content of free amino acids with branched chains and hydroxylized ones increased. The content of glutamic acid in the contents of crop and stomach changed considerably in comparison with feed protein. The amino acid values of the crude protein in the contents of the intestines and in faeces to a large extent differ considerably from those of the wheat fed and are approximate values of body protein. Deficient supply with amino acids and energy did not influence the apparent digestibility of the amino acids.

Model investigations carried out by means of a re-entrant method at the duodenum with dairy cows and with energy-equivalent rations (600 EFU cattle/kg DM), which after the supplementation of 11 g urea/kg DM (150 g/animal and day) contained 13.8 (I), 16.7 (II) and 20.2 (III)% crude protein, had the following results: The amino acid profile of the duodenal protein differed from that of the applied rations and was similar to the microbial protein in the rumen. It only changed inconsiderably with the protein level of the ration. There were differences between the amino acids of the feed as to their apparent rate of fermentation in the rumen. Ser, tyr, lys, and leu apparently proved to be most resistent whereas arg, asp, met, ile and phe were apparently fermented for the most part or completely. The passage rate of amino acids at the duodenum related to intake were, from I ... III 126, 102 and 87%. With all rations there were always net losses of some amino acids (his, arg) and net gains (lys, thr, ser, gly, val, met and tyr) at the duodenum in comparison intake. 15N from urea was incorporated into all the amino acids determined in the duodenal protein, most intensively into glu, ser, asp, ile, gly, his and leu. The apparent digestibility of the total amino acids in the intestines was independent of the crude protein level of the rations and reached 69 ... 71% with a deviation range of 59 ... 81% for the individual amino acids.(ABSTRACT TRUNCATED AT 250 WORDS)