Protein digestability and amino acid absorption in various segments of the digestive tract of pigs. 1. Methods of animal experimentation, protein content and amino acid patterns of the digesta in the small intestine and in feces after feeding different feeds]

Re-entrance cannulae were applied by way of operations at the end of the small intestine of a larger number of growing pigs. After a post-operative phase these animals were fed with various rations (N-free diet, fattening feed for pigs, rations with dried skim milk resp. wheat gluten + lysine and wheat + wheat gluten + lysine). During the main experiment periods the ileum digesta (24 hour-periods of collecting) and the feces were quantitatively registered. The protein and amino acid content ascertained in the feed rations, the digesta and feces samples are reported, comparatively evaluated and discussed. The amount of amino acids (in mg per kg intake of dry matter) contained in the ileum digesta after N-free feeding were statistically calculated with regard to differences occuring between the animals and days. For most amino acids a significant decrease in the ileum digesta could be detected during the course of the N-free feeding period. Moreover, the amount of amino acids in the ileum digesta was compared with the metabolic fecal amino acids, from which conclusions could be drawn concerning the disappearance rate of the individual amino acids in large intestine.     

Protein digestibility and absorption of amino acids in various segments of the digestive tract of pigs. 2. Protein and amino acid balances at the end of the small intestine and of the whole digestive tract (apparent and true protein and amino acid digestibility)]

Growing pigs with ileum and ileocecal re-entrant canulae were given 5 different rations (pig fattening feed 1 and 2, rations with dried skim milk, wheat gluten + lysine and wheat + wheat gluten + lysine). The crude protein and amino acid excretion was quantitatively determined with ileum chyme and feces. The calculation of the amino acid balances (apparent and true digestibility) at the end of the small intestine, at the end of the wholedigestive tract and the isolated colon showed characteristic differences for the individual amino acids. On ileum level the amino acids with relatively high endogenous quotas, threonine, tryptophane, alanine, aspartic acid and glycine showed a distinctly lower, the amino acids arginine, methionine, phenylalanine, glutamic acid, proline and tyrosine a distinctly higher digestibilityhan crude protein. In comparison of the values on the feces level, including the true digestibility, these differences are largely balanced out. At the end of the small intestine the absorption of the amino acids is in the main completed. The disappearance rate of amino acids from the colon shows large differences with reference to the different rations as well as the individual amino acids. They were particularly high for various rations as far as proline, tryptophane, glycine and cystine are concerned. If wheat gluten + lysine rations were given, a net synthesis of methionine in the colon could be proved.     

Protein and amino acid digestibility in various sections of the digestive tract of swine. 2. Protein sources of plant origin

Growing pigs provided with ileocaecal re-entrant cannulae were fed three rations containing plant protein sources and two N-free rations. The crude protein and amino acid flow in the digestive tract as well as the apparent and true digestibility of the crude protein and the amino acids for the individual sections of the intestines are explained. It shows that relating the calculation of metabolic faecal amino acids to live weight results in more realistic values than relating it to feed intake.     

The protein digestibility and amino acid absorption in various segments of the digestive tract of pigs. 6. Results of the application of 15N-lysine]

From two fattening pigs (average live weight 63 kg) with re-entrance cannulae both in the duodenum and the ileocecal region, the intake, the excretion and the flow rates of nitrogen, 15N, lysine and 15N-lysine are measured after the oral application of 15N-lysine as supplement of a wheat-wheat gluten diet. A scheme of the lysine metabolism of pigs is drawn on the basis of the measured values. The absorption of synthetic and native lysine as well as the endogenous and exogenous lysine contents of the duodenal and ileum chyme are estimated.     

The effect of different high levels of soy extract pellets in the ration on the digestibility of crude nutrients, basic and sulfur-containing amino acids of wheat in colostomized laying hybrids

In two digestibility experiments with 4 colostomized laying hybrids each, the influence of 12.5% (ration 1) and 25% soybean meal (ration 2) on the digestibility of the crude nutrients, the basic and sulphur-containing amino acids in the wheat rations was tested. In ration 1 the digestibility of the crude protein was 84.9%, of the crude fat 56.6% and that of the N-free extractives 87.4%; for ration 2 the values were 83.6%, 47.4% and 82.5%. The digestibility values for wheat acquired with the difference method for ration 1 were 85.7% for crude protein, 57.0% for crude fat and 89.8% for N-free extractives; energy concentration was 766 EFUhens. For wheat supplemented with 25% soybean meal the same digestibility value of the crude protein could be ascertained, the digestibility of the crude fat and the N-free extractives, however, was lower than for ration 1 so that an energy concentration lower by 3.9% was calculated. The possible causes of the influence of the different levels of lysine and thioamino acids on the digestibility of these amino acids of wheat are described.     

Nutrient composition of some newly bred high-protein and/or high-lysine cereal strains and digestibility by growing pigs. 2. Protein quality and digestibility of the amino acids

After a first report on the nutrient composition and the digestibility of some newly bred varieties of cereals, information on the apparent digestibility of the amino acids in growing female pigs ascertained with the same test material is given. These data serve the evaluation of the quality of such cultivation products and the completion of the data in of feedstuffs tables and tables of the amino acid content. The newly bred barleystrains meet the requirement of digestible protein of pigs, wheat exceeds it whereas the maize samples fall short of it. The content of digestible lysine in the newly bred barleystrain approximate the requirement of growing pigs. There is ample digestible methionine + cystine in all samples. This again proves that newly cultivated barley and wheat rich in protein and lysine if accordingly supplemented with the limiting amino acid lysine can be used as sole feed for fattening pigs. Moreover, it becomes again obvious that the apparent digestibility of the amino acids can, for practical purposes, be sufficiently exactly evaluated with the help of the apparent digestibility of the crude protein of the respective feedstuff.     

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.     

Evaluation of apparent ileal digestibility of amino acids in Chinese corn by-products for growing-finishing pigs.

Twelve crossbred barrows (BW 47 +/- 2.81 kg) were fitted with a T-cannula in the terminal ileum and fed one of ten diets containing corn gluten meal, dried distillers grain or dried distillers grain with solubles as the sole protein source, according to a 6 x 6 Latin Square design. Lysine, tryptophan and methionine were, the first, second and third limiting amino acids in these by-products. The ileal apparent digestibility of methionine, tyrosine, leucine and phenylalanine in corn gluten meal was high. The ileal apparent digestibility of tryptophan, tyrosine and leucine differed significantly in corn gluten meal. The ileal apparent digestibility of amino acids was higher in dried distillers grain with solubles than in dried distillers grain. To predict the ileal apparent digestibility of tryptophan, methionine and threonine linear regression equations were derived. The results suggested that processing technique can influence the ileal apparent digestibility ofamino acids in corn by-products. It was concluded that the direct technique cannot accurately determine the ileal apparent digestibility of tryptophan in dried distillers grain with solubles and dried distillers grain, due to its low content. The content of an amino acid in a feedstuff used as the sole source of protein must meet the minimum requirement of pigs when the ileal apparent digestibility of constituent amino acids is determined using the direct technique.     

Absorption and utilization of amino acids infused into the cecum of growing pigs. 1. Measurement of N-balance for utilization of lysine and isoleucine; isoleucine requirement for growing pigs

In N-balance experiments with growing pigs (40-60 kg live weight) investigations were made whether lysine or isoleucine that is infused into the caecum can be absorbed there and to what extent these amino acids in that case can be utilised by the animal for protein synthesis. The pigs either received basic rations with insufficient lysine or isoleucine resp. (negative control group) or the amounts of lysine and isoleucine lacking to meet the requirement were supplemented with the feed (positive control group) or continuously infused into the caecum with the help of caecal infusion cannulae (test group). In the experiments with lysine the animals in the negative control group and in the test group showed considerably lower N-balances than the positive control group. There were no differences as regards the apparent digestibility of lysine between the positive control group and the test group. The urine of the test group contained distinctly more NH3. This shows clearly that lysine that is infused into the caecum cannot be utilised by the pigs, it is, on the contrary, microbially decomposed, the nitrogen is chiefly absorbed as NH3 and excreted in urine. As regards isoleucine, the deficit brought about with the basic ration was insufficient in order to achieve significant differences between the N-balance values of the groups so that unambiguous statements on the absorption and utilisation of isoleucine infused into the caecum cannot be made. Concerning apparent digestibility of isoleucine and the NH3 content of the urine, the results of the isoleucine experiments were similar to those in the lysine experiments. According to our N-balance experiments the isoleucine requirement of pigs indicated in relevant literature as 5.6 g/kg dry matter of the feed is by far too high. It should be limited to 3.5 or a maximum of 4.0 g isoleucine per kg dry matter of the feed.     

True ileal digestibility of amino acids in sow's milk for 17-day-old pigs

The digestibility of amino acids in sow's milk consumed by young pigs is currently unknown because of difficulties associated with collecting an adequate quantity of milk, and also problems in cannulating suckling pigs. A total of 14 kg of sow's milk was collected, two soluble indigestible markers (Co-EDTA and YbC13) were added, and the milk was fed to four pigs at 17 d of age that were fitted with a simple T-cannula at the terminal ileum. Another four cannulated pigs were offered a similar amount of a 20% DM liquid diet based on enzymatically hydrolyzed casein and lactose to assess endogenous amino acid losses. All pigs were fed about 875 g of each diet per day in 10 hourly meals from 0700 to 1700. Following 2 d of adaptation, ileal digesta were collected from 0800 to 1800 for 2 d. Diets and digesta were analyzed for amino acids using appropriate hydrolysis and preoxidation procedures. Average nitrogen true digestibility was 88%, whereas amino acid true digestibilities ranged from 84% (cystine and threonine) to 100% (methionine, histidine, and glutamic acid); the average for all amino acids was 92 +/- 4%. Based on average values, true digestibility of essential amino acids was not different from that of nonessential amino acids (P > 0.10). In whole milk, amino acids found in abundance in whey proteins (i.e., cystine, glycine, and threonine) were less (P < 0.05) digestible than amino acids predominating in casein proteins (i.e., glutamic acid, proline, and methionine). When true ileal digestible amino acid concentrations in sow's milk were expressed as ratios to digestible lysine, it appeared that threonine, tryptophan, and arginine were lower than what might be considered optimal. In conclusion, amino acids in sow's milk were highly digestible, but most of the amino acids had true ileal digestibility values significantly less than 100%.     

The effect of straw meal on the crude protein and amino acid metabolism and the digestibility of crude nutrients in broiler breeding hens. 3. Digestibility of amino acids

In two experiments with colostomized broiler hens the influence of a straw meal supplement on the apparent digestibility of the amino acids of the ration and the 15N labelled basic amino acids in wheat was studied. In experiment 1 the animals received 120 g mixed feed plus 0, 20, 30 and 40 g straw meal per animal and day. The digestibility of the amino acids decreased on average from 86% to 83%, 80% and 79% with the growing straw intake. In contrast to the control variant, 20 g straw meal intake resulted in a significant decrease of digestibility for lysine, histidine, glycine, tyrosine, phenylalanine, cystine and methionine. 30 and 40 g straw meal reduced significantly the digestibility of all amino acids with the exception of arginine. The amino acid composition of the crude protein in faeces changed only very slightly due to the straw supplement. In experiment 2 15N labelled wheat was a component of the ration. Of the 15N labelled amino acids lysine, histidine and arginine, 88, 90 and 95% were apparently digested. The adaptation of the animals to straw meal intake did not change the digestibility of the amino acids.     

Apparent digestibility of nitrogen and amino acids in protein feedstuffs by growing pigs

Eight digestion trials were conducted with pigs fitted with ileal T-cannulas to determine the apparent digestibilities of N and amino acids in common protein feedstuffs. Trial-to-trial variation was minimal as determined by the variation in digestibilities for soybean meal, which was evaluated in each trial. Apparent digestibilities varied widely; ileal N digestibility ranged from 88 to 63%, and ileal lysine digestibility ranged from 93 to 40%. In general, ring-dried blood meal, corn gluten meal, Menhaden fish meal, poultry-by-product meal and extruded whole soybeans were the most digestible, followed by canola meal, sunflower meal, peanut meal and meat and bone meal. Cottonseed meal and feather meal were the least digestible. Mean values for each feedstuff agree well with published data. Variation in digestibilities among samples of the same feedstuff was greater for the meat and bone meals. Regression of ileal essential amino acid digestibilities on ileal and fecal N digestibility indicated that amino acid digestibilities can be predicted more precisely from ileal N digestibility than from fecal N digestibility. However, neither ileal nor fecal N digestibility could be used with a high degree of certainty to predict ileal amino acid digestibilities.     

The apparent prececal and fecal crude protein digestibility and amino acid absorption of coarse animal feed in fattening pigs

Digestibility experiments were made with nearly full-grown female fattening pigs supplied with large-scale T-cannulae implanted in the distal ileum to collect the digesta in order to test 11, mainly dried and pelleted, kinds of forage plants (9 samples of lucerne cut at different times as well as green rye and whole plants of maize) as supplements to a basic diet. All samples were analysed to their content of HCl-insoluble ash as marker and their content of amino acids (AA). The calculation of the apparent precaecal and faecal crude protein (CP) digestibility and of the absorption values of the essential AA lysine, methionine, cystine, isoleucine, threonine and tryptophan as well as of glutamic acid was carried out according to the difference method. CP digestibility of the experimental diets was precaecally reduced by 5 to 20 and faecally by 3 to 13 units by supplements of at least 25% of the dry matter; for some of the AA the reduction was even bigger and dispersion between the values of the individual animals was essentially increased in comparison with the basic ration. Faecally, the precaecal differences of CP digestibility and AA absorption caused by the various alfalfa samples, are largely blurred. The CP and AA digestibility of the forage plants partly showed very big individual differences between the animals. Precaecally, a CP digestibility of more than 48% could not be ascertained. Similarly to the lysine content, precaecal lysine absorption from the kinds of roughage showed big differences. Whereas the absorption values for methionine of between 60 and 87% were relatively high, those for cystine were mostly very low, often in the negative range. This underlines that normal digestion processes are strongly influenced by high supplements of forage plants so that the constancy of the digestibility of the basic ration must be doubted under these conditions. The bacterial processes in the large intestine greatly level out the differences found precaecally between the various kinds of feedstuffs. The faecal digestibility and absorption values were considerably above those measured precaecally; methionine digestibility only was mostly considerably diminished in comparison with precaecal values due to synthesis in the large intestine. A significant positive correlation could be calculated between the lysine content of the 9 alfalfa samples (4.0 to 6.6 g/16 g N) and the apparent precaecal values of lysine absorption (2.2 to 67.6%).(ABSTRACT TRUNCATED AT 400 WORDS)     

The effect of different levels of soybean extract meal on the apparent digestibility of crude nutrients and amino acids in colostomized laying hens

Four colostomized laying hens per group were given a ration of barley and soya bean oil meal (SBM) with 12.5, 25.0 and 37.5% SBM resp. The crude protein intakes were 14.0, 17.7 and 21.4 g per animal and day. The lysine intake raised from 681 mg (group 1) to 1275 mg (group 3) per animal and day. The digestibility of dry matter and of the N-free extracts of the ration decreased with the rising SBM portion in the ration. The digestibility of crude protein remained constant. The investigated amino acids (Lys, His, Arg, Cys, Met) were higher digested in the 37.5% SBM ration than in the 12.5% SBM ration. The following digestibility values for SBM were found by means of the difference method: Dry matter 52.5%, crude protein 83.1%, crude fat 51.7%, crude fibre 5.5%, N-free extracts 50.6%. The level of the SBM did not influence the digestibility of the crude nutrients. The apparent digestibility of lysine from SBM depended on the level of intake and was found to be 82.3, 83.4 and 89.0%, resp. There were no differences in the digestibility of other amino acids.     

Effect of thermal treatment of potato products on nutrient decomposition in the digestive tract of swine. 1. Passage and digestibility of nutrients in the various portions of the intestine

In addition to a basic ration (barley, dried green fodder, fishmeal) pigs (castrated males, 100 ... 130 kg live weight) received a supplement of raw potato starch, raw ensiled potatoes, cooked potato starch or steamed ensiled potatoes; nutrient and amino acid passage and digestibility (absorption) were measured in the small intestine, the upper large intestine and the total digestive tract with the help of simple cannulae at the distal ileum and the middle of the hind gut and the estimation of the HCl insoluble ash as an indicator. In addition, the amounts of bacteria in faeces were determined and the influence of raw and cooked potato starch on N retention was ascertained. When raw potato products were fed, distinctly higher amounts of dry matter, organic matter and starch pass the ileum, which get into the colon undigested, i.e. the digestibility of these substances is low at the end of the ileum (raw potato starch 24%, starch of raw ensiled potatoes 36%). Up to the middle of the colon there is intensive bacterial starch degradation so that in this place the difference between raw and thermically treated potatoes is only small. No matter what the previous treatment of the potatoes was, there is hardly any starch in faeces, i.e. it was nearly 100% digested up to the end of the digestive tract. The passage and digestibility resp. of ash and crude cellulose from the basic ration is not influenced by the supplement of raw or thermically treated potato products in the individual sections of the digestive tract. At the end of the ileum there are no differences between the apparent digestibility of the crude protein and absorption of amino acids of supplemented raw or cooked potato starch or steamed ensiled potatoes; after the use of raw ensiled potatoes they are, however, significantly more reduced than the comparison of analyses of faeces shows. In the large intestine the high amount of potato starch stimulates the metabolism and the reproduction of faecal bacteria as is shown by an increase by 20-30% in bacteria N excretion in faeces. Apparent crude protein digestibility and amino acid absorption are diminished by that. The increased N excretion in faeces after the supplement of raw potato starch to the basic ration is-in comparison with the supplement of heated starch-compensated by a commensurately lower N excretion in urine so that N retention practically remains uninfluenced by the supplement of variously treated potato starch.(ABSTRACT TRUNCATED AT 400 WORDS)     

Ileal digestibility of amino acids in pigs fed barleys differing in protein content

The apparent digestibility of nitrogen and amino acids was measured by the ileal and faecal methods in pigs fed nine barleys differing in nitrogen content (from 1.73 to 2.16 per cent/DM). A positive (r = 0.87) and significant relationship was found between the apparent nitrogen digestibility at the end of the ileum and the crude protein content of barley. Generally, the higher the protein of the grain, the higher the ileal digestibilities of the amino acids. For most amino acids the faecal values were greater than the ileal ones. This being specially so for threonine, tryptophan, histidine and cystine belonging to the nutritionally important amino acid group. When the relationship between the amino acid and nitrogen digestibilities at the level of ileum is considered, the values were found to be similar to that of nitrogen in the case of tryptophan, higher for isoleucine, valine (both 2-3 units), cystine, histidine, leucine, methionine (all 5-6 units) and phenylalanine (10 units) and lower only for lysine and threonine (7-8 dig. units).     

Effect of native crude fiber on the digestibility of nitrogen and amino acids in pigs

In experiments with fattening pigs peas and lupines were used, both pealed and unpealed, in order to investigate the influence of native crude fibres on the true digestibility of nitrogen and the amino acids in pigs. The results of the experiments allow the conclusion that native crude fibres, as long as they remain in the normal range between 3 and 7% in the ration does not cause a depression in the true digestibility of nitrogen and the amino acids in the feeding of fattening pigs. Only the increased content of native crude fibres in the ration has a negative effect on true digestibility.     

ORIGINAL ARTICLE: The effect of dietary methionine levels on endogenous nitrogen and endogenous amino acids flows in growing goats

The effect of dietary methionine (Met) levels on endogenous N and amino acids (AA) flows at different part of the digestive tract of growing goats was determined using a ¹⁵N isotope dilution technique. Three goats (25 ± 2.5 kg) were fitted with the ruminal, duodenal and ileal cannulae and allocated to three dietary treatments in a 3 × 3 Latin square design. The dietary treatments consisted of a total mixed ration containing three levels of Met (0.15%, 0.25% and 0.35%) respectively. It was found that at 0.15% Met level, the lowest flow in endogenous N and total AA at the duodenum and ileum occurred. The endogenous N secretion contributed to 26% and 23% of the duodenal and ileal total N flows, respectively, and the proportions were not affected by the dietary Met levels. The duodenal and ileal flows of endogenous total AA were 11.1, 11.8, 11.3 g/d and 2.9, 3.9, 4.1 g/d respectively. The average real digestibility of N was 65%, 87% and 95% in the forestomach, intestine and whole digestive tract respectively.     

Protein and amino acid metabolism in the digestive tract of growing bulls. 6. Apparent digestibility of the amino acids entering the duodenum and of amino acid from feed

After studies with young bulls provided with duodenal cannulas the apparent digestibility (AD) of the individual amino acids getting into the duodenum (AAD) was ascertained on the basis of 28 different rations. The AD of the AAD is defined as follows: AAD--AAfaeces/AAD X 100. The results thus obtained show a relative constancy, only insignificantly impaired by the consideration of the dependence of the AD of the AAD on the AA concentration in the ration. The average value for the AD of the sigma AAD was 72.5 +/- 4.9%. The dependence of the AD of the sigma AAD on the sigma AA concentration in the ration is: y = 67.8 + 0.51x +/- 4.6; r = 0.355x. In addition, the relation between AD AAD and AD AAfeed protein' each in % of AA intake and AA concentration in the ration, was studied and reported on.     

The use of the mobile bag technique in swine. Determination of the apparent crude protein digestibility and amino acid absorption of feed and rations]

The mobile bag technique (MBT) was used in two ileorectostomized and two intact pigs with duodenal cannulae, in order to estimate the precaecal and total crude protein digestibility and amino acid (lysine, methionine, cystine, threonine, tryptophan) absorption of ten single feedstuffs (field bean, lupin, rapeseed meal, fish meal, barley, wheat) and three diets. For each feed 36 bags were applied per animal. After a peptic predigestion in vitro, application of the bags through the duodenal cannula into the intestine and their passage through the gut, the residues remaining in the bags were pooled to collective samples and just as the original feed material analysed on dry matter, nitrogen and amino acids. The directly determined MBT-digestibilities (BV) and the values obtained by regressive calculations (BVb) have been compared with apparent digestibilities (sV) conducted from conventional digestion experiments. 74 per cent of all BV data was higher than the corresponding sV values. Similarities of BV with sV showed in 58 per cent, those of BVb with sV only in 17 per cent. In all cases differences of > +/- 4 digestibility units showed. Checking additivity of diet-BV by means of calculations from the BV of their single ingredients did not generally lead to the same results as the directly estimated diet-BV; in some cases the results were contrary. Therefore the use of MBT for mixed feed diets has to be further investigated. For single feedstuffs the MBT can be used successfully as a rapid and simple technique when regressive calculations are employed.