W. C. Sauer

Digestibility of amino acids in swine: Results and their practical applications. A review

Abstract Many studies have been carried out on the topic of amino acid digestibility in swine during the last two decades. The ileal analysis method should be the method of choice for determining amino acid digestibilities. This method is very sensitive for detecting differences in amino acid digestibilities, as these result from processing conditions or from inherent differences between samples of the same feedstuff. Amino acid digestibility values from the literature, determined with the ileal analysis method, are summarized and show large differences in amino acid digestibilities between feedstuffs and among different samples of the same feedstuff. At present it seems most appropriate to relate to amino acid digestibilities in terms of their apparent values. Studies in which the 15 N isotope dilution technique was used to determine the endogenous amino acid losses have shown that the traditional methods for determining the endogenous amino acid losses should be re-evaluated. Recent studies have clearly shown improvements in diet formulation practices, especially when a good quality protein supplement is replaced by protein supplement(s) of lower quality combined with supplementary amino acids, and when diets are formulated on the basis of digestible rather than total supply of the limiting amino acid(s). In addition, in order to present improved values for amino acid requirements, these should be expressed as digestible rather than as total.

Mucin output in ileal digesta of pigs fed a protein-free diet

Daily outputs of mucin in ileal digesta were estimated in three barrows fed a protein-free diet while administered either saline (SAI) or a complete amino acid mixture (AAI) intravenously. The water soluble-ethanol precipitable fraction of ileal digesta (crude mucin; CM) was used to estimate the composition of mucin in ileal digesta. This fraction exhibited a carbohydrate composition characteristic of mucin and had a high threonine, serine and proline content (40 mol/100 mol). The proportions of soluble gastric and intestinal mucins, approximately 27 and 73 %, respectively, were estimated from the N-acetylglucosamine (GlcNAc)/N-acetylgalactosamine (GalNAc) ratio in CM. The daily outputs of soluble mucin, 2.75 and 3.41 g/day from SAI and AAI pigs (p=0.13), respectively, were determined from the GalNAc outputs in CM, assuming the above contributions of gastric and intestinal mucins. The estimated soluble mucin outputs accounted for more than 99 % of the fucose, galactose, GalNAc and GlcNAc in CM. Total mucin outputs in ileal digesta, 5.32 and 5.65 g/day from SAI and AAI Pigs (p=0.24), respectively, were determined from the total GalNAc output in digesta, assuming soluble and insoluble mucin had similar compositions. Based on these outputs, mucin represented approximately 30, 7 to 22, 15 and 11 % of the endogenous threonine, proline, serine and protein, respectively, in ileal digesta. Approximately 74, 76, 100 and 53 % of the fucose, galactose GalNAc and GlcNAc, respectively, in ileal digesta from pigs in this study was attributed to mucin. The results from this study demonstrate the importance of mucin as a source of some endogenous amino acids and carbohydrates.ZusammenfassungBei kastrierten männlichen Schweinen, die eine proteinfreie Nahrung und intravenös entweder mit Kochsalzlösung (SAI) oder ein Aminosäurengemisch erhielten, wurde die tägliche Aminosäurenausschüttung (AAI) im Ileuminhalt bestimmt. Mit der wasserlöslichen und in Ethanol ausfällbaren Fraktion des Ileuminhalts (Gesamtmucin) (CM) wurde die Zusammensetzung von Mucin im Ileuminhalt gemessen. Diese Fraktion wies eine für Mucin charakteristische Kohlegydratzusammensetzung und einen hohen Gehalt an Treonin, Serin und Prolin (40 mol/100 mol). Die Anteile an Mucinen aus dem Magen und Darm betrugen 27 bezw. 73 % und wurden nach dem Verhältnis zwischen N-Acetylgalactosamin (GiNAc):N-Acetylgalactosamin (GalNAc) im CM ermittelt. Die täglichen Ausschüttungen an löslichem Mucin betrugen bei den SAI- bzw. AAI-Schweinen (p=0,13) und wurden aus den Gal-NAc-Exkretionen im CM bestimmt, wobei die obengenannten Anteile der Magen- und Darmmucine angenommen wurden. Die bestimmten löslichen Mucinausschüttungen im CM bestanden zu mehr als 90 % aus Fucose, Galactose, GaINAc und GlcNAc. Die Gesamtausschüttungen an Mucin im Ileuminhalt beliefen sich bei den SAI- bzw. AAI-Schweinen (p=0,24) auf 5,32 und 5,56 g/Tag und wurden aus der Gesamtausschüttung aus dem Ileuminhalt ermittelt, wobei davon ausgegangen wurde, daß lösliches und unlösliches Mucin die gleichen Zusammensetzungen aufwies. Basierend auf diesen Ausschüttungen, entsprach Mucin im Ileuminhalt ca. 30,7 bis 22, 15 und 11 % Threonin, Prolin, Serin und Protein. Annähernd 74, 76, 100 bezw. 53 % Fucose, Galactose, GAINAc und GlcNAc des Ileuminhalts entfielen in dieser Studie an Schweinen auf Mucin. Die Untersuchungsergebnisse der Studie unterstreichen die Bedeutung von Mucin als Lieferant von endogenen Aminosäuren und endogenen Kohlehydraten.

Amino acid digestibility in soybean meal, extruded soybean and full-fat canola for early-weaned pigs

Studies were carried out with 12 early-weaned pigs (Lacombe × Yorkshire) to determine the amino acid digestibility values in soybean meal, extruded soybean and full-fat canola. The pigs were weaned at 21 days of age and fitted with a simple T-cannula at the distal ileum at 27 and 28 days of age. The pigs were fed on three maize starch-based diets formulated to contain 160 g crude protein kg−1 from soybean meal, soybean meal plus extruded soybean and soybean meal plus full-fat canola, respectively, according to a two-period changeover design for three treatments. The pigs were fed three times daily, equal amounts at 08:00, 14:00 and 20:00 h, at a rate of 5% (wt.wt.) of the average body weight which was determined at the initiation of the first (8.9 kg) and the second (11.8 kg) experimental periods. Each experimental period comprised 9 days. Faeces were collected from 08:00 h on Day 6 to 08:00 h on Day 8. Ileal digesta were collected for a total of 24 h, at 6 h intervals, from 08:00 to 14:00 h on Day 8, from 20:00 h on Day 8 to 02:00 h on Day 9, from 08:00 to 14:00 h on Day 9 and from 20:00 on Day 9 to 02:00 h on Day 10. Chromic oxide was used as a digestibility marker. The apparent ileal digestibility values of extruded soybean and full-fat canola were determined by the difference method. The apparent ileal digestibility values of crude protein and most of the amino acids were higher (P 0.05) in the apparent ileal digestibility values of crude protein and the indispensable amino acids between extruded soybean and full-fat canola.

The concept of digestible amino acids in diet formulation for pigs

There is sufficient evidence that ileal rather than fecal amino acid digestibility values provide a more reliable estimate of protein digestion and amino acid absorption. In addition to differences in ileal amino acid digestibility values between feedstuffs there are large differences in ileal amino acid digestibility values within the same feedstuff. Furthermore, in addition to different processing conditions and inherent differences among samples of the same feedstuff, a large proportion of this variation can be attributed to different methodological approaches. In order to reduce the within variation associated with different methods for determination, methods specifically suitable for different feedstuffs are recommended. Differences in dietary amino acid levels are likely to be the largest single contributor to the variation in ileal amino acid digestibility values. Therefore, it is suggested to determine their plateau values, also referred to as dietary threshold levels, after which apparent digestibility values become independent of the dietary amino acid levels. The correction for non-specific endogenous protein and amino acid recoveries in ileal digesta allow for the transformation of apparent digestibility to standardised ileal digestibility values. The non-specific recoveries are related to the dry matter intake but independent of the type of feedstuff. In principle, standardised digestibility values should be the preferred approach in protein evaluation because these values reflect a fundamental property of the feedstuffs being independent of experimental conditions. However, estimates of endogenous recoveries are still confounded by the method used for determination, and further research is warranted in this area

Effect of β-glucanase supplementation of cereal-based diets for starter pigs on the apparent digestibilities of dry matter, crude protein and energy

Abstract A total of 48 PIC pigs (Camborough × Canabrid), average body weight 6.2 kg and 24 d of age, were allotted to four experiments (12 pigs each, equal numbers of barrows and gilts) to determine the effect of β-glucanase supplementation on the digestibilities of crude protein and energy in cereal-based soybean meal diets without or with supplementation of β-glucanase at 0.05, 0.1 and 0.2% (wt./wt.). The experimental diets were formulated to contain 200 g crude protein kg−1 based on soybean meal and barley (B + SBM, experiment 1), wheat (W + SBM, experiment 2), corn (C + SBM, experiment 3) or rye (R + SBM, experiment 4), respectively. Chromic oxide was used as digestibility marker. Each experiment was carried out according to a balanced two-period change-over design. The pigs were fed 3 times daily, equal amounts, at 08:00, 16:00 and 24:00 h, at a rate of 5% (wt./wt.) of the individual body weight which was determined at the beginning of the first (6.2 kg) and second (8.1 kg) experimental period. Each experimental period lasted 10 days with 7 days of adaptation followed by 3 days of faeces collection. There was a linear increase (P 0.05) of β-glucanase supplementation on the digestibilities of crude protein and energy in the W + SBM, C + SBM and R + SBM diets.

Prediction of in vivo apparent total tract energy digestibility of barley in grower pigs using an in vitro digestibility technique

The DE content within cereal grains can vary 25% mainly due to changes in apparent total tract digestibility (ATTD) of energy. In vitro digestibility techniques have been developed to predict the DE value among feedstuffs. However, these techniques have not been tested properly for their suitability to predict the variation in energy digestibility and DE content within a cereal grain. The objective of the present study was to establish and evaluate an in vitro digestibility technique to predict in vivo ATTD of energy of barley in grower pigs. Barley grain samples (hulled, n = 21) with a large range in quality were collected; the ADF and CP content ranged from 4.5 to 11.4% and 10.0 to 16.4% (DM basis), respectively. The ATTD of energy was determined using barrows (n = 63, 33 +/- 2.1 kg of initial BW) in 2 periods with 6 observations per sample and ranged from 51.9 to 78.5%, with relative errors between 0.4 and 5.0%. A preliminary study, comparing a 2- and a 3-step in vitro digestibility technique using 3 barley samples, indicated that R(2) between in vivo and in vitro energy digestibility was greater using the 3- than the 2-step technique (0.92 vs. 0.76). Therefore, the 3-step in vitro digestibility technique was used solely in subsequent analyses. Briefly, ground barley was subsequently incubated with pepsin for 6 h, pancreatin for 18 h, and cellulase for 24 h. The DM and GE content of samples and residues were measured to calculate digestibility. The in vitro energy digestibility of the 21 barley samples with duplicate measurements ranged from 63.7 to 82.2%, with relative errors between 0.1 and 2.6%. In vitro energy digestibility was strongly related (y = 1.25 x - 25.22; R(2) = 0.81) to in vivo energy digestibility. Finally, a subset of 7 barley samples was analyzed in quadruplicate using the 3-step in vitro technique. The relationship between in vitro and in vivo energy digestibility was very strong (y = 1.23 x - 25.33; R(2) = 0.97) with relative errors between 0.5 and 2.7%. In vitro DE and energy digestibility were perfectly related (R(2) = 1.00). In summary, the 3-step in vitro energy digestibility technique can accurately predict the ATTD of energy in barley in grower pigs. The 3-step in vitro digestibility technique, thus, might be useful as the reference laboratory procedure to calibrate analytical equipment to rapidly predict the ATTD of energy in barley.

Effect of protease treatment of soybean meal on content of total soluble matter and crude protein and level of soybean trypsin inhibitors.

An in vitro study was undertaken to determine the effect of treating soybean meal with protease at different temperature and pH conditions on the content of total soluble matter and crude protein (CP) and the level of soybean trypsin inhibitors (SBTI). Soybean meal (5 g), weighed into 25×150 mm culture tubes, was suspended in 20 ml of distilled water, adjusted to pH 3, 4.5 or 6, with Bacillus subtilis subtilisin-protease (Finnfeeds International) at 0, 0.2 or 1.0 mg g−1 soybean meal. The culture tubes were incubated for 16 h in a temperature-controlled water bath at 40 or 50°C. The soluble and insoluble fractions of soybean meal were separated by centrifuging the culture tubes and decanting the supernatant into separate conical tubes. All tubes were freeze-dried and the contents analyzed for CP. The content of total soluble matter and CP, on a dry matter basis, were determined as the difference between the beginning and end weight of the culture tubes. The content of total soluble matter and CP and the level of SBTI were usually similar (P>0.05) for soybean meal treated with protease at 0 or 0.2 mg g−1. Protease pretreatment at 1.0 mg g−1 soybean meal increased (P<0.05) the content of soluble CP and, with the exception of incubation at 50°C and pH 6, lowered (P<0.05) the level of SBTI compared with soybean meal pre-treated with protease at 0 or 0.2 mg g−1 under all conditions of temperature and pH. Based on the results of this in vitro trial, protease pretreatment at 1.0 mg g−1 soybean meal has the potential to improve the availability and digestion of soybean meal protein in diets for pigs.

Determination of True Ileal Amino Acid Digestibility in Feedstuffs for Pigs with the Linear Relationships between Distal Ileal Outputs and Dietary Inputs of Amino Acids

This study was carried out to investigate the methodological aspects of extrapolating the ileal losses of endogenous amino acids (AA) with linear relationships between the distal ileal outputs and dietary inputs of AA. Six barrows, average initial body weight 35 kg, were fitted with a simple T-cannula at the distal ileum and fed six diets according to a 6×6 Latin square design. Six maize starch-based diets containing six levels of crude protein (CP) and AA from soya bean meal (4, 8, 12, 16, 20 and 24% CP, respectively) were formulated. Chromic oxide (4 g kg-1 diet) was included as the digestibility marker. Each experimental period consisted of 8 days. Ileal digesta were collected, at 2 h intervals, for a total of 24 h during days 7 and 8. There were strong linear relationships (P<0·01) between the ileal outputs and dietary inputs of AA. Differences in ranges of graded dietary levels of AA affected the linearity and caused large differences in the extrapolated levels of ileal endogenous AA. Therefore, the design of a suitable range of graded dietary levels of AA is the most important methodological consideration for the determination of endogenous AA losses and the true ileal digestibility values of AA with the linear relationship. For CP and the essential AA, the true ileal digestibility values (%) in soya bean meal and the ileal endogenous losses (g kg-1 dry matter intake, in parentheses) were as follows: CP, 89·4 (16·4); arginine, 96·1 (0·68); histidine, 92·4 (0·24); isoleucine, 91·7 (0·45); leucine, 90·7 (0·69); lysine, 90·5 (0·48); methionine, 93·6 (0·13); phenyl-alanine, 92·5 (0·38); threonine, 86·5 (0·71) and valine, 90·3 (0·56). Furthermore, the levels of endogenous AA extrapolated with the linear relationships between the ileal outputs and dietary inputs of AA were very close to the values estimated with the linear relationships between the dietary contents of apparent ileal digestible and total AA, suggesting that both models of linear relationships can be used as the regression analysis technique for determination of ileal losses of endogenous AA and true ileal digestibility values of AA in feedstuffs for pigs.

The effect of dietary level of fat on amino acid digestibilities in soybean meal and canola meal and on rate of passage in growing pigs

The objectives were to determine the effect of fat level on amino acid (AA) digestibility and rate of passage in digesta collected from the ileum. Six barrows, 45 kg, fitted with a T-cannula at the distal ileum were fed three diets that contained 15% crude protein from soybean meal (SBM) and 2, 6 or 10% canola oil (CO), respectively, and 0.5 chromic oxide. The experiment was carried out according to a repeated 3 × 3 Latin square design. The studies were repeated with another six barrows with diets that contained 15% crude protein from canola meal (ICM). The pigs were fed 800 g twice daily. The ileal digestibilities (%) of the average of the indispensable AA were 82.5 ± 2.0, 83.8 ± 1.9, 85.0 ± 1.6 and 75.4 ± 1.9, 72.4 ± 2.3 and 77.4 ± 1.9 for the SBM and CM diets with 2.6 and 10% CO, respectively. The relationship between AA digestibility in SMB and fat level was quadratic (P < 0.05) for most indispensable AA; a curvilinear relationship (P < 0.05) was observed for the CM diets. Dietary fat level had little effect on the fecal digestibilities in SBM and CM. The rate of passage was higher (P < 0.05) for the CM than SBM diets. In conclusions, these studies show that the level of fat may affect ileal AA digestibilities, albeit to a small extent.

Supplementation of xylanase and phospholipase to wheat‐based diets for weaner pigs

The effects of supplementing a wheat-based diet for weaner pigs with exogenous xylanase and phospholipase on ileal and faecal nutrient digestibilities and on the level of microbial metabolites in ileal digesta were examined. Fourteen piglets, weaned at 11 days, were fitted with a simple T-cannula at the distal ileum. The pigs were offered a control diet or diets supplemented with xylanase and phospholipase individually or in combination, in a two period crossover design. The combination of xylanase and phospholipase tended to increase the ileal recovery of the amino sugar galactosamine, whereas the concentration expressed in mg/kg dry matter intake of glucosamine was slightly decreased (p < 0.10). There was neither an effect of enzyme supplementation on ileal and faecal digestibility of the other nutrients and energy, nor was there an effect on pH and on the level of microbial metabolites in ileal digesta. However, an increase in ileal and faecal nutrient and energy digestibility with increasing age was observed. The ileal and faecal digestibility coefficients (except for ether extract) were significantly (p < 0.05) higher in experimental period I than in period II. These higher values may be attributed to a lower feed intake during period I. Since a lower level of feed intake is generally associated with a slower rate of passage and a longer retention time of digesta, a positive impact on digestion and absorption of nutrients can be assumed, which, on the other hand, limits the potential of additional enzyme effects.