True Ileal Digestibility Research Articles

Basal endogenous losses of amino acids in protein nutrition research for swine and poultry

In this review, the definition and terminology of amino acid (AA) digestibility and ileal endogenous losses of AA (IAAend) in poultry and swine nutrition are discussed. Compared with apparent (AID) and true (TID) ileal digestibility, standardised ileal digestibility (SID) of AA is recommended for the expression of digestible AA contents of feed ingredients and for describing nutritional requirements of poultry and swine. To determine the SID of AA, total ileal flow of AA should be corrected for basal IAAend. Therefore, the measurement of basal IAAend is of great importance for the accuracy of the SID estimation in feed ingredients. The techniques for measuring basal IAAend in poultry and swine include the use of a nitrogen-free diet (NFD), a highly digestible or enzyme hydrolyzed protein diet, and the regression method. The classic method for basal IAAend determination involves the feeding of a NFD to experimental animals and measuring the ileal AA flow. This IAAend output is considered as basal IAAend, and it is assumed that the excretion of basal IAAend depends only on DM intake, regardless of dietary composition. There are criticisms with the NFD method about the abnormal physiological state induced by severe AA deficiency. Although this AA deficiency may affect the estimate of basal IAAend for dispensable AA, especially proline and glycine because of the degradation of body protein, the NFD method is still the most widely used method for basal IAAend measurements. According to the definition of basal IAAend, the NFD should be the preferred methodology in SID determination, because the basal IAAend should be only related to dry matter intake. Additionally, the SID coefficients in feed ingredients generated by NFD method are considered to be additive in a complete diet. However, the results generated from NFD method can vary among studies due to the variance in the experimental animals and diet composition. To improve the accuracy of estimating the SID of AA in feed ingredients, it is suggested that a mandatory NFD be included in individual studies to generate basal IAAend for correcting total ileal amino acid flow in determining SID of AA. In addition, research is needed to investigate the standard diet formulation of NFD.

Herring roe protein has a high digestible indispensable amino acid score (DIAAS) using a dynamic in vitro gastrointestinal model

It is hypothesized that the digestible indispensable amino acid score (DIAAS) can be determined based on dynamic in vitro gastrointestinal digestion experiments as replacement for invasive animal studies. We determined the in vitro DIAAS for immature herring eggs (roe) proteins in comparison with reference proteins. The true ileal digestibility of protein and indispensable amino acids (IAA) was measured under human conditions simulated in a gastrointestinal model (tiny-TIM). The in vitro true ileal digestibility of ovalbumin, cooked and raw chicken egg white, and casein was similar to that found in humans (r2 = 0.96), providing a casual observation to support the validity of tiny-TIM. The digestibility of the immature herring egg proteins was 71% to 92%. The highest IAA digestibility was found for immature whole herring egg protein (55%-80%) in comparison to immature herring egg membrane and immature de-membraned herring protein (50%-70%). The DIAAS as recommended by FAO for children and adults, but measured in vitro, were 91% for immature whole herring egg protein (lysine first limiting), 71% for immature herring egg membrane protein (histidine first limiting), and 88% for immature herring egg de-membraned protein (sulfur AA first limiting). True ileal protein and amino acid digestibility can be determined in a dynamic gastrointestinal model, such as tiny-TIM, which can be used for estimating the DIAAS. Immature herring egg proteins, a previously underutilized resource, were determined to be an important and valuable source of IAA for human consumption.

Effects of calcium feeding strategy on true ileal phosphorus digestibility and true phosphorus retention determined with growing broilers

An experiment utilizing 960 Ross × Ross 708 male broilers was conducted to determine the effects of Ca feeding strategy on true ileal (prececal) P digestibility (TIPD) and true P retention (TPR) of corn. Experimental diets were formulated with 1 of 3 dietary Ca feeding strategies (0.95%, 0.13%, or variable Ca concentrations to maintain a 2.1:1 Ca:P ratio) and contain 0, 25, 50, or 75% corn. A practical corn-soybean meal diet (1.4:1 Ca:P ratio) was fed as a control. After receiving a common starter diet, experimental diets were fed from 19 to 26 d of age. After a 48-h dietary adaptation period, a 48-h retention assay was conducted. At 25 and 26 d of age, ileal digesta were collected from 8 birds per cage. Broilers consuming the control diet had higher (P < 0.001) BW gain, feed intake, digesta P, and excreta P than broilers consuming the corn titration diets. Digesta and excreta P increased (linear, P < 0.05) with graded increases of corn. True ileal P digestibility and TPR were highest (P < 0.05) for diets with 0.13% Ca (57.3 and 69.5%, respectively) compared with diets formulated with a 2.1:1 Ca:P ratio (41.2 and 37.8%, respectively) or 0.95% Ca (25.4 and 39.0%, respectively). Values for TPR were higher (P < 0.05) than those for TIPD except when the dietary Ca:P ratio was fixed. Additionally, negative endogenous P losses were predicted by regression equations when TPR was estimated for birds fed titration diets with the fixed Ca:P ratio. Changing the Ca concentration of the diets to maintain a fixed Ca:P ratio influenced (P < 0.001) apparent P retention, which affected the estimate for TPR due to the prediction of negative endogenous P losses. These data demonstrated that regression analysis may have limitations when estimating the TIPD or TPR of corn when formulating diets with different Ca feeding strategies. More research is necessary to elucidate the factors that contributed to regression equations predicting negative endogenous P losses.

Effects of distillers' dried grains with solubles and soybean oil on dietary lipid, fiber, and amino acid digestibility in corn-based diets fed to growing pigs.

The use of corn coproducts increases the concentration of fiber and, often, the use of supplemental lipids in swine diets, which may affect energy and nutrient digestibility. An experiment was conducted to determine the effects of reduced-oil distillers' dried grains with solubles (DDGS) and soybean oil (SBO) on dietary AA, acid hydrolyzed ether extract (AEE), and NDF digestibility in corn-based diets fed to growing pigs. Eighteen growing pigs (33.8 ± 2.2 kg BW) were surgically fitted with a T-cannula in the distal ileum and allocated to 1 of 6 dietary treatment groups in a 3-period incomplete Latin square design, with 9 observations per treatment. Six dietary treatments were obtained by adding 0, 20, and 40% DDGS to corn-casein diets formulated with 2 and 6% SBO. Ileal digesta and fecal samples were collected and the apparent ileal digestibility (AID) and apparent total tract digestibility (ATTD) of AEE and NDF and the AID of AA were determined. Apparent values were corrected for endogenous losses of lipids, and true ileal (TID) and true total tract digestibility (TTTD) values of lipids were calculated. Results showed that the AID of Lys decreased ( < 0.001) with the inclusion of DDGS but was not affected ( = 0.63) by the inclusion of SBO. An interaction between DDGS and SBO on the AID ( = 0.002) and ATTD ( = 0.009) of NDF was observed, where the AID and ATTD of NDF decreased with DDGS at 6% SBO but no effect was observed at 2% SBO. The AID of NDF increased with SBO at 0% DDGS, but no effect was observed at 20 or 40% DDGS. An interaction between DDGS and SBO on the AID ( = 0.011) and ATTD ( = 0.008) of AEE was observed, where the AID and ATTD of AEE increased with SBO. The AID and ATTD of AEE increased with DDGS at 2% SBO, but no effect was observed at 6% SBO. Correction by ileal and fecal endogenous loss of AEE (9.5 and 13.6 g/kg of DMI, respectively) showed that increasing dietary AEE had no effect on the TID and TTD of AEE ( > 0.05). In conclusion, the AID of Lys decreased with DDGS and was not affected by lipids from SBO. The greatest AID and ATTD of NDF was observed in diets with a high AEE and low NDF content. Low values of apparent digestibility of AEE in lower-lipid diets are possibly the result of endogenous losses of lipids, because the true digestibility of AEE was not affected by the dietary increase of AEE.

Measurement of true ileal calcium digestibility in meat and bone meal for broiler chickens using the direct method

The objective of the study that is presented herein was to determine the true ileal calcium (Ca) digestibility in meat and bone meal (MBM) for broiler chickens using the direct method. Four MBM samples (coded as MBM-1, MBM-2, MBM-3 and MBM-4) were obtained and analyzed for nutrient composition, particle size distribution and bone to soft tissue ratio. The Ca concentrations of MBM-1, MBM-2, MBM-3 and MBM-4 were determined to be 71, 118, 114 and 81 g/kg, respectively. The corresponding geometric mean particle diameters and bone to soft tissue ratios were 0.866, 0.622, 0.875 and 0.781 mm, and 1:1.49, 1:0.98, 1:0.92 and 1:1.35, respectively. Five experimental diets, including four diets with similar Ca concentration (8.3 g/kg) from each MBM and a Ca and phosphorus-free diet, were developed. Meat and bone meal served as the sole source of Ca in the MBM diets. Titanium dioxide (3 g/kg) was incorporated in all diets as an indigestible marker. Each experimental diet was randomly allotted to six replicate cages (eight birds per cage) and offered from d 28 to 31 post-hatch. Apparent ileal Ca digestibility was calculated by the indicator method and corrected for ileal endogenous Ca losses to determine the true ileal Ca digestibility. Ileal endogenous Ca losses were determined to be 88 mg/kg dry matter intake. True ileal Ca digestibility coefficients of MBM-1, MBM-2, MBM-3 and MBM-4 were determined to be 0.560, 0.446, 0.517 and 0.413, respectively. True Ca digestibility of MBM-1 was higher (P < 0.05) than MBM-2 and MBM-4 but similar (P > 0.05) to that of MBM-3. True Ca digestibility of MBM-2 was similar (P > 0.05) to MBM-3 and MBM-4, while that of MBM-3 was higher (P < 0.05) than MBM-4. These results demonstrated that the direct method can be used for the determination of true Ca digestibility in feed ingredients and that Ca in MBM is not highly available as often assumed. The variability in true Ca digestibility of MBM samples could not be attributed to Ca content, percentage bones or particle size.

Canola meal on starting pigs feeding

Three experiments were carried out to determine the nutritional values and evaluate the performance of piglets fed on canola meal. In experiment I, a digestibility assay was conducted using fourteen barrow pigs, with an initial body weight of 20.62±3.30 kg. The evaluated feedstuff was canola meal, with a level of 250 g/kg in the basal diet (corn + soybean meal-based). The experimental unit consisted of one pig, with a total of seven experimental units per diet. The values as (fed basis) of digestible (DE) and metabolizable (ME) energy of canola meal were 2,995 kcal/kg and 2,796 kcal/kg, respectively. In experiment II, ileal digestibility assays were carried out to determine the apparent and true ileal digestibility coefficient and digestible amino acids. Three crossbred pigs were used, with a BW of 38.6±1.98 kg. The treatments consisted of two diets, with a single source of protein (canola meal) and one protein-free diet (OFD). The values of digestible amino acids in canola meal were as follows: lysine: 11.8 g/kg; methionine+cystine: 9.1 g/kg; threonine: 7.9 g/kg; tryptophan: 2.4 g/kg; leucine: 15.7 g/kg; and isoleucine: 8.7 g/kg. In experiment III, 60 piglets (BW= 15.08±0.72 kg to 30.26±2.78 kg) were allotted in a completely randomized design. The treatments consisted of four diets with increasing levels of canola meal (50, 100, 150 and 200 g/kg), six replicates and experimental unit consisted of two pigs. Additionally, a control diet was formulated containing 0.0 g/kg CM. Regression analysis indicates that there was no effect (P?0.05) of the level of canola meal inclusion on pigs performance. The performance results suggest that it is feasible to use up to 200 g/kg of canola meal in starting pigs diet, without impairing performance and the feeding cost.

High True Ileal Digestibility but Not Postprandial Utilization of Nitrogen from Bovine Meat Protein in Humans Is Moderately Decreased by High-Temperature, Long-Duration Cooking1–3

Background: Meat protein digestibility can be impaired because of indigestible protein aggregates that form during cooking. When the aggregates are subsequently fermented by the microbiota, they can generate potentially harmful compounds for the colonic mucosa.Objective: This study evaluated the quantity of bovine meat protein escaping digestion in the human small intestine and the metabolic fate of exogenous nitrogen, depending on cooking processes.Methods: Sixteen volunteers (5 women and 11 men; aged 28 ± 8 y) were equipped with a double lumen intestinal tube positioned at the ileal level. They received a test meal exclusively composed of 120 g of intrinsically 15N-labeled bovine meat, cooked either at 55°C for 5 min (n = 8) or at 90°C for 30 min (n = 8). Ileal effluents and blood and urine samples were collected over an 8-h period after the meal ingestion, and 15N enrichments were measured to assess the digestibility of meat proteins and the transfer of dietary nitrogen into the metabolic pools.Results: Proteins tended to be less digestible for the meat cooked at 90°C for 30 min than at 55°C for 5 min (90.1% ± 2.1% vs. 94.1% ± 0.7% of ingested N; P = 0.08). However, the particle number and size in ileal digesta did not differ between groups. The appearance of variable amounts of intact fibers was observed by microscopy. The kinetics of 15N appearance in plasma proteins, amino acids, and urea were similar between groups. The amount of exogenous nitrogen lost through deamination did not differ between groups (21.2% ± 0.8% of ingested N).Conclusions: Cooking bovine meat at a high temperature for a long time can moderately decrease protein digestibility compared with cooking at a lower temperature for a short time and does not affect postprandial exogenous protein metabolism in young adults. The study was registered at www.clinicaltrials.gov as NCT01685307.

Measurement of true ileal phosphorus digestibility in meat and bone meal for broiler chickens

An experiment was conducted to estimate true ileal phosphorus (P) digestibility of 3 meat and bone meal samples (MBM-1, MBM-2, and MBM-3) for broiler chickens. Four semipurified diets were formulated from each sample to contain graded concentrations of P. The experiment was conducted as a completely randomized design with 6 replicates (6 birds per replicate) per dietary treatment. A total of 432 Ross 308 broilers were assigned at 21 d of age to the 12 test diets. The apparent ileal digestibility coefficient of P was determined by the indicator method, and the linear regression method was used to determine the true P digestibility coefficient. The apparent ileal digestibility coefficient of P in birds fed diets containing MBM-1 and MBM-2 was unaffected by increasing dietary concentrations of P (P > 0.05). The apparent ileal digestibility coefficient of P in birds fed the MBM-3 diets decreased with increasing P concentrations (linear, P < 0.001; quadratic, P < 0. 01). In birds fed the MBM-1 and MBM-2 diets, ileal endogenous P losses were estimated to be 0.049 and 0.142 g/kg DM intake (DMI), respectively. In birds fed the MBM-3 diets, endogenous P loss was estimated to be negative (−0.370 g/kg DMI). True ileal P digestibility of MBM-1, MBM-2, and MBM-3 was determined to be 0.693, 0.608, and 0.420, respectively. True ileal P digestibility coefficients determined for MBM-1 and MBM-2 were similar (P < 0.05), but were higher (P < 0.05) than that for MBM-3. Total P and true digestible P contents of MBM-1, MBM-2, and MBM-3 were determined to be 37.5 and 26.0; 60.2 and 36.6; and 59.8 and 25.1 g/kg, respectively, on an as-fed basis.

Standardized and true ileal amino acid digestibilities in field pea and pea protein isolate fed to growing pigs

Four ileal-cannulated Cotswold barrows (50.41 ± 5.05 kg body weight) were used to determine apparent (AID), standardized (SID) and true (TID) ileal digestibility of amino acids (AA) in field pea and pea protein isolate (PPI) processed from the same batch of the whole field pea. Pigs were allotted to 2 experimental diets in a simple cross-over design. Diets contained either field pea or PPI as the sole source of protein and were formulated to contain 155 g/kg CP. The AID of nutrients was determined by the indicator method. The SID of AA was calculated using published values for basal endogenous AA losses obtained from our laboratory. The total endogenous flow of lysine and the TID of lysine were determined by the homoarginine method. The TID of AA other than lysine were estimated using their published ratios in endogenous protein relative to lysine. The AID coefficient of CP (0.88 vs. 0.80), Ile (0.91 vs. 0.79), leucine (0.92 vs. 0.81), lysine (0.93 vs. 0.84), phenylalanine (0.92 vs. 0.84) and valine (0.89 vs. 0.76) were greater (P < 0.05) in PPI than in field pea. The total (363 vs. 2167 mg/kg [dry matter intake (DMI)] and endogenous (312 vs. 1777 mg/kg DMI) lysine flow were lower (P < 0.05) in PPI compared with field pea. Likewise, field pea had greater (P < 0.05) total and endogenous nitrogen (N) and AA (other than lysine) flow compared with PPI. The SID of indispensable AA for PPI was greater (P < 0.05) than that for field pea. However, PPI and field pea were similar in the TID of all indispensable amino acid except lysine whose TID coefficient in PPI (0.99) was greater (P < 0.05) than for field pea (0.94). In conclusion, the results indicate that processing of field pea to produce pea protein isolate improved apparent AID of AA and reduced ileal endogenous AA losses. However, the processing of field pea to produce pea protein isolate had limited effect on TID of AA.

Measurement of true ileal calcium digestibility in meat and bone meal for broiler chickens

The objective of the present experiment was to determine the true ileal calcium (Ca) digestibility in three samples of meat and bone meal (coded as MBM-1, MBM-2 and MBM-3) for broiler chickens. Four experimental diets, containing graded concentrations of Ca, were formulated from each MBM sample with inclusion levels of 20, 40, 60 and 80g/kg diet. Each experimental diet was randomly allotted to four replicate cages (six birds per cage) and fed for three days from day 28 post-hatch. Apparent ileal digestibility coefficient of Ca was measured by the indicator method and linear regression analysis was used to determine the true Ca digestibility coefficient. Apparent Ca digestibility was unaffected (P>0.05) by increasing Ca concentrations. The apparent digestibility coefficients in MBM-1, MBM-2 and MBM-3 were 0.50, 0.44 and 0.45, respectively. Significant linear (P<0.001) relationship was observed between dietary Ca intake and digesta Ca output for MBM-1, MBM-2 and MBM-3 with R2 values of 0.82, 0.93 and 0.95, respectively. The true ileal digestibility coefficients of Ca in MBM-1, MBM-2 and MBM-3 were determined to be 0.60, 0.46 and 0.50, respectively. The corresponding ileal endogenous Ca losses were 292, 123 and 174mg/kg dry matter intake, respectively.

Measurement of true ileal phosphorus digestibility in maize and soybean meal for broiler chickens: Comparison of two methodologies

An experiment was conducted to determine the true ileal P digestibility of maize and soybean meal for broiler chickens using two methodologies based on the regression method. The two methods differed in dietary protein content and dietary Ca:P ratios in the assay diets used. In Method 1, the test ingredient was used as the sole dietary source of protein and P and a dietary Ca:non-phytate P ratio of around 2:1 was maintained by the addition of limestone. In Method 2, dried egg albumen was used as the additional protein supplement and a dietary Ca:total P ratio of 1.3:1 was maintained by the addition of limestone. For the maize-based diets, disodium phosphate was used as an additional P supplement. Two sets of sequential semi-purified diets containing 200, 460 and 720g/kg of maize or 400, 510 and 620g/kg of soybean meal were formulated. Each set was evaluated as a 2×3 factorial arrangement of treatments, which included two methods and three inclusion levels. The experiment was conducted as a randomised complete block design and a total of 288 of 21-day old male broilers (Ross 308) were assigned to four blocks based on body weights. Each block had 12 cages (six birds per cage) and the 12 test diets were assigned to a cage within each block. Apparent ileal digestibility coefficient of P was determined by the indicator method and linear regression was used to determine true ileal P digestibility. In both methods, ileal P output and ileal digestible P increased linearly with increasing inclusion levels of maize (P<0.01) and soybean meal (P<0.001). Apparent ileal P digestibility coefficients of P determined for maize were higher (P<0.001) in Method 2 compared with Method 1 whereas the opposite trend was observed for soybean meal. True ileal P digestibility coefficients determined for maize in Methods 1 and 2 were 0.728 and 0.426, respectively, and were different (P<0.01). True ileal P digestibility coefficients determined for soybean meal in Methods 1 and 2 were 0.740 and 0.523, respectively, and were different (P<0.01). The present findings showed that estimation of true ileal P digestibility in maize and soybean meal was influenced by the assay methodology employed.

Use of homoarginine for measuring true ileal digestibility of amino acids in food protein.

A useful application of homoarginine in animal nutrition is the determination of the true ileal digestibility (TID) of amino acids (AA) in swine complete diets and feed ingredients. The homoarginine method involves the conversion of dietary lysine to homoarginine in a guanidination reaction with methylisourea. Accurate determination of TID of AA, especially in heat-treated feed ingredients, is a key prerequisite for accurate diet formulation with respect to the provision of dietary AA. Thus, the aim of this review is to highlight the homoarginine methodology and its application in animal nutrition. Based on the data from published studies, the homoarginine method can be used to accurately determine the digestibility of lysine and the majority of other acid-stable AA in complete diets and feed ingredients fed to animals.

Protein Digestibility-Corrected Amino Acid Scores and Digestible Indispensable Amino Acid Scores Differentially Describe Protein Quality in Growing Male Rats1–3

The FAO has recommended replacing the protein digestibility-corrected amino acid score (PDCAAS) with the digestible indispensable amino acid score (DIAAS). The objective of this study was to compare aspects underlying the calculation of the DIAAS and PDCAAS, including 1) fecal digestibility vs. ileal digestibility, 2) using a single nitrogen digestibility value for all amino acids, and 3) the effect of truncation. Truncated PDCAAS and untruncated DIAAS values calculated as formally defined were also compared and DIAAS data presented for 14 dietary protein sources. Semisynthetic wheat starch-based diets were formulated to contain the test protein (as consumed by humans) source (whey- and soy-protein isolates, milk-, whey-, rice- and pea- protein concentrates, cooked kidney beans, roasted peanuts, cooked peas, corn-based breakfast cereal, cooked rice, cooked rolled oats, and wheat bran) as the sole nitrogen source and with an indigestible marker (titanium dioxide). Growing male rats (∼250 g bodyweight) were given a basal casein-based diet from day 1 to day 7 and then allocated (n = 6) to the test diets for day 8 to day 14 before ileal digesta were collected after the rats were killed. Total feces were collected from day 11 to day 14. True fecal nitrogen digestibility was different (P < 0.05; 10% difference on average) from true ileal nitrogen digestibility for 11 of the 14 protein sources. True ileal nitrogen digestibility was different (P < 0.05) from true ileal amino acid digestibility for almost half of the indispensable and conditionally indispensable amino acids (differences ranged from 0.9% to 400%). DIAAS values ranged from 0.01 for a corn-based cereal to 1.18 for milk protein concentrate. Untruncated PDCAAS values were generally higher than a DIAAS values, especially for the poorer quality proteins; therefore, the reported differences in the scores are of potential practical importance for populations in which dietary protein intake may be marginal.

Dietary Protein Structure Affects Endogenous Ileal Amino Acids But Not True Ileal Amino Acid Digestibility in Growing Male Rats1–3

Background: The amount of endogenous, as opposed to undigested dietary, protein in digesta is a measure of fundamental interest related to gut physiology and function.Objective: The objective of this study was to determine whether alimentation with proteins having differing amino acid compositions influenced endogenous ileal amino acids (EIAAs) and true ileal amino acid digestibility (TIAAD) values.Methods: Male rats (n = 8) were fed a purified diet containing 100 g/kg of 1 of 5 protein hydrolysates, each derived from a different semipurified intact protein source [gelatin, beef muscle (BM), casein, soy protein isolate (SPI), and lactalbumin] devoid of antinutritional factors or fiber. The rats were fed their respective hydrolysate-based diet for 1 d after receiving the same diet but containing the corresponding intact protein source for 7 d. Titanium dioxide was used as an indigestible marker. Ileal digesta were collected after the rats were killed, and EIAAs were determined (precipitate + retentate) after centrifugation and ultrafiltration of the digesta. The TIAAD values of the intact protein sources were determined using EIAA flows based on each protein hydrolysate.Results: Mean EIAA flows differed (P < 0.05) across protein hydrolysates for most amino acids, with the mean ± SEM EIAA flows across amino acids being 262 ± 17, 253 ± 12, 248 ± 18, 226 ± 14, and 191 ± 20 mg/kg dry matter intake for the gelatin, BM, casein, SPI, and lactalbumin hydrolysates, respectively. The only difference (P < 0.05) for the mean EIAA flows across amino acids within each protein hydrolysate was observed between gelatin (262 ± 17 mg/kg) and lactalbumin (191 ± 20 mg/kg) hydrolysates. Except for Trp (P < 0.001) in gelatin and lactalbumin hydrolysates, EIAA flows determined using the casein hydrolysate were not different (P ≥ 0.05) from EIAA flows determined using the other protein hydrolysates. TIAAD values were not generally different (P ≥ 0.05) regardless of the hydrolysate used to determine the EIAA flows.Conclusions: Protein source affected EIAA flows, although the differences had little effect on TIAAD. Enzyme hydrolyzed casein is a suitable model hydrolysate for determining TIAAD with the enzyme-hydrolyzed protein-ultrafiltration technique.

Dietary protein and amino acids—Consideration of the undigestible fraction

A case is made for the application of true ileal amino acid digestibility and true ileal reactive lysine digestibility (lysine availability) in poultry nutrition. Technical aspects of the true ileal digestibility assays are reviewed, as are factors influencing amino acid digestibility in the broiler. There is considerable variation in amino acid digestibility and lysine availability both within and among diverse feedstuffs. Differences in mean amino acid digestibility among feedstuffs, and the variability in the digestibility of an amino acid within a feedstuff should both be taken into account during least-cost dietary formulation.

Evaluation of amino Acid and energy utilization in feedstuff for Swine and poultry diets.

An accurate feed formulation is essential for optimizing feed efficiency and minimizing feed cost for swine and poultry production. Because energy and amino acid (AA) account for the major cost of swine and poultry diets, a precise determination of the availability of energy and AA in feedstuffs is essential for accurate diet formulations. Therefore, the methodology for determining the availability of energy and AA should be carefully selected. The total collection and index methods are 2 major procedures for estimating the availability of energy and AA in feedstuffs for swine and poultry diets. The total collection method is based on the laborious production of quantitative records of feed intake and output, whereas the index method can avoid the laborious work, but greatly relies on accurate chemical analysis of index compound. The direct method, in which the test feedstuff in a diet is the sole source of the component of interest, is widely used to determine the digestibility of nutritional components in feedstuffs. In some cases, however, it may be necessary to formulate a basal diet and a test diet in which a portion of the basal diet is replaced by the feed ingredient to be tested because of poor palatability and low level of the interested component in the test ingredients. For the digestibility of AA, due to the confounding effect on AA composition of protein in feces by microorganisms in the hind gut, ileal digestibility rather than fecal digestibility has been preferred as the reliable method for estimating AA digestibility. Depending on the contribution of ileal endogenous AA losses in the ileal digestibility calculation, ileal digestibility estimates can be expressed as apparent, standardized, and true ileal digestibility, and are usually determined using the ileal cannulation method for pigs and the slaughter method for poultry. Among these digestibility estimates, the standardized ileal AA digestibility that corrects apparent ileal digestibility for basal endogenous AA losses, provides appropriate information for the formulation of swine and poultry diets. The total quantity of energy in feedstuffs can be partitioned into different components including gross energy (GE), digestible energy (DE), metabolizable energy (ME), and net energy based on the consideration of sequential energy losses during digestion and metabolism from GE in feeds. For swine, the total collection method is suggested for determining DE and ME in feedstuffs whereas for poultry the classical ME assay and the precision-fed method are applicable. Further investigation for the utilization of ME may be conducted by measuring either heat production or energy retention using indirect calorimetry or comparative slaughter method, respectively. This review provides information on the methodology used to determine accurate estimates of AA and energy availability for formulating swine and poultry diets.

Effect of Actigen and threonine interaction on the development of gut immunity of nursery pigs (816.3)

Weaned piglets were allocated to six treatment groups (n = 6/treatment) in a 2 x 3 factorial design experiment: Actigen (0 or 400 g/T), true ileal digestible (TID) threonine (Thr):lysine (Lys) ratio (57 [low], 67[recommended], and 77 [high]). After 6 wk of feeding, duodenum, jejunum and ileum tissues were sampled for qPCR analysis. Expression of cytokines was reported relative to the control (no Actigen + 67 TID Thr:Lys). In jejunum, interleukin 6 (IL6) was down‐regulated (P &lt; 0.05) with Actigen + 57 or 77 TID Thr:Lys, (‐5.89 and ‐4.14‐fold, respectively). In ileum, interleukin 1 beta (IL1B) was down‐regulated (P &lt; 0.05) with Actigen + 57 and 77 TID Thr:Lys (‐1.35 and ‐1.75‐fold, respectively). In duodenum, IL1B was up‐regulated (P &lt; 0.05) (1.89‐fold) with Actigen +57 TID Thr:Lys. In duodenum and jejunum, tumor necrosis factor (TNF) was up‐regulated (P &lt; 0.05) with Actigen + 67 TID Thr:Lys (1.21‐fold and 1.33‐fold, respectively). In duodenum, IL6 (‐1.51‐fold) and TNF (1.32‐fold) differed (P &lt; 0.05) in response to no Actigen +57 and 77 TID Thr:Lys, respectively. Relative to the control, Actigen and Thr, in combination, were associated with decreased mRNA levels of the inflammatory cytokines IL6, IL1B in the intestine of weaned pigs.

Effect of feeding level on ileal and total tract digestibility of nutrients and energy from soybean meal‐based diets for piglets

A total of 36 piglets with an initial body weight (BW) of 5.6 ± 0.7 kg, fitted with simple T-cannulas at the distal ileum, were used to evaluate the effect of three graded feeding levels (50, 75 or 100 g/kg BW(0.75) day) on apparent ileal digestibility (AID) and total tract digestibility (ATTD) of dry matter (DM), nitrogen (N) and energy, and on ATTD of organic matter (OM), ether extracts (EE), neutral detergent fibre (NDF), acid detergent fibre (ADF) and digestible (DE), metabolisable (ME) and net energy (NE) content in soybean meal (SBM)-casein-cornstarch-based diets. The AID of DM, N and energy and ATTD of NDF, ADF and EE in the diets were not affected (p > 0.05) by the feed intake (FI) level. There was a small decrease in ATTD of DM, N (CP), OM, ash and energy, and in DE, ME and NE content in the diets (p < 0.05) with increasing FI level. The net disappearance in the large intestine (in % of ileal recovery) decreased for DM, N and energy (p < 0.05) with increasing FI level. The design of the study allowed for estimating ileal endogenous loss of N and total tract endogenous loss of ash, N and EE, for estimating corresponding true ileal and total tract digestibility values, and for estimating urinary endogenous N loss. High variability in estimates of ileal endogenous N loss and total tract endogenous losses of N, EE and ash reflects great variation in individual endogenous losses between animals. Estimation of true total tract digestibility of N, EE and ash by regression analysis was affected by their decrease in ATTD with increasing FI level, as estimates for true digestibility were lower compared to their apparent values. The present results suggest that FI level can affect both apparent and true total tract nutrient digestibility in piglets.

Complete replacement of soybean meal in pig diets with hydrolyzed feather meal with blood by amino acid supplementation based on standardized lleal amino acid digestibility

The current study was conducted to determine the possibility of replacing soybean meal (SBM) in finisher pig diet completely with hydrolyzed feather meal (FM) with blood by supplementing with appropriate amino acids (AA) based on standardized ileal digestible (SID) AA in FM. Corn–SBM, positive control (POS) diets were formulated to contain 6.6 and 5.2g true ileal digestible (TID)Lys/kg to satisfy the requirements during the finisher-1 and finisher-2 phases, respectively. Corn–FM negative control (NEG) diets were formulated to be iso-N and iso-caloric to the POS diets. The NEG diets were supplemented with Lys and Trp to alleviate AA deficiencies based on TID AA values in FM reported by the NRC in 1998 (NRC). In addition, the NEG diets were supplemented with Lys and Trp to alleviate AA deficiencies based on the determined SID AA in FM (SID). When pigs weighed 50.0±2.9kg, 32 gilts and 32 castrated males (2 gilts or 2 castrated males/pen) were randomly assigned to 1 of 4 finisher-1 diets with 4 gilt pens and 4 castrated male pens/diet, and they were switched to finisher-2 diets when the average pen weight reached 79.0±2.0kg. Pigs had ad libitum access to feed and water throughout the study. At the end of the finisher-2 phase (107.7±3.3kg), blood samples were collected to determine serum metabolite profile and pigs were slaughtered to assess carcass characteristics. Pigs fed the POS diets ended to have greater overall average daily feed intake (ADFI; P=0.083) and had greater total Lys intake (P=0.029) than those fed the SID diets, which may have resulted in a tendency for slightly greater average daily gain (ADG; P=0.094) in pigs fed the POS diets. However, there was no difference in the efficiency of feed or Lys utilization. Pigs fed the SID diets tended to have greater gain:feed (G:F; P=0.057) and had greater gain:total Lys intake (P<0.001) than those fed the NRC diets. Pigs fed the POS diets tended to have greater ADFI (P=0.079) and had greater ADG (P<0.001) and G:F (P<0.001) than those fed the NEG diets, but, as expected, they had lower gain:total Lys intake (P<0.001) mostly because of the increased total Lys intake (P<0.001). Serum glucose was not affected by dietary treatments. Pigs fed the POS diets had greater urea-N (P=0.003) and lower cholesterol (P=0.002) than those fed the SID diets. As expected, pigs fed the NEG diet had reduced total protein (P<0.001) and increased urea-N (P=0.001), triglyceride (P<0.001), and cholesterol (P<0.001) compared with those fed the POS diets. Pigs fed the POS diets had greater fat-free lean gain (P=0.020) that those fed the SID diets, but similar loin muscle area, fat-free carcass percentage, and efficiency of fat-free lean gain. Results indicated that pigs fed the SID diets utilized feed and Lys as efficiently as those fed the POS diets, but they had slightly reduced body weight and fat-free lean gain, perhaps, because of slightly reduced intake of feed and total Lys, as well as other AA.

Measurement of true ileal digestibility and total tract retention of phosphorus in corn and canola meal for broiler chickens

The study reported herein was conducted to determine and compare the nonphytate P, digestible P, and retainable P contents of corn and canola meal for broiler chickens. Four semipurified diets were formulated from each of ingredient to contain graded concentrations of nonphytate P. The experiment was conducted as a randomized complete block design with 4 weight blocks of 8 cages each (6 birds per cage). A total of 192 broilers (Ross 308), 21 d old, were assigned to the 8 test diets. Ileal digestibility and total tract retention coefficients of P were determined by the indicator and total collection methods, respectively, and linear regression method was used to determine the true P digestibility and true P retention coefficients. The apparent ileal digestibility of P in corn was influenced (quadratic, P < 0.05) by increasing dietary nonphytate P concentrations, whereas P retention was unaffected (P > 0.05). The apparent ileal P digestibility in broilers fed diets based on canola meal was similar (P > 0.05) at different P concentrations. Phosphorus retention in broilers fed diets based on canola meal (linear, P < 0.01) decreased with increasing P concentrations. True ileal P digestibility and true P retention coefficients of corn were determined to be 0.676 and 0.632, respectively. The corresponding values for canola meal were 0.469 and 0.486, respectively. In both ingredients, the determined true ileal digestibility and total tract retention coefficients were not different (P > 0.05). Total P, nonphytate P, true digestible P, and true retainable P contents of corn were determined to be 2.5, 0.8, 1.7, and 1.6 g/kg (as received), respectively. The corresponding values for canola meal were 9.7, 2.8, 4.6, and 4.7 g/kg (as received), respectively. The present data demonstrated that the regression method can be successfully used to measure true P digestibility of low and high P feed ingredients and that both true ileal digestibility and retention coefficients are suitable to assess P availability in broilers.