True Ileal Digestibility Research Articles

Ileal digestibility of intrinsically labeled hen's egg and meat protein determined with the dual stable isotope tracer method in Indian adults

ABSTRACTBackgroundProtein quality assessment through the Digestible Indispensable Amino Acid Score requires accurate measurements of true ileal protein and amino acid digestibility, for which a dual isotope technique was recently developed. However, the ileal digestibility of indispensable amino acids (IAA) in humans from high-quality proteins is not well known.ObjectiveThe aim of this study was to intrinsically label hen's egg and meat protein by the use of uniformly 2H-labeled amino acids, and to measure their true ileal indispensable amino acid (IAA) digestibility via the dual isotope method in humans.Design 2H-labeled lyophilized boiled egg white protein, whole boiled egg, and cooked meat were obtained from layer hens (BV-300) administered a uniformly 2H-labeled amino acid mix orally for 35 d with their daily feed. The ileal IAA digestibility of these proteins was determined with reference to digestibility of previously characterized [U-13C]spirulina in a dual tracer method in healthy Indian subjects whose intestinal health was measured by the plasma kynurenine-to-tryptophan (KT) ratio.ResultsAll subjects had normal KT ratios. The mean ± SD true ileal IAA digestibility of 2H-labeled egg white protein, whole boiled egg, and cooked meat was 86.3% ± 4.6%, 89.4% ± 4.5%, and 92.0% ± 2.8%, respectively. Leucine digestibility correlated with the KT ratio (r = −0.772; P = 0.009).ConclusionsUniformly 2H-labeled hen's egg and meat protein can be used to measure ileal IAA digestibility by the dual isotope tracer approach in humans. The mean IAA digestibility values for these high-quality proteins in the healthy Indians studied were similar to values obtained in earlier human and animal experiments. Leucine digestibility in these meal matrices correlated with the KT ratio, but this aspect needs further evaluation. This trial was registered at the Clinical Trials Registry of India (http://ctri.nic.in) as CTRI/2018/03/012265.

Cooking Conditions Affect the True Ileal Digestible Amino Acid Content and Digestible Indispensable Amino Acid Score (DIAAS) of Bovine Meat as Determined in Pigs

Cooking processes affect the physical, chemical, and structural properties of meat proteins. Cooking may also affect the protein quality of meat, as indicated by the true ileal digestibility of individual amino acids, the content of each truly digestible amino acid, and the digestible indispensable amino acid score (DIAAS). The study aimed to determine the effect of the cooking process (raw, not cooked; boiled; grilled; pan-fried; roasted) of beef on true (standardized) ileal amino acid digestibility, true ileal digestible amino acid content, and DIAAS. Beef topside steak was subjected to one of the following conditions: raw, boiled, grilled, pan-fried, or roasted, followed by mincing. The growing pig was used as an animal model for the adult human. Diets containing the raw or cooked meats (10% crude protein content) were fed to growing pigs (n=6 per diet; mean±SEM bodyweight, 23.6±0.48 kg) and samples of terminal ileal digesta were collected under anesthesia. True ileal amino acid digestibility of the beef was determined and DIAAS values were calculated. There were only minor differences in true ileal amino acid digestibility across cooking conditions with all amino acids having true ileal amino acid digestibility in the range of 90-100%. In general, boiled meat had the highest true ileal digestible amino acid content (total of 724 g/kg dry matter), and roasted meat the lowest (total of 641 g/kg dry matter; P<0.001). The DIAAS was greater (P<0.001) for the raw, boiled, and pan-fried meat treatments (97-99%) than for roasted meat (91%) or grilled meat (80%). The high DIAAS (range 80-99%) across cooking conditions confirms that bovine meat is a high-quality protein source. Cooking conditions affect the true ileal digestible amino acid content and DIAAS of beef, as determined with the use of the pig model.

Determination of true ileal phosphorus digestibility of maize and soybean meal and true ileal calcium digestibility of soybean meal for broiler chickens

Two experiments were conducted, using the regression method, to determine the true ileal phosphorus (P) digestibility of maize and soybean meal (SBM), and true ileal calcium (Ca) digestibility of SBM for broiler chickens. The aim of Experiment 1 was to determine true ileal P digestibility of maize and SBM. The experimental diets were formulated with four inclusion levels of each test ingredient to achieve graded concentrations of total P (2.5, 3.0, 3.5 and 4.0 g/kg, respectively). The P concentrations in maize-based diets were adjusted by the inclusion of monosodium phosphate. The Ca:total P ratio in all diets was maintained at 1.35 by the addition of limestone. Experiment 2 was conducted to determine true ileal Ca digestibility of SBM. Experimental diets were formulated to contain four levels of SBM to achieve graded concentrations of Ca (2.5, 3.0, 3.5 and 4.0 g/kg, respectively). Because of the low concentration of Ca in SBM, all diets were supplemented with a similar level of limestone to prevent any Ca deficiency. The Ca:total P ratio in all diets was adjusted to be equal by the addition of monosodium phosphate. In both experiments, titanium dioxide (3 g/kg) was used as the indigestible marker. One-day-old male broiler chicks were fed a commercial starter diet from 1 to 21 days of age. On Day 22, a total of 240 and 120 birds were assigned to eight and four dietary treatments in Experiments 1 and 2, respectively, with five replicate cages and six birds per cage. Birds were fed the experimental diets for 7 days. On Day 29, ileal digesta were collected from the posterior half of ileum, and the true P and Ca digestibility of test ingredients were calculated by linear regression analysis. True P digestibility of maize and SBM were determined to be 33.8% and 42.3%, respectively. True Ca digestibility of SBM was determined to be 45.9%.

True ileal phosphorus digestibility of monocalcium phosphate, monodicalcium phosphate and dicalcium phosphate for broiler chickens

This study was conducted to determine the true ileal phosphorus (P) digestibility of monocalcium phosphate (MCP), monodicalcium phosphate (MDCP) and dicalcium phosphate from bones (DCP) for broiler chickens using the regression method. A corn-soy basal diet was formulated to contain 2.5 g/kg total P. Each test ingredient was then included at three levels to the basal diet to achieve graded concentrations of total P (3.0, 3.5 and 4.0 g/kg, respectively). The calcium (Ca):P ratio was maintained at 1.35–1.40:1 by the addition of limestone. Titanium dioxide (3 g/kg) was included in all diets as an indigestible marker. Day-old male broiler chicks were fed a commercial broiler starter diet from 1 to 20 days of age. On day 21, birds were individually weighed and assigned to 60 cages (6 birds/cage) and the 10 experimental diets (basal diet and 9 diets with 3 inclusion levels of each test ingredient) were then randomly allocated to 6 replicate cages each. The birds were fed the experimental diets ad libitum for 8 days. On day 29, all birds were euthanized and ileal digesta were collected from the posterior half of the ileum. True P digestibility of MCP, MDCP and DCP were calculated by the linear regression analysis. True P digestibility of MCP, MDCP and DCP were determined to be 64.6, 60.2 and 69.3%, respectively. The present results suggest that the P digestibility from two inorganic sources (MCP and MDCP) and one organic source (DCP from bones) were lower than the values of available P currently assumed in poultry feed formulations.

Amino acid digestibility of larval meal (Musca domestica) for broiler chickens

Work was undertaken to investigate the potential use of housefly (Musca domestica) larvae reared on broiler manure as a source of nutrition for poultry production in the United Kingdom. Nutritional analysis showed that larvae have a high (>45% dry wt.) protein content and a favorable amino acid profile that is rich in key amino acids, such as lysine and methionine. A broiler digestibility trial was carried out to determine the apparent ileal digestibility coefficients (AIDC) and true ileal digestibility coefficients (TIDC) of amino acids (AA) from insect larval meal (ILM) from M. domestica and fishmeal (FM) in broiler chickens. This was calculated using multiple linear regression technique based upon 3 inclusions of each protein source in a semisynthetic diet. One-hundred-forty-four day-old male (Ross 308) broilers were fed from hatch on a commercial starter diet for 20 days. Experimental diets were fed from d 21 to 28, and feed intakes were measured daily. On d 28, the trial was terminated, ileal digesta were collected for the determination of AIDC and TIDC of AA, and inflammatory responses (gizzard erosion and eye discharge) were measured. No significant differences were observed in digestibilities between protein sources for any AA. Furthermore, ILM feeding did not induce gizzard erosion or eye discharge at any inclusion. These results provide strong evidence to suggest that ILM of the common housefly can provide a successful alternative protein source to FM in broiler diets.

Measurement of the true ileal calcium digestibility of some feed ingredients for broiler chickens

Results from three experiments relating to the measurement of ileal calcium (Ca) digestibility in feed ingredients for broiler chickens are presented herein. The first experiment was conducted to determine the true ileal Ca digestibility of dicalcium phosphate (DCP), monocalcium phosphate (MCP), poultry by-product meal (PBPM), fish meal (FM) and canola meal (CM). Five semi-purified diets containing DCP, MCP, PBPM and FM with a dietary Ca concentration of 9 g/kg, and CM with a dietary Ca concentration of 5.71 g/kg were generated. A Ca- and phosphorus (P)-free diet was used to determine the basal ileal endogenous Ca losses. Titanium dioxide was incorporated in all diets as an indigestible marker. Each diet was randomly allotted to six replicate cages (eight birds per cage) and fed from 21 to 24 days post-hatch. True Ca digestibility coefficients of DCP, MCP, PBPM, FM and CM were determined to be 0.28, 0.33, 0.29, 0.24 and 0.31, respectively. These lower digestibility coefficients were unexpected and it was speculated that this finding may be due to the length of adaptation to assay diets and/or assay methodology. To investigate these possibilities, two more experiments were conducted. In the second experiment, the influence of dietary adaptation length was examined with DCP and MCP. The assay diets with DCP and MCP, and the Ca- and P-free diet were similar to those used in Experiment 1. Each diet was randomly allocated to four replicate cages (15 birds per cage) and fed from 21 to 24 days post-hatch. Digesta samples of five birds from each replicate were collected after 24, 48 and 72 h of feeding. Dietary adaptation length had no influence (P > 0.05) on the true Ca digestibility of MCP, but increased that of DCP at 24 h. True ileal Ca digestibility of DCP and MCP after 24, 48 and 72 h of adaptation were 0.45, 0.36, and 0.35, and 0.30, 0.32 and 0.34, respectively. The third experiment was conducted to determine the effect of assay methodology (direct, regression and difference methods) and Ca:non-phytate P ratio (2:1 and 1.16:1) on the Ca digestibility of DCP. The true Ca digestibility coefficients of DCP determined by the direct, difference and regression methods with Ca:non-phytate P ratio of 1.16:1 were 0.34, 0.21 and 0.13, respectively. The true Ca digestibility of DCP determined by the direct method was higher (P < 0.05) than those determined by difference and regression methods The true Ca digestibility coefficient of DCP with Ca:non-phytate P ratios of 2:1 and 1.16:1 were 0.25 and 0.21, respectively, and was not influenced (P > 0.05) by the Ca to non-phytate P ratio.

Factors contributing to the selection of dietary protein food sources

Protein is the only dietary macronutrient required for life. As such, it is reasonable to consider dietary protein as the centerpiece of a healthy eating pattern. To do so requires consideration of what type of protein should be eaten. Account should be taken of the quality of the protein, the density of the protein in the protein food source, and the non-protein components of protein food source. The quality of protein can be quantified based on the amount and profile of essential amino acids (EAAs), as well as the true ileal digestibility of the EAAs in the protein. The density of protein in a food source can be quantified on the basis of the amount of total calories ingested to achieve intake of the daily requirement of all EAAs. Non-protein components of protein food sources can be considered in terms of the amount and nature of fat, carbohydrate and fiber, as well as the content of micronutrients. Potential beneficial effects of high-quality protein food sources should be balanced against any possible adverse effects. When all of these factors are considered we conclude that animal-based protein foods (e.g., eggs, dairy, meat, fish, poultry) occupy an important place in a healthy eating pattern.

Protein Digestion and Quality of Goat and Cow Milk Infant Formula and Human Milk Under Simulated Infant Conditions.

ABSTRACTObjective:The aim of this study was to determine the kinetics of true ileal protein digestion and digestible indispensable amino acid score (DIAAS) of a goat milk-based infant formula (GIF), a cow milk-based infant formula (CIF), and human milk (HM).Methods:The GIF, CIF, and HM were investigated in an in vitro gastrointestinal model simulating infant conditions. Digested compounds were dialyzed from the intestinal compartment as bioaccessible fraction. Dialysate was collected in 15 to 60-minute periods for 4 hours. True ileal protein digestibility and DIAAS were determined as bioaccessible nitrogen (N) and amino acids.Results:N bioaccessibility from the GIF showed similar kinetics to that of HM. The CIF showed a delay in N bioaccessibility versus the GIF and HM. In the 1st hour of digestion, N bioaccessibility was 19.9% ± 3.5% and 23.3% ± 1.3% for the GIF and HM, respectively, and 11.2% ± 0.6% for CIF (P < 0.05 vs HM). In the 3rd hour of digestion, the N bioaccessibility was higher (P < 0.05) for the CIF (28.9% ± 1.2%) than for the GIF (22.5% ± 1.6%) and HM (20.6% ± 1.0%). After 4 hours, the true ileal protein digestibility of the GIF, CIF, and HM was 78.3% ± 3.7%, 73.4% ± 2.7%, and 77.9% ± 4.1%, respectively. The DIAAS for the GIF, CIF, and HM for 0- to 6-month-old infants was 83%, 75%, and 77% for aromatic AA.Conclusion:The protein quality is not different between the GIF, CIF, and HM, but the kinetics of protein digestion of the GIF is more comparable to that of HM than that of the CIF.

Influence of dietary crude protein and phosphorus on ileal digestion of phosphorus and amino acids in growing pigs.

A study was conducted to investigate the effect of dietary CP levels on ileal P digestion in growing pigs. A total of 18 ileal-cannulated pigs (44.2 ± 3.2 kg initial BW) were used in a duplicated 9 × 3 incomplete Latin square design, with 9 treatments and three 7-d experimental periods giving 6 replicates per treatment. The 9 treatments consisted of 1 N-free diet to estimate basal endogenous loss of AA and 8 corn-soybean meal-based diets in a 2 × 4 factorial arrangement, which included 2 CP levels (6.9 or 13.4%) and 4 apparent total tract digestible P (ATTDP) levels (0.09, 0.16, 0.24, or 0.32%). Soybean meal and monocalcium phosphate were used to adjust the CP level and ATTDP level, respectively. Limestone was included in diets to maintain a Ca:ATTDP ratio of 2.5 across treatments. Ileal digesta was continuously collected for 10 h on the last 2 d of each 7-d experimental period. The ileal digesta samples were lyophilized and analyzed to calculate ileal digested N and P. Data were analyzed using PROC MIXED of SAS (9.3) and contrasts were used to test the linear and quadratic effects of increasing levels of P within each CP level. In the low-CP group (6.9%), the ileal digested P was 0.71, 1.16, 1.64, and 2.03 g/kg DMI for diets that contained 0.09, 0.16, 0.24, and 0.32% ATTDP, respectively, and was 0.70, 1.54, 2.03, and 1.99 g/kg DMI, respectively, for their counterparts in the high-CP group (13.4%). A low dietary CP level decreased ( < 0.05) ileal digested P (g/kg DMI). The ileal digested P (g/kg DMI) linearly increased ( < 0.01) with increasing ATTDP levels in the low-CP group, but the pattern was linear ( < 0.01) and quadratic ( < 0.01) in the high-CP group. In the low- and high-CP diets, the determined true ileal digestibility of P in monocalcium phosphate was 54.4 and 75.6%, respectively. In conclusion, this research indicated that the ileal digestion of P could be limited by protein deficiency. The dietary CP level should be considered in P digestibility-related studies.

Methodology affects measures of phosphorus availability in growing broilers: Effects of calcium feeding strategy and dietary adaptation period length on true ileal phosphorus digestibility and predicted endogenous phosphorus losses

An experiment was conducted to determine the effects of Ca feeding strategy and dietary adaptation period length (DAPL) on the apparent ileal P digestibility (AIPD) and apparent ileal myo-inositol 1,2,3,4,5,6 hexakis dihydrogen phosphate (IP6) hydrolysis (AIIP6H) of corn titration diets. Nine hundred sixty Ross × Ross 708 male broiler chicks were placed into 80 battery cages. Broilers received a common starter diet until 18 d of age and then were fed one of 10 experimental treatments from 19 to 21 d of age. Nine diets were formulated to evaluate 5 corn inclusion concentrations (15, 30, 45, 60, or 75%) and 2 Ca feeding strategies (fixed at 0.35% or 1.4:1 Ca:P) after 3 DAPL (zero, 24, and 48 h). As a control for DAPL, one treatment group received the common starter diet for the duration of the experiment. Broilers consuming the control diet had higher (P < 0.001) BW gain and feed intake than broilers fed the corn titration diets. Apparent ileal P digestibility of the control diet was affected (P = 0.038) by DAPL. For diets formulated with a 1.4:1 Ca:P ratio, negative linear effects (P < 0.05) on AIPD and AIIP6H were observed with increasing corn. Conversely, for diets formulated with 0.35% Ca, positive linear effects (P < 0.05) were measured for AIPD after a 48 DAPL while no linear or quadratic effects (P > 0.05) were measured for AIPD or AIIP6H for other DAPL. Broilers fed diets formulated with 1.4:1 Ca:P had variable (P < 0.05) true ileal P digestibility (TIPD; 32.2, 15.1, and 35.4%) and negative endogenous P losses (EPL; −190, −499, and −262 mg/kg DM intake) for zero, 24, and 48 h DAPL, respectively. Conversely, TIPD values (41.2, 39.1, and 47.3%) were similar (P > 0.05) and EPL were positive (102, 197, and 154 mg/kg DM intake), regardless of DAPL, for broilers fed diets formulated with 0.35% Ca. These data demonstrated that formulating diets with a 1.4:1 Ca:P ratio affected AIPD of the titration diets, shifting the regression line and predicted negative EPL and an underestimation of TIPD.

Apparent and true ileal and total tract digestibility of fat in canola press-cake or canola oil and effects of increasing dietary fat on amino acid and energy digestibility in growing pigs

Apparent and true ileal and total tract digestibility of fat in canola press-cake or canola oil and effects of increasing dietary fat on amino acid and energy digestibility in growing pigs

Procedures for determining digestibility of amino acids, lipids, starch, fibre, phosphorus, and calcium in feed ingredients fed to pigs

The proportion of nutrients that is absorbed from the intestinal tract of the pig differs among dietary ingredients; therefore, it would be desirable to determine the proportion of nutrients that is absorbed for each ingredient, but, for practical reasons, values for the digestibility of nutrients in each ingredient are used as predictors of absorption. For amino acids, starch and lipids, ileal digestibility must be determined because nutrients not absorbed in the small intestine will be fermented or changed in the large intestine, which invalidates data for total tract digestibility of these nutrients. For starch, apparent ileal digestibility is a reasonable predictor of its disappearance from the small intestine, but because of endogenous secretions of amino acids and lipids into the small intestine, standardised ileal digestibility of amino acids and true ileal digestibility of fat must be determined. For fibre, total tract digestibility is used to estimate fermentation and subsequent absorption of short-chain fatty acids, but it must be corrected for endogenous secretions. Likewise, for phosphorus and calcium, values for apparent total tract digestibility must be corrected for basal endogenous losses; consequently, standardised total tract digestibility of phosphorus and calcium is calculated and used in diet formulation. These procedures for determining the digestibility of nutrients in feed ingredients make it possible to formulate diets in which concentrations of digestible nutrients can be predicted from values for individual feed ingredients.

Effect of calcium source and particle size on the true ileal digestibility and total tract retention of calcium in broiler chickens

The influence of calcium (Ca) source and particle size on true ileal digestibility coefficient (TIDC) of Ca and apparent total tract retention coefficient (ATTRC) of Ca in broilers was assessed. Four experimental diets containing limestone and oyster shell, each as fine (<0.5mm) and coarse (1–2mm) particles, were fed to broiler chickens from 21 to 24days of age. A Ca- and phosphorus-free diet was used to determine the ileal endogenous Ca losses. Limestone and oyster shell were obtained from commercial sources and ground to pass through a set of sieves to obtain the fine and coarse particles. Titanium dioxide was incorporated in all diets as an indigestible marker. Each experimental diet was randomly allotted to six replicate cages (eight birds per cage). Apparent ileal digestibility coefficient and ATTRC of Ca were calculated using the indicator method and the TIDC values were calculated by correcting for endogenous Ca losses. Ileal endogenous Ca losses were determined to be 115mg/kg of dry matter intake. The main effect of Ca source and the interaction between Ca source and particle size were not significant (P>0.05) for the TIDC and ATTRC of Ca. Both TIDC and ATTRC of Ca were influenced (P<0.05) by particle size, with coarser particles increasing the digestibility and retention values. Increased particle size increased the TIDC of Ca in limestone from 0.38 to 0.62 and that of oyster shell from 0.33 to 0.56. The corresponding increases in ATTRC of Ca were from 0.44 to 0.66 in limestone and from 0.40 to 0.60 in oyster shell. Calcium concentration in the gizzard contents of birds was higher (P<0.05) for limestone as compared to oyster shell and increased with increase in particle size. Calcium concentration in the gizzard contents was strongly correlated with the TIDC (r=0.81; P<0.01) and ATTRC (r=0.82; P<0.01) of Ca. A strong correlation (r=0.80, P<0.01) was also observed between TIDC and ATTRC of Ca.

Metabolizable energy and digestible amino acids of full-fat soybean without or with protease supplementation in diets for broilers

ABSTRACT Two experiments were carried out to determine the energy values and the true ileal digestibility of amino acids of nine toasted full-fat soybeans (FFSB), without or with the addition of monocomponent protease. In the first experiment, to determine the energy values, the method of excreta collection was used with 1120 broiler chicks at 14 days old, distributed in randomized blocks in a 10x2 factorial arrangement with nine full-fat soybeans (30% included) plus a control diet (70%) without or with the addition of protease, totaling 20 treatments with 8 replicates and 7 birds per cage. In the second experiment, 1120 broiler chickens from 24 to 28 days of age were distributed in randomized blocks in a 10x2 factor arrangement, with nine full-fat soybeans (40% included) + a protein free diet (60%), without or with the addition of protease, totaling 20 treatments with 8 replicates and 7 birds per cage. Ileal digesta collection was used to determine the true digestibility coefficients and the digestible amino acid content of full-fat soybean. The average values of nitrogen-corrected apparent metabolizable energy (AMEn) and their respective metabolization coefficients (CAMEn) were 3207 kcal/kg and 62.57%, respectively. The average values of digestibility coefficients of crude protein and essential and nonessential amino acids were 86.79, 87.90 and 84.34%, respectively. The inclusion of protease improved (P&lt;0.05) all evaluated parameters. Therefore, its use is recommended in diets containing full-fat soybeans for broiler chickens.

Effect of limestone particle size and calcium to non-phytate phosphorus ratio on true ileal calcium digestibility of limestone for broiler chickens

The purpose of this study was to determine the effect of limestone particle size and calcium (Ca) to non-phytate phosphorus (P) ratio on the true ileal Ca digestibility of limestone for broiler chickens. A limestone sample was passed through a set of sieves and separated into fine (<0.5 mm) and coarse (1–2 mm) particles. The analysed Ca concentration of both particle sizes was similar (420 g/kg).Six experimental diets were developed using each particle size with Ca:non-phytate P ratios of 1.5:1, 2.0:1 and 2.5:1, with ratios being adjusted by manipulating the dietary Ca concentrations. A Ca-free diet was also developed to determine the basal ileal endogenous Ca losses. Titanium dioxide (3 g/kg) was incorporated in all diets as an indigestible marker.Each experimental diet was randomly allotted to 6 replicate cages (8 birds per cage) and fed from d 21 to 24 post hatch. Apparent ileal digestibility of Ca was calculated using the indicator method and corrected for basal endogenous losses to determine the true Ca digestibility.The basal ileal endogenous Ca losses were determined to be 127 mg/kg of dry matter intake.Increasing Ca:non-phytate P ratios reduced the true Ca digestibility of limestone. The true Ca digestibility coefficients of limestone with Ca:non-phytate P ratios of 1.5, 2.0 and 2.5 were 0.65, 0.57 and 0.49, respectively.Particle size of limestone had a marked effect on the Ca digestibility, with the digestibility being higher in coarse particles (0.71 vs. 0.43).

Effect of the addition of β-mannanase on the performance, metabolizable energy, amino acid digestibility coefficients, and immune functions of broilers fed different nutritional levels

Three experiments were conducted to evaluate the effect of β-mannanase (BM) supplementation on the performance, metabolizable energy, amino acid digestibility, and immune function of broilers. A total of 1,600 broilers were randomly distributed in a 4 × 2 factorial arrangement (4 nutritional levels × 0 or 500 g/ton BM), with 10 replicates and 20 broilers per pen. The same design was used in the energy and digestibility experiments with 8 and 6 replicates, respectively, and 6 broilers per pen. The nutritional levels (NL) were formulated to meet the nutritional requirements of broilers (NL1); reductions of 100 kcal metabolizable energy (NL2); 3% of the total amino acids (NL3); and 100 kcal metabolizable energy and 3% total amino acids (NL4) from NL1. The serum immunoglobulin (Ig) concentration was determined in two broilers per pen, and these broilers were slaughtered to determine the relative weight of spleen, thymus, and bursa of Fabricius. Throughout the experiment, the lower nutritional levels reduced (P < 0.05) body weight gain (BWG) and increased (P < 0.05) feed conversion (FCR) for the NL4 treatment. The BM increased (P < 0.05) the BWG values and improved (P < 0.05) the FCR of the broilers. The apparent metabolizable energy corrected for nitrogen balance (AMEn) values were reduced (P < 0.05) for NL2 and NL3. The BM increased (P < 0.05) the AMEn values and reduced (P < 0.05) the excreted nitrogen. NL3 and NL4 reduced (P < 0.05) the true ileal digestibility coefficients (TIDc) of the amino acids cystine and glycine, and BM increased (P < 0.05) the TIDc for all amino acids. The addition of BM reduced (P < 0.05) the relative weights of the spleen and bursa. NL2 increased (P < 0.05) the Ig values, whereas BM reduced (P < 0.05) the serum IgA, IgG, and IgM values of the broilers. This study indicates that using suboptimal nutrient levels leads to losses in production parameters, whereas BM-supplemented diets were effective in improving performance, energy values, and TIDc levels of amino acids and immune response of broilers.

Protein quality as determined by the Digestible Indispensable Amino Acid Score: evaluation of factors underlying the calculation.

The Food and Agriculture Organization of the United Nations recently recommended the adoption of a new and improved scoring system (Digestible Indispensable Amino Acid Score [DIAAS]) to quantify dietary protein quality. The DIAAS is based on the relative digestible content of the indispensable amino acids (IAAs) and the amino acid requirement pattern. Factors involved in calculation of the DIAAS include: use of the content and profile of IAAs as the basis for quality; methods for determination of the protein and amino acid content of the protein source; accuracy of individual requirement values for IAAs; normalization of IAA requirements by the estimated average requirement for protein; and basing the DIAAS on the true ileal digestibility of each IAA in the test protein. This review outlines the rationale for including each of these factors in the calculation of the DIAAS and describes associated potential errors.

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

The aim of the present study was to determine the true ileal phosphorus (P) 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 analysed for nutrient composition, particle size distribution and bone to soft tissue ratio. The total P concentration of MBM-1, MBM-2, MBM-3 and MBM-4 were determined to be 38, 60, 60 and 41g/kg, respectively. The corresponding geometric mean particle diameter and bone to soft tissue ratio were 0.866, 0.622, 0.875 and 0.781mm, and 1:1.49, 1:0.98, 1:0.92 and 1:1.35, respectively. Five experimental diets, including four diets with similar P concentration (4.4g/kg) from each MBM and a P-free diet, were developed. Meat and bone meal served as the sole source of P in the MBM diets. Titanium dioxide (3g/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 day 28–31 posthatch. Apparent ileal P digestibility was calculated by the indicator method and basal ileal endogenous P losses, determined following the feeding of the P-free diet, were used to calculate the true ileal P digestibility. Basal ileal endogenous P losses were determined to be 354mg/kg dry matter intake. True ileal P digestibility coefficients of MBM-1, MBM-2, MBM-3 and MBM-4 were determined to be 0.623, 0.617, 0.615 and 0.444, respectively. True ileal P digestibility of MBM-1, MBM-2 and MBM-3 were similar (P>0.05) and higher (P<0.05) than that of MBM-4. The present findings suggest that the direct method may be considered for use in the determination of true P digestibility in feed ingredients for poultry, but further studies are clearly needed to validate this possibility. The present data also suggest that the general assumption that P in MBM is highly available is not valid.

Nitrogen and amino acid ileal and faecal digestibility of rabbit feeds predicted by an in vitro method

Predicting the amino acid digestibility of ingredients is one of the main challenges in animal nutrition, due to its effect on animal performance, gut health and the environment. The aim of this work was to predict in vivo ileal and faecal digestibility of nitrogen and amino acids by using an in vitro method. Eleven ingredients (soybean meal 480, toasted full-fat soybean, sunflower meal 280 and 360, peas, wheat, wheat shorts, corn, gluten feed, dehydrated alfalfa and soybean hulls), commonly used in rabbit diets, were simultaneously evaluated in vivo, and subjected to a three step enzymatic in vitro digestion. Dry matter (DM), nitrogen (N) and amino acids (AA) were analysed in the residues in order to determine their in vitro digestibility (NDiv, AADiv). The correlation among in vivo apparent faecal and ileal, and true ileal digestibilities (AFD, AID and TID, respectively) of N and AA of the ingredients and the corresponding in vitro values were analysed using a regression procedure. The average NDiv was 0.875 and ranged from 0.764 of soybean hulls to 0.946 of full-fat soybean, AADiv showed similar ranges of variation and their average values varied with the AA (from GLY and CYS: 0.83 to GLU and ARG 0.92). Values of NDiv were higher than the corresponding in vivo values (0.21, 0.10 and 0.05 points as average for AID, AFD and TID, respectively), but the correlation among them was relatively high (averaged 0.77, 0.76 and 0.65, respectively). An average of 72% of the variation in AA ileal digestibility was explained by the NDiv variation, but the latter only explained 55% of AFD AA variation. The accuracy of the prediction was similar among units, its RSD averaged 0.074. Methionine was the limiting amino acid most precisely predicted, as opposed to CYS and THR, which were predicted with the lowest accuracy. In conclusion, NDiv can help to discriminate among feedstuffs that are more or less digestible at ileal level better than chemical analysis.

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.