Additivity of apparent and standardized ileal amino acid digestibility of corn and soybean meal in broiler diets

Metabolizable energy and digestible nutrient values of protease-supplemented field pea for broiler chicken

A study was conducted to determine the effects of protease supplementation of field pea (in comparison with soybean meal; SBM) for broilers on apparent metabolizable energy (AMEn) and standardized ileal digestibility (SID) of amino acids (AA). One hundred and forty broiler chicks were divided into 35 groups of 4 birds/group and fed 5 diets in a completely randomized design (7 groups/diet) from 14 to 21 d of age. The diets were cornstarch-based containing SBM or field pea as the sole protein source without or with protease (ProSparity 250TM; CBS Bio Platforms, Calgary, AB, Canada) in 2 × 2 factorial arrangement, and N-free diet. Protease was added to diets to supply 6,250 U/kg. Digestibility of AA and N retention for feedstuffs were determined by the direct method, whereas digestibility and retention of energy for feedstuffs were determined by the difference from the N-free diet. On as fed basis, SBM and field pea contained 90.0 and 88.9 dry matter, 46.6 and 20.2 % crude protein, 2.88 and 1.47 % Lys, and 14.3 and 14.7 % non-starch polysaccharides, respectively. On as fed basis, the AMEn value for field pea was lower (P < 0.05) than that of SBM (2,006 vs. 2,414 kcal/kg). Also, the SID values of most indispensable AA in field pea were lower (P < 0.05) than those in SBM. Feedstuff (field pea vs. SBM) and protease did not interact on AMEn and SID of AA values. The supplemental protease increased (P < 0.05) AMEn values of the SBM and field by an average of 187 kcal/kg but decreased (P < 0.05) the SID values of all indispensable AA (except His) for the SBM and field, by an average of 2.7 percentage points. Results indicate that the protease product used in the current study marginally reduced the SID of AA for both SBM and field pea. However, the protease product can be beneficially included in diets based on SBM or field pea for broilers to enhance their AMEn values. The response to the protease on the AMEn was consistent regardless of the protein source in the diet, implying that the protease used in this study has similar positive impact on energy availability in both field pea and SBM.

Determination and prediction of the apparent and standardized ileal amino acid digestibility in soybean meal fed to the pullets

This experiment was conducted to evaluate the chemical composition, apparent ileal digestibility (AID) and standardized ileal digestibility (SID) of amino acid (AA) in 10 different sources of soybean meal (SBM) fed to the pullets and established prediction equations based on the chemical composition of SBM. 792 Hy Line Brown hens aged 12-15 weeks were divided into 11 diet groups, the diets included one nitrogen-free diet (NFD) used to measure the basal endogenous losses of AA and 10 SBM test diets containing 35.2 % SBM as the sole source of AA. The 0.5 % titanium dioxide (TiO2) was used as an indigestible marker. The results shown that there was considerable variation in crude ash (Ash), ether extract (EE), and acid detergent fiber (ADF) content in the 10 SBM samples with a coefficient of variation greater than 10 %. The AID and SID of both indispensable and dispensable AA except for the Cys and Ala among the 10 SBM differed (P < 0.05). The AID of AA was correlated with the dry matter (DM), gross energy (GE), crude protein (CP), EE, Ash, and reactive Lys (rLys) (P < 0.05), and SID of AA was correlated with the GE, CP, EE, CF, neutral detergent fiber (NDF) and rLys (P < 0.05). With R2 values exceeding 0.39, significant linear regression equations for the AID of Met, Phe, Lys, Asp, and Gly, as well as SID of Met, Phe, Lys, Ser and Tyr were obtained. The best fit equation for the AID of Asp was the DM, GE, Ash and rLys (R2 = 0.820, P = 0.042), and the SID of Lys was the GE, CP, CF, Ash, ADF and rLys (R2 = 0.989, P = 0.005), respectively. In conclusion, this experiment suggested that the rLys can be used to predict the AID and SID of AA in SBM with reasonable accuracy together with the basal chemical composition, and prediction equations for AID and SID could be used to evaluate the digestibility of SBM in the pullets.

Effect of age on the standardized ileal amino acid digestibility of soybean meal and canola meal in broilers

Standardized ileal digestibility coefficients (SIDC) of nitrogen (N) and amino acids (AA) in two protein sources (soybean meal [SBM] and canola meal [CM]) were investigated at six broiler ages (d 7, 14, 21, 28, 35, and 42). Two assay diets were formulated to contain either SBM (413 g/kg) or CM (553 g/kg) as the sole dietary AA source. Titanium dioxide (5 g/kg) was added as an indigestible marker. A total of 696 male broilers at 1 d old were allotted to 12 replicate cages per age group. Each assay diet was offered to birds for 4 d prior to the ileal digesta collection on d 7 (14 birds/cage), 14 (12 birds/cage), 21 (10 birds/cage), 28 (8 birds/cage), 35 (8 birds/cage) and 42 (6 birds/cage), respectively. The apparent digestibility coefficients were standardized using age-specific basal endogenous AA flows. In the SBM group, though the SIDC of N tended to be influenced (quadratic; P = 0.075) by age, no linear or quadratic response of age effect was observed on the average SIDC of indispensable (IAA) and total AA (TAA). An age effect (quadratic; P < 0.05) was observed on the average SIDC of dispensable AA (DAA) in SBM with the highest value recorded at d 7, followed by a decrease from d 14 to 28, which increased beyond d 35. The SIDC of some individual AA (Arg, Thr, Trp, Cys, Pro) were affected (P < 0.05 or P < 0.001) in a quadratic manner by age. In the CM, the SIDC of N, average SIDC of IAA, DAA and TAA were influenced (quadratic; P < 0.05 or P < 0.001) by age. The SIDC of N and average SIDC of DAA and TAA were higher from d 7 to 14, declined at d 21, and then increased beyond d 28. The average SIDC of IAA was low between d 7 and 28 and increased thereafter. The SIDC of individual AA were affected (linear or quadratic; P < 0.05 or P < 0.001) by different magnitudes by age. The age influence on the SIDC AA was variable, depending on the protein source and AA. The results demonstrate that age-specific SIDC AA data might need consideration in broiler feed formulations.

Comparison of methods for estimating basal endogenous losses of amino acids and additivity of digestibility of amino acids in corn and soybean meal for broilers

This study was to compare the estimates of basal endogenous losses (BEL) of amino acids (AA) determined by 3 methods including feeding a nitrogen-free diet (NFD) or a low-casein diet (LCD, containing casein at 30 g/kg diet) or using the regression method. Another objective was to investigate whether the ileal AA digestibility of corn calculated from a casein-supplemented corn diet is additive for a corn-soybean meal (SBM) mixed diet in broilers. On d 31 of age, 168 Ross 308 male broilers were assigned to 8 dietary treatments with 6 replicates in a randomized complete block design. An NFD and 3 diets containing 30, 60, or 90 g/kg of casein were formulated to determine the BEL of AA and ileal AA digestibility of casein. The other 4 diets consisted of a corn diet, SBM diet, casein-supplemented corn diet, and corn-SBM mixed diet. On d 35 of age, digesta from the distal section of the ileum were collected. The BEL of AA in birds fed the LCD were greater (P < 0.05) than those of the NFD and the regression method. There were no differences in the BEL of AA determined between the NFD and the regression method. Apparent ileal digestibility (AID) and standardized ileal digestibility (SID) of AA for corn calculated from the casein-supplemented corn diet were greater (P < 0.05) than those of the corn diet. The predicted AID of Thr in the corn-SBM mixed diet based on the AID of AA for corn in the corn diet was lower (P < 0.05) than the measured AID. However, the predicted AID of AA in the mixed diet based on the AID of AA for corn in the casein-supplemented corn diet did not differ from the measured AID. The predicted SID of AA in the mixed diet did not differ from the measured SID irrespective of casein supplementation. In conclusion, feeding an NFD or using the regression method yields similar BEL of AA, but not feeding an LCD. Casein supplementation in the corn diet increases the ileal AA digestibility for corn, which is additive for the corn-SBM mixed diet.

Determination of standardised ileal digestibility of amino acids in high-fibre feedstuffs and additivity of apparent and standardised ileal amino acids digestibility of diets containing mixtures of maize, sorghum, and soybean meal

1. Two experiments were conducted to determine the coefficients of standardised ileal amino acid digestibility for selected high-fibre feedstuffs (Expt.1) and to assess the additivity of coefficients of apparent (cAIAAD) and standardised (cSIAAD) ileal amino acid digestibility for diets containing combinations of sorghum, maize and soybean meal.2. In Expt. 1, broiler chickens (324) were allocated to 54 metabolism cages (nine diets with six replicates). In Expt. 2, broiler chickens (315) were allocated to 63 metabolism cages (seven diets with nine replicates). The diets in Expt. 1 were a nitrogen-free diet plus eight semi-purified diets in which soybean meal (SBM), low-protein SBM (LPSBM), soybean hull, wheat bran, maize bran, rice bran, dried sugarbeet pulp or maize gluten feed were the only sources of protein in the respective diets. In Expt. 2, the seven diets were a nitrogen-free diet, and six semi-purified diets consisting of individual feedstuffs (SBM, maize, or sorghum) or combinations (maize and SBM; sorghum and SBM; or maize, sorghum, and SBM) as the only sources of protein.3. In both experiments, all the broiler chickens received the same maize-SBM diet formulated to meet nutrient requirements according to the breeder's recommendations from d 0 to 16. Allocated experimental diets were provided on d 16, and ileal digesta were collected on d 21.4. In Expt. 1, SBM and LPSBM had greater (P < 0.01) cSIAAD for indispensable and dispensable amino acids than the other feedstuffs. The rice bran had greater (P<0.01) cSIAAD values than wheat bran and maize bran, except for Leu, Cys, and Pro.5. In Expt. 2, predicted cAIAAD values for maize-SBM and maize-sorghum-SBM were generally lower (P<0.01) than actual values. The actual and predicted cSIAAD values for maize-SBM, sorghum-SBM and maize-sorghum-SBM combinations were not significantly different.6. It was concluded that the standardised amino acid digestibility of sorghum, when combined with other feedstuffs, was additive and that approximately three-quarters of total amino acids in the assayed high-fibre feedstuffs, except for dried sugarbeet pulp and maize gluten feed, were digestible.

Influence of dietary crude protein on growth performance and apparent and standardized ileal digestibility of amino acids in corn-soybean meal-based diets fed to broilers

This study aimed to examine the influence of dietary CP on the apparent ileal digestibility (AID) and standardized ileal digestibility (SID) of amino acids (AA) and test the additivity of AA digestibility in corn-soybean meal-based diets fed to broilers. Six experimental diets comprising a nitrogen-free diet and five corn-soybean meal-based diets containing 6.0%, 9.5%, 13.0%, 16.5%, and 20.0% CP were prepared. Increments in CP and AA concentrations were achieved by increasing the inclusion rate of corn and soybean meal at the expense of cornstarch. All diets contained 0.5% chromic oxide, which was included as an indigestible index. A total of 960 Ross 308 male broilers 19-day-old male broilers (Ross 308), with a mean BW of 628 g (SD = 58.0), were allocated to six dietary treatment groups in a randomized complete block design, with each treatment group have eight replicate cages and 20 birds per cage. All birds were fed the experimental diets for 4 days. On d 23, individual BW and feed intake were recorded, followed by collection of ileal digesta samples from the distal ileum. Regarding growth, the final BW, weight gain, feed intake, and gain to feed ratio increased linearly (P < 0.001) as dietary CP concentrations increased. With the increase in dietary CP concentrations from 6.0% to 20.0%, the AID of all AA, except Arg, increased linearly (P < 0.05). However, the SID of all AA, except Arg, Cys, and Pro, remained unaffected by CP concentrations in the diets. This study indicated that dietary CP concentrations from 6.0% to 20.0% have an effect on the growth performance of birds and the AID of most AA; however, the SID of most AA was not affected by dietary CP concentrations in the corn-soybean meal-based diets. In conclusion, the SID of AA is more additive than the AID of AA in poultry diets containing CP in the range of 6.0% to 20.0%.

Comparison of amino acid digestibility and its additivity determined with slaughter or cecectomy method for yellow-feather chicken

The objective of this experiment was to compare the slaughter and cecectomy methods to determine amino acid (AA) digestibility of corn and soybean meal and their additivity in a corn-soybean meal diet. A completely randomized design was adopted to determine endogenous AA losses (EAAL) and AA digestibility in each of corn, soybean meal, and a corn-soybean meal diet using either slaughter or cecectomy methods. Each treatment contained 6 replicates with 3 chickens per replicate. The endogenous loss (EL) of histidine and glycine was lower and the EL of methionine and phenylalanine was greater when determined by slaughter vs. cecectomy (P < 0.05). The EL of arginine, isoleucine, leucine, lysine, methionine, phenylalanine, valine, alanine, aspartic acid, glutamic acid, and serine determined by slaughter were 1.2 to 3.2 times of those from cecectomy. The standard error (SE) of EL of 14 AA (excluding histidine and glycine) obtained by slaughter method was 2.1 to 9.6 times of those by cecectomy method. The apparent and standardized digestibility was not affected by methods for most AA except apparent digestibility of methionine, phenylalanine and glycine, and standardized digestibility of glycine in corn. The apparent and standardized digestibility of most AA except apparent digestibility of glycine and standardized digestibility of lysine, cysteine and glycine were less for slaughter versus cecectomy methods in soybean meal (P < 0.05). Using slaughter method resulted in reduced apparent digestibility of 15 AA (except glycine) and reduced standardized digestibility of 7 AA (arginine, isoleucine, leucine, valine, aspartic acid, glutamic acid, and proline) relative to cecectomy method (P < 0.05), but the standardized digestibility of glycine was greater when determined by slaughter vs. cecectomy methods in corn-soybean meal diet (P < 0.05). The mean value of SE of 16 AA digestibility in slaughter method was 2.9 times of that by cecectomy method. The apparent digestibility of 2 and 9 of 16 AA and the standardized digestibility of 15 and 7 of 16 AA were additive when using slaughter and cecectomy determinations, respectively. In conclusion, compared to the slaughter method, cecectomy method had less SE and EAAL but greater apparent digestibility of methionine and phenylalanine in corn, and the apparent digestibility of 15 AA (except glycine) in soybean meal and corn-soybean meal diet. Additivity in apparent and standardized AA digestibility was more inconsistent when determined with slaughter vs. cecectomy methods. These findings suggest that the cecectomy method is more suitable than the slaughter method to determine the digestibility of AA.

Accuracy of predicting metabolizable energy from in vitro digestible energy determined with a computer-controlled simulated digestion system in feed ingredients for ducks

Two experiments were conducted to study the accuracy of predicting true metabolizable energy (TME) of ingredients for ducks from in vitro digestible energy (IVDE) determined with a computer-controlled simulated digestion system. Experiment 1 was to establish TME prediction models from the IVDE of 9 energy feed ingredients and 12 protein feed ingredients using regression analysis. Experiment 2 was to validate the accuracy of the predicted ME of 10 ingredients randomly selected from Exp. 1. Ten diets were formulated with 2 to 6 of 10 ingredients. Dietary in vivo TME values were compared with calculated values based on the TME predicted in Exp. 1. In Exp. 1, the correlation coefficients between TME and IVDE were 0.9339 (P < 0.05) in 9 energy feed ingredients and 0.8332 (P < 0.05) in 12 protein feed ingredients. No significant difference was observed on the slope and intercept of TME regression models between 9 energy feed ingredients and 12 protein feed ingredients. Therefore, the regression model of TME on IVDE for 21 feed ingredients was TME = 0.7169 × IVDE +1,224 (R² = 0.7542, P < 0.01). Determined and predicted TME differed by less than 100 kcal/kg of DM in 11 ingredients, and the difference ranged from 100 to 200 kcal/kg of DM in 5 ingredients. However, the difference between determined and predicted TME varied from 410 to 625 kcal/kg of DM in rice bran, rapeseed meal, corn gluten meal, and citric acid meal. In Exp. 2, the determined and calculated TME were comparable (3,631 vs. 3,639 kcal/kg of DM) and highly correlated (r = 0.9014; P < 0.05) in 10 diets. Determined and calculated TME differed by less than 100 kcal/kg of DM in 7 diets and by 106 to 133 kcal/kg of DM in 3 diets. These results have demonstrated that TME can be accurately predicted from IVDE in most feed ingredients, but it is less accurate for rice bran, rapeseed meal, corn gluten and citric acid meal.

Dietary Enteromorpha polysaccharide-Zn supplementation regulates amino acid and fatty acid metabolism by improving the antioxidant activity in chicken

Background

Enteromorpha prolifera (E. prolifera) polysaccharide has become a promising feed additive with a variety of physiological activities, such as anti-oxidant, anti-cancer, anti-diabetic, immunomodulatory, hypolipidemic, and cation chelating ability. However, whether Enteromorpha polysaccharide-trace element complex supplementation regulates amino acid and fatty acid metabolism in chicken is largely unknown. This study was conducted to investigate the effects of E. prolifera polysaccharide (EP)-Zn supplementation on growth performance, amino acid, and fatty acid metabolism in chicken.

Methods

A total of 184 one-day-old Ross-308 broiler chickens were randomly divided into two treatment groups with 8 replicates, 12 chickens per replicate, and fed either the basal diet (control group) or basal diet plus E. prolifera polysaccharide-Zinc (400 mg EP-Zn/kg diet).

Results

Dietary EP-Zn supplementation significantly increased (P < 0.05) the body weight, average daily gain, muscle antioxidant activity, serum HDL level, and reduced serum TG and LDL concentration. In addition, dietary EP-Zn supplementation could modulate ileal amino acid digestibility and upregulate the mRNA expression of amino acid transporter genes in the jejunum, ileum, breast muscle, and liver tissues (P < 0.05). Compared with the control group, breast meat from chickens fed EP-Zn had higher (P < 0.05) Pro and Asp content, and lower (P < 0.05) Val, Phe, Gly, and Cys free amino acid content. Furthermore, EP-Zn supplementation upregulated (P < 0.05) the mRNA expressions of mTOR and anti-oxidant related genes, while down-regulated protein degradation related genes in the breast muscle. Breast meat from EP-Zn supplemented group had significantly lower (P < 0.05) proportions of Σn-3 PUFA, and a higher percentage of Σn-6 PUFA and the ratio of n-6/n-3 PUFA. Besides, EP-Zn supplementation regulated lipid metabolism by inhibiting the gene expression of key enzymes involved in the fatty acid synthesis and activating genes that participated in fatty acid oxidation in the liver tissue.

Conclusions

It is concluded that EP-Zn complex supplementation regulates apparent ileal amino acid digestibility, enhances amino acid metabolism, and decreases oxidative stress-associated protein breakdown, thereby improving the growth performance. Furthermore, it promotes fatty acid oxidation and restrains fat synthesis through modulating lipid metabolism-related gene expression.

Graphical abstract

Influence of Age on the Standardized Ileal Amino Acid Digestibility of Corn and Barley in Broilers

The aim of this study was to determine the standardized ileal digestibility coefficients (SIDCs) of nitrogen (N) and amino acids (AAs) in corn and barley at six different ages (days 7, 14, 21, 28, 35 and 42) of broilers using the direct method. The apparent AA digestibility coefficients were corrected using age-appropriate basal endogenous AA losses. No age effect (p > 0.05) was noted for the SIDC of N in corn. The average SIDC of indispensable AAs (IAAs) and total AAs (TAAs) was influenced in a quadratic manner (p < 0.05) with the values being higher at day 7 that decreased at day 14, increased and plateaued between days 21 and 35 and dropped again at day 42. The average SIDC of dispensable AAs (DAAs) was influenced linearly (p < 0.05). In barley, the SIDC of N and average IAAs, DAAs and TAAs was affected (quadratic; p < 0.001) by age. The digestibility increased from day 7 to 21 and then plateaued up to day 42. The present findings confirm that the SIDC of AA in corn and barley are influenced by broiler age and that the age effect on AA digestibility may need to be considered for precise feed formulation.

An investigation into the influence of age on the standardized amino acid digestibility of wheat and sorghum in broilers

Standardized ileal digestibility coefficients (SIDC) of nitrogen (N) and amino acids (AA) in wheat and sorghum at 6 different ages (d 7, 14, 21, 28, 35, and 42) of broilers were determined. Two assay diets were formulated to contain 93.8% of each grain as the sole source of AA in the diet. Titanium dioxide (0.5%) was added as an indigestible marker. Each assay diet was fed to 6 replicate cages housing 14 (d 7), 12 (d 14), 10 (d 21), 8 (d 28), 8 (d 35), and 6 (d 42) birds per cage for 4 d prior to ileal digesta collection. The apparent ileal digestibility coefficients (AIDC) were standardized by using the age-appropriate basal endogenous AA losses. In the case of wheat, AIDC of N and all AA increased (linear or quadratic, P < 0.05 to 0.001) with advancing age. No age effect was noticed on the SIDC of N, average of indispensable (IAA) and dispensable AA (DAA), though the average of total AA (TAA) tended (linear, P = 0.09) to increase as birds grew older. In sorghum, the AIDC of N, average of IAA and DAA were unaffected (P > 0.05) by age. The SIDC of N, average SIDC of IAA, DAA and TAA were higher at d 7, reduced at d 14 and then plateaued. Among the IAA, the SIDC of Arg, His, Ile, Leu, Lys, Thr, Val, and the SIDC of all individual DAA (except Cys) decreased with age (linear or quadratic, P < 0.05 to 0.001) with higher values at d 7. The higher SIDC values determined at d 7 were due to higher EAA losses during wk 1. The results showed that broiler age influences AA digestibility and this may need be considered in practical feed formulations. The age effect is variable depending on the grain type and specific AA.

Mathematical prediction of ileal energy and protein digestibility in broilers using multivariate data analysis

A proportional mixture design was used to systematically create a total of 56 diets using ten feed ingredients. Diets differed widely with regards to chemical characteristics and ingredient inclusion levels. Apparent ileal digestibility of energy and protein of the diets were determined in broiler growers fed ad libitum from 21 to 24 d post-hatch. The chemical composition and the in vivo digestibility values were used to establish prediction equations for energy and protein digestibility, using multivariate data analysis. Root mean square error as percentage of the observed means (RMSE%) and residual error were used to evaluate the strength and accuracy of the predictions and to compare predictions based on chemical characteristics with estimates based on table values. The estimates of ileal digestibility of energy from table values were relatively accurate (RMSE% = 5.15) and was comparable to those predicted based on the chemical composition of diets. Estimates of ileal digestibility of protein based on table values were less accurate (RMSE% = 8.21); however, the prediction was improved by multivariate regression (RMSE% = 5.46) based on chemical composition of diets. The best predictors for ileal energy digestibility were starch, crude fiber and phytate contents (P < 0.01) and the best predictors for crude protein digestibility were starch, CF and fat contents (P < 0.05). In conclusion, the ileal digestibility of energy can be accurately predicted using table values; however, the accuracy of prediction of the ileal digestibility of protein can be improved when chemical characteristics of the diet are considered.

Soybean processing effects on the performance, carcass traits, and blood metabolites of broiler chickens

Processing methods are used to increase the nutritional value of soybean. The purpose of this research was to study the effect of different processing methods of soybean on performance, carcass traits, and blood metabolites of Ross broiler chickens. A factorial experiment was used in the form of a completely random design using 600 male Ross 308 broiler chickens for 42 days (in 3 feeding phases: starter, grower, and finisher). The experimental factors included the 2 soybean varieties (Katol and Caspian) and 4 processing methods (unprocessed, extruded, thermal, and gamma radiation). Data were measured and analyzed with the Lsmeans procedure by SAS package. Processing methods had a significant effect on the feed conversion ratio (FCR) at the starter and finisher phase. Soybean varieties had a significant effect on the FCR at the whole phase. Interaction of processing methods and soybean variety had a significant effect on the FCR at the finisher and whole phase. Processing methods had a significant effect on the albumin. Soybean varieties, processing methods and interaction of them had a significant effect on the phosphorus. Interaction of processing methods and soybean varieties had a significant effect on the live weight, thigh, wings, pancreas weight, uric acid, and Alkaline phosphatase (ALP). Results showed that extruded and thermal methods are the most suitable for soybean processing.

Progress in ileal endogenous amino acid flow research in poultry

The progress in our understanding of the endogenous protein concept over the past century is reviewed. Non-dietary proteins found in the digesta at the terminal ileum of poultry, known as endogenous protein loss, are comprised of digestive secretions, mucus and sloughed gut epithelial cells. The measurement of this loss is of fundamental importance because it is an indicator of gut metabolism and is essential to adjust apparent estimates of ileal amino acid digestibility. The ileal endogenous amino acid losses comprise of two components, namely basal and specific losses. The basal losses are fixed and associated with feed dry matter intake, whereas the specific losses are variable and induced by the presence of dietary components such as fibre and anti-nutrients. Currently there is no methodology available to directly measure the specific endogenous losses and these losses are calculated by determining the basal and total (basal plus specific) losses and, then subtracting the basal losses from total losses. The seminal features, specific applications and shortcomings of available methodologies are briefly outlined as well as the practical challenges faced in using the published endogenous amino acid loss values for true digestibility corrections. The relevance of taurine as a component of endogenous protein flow in poultry is identified for the first time.

Standardized ileal amino acid digestibility of protein sources for broiler chickens is influenced by the feed form

The aim of present study was to determine the influence of the feed form (FF) on standardized ileal digestibility (SID) of nitrogen (N) and amino acids (AA) in 3 protein sources (PS) for broiler chickens. Six diets were tested in a 3 × 2 factorial arrangement of treatments involving 3 PS (meat and bone meal [MBM], soybean meal [SBM], and canola meal [CM]) in mash and pelleted forms. The basal endogenous N and AA losses were determined by offering a N-free diet in the mash form. From day 1 to 18, the birds were offered a broiler starter diet. The diets and the N-free diet were randomly assigned to 6 replicate cages (8 birds per cage) and fed from day 19 to 23. The ileal digesta were collected on day 23. The SID of N was higher (P < 0.05) in SBM followed by MBM and CM. The average SID of AA in SBM and MBM were similar (P > 0.05), and greater (P < 0.05) than that in CM. The FF had no influence (P > 0.05) on the SID of indispensable AA, the only exception being His, which was reduced (P < 0.05) by pelleting. Pelleting, however, resulted in reduction (P < 0.001) in the SID of all dispensable AA and average of AA. The AA most affected by pelleting was Cys, with a 15.4% decrease in the SID. The standardized ileal digestible contents of protein and the average of indispensable AA and dispensable AA were higher in MBM than in SBM, with CM being the lowest. Pelleting decreased (P < 0.05) the digestible protein and total digestible AA contents. These findings reveal that the FF has a substantial impact on AA digestibility estimates of feed ingredients and it must be considered in AA digestibility assays of ingredients with high protein and AA contents.

Possible role of available phosphorus in potentiating the use of low-protein diets for broiler chicken production

A total of 945 male Ross 308 broiler chicks were used in a growth study to explore the interaction between dietary crude protein concentration and available phosphorus. Nine experimental treatments were constructed factorially by offering low, medium, or standard protein concentrations without or with low, standard, or high available phosphorus. Diets were based on corn, wheat, and soybean meal and all nutrients other than protein/amino acids and available phosphorus were maintained at or above breeder guidelines. Additional synthetic amino acids were used in the diets with low protein concentration in attempt to maintain digestible amino acid supply. Diets were offered to 7 replicate pens of 15 chicks per pen from day 8 to 35. Growth performance was measured during the grower (day 8-24) and finisher (day 25-35) periods. On day 35 carcass composition was determined, blood was drawn for various biochemical measurements and the tibia was excised for mechanical and compositional analyses. Birds that received the low-protein diet had lower terminal body weight and higher feed conversion ratio compared with those that received diets with adequate crude protein content. However, addition of available phosphorus to the low-protein diet resulted in significant reductions in weight-corrected feed conversion that were not evident in the diet with adequate protein content. Bone architecture was only moderately influenced by dietary treatment but birds that ingested the diets containing low and medium protein concentrations had relatively heavier abdominal fat pad weight. Blood biochemistry, especially ammonia, uric acid, and phosphorus, was influenced by both dietary protein and available phosphorus and trends suggested that both axes are involved in protein accretion and catabolism. It can be concluded that performance losses associated with feeding low protein diets to broiler chickens may be partially restored by additional available phosphorus. The implications for use of exogenous enzymes such as protease and phytase and protein nutrition per se warrants further examination.

Toward standardized amino acid matrices for exogenous phytase and protease in corn-soybean meal-based diets for broilers

A total of 468 male Ross 308 broilers were used in a digestibility study to determine the additivity of apparent or standardized amino acid (AA) digestibility values for corn, soybean meal (SBM), or a mixture of corn and SBM that were supplemented, or not, with either phytase, protease, or a combination of phytase and protease. These treatments generated a total of 12 experimental diets that were arranged in a 3 × 4 design. A nitrogen-free diet was also fed to estimate endogenous AA loss. Apparent and standardized AA digestibility values were assessed on day 28 posthatch. The apparent digestibility of AA in the complete diet was higher (P < 0.05) than expected based on the digestibility of the corn and SBM individually. However, this overestimation was corrected by the adjustment to standardized values. Importantly, addition of protease or the combination of protease and phytase increased (P < 0.05) the digestibility of AA in corn and SBM. Furthermore, these effects were arithmetically coherent with respect to the measured effects of the enzymes in the mixture of corn and SBM, even improving the additivity of AA digestibility values when assessed on an apparent basis. This study demonstrates that the effect of exogenous protease and phytase on AA digestibility in complete diets is predictable based on measurements made in individual ingredients. In addition to improving digestibility values per se, exogenous protease and phytase may enhance precision in least cost formulation systems.

Additivity of Ileal Amino Acid Digestibility in Diets Containing Corn, Soybean Meal, and Corn Distillers Dried Grains with Solubles for Male Broilers

The aim was to test additivity of apparent ileal digestibility (AID) and standardized ileal digestibility (SID) of amino acids (AAs) in mixed diets for Ross 308 broiler chickens. Two hundred and eighty-eight, 20-d-old male broiler chickens were assigned to one of six diets, with six birds per cage using a randomized complete block design. The diets consisted of a nitrogen-free diet, three diets containing corn, soybean meal (SBM), and corn distillers dried grains with solubles (CDDGS) as the sole source of nitrogen, respectively, and two mixed diets containing corn, SBM or CDDGS. Chromic oxide was added to the diets as an indigestible index. On day 24, birds were euthanized for ileal digesta collection. Relative proportion of the basal endogenous loss of AAs to total ileal outflow of AAs in corn was greater (p < 0.05) than that of SBM and CDDGS. For the corn-SBM and corn-SBM-CDDGS mixed diets, the AID of AAs differed (p < 0.05) from the predicted values. No difference was observed between the measured and predicted SID of AA. In conclusion, the SID of AAs is more additive in mixed diets containing corn, SBM, or CDDGS compared to AID values.