Evaluation of barley and triticale as feed ingredients in growing Iberian pigs: amino acid and carbohydrate ileal digestibility

BACKGROUND: Iberian pig production is linked to the use of the Mediterranean woodland, where the use of local feed resources is of paramount importance for the sustainability of the system. The aim of the present work was to explore the potential of triticale cv. Camarma as compared to barley cv. Esgueva in Iberian pig feeding by studying their respective ileal digestibilities of amino acids and carbohydrates in animals cannulated at the end of the ileum. RESULTS: Leu, Met and Tyr had (P < 0.05) greater standardised ileal digestibilities (SID) in pigs fed triticale diet. There was a trend (P = 0.07) towards greater SID of Thr in pigs fed the barley diet. The least digestible indispensable amino acids were Ile (74.6% SID) for barley and Thr (78.9% SID) for triticale. Except for β‐glucans, apparent ileal digestibilities (AIDs) of individual non‐starch polysaccharide (NSP), sugars and starch were greater in pigs fed triticale (P < 0.05). Nevertheless, total amounts of NSP digested were greater in pigs fed the barley diet (P < 0.05). CONCLUSION: Overall, triticale cv. Camarma had greater amino acid and carbohydrate AID than barley cv. Esgueva and may represent a valuable grain for Iberian pig feeding. Copyright © 2008 Society of Chemical Industry     

Effect of feed intake level on ileal digestibilities of crude protein and amino acids in diets for piglets

BACKGROUND: The study was conducted to determine the effect of graded levels of feed intake on apparent (AID) and standardized (SID) ileal digestibilities of crude protein (CP) and amino acids (AA) in diets for piglets. The piglets were surgically fitted with simple T‐cannulas at the distal ileum. The cornstarch–casein–soybean meal‐based diets were fed at three graded levels of feed intake corresponding to 30, 45 and 60 g kg^?1 body weight (BW) per day. RESULTS: The AID and SID of most AA were quadratically affected by the feed intake level (P?0.05). Initially, both AID and SID of most AA increased up to 1.9 percentage units as the feed intake level was increased from 30 to 45 g kg^?1 BW. Thereafter, these AID and SID values decreased by 2.6 and 2.7 percentage units, respectively, as the feed intake level was further increased from 45 to 60 g kg^?1 BW. CONCLUSION: Because the voluntary feed intake is highly variable in piglets after weaning, comparison of ileal AA digestibilities between and within studies may be confounded by variations in feed intake level. Thus, when designing digestibility studies with piglets, a standardization of feed intake should be taken into consideration. Copyright © 2011 Society of Chemical Industry     

Influence of dehulling on the apparent metabolisable energy and ileal amino acid digestibility of grain legumes for broilers

BACKGROUND: Removal of hulls may be an effective means of reducing the level of some antinutritional factors and improving the feeding value of grain legumes. Published data on the effects of dehulling on the energy utilisation and amino acid digestibility of grain legumes are limited. This study was designed to investigate the influence of dehulling on the nitrogen‐corrected apparent metabolisable energy (AMEn) and apparent ileal amino acid digestibility of faba beans, Australian sweet lupins and peas for broilers. RESULTS: The non‐starch polysaccharide contents of all three legume species were decreased by the removal of hulls. Dehulling increased (P < 0.05) the content and ileal digestibility of starch in faba beans but had no effect (P > 0.05) on those in peas. Dehulling increased (P < 0.05) the AMEn of faba beans and lupins but had no effect (P > 0.05) on that of peas. Removal of hulls increased the amino acid concentrations in all three legume species, but the apparent ileal digestibility coefficients of most amino acids were unaffected (P > 0.05). CONCLUSION: Dehulling of grain legumes is nutritionally beneficial in view of the improved amino acid concentrations and metabolisable energy values. Copyright © 2010 Society of Chemical Industry     

Estimates of basal ileal endogenous losses of amino acids by regression analysis and determination of standardised ileal amino acid digestibilities from casein in newly weaned pigs

BACKGROUND: This study was carried out to estimate basal ileal endogenous crude protein (CP) and amino acid (AA) losses (IAAL_B) in newly weaned pigs by regression analysis from apparent ileal digestible and the corresponding total dietary contents of CP and AA in order to obtain standardised ileal digestibilities (SID) of CP and AA originating from casein. A total of fourteen 3‐week‐old barrows were fitted with simple T cannulas at the distal ileum and were fed six diets with two pigs per diet in 4 weekly repeated measurements. Corn starch‐based diets containing six graded levels of CP from casein with 90, 155, 220, 285, 350 and 415 g kg^?1 CP (as‐fed basis) were formulated. RESULTS: Linear relationships (P < 0.001) between apparent ileal digestible and total dietary contents of CP and AA (g kg^?1 dry matter intake (DMI)) exist for CP and all AA in the range of 90–220 g kg^?1 CP content in the diet. The IAAL_B extrapolated from the range of 90–220 g kg^?1 CP content are different from zero (P < 0.001 to P = 0.019) except for tryptophan (P = 0.220). Based on regression analysis in the range of 90–220 g kg^?1 CP, estimates of IAAL_B, expressed as g kg^?1 DMI, and SID of CP and AA in casein (in parentheses, %) were as follows: CP 9.3 (98.0); arginine 0.4 (98.9); histidine 0.2 (98.5); isoleucine 0.2 (98.1); leucine 0.5 (99.2); lysine 0.4 (99.0); methionine 0.1 (99.1); phenylalanine 0.4 (99.9); threonine 0.6 (97.8); tryptophan 0.1 (96.2); valine 0.4 (98.5). CONCLUSION: The IAAL_B and SID of CP and AA originating from casein in newly weaned pigs are in close agreement with values obtained in grower finisher pigs. Copyright © 2007 Society of Chemical Industry     

Ileal amino acid digestibility of some novel dietary protein sources for growing chickens

The apparent ileal digestibility coefficients of amino acids in five high‐protein ingredients (casein, isolated soyprotein, maize gluten meal, spray‐dried bovine plasma (SBP) and spray‐dried porcine plasma (SPP)) and soybean meal were determined using 3‐week‐old broiler chickens. The amino acids in casein were highly digestible. Isolated soyprotein was also well digested by the birds, but the digestibility coefficients of all amino acids in isolated soyprotein were lower (P < 0.05) than those in casein. The amino acid digestibility coefficients in isolated soyprotein were greater (P < 0.05) than those in soybean meal, which may be reflective of reduced concentrations of anti‐nutritive factors, particularly indigestible oligosaccharides. The digestibilities of amino acids in maize gluten meal were higher (P < 0.05) than those in soybean meal, except for the digestibilities of arginine, histidine, threonine and aspartic acid, which were similar (P > 0.05) between the two protein sources. The ileal digestibilities of all indispensable amino acids in SBP and SPP were lower (P < 0.05) than those in casein and isolated soybean meal but higher (P < 0.05) than those in soybean meal. No differences (P > 0.05) were observed in the digestibility of amino acids between SBP and SPP. The overall mean amino acid digestibility coefficients of casein, isolated soyprotein, soybean meal, maize gluten meal, SBP and SPP were 0.955, 0.888, 0.823, 0.849, 0.860 and 0.856 respectively. Copyright © 2006 Society of Chemical Industry     

Influence of polyethylene glycol on the excretion and digestibility of amino acids in casein and tannic acid‐fed broilers

Using the precision feeding technique, an experiment was conducted to evaluate the influence of tannic acid (TA) and polyethylene glycol (PEG) on the excretion of amino acids and the apparent and true digestibilities of casein protein in broilers. Seventy‐two 9‐week‐old broiler cockerels grouped in nine treatments of eight replicates were fed warm water (50 mL, control birds), casein alone (12 or 18 g) or casein (12 or 18 g) with TA solution (4.5 g per 10 mL) or/and PEG solution (2 g per 10 mL). Total excreta were collected for 48 h and freeze‐dried. The amino acid content of casein and excreta was determined by reverse phase high‐performance liquid chromatography. In the absence of TA the digestibility of casein was almost complete. TA increased the excretion of amino acids to a varying extent (P < 0.01). Although the digestibility of all essential and non‐essential amino acids was adversely affected by the presence of TA, raising the amount of casein from 12 to 18 g improved significantly (P < 0.05) the apparent and true digestibilities of all amino acids. PEG reduced significantly (P < 0.01) the excretion of amino acids and improved significantly (P < 0.01) the amino acid digestibility of casein in TA‐dosed birds. However, the improvement was greater when the lower level of casein (12 g) was fed. Thus PEG might play an important role in inactivating dietary tannins in the gastrointestinal tract of birds and improving protein digestibility and utilisation, particularly when the diet is low or intermediate in protein. Copyright © 2007 Society of Chemical Industry     

The apparent ileal digestibility,determined with young broilers,of amino acids in near‐isogenic lines of peas (Pisum sativum L) differing in trypsin inhibitor activity

Two pairs of near‐isogenic lines of peas were developed to have high and low concentrations of seed trypsin inhibitor. HA5 and LA5 contained 8.73 ± 0.19 and 1.45 ± 0.19 trypsin inhibitor units per mg dry weight respectively, whereas HB5 and LB5 contained 7.40 ± 0.65 and 1.78 ± 0.15 trypsin inhibitor units per mg dry weight respectively. The four pea samples were included in semi‐synthetic diets and evaluated in a poultry metabolism experiment, using birds aged 3 weeks, to determine the coefficient of apparent ileal amino acid digestibility (CAID). There was a significant difference in CAID for the amino acids reported that correlated with pea genotype. Thus, for example, CAID for cystine was 0.738 ± 0.0196 and 0.812 ± 0.0128 for HA5 and LA5 respectively and 0.721 ± 0.0139 and 0.804 ± 0.0178 for HB5 and LB5 respectively. Corresponding data for methionine, the other main nutritionally deficient amino acid in peas, were 0.887 ± 0.0103, 0.930 ± 0.0089, 0.885 ± 0.0083 and 0.929 ± 0.0125 respectively. Other amino acids followed similar patterns. These data provide information on the nutritional consequences of variation in trypsin inhibitor content of pea seeds in near‐isogenic backgrounds. Plant breeding for low trypsin inhibitor activity in seeds accordingly offers potential for improving nutritional value. © 2003 Society of Chemical Industry     

Chemical composition,antinutritional constituents,precaecal crude protein and amino acid digestibility in three unconventional tropical legumes in broilers

Three tropical crop seeds, namely Enterolobium cyclocarpum, Mucuna pruriens and Centrosema pubescens, were assessed for their contents of chemical constituents, antinutritional factors (ANFs), crude protein (CP) and amino acid (AA) digestibility. Their meals were incorporated into broiler diets in place of maize starch at two levels (150 and 300 g kg^?1). Four hundred and twenty 1‐day‐old broilers were randomly assigned to seven experimental diets on a weight basis and used to determine CP and AA digestibility in the diets and seeds, and performance of the birds. The CP contents were 237, 278 and 252 g kg^?1 DM in E. cyclocarpum, M. pruriens and C. pubescens, respectively. Compared to the basal diet, the digestibility of CP and AAs in the diets and seeds was significantly (p < 0.05) reduced at higher level of inclusion of E. cyclocarpum and M. pruriens but increased at higher C. pubescens inclusion. Digestibility of arginine, threonine and lysine in the C. pubescens meal diets was similar to that in the basal diet. Digestibility values of CP and AAs were least in E. cyclocarpum. Aspartic acid was the least and glutamic acid the most digested AA in all the seeds. Among the essential AAs, threonine was the least digested AA, while leucine (in E. cyclocarpum and M. pruriens) and lysine (in C. pubescens) had the highest digestibility with values of 65, 73 and 72%, respectively. Feed intake, body weights and weight gain in the birds were significantly (P < 0.05) reduced in the E. cyclocarpum and M. pruriens diets but increased in the C. pubescens diets compared to the basal diet. Results of the study suggest that, based on the CP content and AA profiles in the seeds, they have potential for poultry feeding. The presence of ANFs, especially in E. cyclocarpum and M. pruriens, however, could be a major limitation in their use in poultry feeding. Copyright © 2006 Society of Chemical Industry     

The apparent ileal digestibility of amino acids and the digestible energy content of naked oats (Avena sativa cv Bandicoot) fed to growing pigs

An experiment was conducted to determine the apparent ileal digestibility of amino acids and the digestible energy (DE) content of two samples of naked oats (Avena sativa cv Bandicoot) and to compare these parameters in wheat (Triticum aestivum cv Machete) and dehulled oats (groats; Avena sativa cv Echidna). Four Large White male pigs were fitted with simple T-piece ileal cannulae and allocated to experimental diets in a 4×4 Latin square design. Amino acid digestibility coefficients were determined after continuous eight hour collections of digesta over two consecutive days using acid-insoluble ash as an indigestible marker. Digestible energy was determined using grab samples of faeces. No significant difference between the four test cereals was found in the digestibility of all amino acids, except for proline and lysine. The apparent ileal digestibility of lysine in wheat (0·87) and two samples of naked oats (0·89 and 0·82, respectively) was lower (P<0·05) than dehulled oats (0·91). The mean DE value of the naked oats samples was 16·96 MJ kg⁻¹ (air-dry basis). The results suggest that Bandicoot naked oats and dehulled oats are superior amino acid and DE sources to wheat and have potential for use in weaner and grower pig diets. © 1998 SCI.     

True ileal amino acid digestibility of goat and cow milk infant formulas

Goat milk is used as an alternative to cow milk for the production of infant formulas. However, little is known about the protein quality and, specifically, about the digestible AA pattern of goat milk formulas compared with their cow milk counterparts. In this study, the true ileal AA digestibility of a goat milk infant formula was compared with a premium cow milk infant formula. The 3-wk-old piglet was used as a model for the 3-mo-old infant. Both milk formulas were prepared as described by the manufacturer, with titanium dioxide added as an indigestible marker. The formulas were fed to the piglets over a 2-wk trial period. Digesta from the terminal ileum were collected post euthanasia and analyzed for AA content, along with samples of the formulas. True AA digestibility was determined after correcting for endogenous AA loss at the terminal ileum of pigs fed an enzyme-hydrolyzed casein-based diet, followed by ultrafiltration (5,000 Da) of the digesta. Total urine and feces collection was also undertaken to determine the nitrogen retention from the diets. The true ileal AA digestibility was similar between the goat and cow milk infant formulas for all AA except Gly and Trp. There was no significant difference in the nitrogen retention of piglets fed the two different formulas. The goat milk infant formula and the premium cow milk infant formula were similar in terms of protein quality.     

The effects of genetic variation at r,rb and Tri loci in Pisum sativum L. on apparent ileal digestibility of amino acids in young broilers

The nutritional effect of genetic variation at r and rb loci was investigated by determining apparent and true amino acid digestibility of four near‐isogenic lines of pea (RRRbRb, RRrbrb, rrRbRb, rrrbrb) fed to young broilers in a metabolism study. The results demonstrated that the round‐seeded line (RRRbRb) generally had the lowest amino acid content with, for example, 2.5 g cystine kg^?1 dry matter (DM) and 1.6 g methionine kg^?1 DM, compared with contents in the three wrinkled‐seeded lines (rrRbRb, RRrbrb and rrrbrb). The double mutant line (rrrbrb) generally had the highest amino acid content, with 3.2 g cystine kg^?1 DM and 2.3 g methionine kg^?1 DM, and an elevated amino acid content compared with the single mutant lines (RRrbrb, rrRbRb). However, the round‐seeded line (RRRbRb) consistently had the highest coefficient of true (CTID), and apparent (CAID), ileal digestibility for all amino acids (e.g. 0.959 and 0.928 respectively for CTID and CAID for methionine) when compared with the three wrinkled lines RRrbrb, rrRbRb and rrrbrb (0.853, 0.877 and 0.866, respectively, for CTID, and 0.862, 0.882 and 0.874 for CAID). A second experiment examined the digestibility of amino acids in a pair of lines, HC8 and LC8, near‐isogenic except for the locus controlling the concentration of seed trypsin inhibitor (H, high; L, low). The results showed that the CAID and CTID obtained for all amino acids were consistently higher for LC8 than for HC8 (for methionine: 0.905 and 0.709 for CTID, respectively, for LC8 and HC8; 0.887 and 0.729, respectively, for CAID), indicating the very specific effects of quantitative variation in these proteins on nutritional value of peas for poultry. Copyright © 2005 Society of Chemical Industry     

Technical note: Methodological and feed factors affecting prediction of ruminal degradability and intestinal digestibility of essential amino acids

We hypothesized that ruminal degradability of essential AA (EAA) and the intestinal digestibility of the ruminally undegraded EAA residue in feeds could be evaluated in a meta-analysis. The objective was to characterize methodological factors for ruminal incubation (time of incubation of feed in situ) and method of simulating digestion of the ruminally undegraded AA (incubation of residue in digestive enzymes in vitro or in mobile bags inserted into the duodenum). To increase numbers of observations, feeds were categorized before ANOVA. An approach is described to predict differential ruminal degradability (or undegradability) of individual EAA by normalizing them as a proportion of total AA (TAA) degradability (undegradability) and similarly to normalize the intestinal digestibility of EAA using TAA. Interaction of feed category with individual EAA justifies future studies with a broader range of feeds and more replication within feed to bolster this approach. With broader data, the approach to normalize EAA as a proportion of TAA should allow a better defined EAA library to be integrated with more robust CP databases (that can be updated with specific feed information from more routine laboratory analyses) in dairy supply-requirement models.     

Total and ileal digestible tryptophan contents of feedstuffs for broiler chickens

Reliable values of total and digestible tryptophan in components of feed formulation matrices are needed because tryptophan is often the third limiting amino acid in practical poultry diets. However, tryptophan is oxidatively destroyed during acid hydrolysis in routine amino acid analysis and its determination requires a separate analytical procedure. The variability in contents and apparent ileal digestibility for 6‐week‐old broiler chickens of tryptophan in 74 samples representing 24 feedstuffs are presented in this paper. The average ileal tryptophan digestibility coefficient in wheat was 0.83, in sorghum and triticale 0.75, maize 0.71, soybean meal 0.84, sunflower meal 0.81, canola meal 0.78 and cottonseed meal 0.75. Among the grain legumes, tryptophan in lupins was better digested than that in chickpeas, fababeans and field peas. Among the animal protein meals, the tryptophan digestibility coefficients in fish meal (0.77) and blood meal (0.84) were substantially higher than those in meat meal (0.62), meat‐and‐bone meal (0.63) and feather meal (0.52). Marked variations in tryptophan digestibility were also observed among samples of fish meal, meat‐and‐bone meal and meat meal, highlighting significant batch‐to‐batch differences. For most feedstuffs, considerable variability was observed in the tryptophan concentrations, but such variations were not reflected in digestibility coefficients. Copyright © 2006 Society of Chemical Industry     

The choline content of feed ingredients and mixed feeds determined by an enzymatic assay

A recently developed procedure for the determination of choline in ingredients and feeds was utilised to establish the levels and the variability of choline in a series of ingredients and to compare the analysed and calculated choline values of mixed feeds. The concentrations of choline in samples of maize (7), canola meal (3), wheat middlings (1) and dehydrated bakery product (1) were, respectively, 1·55±0·18, 7·59±0·08, 2·35 and 2·39 g kg⁻¹, all higher than ingredient composition table values. Choline contents lower than table values were found in samples of poultry by-products (7) and meat and bone meal (6): 2·18±0·87 and 1·08±0·29 g kg⁻¹, respectively. The average choline concentration found in samples of dehulled soybean meal (7) was 2·73±0·18 g kg⁻¹, similar to table values. The choline in samples of poultry fat (2) averaged 0·48±0·02 g kg⁻¹. Significant correlations between the concentrations of choline and of some components of the proximate analysis were found. The analysed choline concentrations in mixed feeds were only 1·4% lower than the calculated levels based on the ingredient analyses. The procedure was adequate for choline determination in ingredients or mixed feeds. The high variability in the choline content of some ingredients may require analysis for proper feed formulation. © 1998 Society of Chemical Industry.     

Ruminal degradability and intestinal digestibility of protein and amino acids in treated soybean meal products

Four lactating dairy cows equipped with ruminal and duodenal cannulas were used to determine the impact of different methods of treating soybean meal (SBM) on the ruminal degradability and intestinal digestibility of crude protein and AA. Solvent-extracted SBM (SE), expeller SBM (EP), lignosulfonate SBM (LS), and heat and soyhulls SBM (HS) were incubated in the rumen in nylon bags for 48, 24, 16, 8, 4, 2, and 0 h according to National Research Council (2001) guidelines. Additional samples of each SBM product were also incubated for 16 h in the rumen; the residues from these bags were transferred to mobile bags, soaked in pepsin HCl, and then used for determination of intestinal digestibility in situ or in vitro. Treatment of SBM (EP, LS, HS) protected the crude protein and AA from ruminal degradation, increasing rumen undegradable protein from 42% in SE to 68% in EP. Kinetic analysis of crude protein and AA degradation in the rumen revealed that, compared with LS and HS, EP exhibited slower rates of degradation but a shorter lag phase and a higher proportion of soluble protein. For all SBM products, the pattern of ruminal degradation, at 16 h of incubation, was characterized by extensive degradation of Lys and His, whereas Met and the branched-chain AA were degraded to the least extent. Estimates of intestinal digestibility of AA and crude protein were lower when measured in vitro than in situ; the magnitude of the difference between the 2 methods was greater (25%) with treated SBM products than with SE (10%). The availability of essential and nonessential AA was consistently greater (30%) with treated SBM than with SE. Among the treated SBM products, 4 essential AA (Ile, Leu, Phe, and Val) showed differences in availability, with values consistently lower for HS than for LS. This study showed that, based on in situ measures, heat and chemical treatment of SBM enhanced AA availability, and that compared with HS, EP and LS had a higher potential to enhance the AA supply to the small intestine of high-producing dairy cows.     

发酵非常规蛋白饲料对肉仔鸡生长性能和养分消化率的影响

研究了发酵非常规蛋白饲料(后称发酵饲料)对肉仔鸡生产性能和养分消化率的影响,选用250只肉仔鸡,随机分为5个处理组,试验期6周。A组饲料为基础玉米豆粕日粮,B组添加10%未发酵饲料替代部分豆粕,处理组C、D、E分别添加发酵饲料5%、10%、15%替代部分豆粕。处理组平均日采食量、平均日增重均高于B组,与A组相比差异不显著(P>0.05),D组与A组最为接近。通过代谢试验可得出,发酵饲料与未发酵饲料相比粗蛋白质消化率显著增加(P<0.05),氨基酸消化率差异不显著(P>0.05)。因此,在发酵饲料替代10%豆粕是可行的。     

Effects of dietary probiotic supplementation on ileal digestibility of nutrients and growth performance in 1‐ to 42‐day‐old broilers

This study was conducted to determine the effects of dietary probiotic supplementation on the ileal digestibilities of nutrients and growth performance in broilers. Two thousand, eight hundred and eighty male broiler chickens at 1 day of age were randomly allotted to eight treatment groups and fed for 6 weeks the maize–soybean meal‐based diets containing 0, 0.2, 0.4 or 0.6% AgiPro A100® (a probiotic) and 0 or 6 ppm flavomycin (an antibiotic). This well‐established antibiotic was used as a positive control for the efficacy of AgiPro A100®. Dietary supplementation with either the probiotic or the antibiotic alone did not affect (P > 0.05) feed intake or average daily gain (ADG) of broilers between days 1 and 42 of life. However, there was a significant antibiotic × probiotic interaction effect (P < 0.05) in increasing ADG during the entire experimental period. Notably, dietary supplementation with the probiotic or the antibiotic consistently improved (P < 0.05) the ileal digestibilities of crude protein and most amino acids in 21‐ and 42‐day‐old chickens. Supplementing the probiotic to broiler diets also improved (P < 0.05) the ileal digestibilities of dry matter, energy, calcium and phosphate in the birds. Collectively, these results indicated that AgiPro A100® is an effective alternative to flavomycin in chicken production. Copyright © 2007 Society of Chemical Industry     

Ruminal degradability and intestinal digestibility of protein and amino acids in soybean and corn distillers grains products

New fractionation and fermentation technologies in the ethanol industry have resulted in the production of different forms of distillers grains (DG). Such products are reduced-fat, high-protein, and “modified” wet feeds. Characterization of protein fractions of these co-products and other commonly used feedstuffs is important for the formulation of dairy cattle diets. In situ and in vitro techniques were conducted to compare crude protein (CP) availability in 4 DG products with commonly used soybean proteins. Soybean protein products included solvent-extracted soybean meal (SBM; 44% CP), expeller soybean meal (ESBM), and extruded soybeans (ES). The DG products were conventional distillers dried grains with solubles, reduced-fat distillers dried grains with solubles (RFDGS), high-protein distillers dried grains, and modified wet distillers grains with solubles (MWDGS). Nylon bags containing 5 g of each feed were incubated in the rumen of 3 cannulated lactating cows for 2, 4, 8, 16, 24, and 48 h. The rapidly degradable CP fraction varied from 8.1 to 37.2% for SBM and MWDGS, respectively. The slowly degradable CP fraction was greatest for SBM, ES, and high-protein distillers dried grains (88.0% ± 3.7), followed by ESBM, distillers dried grains with solubles, and RFDGS (76.8 ± 4.1%). The MWDGS had the lowest slowly degradable CP fraction (61.1%). The rate of degradation of the slowly degradable CP fraction ranged from 11.8 for SBM to 2.7%/h for RFDGS. Rumen-undegradable protein varied widely (32.3 to 60.4%), with RFDGS having the greatest and SBM the lowest concentrations. Intestinal digestibility of rumen-undegradable protein (IDP) was estimated by pepsin-pancreatin digestion of ruminally preincubated (16 h) samples. The IDP was greatest for SBM, ESBM, and ES (97.7% ± 0.75), whereas IDP of DG products was 92.4% ± 0.87. Similarly, total digestible protein was greatest (99.0%) for soybean products, whereas DG products had a total digestible protein of 96.0%. Intestinal digestibility of most AA in DG products exceeded 92% and was slightly lower than for soybean products, except for Lys, where the digestibility was 84.6% for DG compared with 97.3% for soybean products. Absorbable Lys was lower for DG (7.0 g/kg of CP) compared with ESBM and ES (average of 23.8 g/kg of CP). Dried DG, ESBM, and ES provided more absorbable AA compared with SBM and MWDGS. These results suggest that the AA availability from DG products is comparable with that from soybean products.