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.     

Ruminal degradation and intestinal digestibility of protein and amino acids in high-protein feedstuffs commonly used in dairy diets

A study was conducted to determine the rumen degradation and intestinal digestibility of crude protein (CP) and AA, and AA composition of the rumen-undegradable protein (RUP) from 3 sources of blood meal (BM1, BM2, and BM3), canola meal (CM), low-fat distillers dried grains with solubles (LFDG), soybean meal (SBM), and expeller soybean meal (ESBM). Two Holstein cows fitted with ruminal and proximal duodenal cannulas were used for in situ incubation of 16 h and for the mobile bag technique. To correct for bacterial contamination of the RUP, 2 methods were used: purines and DNA as bacterial markers. Ruminal degradations of CP were 85.3, 29.8, 40.7, 75.7, 76.9, 68.8, and 37.0 ± 3.93% for BM1, BM2, BM3, CM, LFDG, SBM, and ESBM, respectively. Ruminal degradation of both total essential AA and nonessential AA followed a similar pattern to that of CP across feedstuffs. Based on the ratio of AA concentration in the RUP to AA concentration in the original feedstuff, ruminal incubation decreased (ratio <1) the concentrations of His, Lys, and Trp, and increased (ratio >1) the concentrations of Ile and Met across feedstuffs. Compared with purines, the use of DNA as bacterial marker resulted in a higher estimate of bacterial CP contamination for CM and lower estimates for LFDG and ESBM. Intestinal digestibility of RUP could not be estimated for BM1, BM3, and SBM due to insufficient recovery of residue. For the remaining feedstuffs, intestinal digestibility of RUP was highest for ESBM, followed by BM2 and LFDG, and lowest for CM: 98.8, 87.9, 89.7, and 72.4 ± 1.40%, respectively. Intestinal absorbable dietary protein was higher for BM2 compared with CM and LFDG, at 61.7, 17.9, and 20.7 ± 2.73% CP, respectively. As prices fluctuate, intestinal absorbable protein or AA may be used as a tool to aid in the selection among feedstuffs with different protein quality.     

Ruminal degradability of dry matter,crude protein,and amino acids in soybean meal,canola meal,corn, and wheat dried distillers grains

Different protein sources, such as canola meal (CM) or dried distillers grains (DDG), are currently used in dairy rations to replace soybean meal (SBM). However, little data exists comparing their rumen degradation in a single study. Therefore, the objective of this study was to compare the ruminal degradation of dry matter (DM), crude protein (CP), and AA of SBM, CM, high-protein corn DDG (HPDDG), and wheat DDG plus solubles (WDDGS). In situ studies were conducted with 4 rumen-fistulated lactating Holstein cows fed a diet containing 38% grass hay and 62% corn-based concentrate. Each protein source was incubated in the rumen of each cow in nylon bags for 0, 2, 4, 8, 16, 24, and 48 h to determine DM and CP rumen degradation kinetics, whereas additional bags were also incubated for 16 h to evaluate AA ruminal disappearance. Rumen DM and CP degradability was calculated from rumen-undegraded residues corrected or not for small particle loss. Data were fitted to an exponential model to estimate degradation parameters and effective degradability (ED) was calculated with a passage rate of 0.074 h⁻¹. The WDDGS and SBM had higher uncorrected ED (DM = 75.0 and 72.6%; CP = 84.8 and 66.0%, respectively) than CM and HPDDG (DM = 57.2 and 55.5%; CP = 59.3 and 48.2%, respectively), due to higher soluble fraction in WDDGS and a combination of higher potentially degradable fraction and rate of degradation in SBM. Correction for small particle loss from bags, higher for WDDGS than for the other protein sources, decreased estimated ED but did not alter feed ranking. The ruminal disappearance of AA after 16 h of incubation reflected the overall pattern of CP degradation between protein supplements, but the ruminal disappearance of individual AA differed between protein supplements. Overall, these results indicate that, in the current study, (1) SBM and WDDGS were more degradable in the rumen than CM and HPDDG, and (2) that small particle loss correction is relevant but does not alter this ranking.     

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.     

Effects of pressure toasting on in situ degradability and intestinal protein and protein‐free organic matter digestibility of rapeseed

BACKGROUND: Rapeseed is a protein supplement that contains up to 40% crude protein (CP) on a dry matter (DM) basis, but a large part of its protein can be easily degraded in the rumen. Therefore, before inclusion in ruminant's diet, the extent of its protein degradation in the rumen must be reduced without altering its intestinal digestibility. A study was conducted to investigate the effects of pressure toasting (T, 130 °C) at two residence times (1.5 and 10 min) alone or in combination with soaking in water (ST, 4 h) on ruminal degradability and intestinal digestibility of CP and protein‐free organic matter (PFOM) in whole full‐fat rapeseed. RESULTS: Regardless of the processing time (1.5 or 10 min), T significantly (P < 0.05) increased the fraction of undegraded intake protein (UIP) compared to the untreated rapeseed samples. Soaking prior to further toasting did not improve the rumen degradation characteristics of rapeseed CP. Compared to the untreated rapeseed samples, both T and ST significantly (P < 0.0001) improved the true protein digested in the small intestine (DVE) and degraded protein balance (OEB), effects that were more evident in samples heated for 10 min. Soaking prior to pressure toasting, however, did not further improve the DVE or OEB in the rapeseed samples in comparison with T treatment. CONCLUSIONS: It was concluded that ruminal protein degradability of rapeseed decreased after pressure toasting, without seriously affecting its intestinal digestibility. Copyright © 2008 Society of Chemical Industry     

Supplementation of pearl millet flour with soybean protein: effect of cooking on in vitro protein digestibility and essential amino acids composition

In vitro protein digestibility (IVPD) and amino acids profile of pearl millet (Dempy cultivar) supplemented with soybean protein (5–15%) were investigated. Supplementation of dempy flour with soybean protein steadily decreased IVPD with increasing the portion of soybean in the blend. The in vitro protein digestibilities of the cooked supplemented dempy flours were higher when compared with the raw ones, whereas the highest value was that of the 5% soybean protein. All essential amino acids of dempy flour were enriched on supplementation with soybean protein. The levels of amino acids increased with increasing the amount of soybean protein in the blend. Essential amino acids in dempy supplemented with 15% soybean are comparable to those in the FAO reference pattern. Supplementation increased significantly lysine to 1.5–2.4 folds. Essential amino acids content remained higher in the cooked composite flours when compared with the cooked native dempy flour.     

In vitro digestibility of protein and amino acids in protein mixtures

Six protein sources, casein, field peas, peanut meal, wheat flour, rapeseed and soya bean concentrate and their blends (ratio 1:1) were subjected to in vitro enzymic digestion. Wheat flour had the lowest in vitro digestibility (30% in 6 h) while the other sources had similar digestibilities (40%). Basic and aromatic amino acids were the most readily liberated from these protein sources. Some protein combinations, such as a rapeseed/field pea blend, gave in vitro digestibilities higher than calculated from individual proteins. The type of response observed could not be predicted from either nitrogen digestibility or amino acid composition of the individual sources. The digestibility of some amino acids was modified and this could be due to varying affinity of digestive enzymes for the protein.     

Dietary replacement of soybean meal with heat-treated soybean meal or high-protein corn distillers grains on nutrient digestibility and milk composition in mid-lactation cows

Lactation diets dependent on rumen undegradable protein (RUP) sources derived from soybean meal (SBM) products are generally high in Lys and poor in Met. We conducted an experiment to evaluate the effects of increasing dietary RUP and altering digestible AA supply by inclusion of heat-treated soybean meal (HTSBM) or high-protein corn dried distillers grains with soluble (DDGS) on performance in mid-lactation dairy cows. Twenty-four Holstein cows (200 ± 40 d in milk and 30.0 ± 3.92 kg/d of milk yield) blocked according to parity, milk yield, and days in milk were used in a 3 × 3 Latin square design experiment with 21-d periods. Treatments were (1) control (CON), a diet with 6.0% RUP containing 15.9% SBM as the main protein source; (2) HTSBM, a diet with 6.7% RUP containing 4.4% HTSBM partially replacing SBM; and (3) high-protein DDGS (FP; FlexyPro, SJC Bioenergia), a diet with 6.9% RUP containing 5.34% FP partially replacing SBM and ground corn. Diets had similar crude protein (16.9%) and net energy of lactation. Data were submitted to ANOVA using the mixed procedure of SAS software (SAS Institute Inc.). Treatment differences were evaluated using orthogonal contrasts: (1) increasing RUP (SBM vs. HTSBM + FP) and (2) altering digestible AA supply (HTSBM vs. FP). Cows fed HTSBM and FP had greater intake (values in parentheses represent treatment means of CON, HTSBM, and FP, respectively) of neutral detergent fiber (7.14, 7.35, and 7.69 kg/d), crude protein (4.27, 4.37, and 4.51 kg/d), and ether extract (0.942, 0.968, and 1.04 kg/d) compared with cows fed CON. Feeding FP resulted in greater intake of neutral detergent fiber and ether extract compared with HTSBM. Cows fed HTSBM and FP had lower sorting index for feed particles <4 mm than cows fed CON (1.029, 1.008, and 1.022). Feeding FP resulted in greater intake of feed particles <4 mm compared with HTSBM. Treatments containing HTSBM or FP tended to decrease organic matter digestibility (72.4, 71.2, and 71.1%), but no other effects were detected in digestibility of neutral detergent fiber, crude protein, or ether extract. No evidence for differences among treatments was detected in excretion of purine derivatives in milk and urine. Milk yield was greater in cows fed HTSBM or FP than in cows fed CON (28.0, 28.9, and 28.8 kg/d, respectively). Cows fed HTSBM or FP tended to have greater energy-corrected milk and protein yield compared with those fed CON. Milk protein concentration was greater in DDGS cows than those in the HTSBM group (3.45 and 3.40%, respectively). No differences were detected in milk fat yield and concentration, milk urea nitrogen, feed efficiency, or serum concentrations of urea and glucose. Overall, increasing dietary RUP by feeding HTSBM or FP improved intake of nutrients and milk yield without affecting feed efficiency. Altering digestible AA supply while maintaining similar dietary RUP had negligible effects on performance of cows.     

Ruminal degradability and lysine bioavailability of soybean meals and effects on performance of dairy cows

Evaluations of 4 soybean meal (SBM) products were conducted in 3 experiments. The 4 products were 1) solvent SBM (SSBM), 2) SSBM treated with 0.05% baker's yeast and toasted at 100°C (YSBM), 3) expeller SBM (ESBM), and 4) lignosulfonate-treated SBM (LSBM). Multiparous Holstein cows (n = 32; 152 ± 63 d in milk; body weight = 708 ± 77 kg; producing 41 ± 7 kg/d of milk at the beginning of the study) were used in a 4 × 4 Latin square design with 28-d periods to investigate cow responsiveness to supplemental ruminally undegradable protein (RUP) from the SBM products. Dietary treatments were formulated by substituting all of the SSBM and part of the ground corn with YSBM, ESBM, or LSBM to yield isonitrogenous diets. Diets were formulated to provide adequate ruminally degradable protein, but deficient RUP and metabolizable protein supplies. No differences among dietary treatments were observed for dry matter intake, body weight gain, milk and component yields, or efficiency of milk production. The lack of response to changes in SBM source was likely due to an adequate RUP and metabolizable protein supply by all the diets. In situ ruminal degradations of YSBM and LSBM were slower than those of SSBM or ESBM; thus, RUP contents of YSBM and LSBM were greater than those of SSBM or ESBM. The RUP of all SBM products had similar small intestinal digestibility. Available Lys contents, estimated chemically or by using a chick growth assay, were less for YSBM and LSBM than for SSBM or ESBM, suggesting deleterious effects of processing on Lys availability in YSBM and LSBM.     

不同产地原料大豆粕分离蛋白提取率研究

以不同产地大豆粕为原料制取大豆分离蛋白(SPI),对比研究在工厂实际生产中相同工艺条件下大豆粕质量对SPI提取率影响;结果表明,高蛋白大豆粕提取SPI相对困难,有待提取新工艺开发。     

Ruminal bacteria and protozoa composition,digestibility, and amino acid profile determined by multiple hydrolysis times

Microbial samples from 4 independent experiments in lactating dairy cattle were obtained and analyzed for nutrient composition, AA digestibility, and AA profile after multiple hydrolysis times ranging from 2 to 168 h. Similar bacterial and protozoal isolation techniques were used for all isolations. Omasal bacteria and protozoa samples were analyzed for AA digestibility using a new in vitro technique. Multiple time point hydrolysis and least squares nonlinear regression were used to determine the AA content of omasal bacteria and protozoa, and equivalency comparisons were made against single time point hydrolysis. Formalin was used in 1 experiment, which negatively affected AA digestibility and likely limited the complete release of AA during acid hydrolysis. The mean AA digestibility was 87.8 and 81.6% for non-formalin-treated bacteria and protozoa, respectively. Preservation of microbe samples in formalin likely decreased recovery of several individual AA. Results from the multiple time point hydrolysis indicated that Ile, Val, and Met hydrolyzed at a slower rate compared with other essential AA. Singe time point hydrolysis was found to be nonequivalent to multiple time point hydrolysis when considering biologically important changes in estimated microbial AA profiles. Several AA, including Met, Ile, and Val, were underpredicted using AA determination after a single 24-h hydrolysis. Models for predicting postruminal supply of AA might need to consider potential bias present in postruminal AA flow literature when AA determinations are performed after single time point hydrolysis and when using formalin as a preservative for microbial samples.     

Effect of substitution of soybean meal by canola meal or distillers grains in dairy rations on amino acid and glucose availability

Canola meal (CM) or by-products of ethanol production (dried distillers grain, DDG) may offer an economical alternative to soybean meal (SBM) in North American dairy rations. These protein supplements can effectively replace SBM and, in 2 recent meta-analyses, CM had a positive effect on milk and milk protein yields compared with SBM. The objective of this study was to determine if the positive responses observed with inclusion of CM in dairy rations could be explained by an increased availability of His, Lys, Met, or glucose. Eight Holstein dairy cows were used in a replicated 4 × 4 Latin square with 14-d periods. Cows were fed isonitrogenous (17.2% crude protein) and isoenergetic (1.56 Mcal/kg of net energy of lactation) diets formulated to slightly exceed nutrient requirements. Diets contained 38% grass hay and 62% corn-based concentrate including SBM, CM, corn high-protein DDG (HPDDG), or wheat DDG plus solubles (WDDGS) as the single protein supplement. The effect of protein supplements on availability of His, Lys, Met, and glucose was estimated using variations in the whole-body (WB) flux of these nutrients, determined by isotopic dilution. As planned, dry matter intake and milk and milk protein yields were not affected by treatments and averaged 23.7, 31.4, and 1.14 kg/d, respectively. Lactose yield did not differ among diets although milk lactose content tended to be lower with CM and WDDGS diets than with SBM and HPDDG diets. Lysine availability was affected by treatments: the highest WB irreversible loss rate (ILR) was observed for the CM diet (371 g/d) and the lowest for HPDDG diet (290 g/d); values for SBM and WDDGS were intermediate (330 and 316 g/d, respectively). Availability of His and Met did not vary among diets and WB ILR averaged, respectively, 129 and 124 g/d; the CM diet, however, had numerically the highest His and Met ILR. Plasma concentrations of most of the essential AA were higher with the CM diet and lower with the HPDDG diet, the exception being Leu for which the concentration was highest for the HPDDG diet. Glucose WB rate of appearance was altered by diet, with the highest mean observed for SBM (3,036 g/d) and the lowest for CM (2,795 g/d); the 2 diets with the lowest WB glucose rate of appearance (CM and WDDGS) also had the lowest dietary starch concentration. Overall, this study suggested that positive responses in milk and milk protein yields observed with inclusion of CM in dairy rations could be linked to a greater supply of metabolizable protein, including some essential AA, especially His, Lys, and Met, as glucose availability was certainly not increased in cows fed the CM diet.     

Apparent ileal digestibility of amino acids in feed ingredients determined with broilers and layers

The apparent ileal digestibility of amino acids in eight feed ingredients were determined using broilers and layers. The ingredients included three cereals (wheat, sorghum and maize), one cereal by‐product (wheat middlings), three oilseed meals (canola, cottonseed and soybean meals) and one animal protein meal (meat and bone meal). Dietary protein in the assay diets was supplied solely by the test ingredient. All diets contained 20 g kg^?1 acid‐insoluble ash as an indigestible marker, and each diet was offered ad libitum in mash form to five replicate pens of 42‐day‐old broilers and 60‐week‐old layers. The digestibility coefficients of most amino acids for wheat and sorghum were similar (P > 0.05) in broilers and layers. The digestibility of most amino acids for maize was higher (P < 0.05) in broilers compared to those in layers. The digestibility of individual amino acid for wheat middlings was higher (P < 0.05) in layers than in broilers. In general, the digestibility of amino acids for cottonseed meal, soybean meal, and meat and bone meal were similar (P > 0.05) between broilers and layers. The influence of class of bird on digestibility in canola meal was variable. The digestibility of threonine, valine, isoleucine, leucine, phenylalanine, glutamic acid and alanine were higher (P < 0.05), and those of methionine, histidine and lysine were lower (P < 0.05) in broilers compared to layers. These results suggest that the practice of using amino acid digestibility values generated with broilers for layers may not be appropriate for all feed ingredients. Copyright © 2006 Society of Chemical Industry     

Intestinal digestibility of amino acids in rumen-undegraded protein estimated using a precision-fed cecectomized rooster bioassay: II. Distillers dried grains with solubles and fish meal

The objectives of this experiment were to measure intestinal digestibility of AA in the rumen-undegraded protein fraction (RUP-AA) of distillers dried grains with solubles (DDGS) and fish meal (FM) samples and to determine whether these feeds contain a constant protein fraction that is undegradable in the rumen and indigestible in the small intestine, as assumed in the French Institut National de la Recherche Agronomique (Paris, France) and Scandinavian AAT-PBV (AAT = AA absorbed from small intestine; PBV = protein balance in the rumen) models. Five sources of DDGS and 5 sources of FM were obtained from Feed Analysis Consortium, Inc. (Champaign, IL). To obtain the rumen-undegradable protein fraction, samples were ruminally incubated in situ for 16 h in 4 lactating cows, and the collected rumen-undegraded residues (RUR) were pooled by sample. Subsamples of the intact feeds and RUR were crop-intubated to 4 cecectomized roosters, and total excreta were collected for 48 h. Intact feeds, RUR, and excreta were analyzed for AA. Basal endogenous AA loss estimates were obtained from fasted birds and were used to calculate standardized digestibility of RUP-AA and AA in the intact feeds. Indigestibility coefficients of the intact feeds were calculated as (100 − % standardized AA digestibility), and indigestibility of the RUR was calculated as [(100 − % ruminal degradation of AA) × (100 − % standardized RUP-AA digestibility)/100]. Results indicate that standardized digestibility of feed-AA differs from RUP-AA for DDGS samples but not for FM samples, and that standardized digestibility of individual AA differs within samples. For the DDGS samples, standardized feed-AA and RUP-AA digestibility values were most often lowest for His and Lys and highest for Met and Trp. For FM samples, standardized feed-AA and RUP-AA digestibility values were most often lowest for His and highest for Trp. Results also indicate that DDGS and most FM samples do not contain a constant protein fraction that is both undegradable in the rumen and indigestible in the small intestine. Indigestibility values of RUR were lower than in intact feeds, suggesting that the feed ingredients used in this experiment contain a protein fraction that is indigestible in the intestine but partly degradable in the rumen or digestible in the intestine after rumen incubation, or both.     

苎麻籽油脂肪酸组成及其粕氨基酸组成分析

用气相色谱法对苎麻籽油脂肪酸组成进行了分析,同时用氨基酸全自动分析仪对苎麻粕进行分析,为苎麻籽的开发利用提供基础数据。结果表明,苎麻籽油中不饱和脂肪酸含量90%以上,多不饱和脂肪酸含量79%以上,亚油酸含量尤为丰富,达77.40%~78.84%;苎麻粕含17种氨基酸,总含量为209.02~278.46 mg/g,其中7种必需氨基酸占总氨基酸的32.06%~33.17%。     

Production of a high‐protein meal and fermentable sugars from defatted soybean meal,a co‐product of the soybean oil industry

The goal of this research was to produce a high‐protein meal by treating defatted soybean meal, a by‐product of soybean oil production, with dilute acid. Treatments were a mild hydrolysis at 80 °C with sulphuric acid at concentrations ranging from 0.5% to 2.0% (w/v) and times varying from 1 to 16 h that were arranged according to a central composite rotatable experimental design. The end products were an enhanced‐protein meal and a carbohydrate concentrate of fermentable and nonfermentable sugars. The highest protein content rise, from 48% to 58%, was for treatments with concentrations of acid ranging between 1.2% and 1.7% and times between 1.0 and 2.6 h. The maximum yield of fermentable sugar was 21.0% d.b. at 2.0% H₂SO₄ and treatments of at least 6 h. The conditions that provide a highest protein and sugar contents were the treatments with concentrations of sulphuric acid ranging from 0.9 to 1.9% H₂SO₄ for 1–4 h.     

In vitro digestibility of individual amino acids in rumen-undegraded protein: The modified three-step procedure and the immobilized digestive enzyme assay

Three soybean meal, 3 SoyPlus (West Central Cooperative, Ralston, IA), 5 distillers dried grains with solubles, and 5 fish meal samples were used to evaluate the modified 3-step in vitro procedure (TSP) and the in vitro immobilized digestive enzyme assay (IDEA; Novus International Inc., St. Louis, MO) for estimating digestibility of AA in rumen-undegraded protein (RUP-AA). In a previous experiment, each sample was ruminally incubated in situ for 16 h, and in vivo digestibility of AA in the intact samples and in the rumen-undegraded residues (RUR) was obtained for all samples using the precision-fed cecectomized rooster assay. For the modified TSP, 5 g of RUR was weighed into polyester bags, which were then heat-sealed and placed into Daisy^II incubator bottles. Samples were incubated in a pepsin/HCl solution followed by incubation in a pancreatin solution. After this incubation, residues remaining in the bags were analyzed for AA, and digestibility of RUP-AA was calculated based on disappearance from the bags. In vitro RUP-AA digestibility estimates obtained with this procedure were highly correlated to in vivo estimates. Corresponding intact feeds were also analyzed via the pepsin/pancreatin steps of the modified TSP. In vitro estimates of AA digestibility of the feeds were highly correlated to in vivo RUP-AA digestibility, which suggests that the feeds may not need to be ruminally incubated before determining RUP-AA digestibility in vitro. The RUR were also analyzed via the IDEA kits. The IDEA values of the RUR were good predictors of RUP-AA digestibility in soybean meal, SoyPlus, and distillers dried grains with solubles, but the IDEA values were not as good predictors of RUP-AA digestibility in fish meal. However, the IDEA values of intact feed samples were also determined and were highly correlated to in vivo RUP-AA digestibility for all feed types, suggesting that the IDEA value of intact feeds may be a better predictor of RUP-AA digestibility than the IDEA value of the RUR. In conclusion, the modified TSP and IDEA kits are good approaches for estimating RUP-AA digestibility in soybean meal products, distillers dried grains with solubles, and fish meal samples.     

The effect of feeding canola meal on concentrations of plasma amino acids

An initial meta-analysis on isonitrogenous experiments where a protein source was replaced by canola meal (CM) showed that CM feeding increased yields of milk and milk protein and apparent N efficiency. The objective of the current study was to determine if these responses were related to increased changes in plasma AA concentrations. Although only half of the experiments of the initial meta-analysis reported concentrations of plasma AA and could be used in the current meta-analysis, lactational responses to CM feeding were similar to those reported previously. In the current meta-analysis, CM feeding increased plasma concentrations of total AA, total essential AA (EAA) and all individual EAA, but decreased concentrations of blood and milk urea-N. The current meta-analysis suggests that CM feeding increased the absorption of EAA, which would be responsible for the increased milk protein secretion and the increased apparent N efficiency.     

利用高温豆粕生产醇洗大豆浓缩蛋白的研究

分别以高温豆粕和低温豆粕为原料采用醇洗工艺制取大豆浓缩蛋白。测定高温豆粕和低温豆粕醇洗浓缩蛋白的蛋白质含量、NSI以及乙醇萃取液糖蜜中皂甙、异黄酮、总糖、蛋白质含量。结果显示:高温豆粕(蛋白质含量47.16%)醇洗浓缩蛋白的蛋白质含量(59.64%)虽然低于低温豆粕(蛋白质含量51.83%)醇洗浓缩蛋白的蛋白质含量(67.71%),但已接近60%,且高温豆粕乙醇萃取液糖蜜中皂甙、异黄酮含量(分别为8.04%、2.67%)与低温豆粕乙醇萃取液糖蜜中的含量接近(8.53%、2.13%)。表明利用高温豆粕生产饲用大豆浓缩蛋白应该是可行的,且副产物糖蜜是提取大豆皂甙、异黄酮、低聚糖的优质原料。