Variation of in situ rumen degradation of crude protein and amino acids and in vitro digestibility of undegraded feed protein in rapeseed meals

In this study, 10 samples of rapeseed meal (RSM) from 10 different oil plants in Germany were examined. In situ rumen degradation of CP was determined by incubation over 1, 2, 4, 8, 16, 32 and 72 h in duplicate per time point using three rumen fistulated dry cows. Degradation kinetics were estimated by an exponential model and effective CP degradation was calculated. Degradation was corrected for small particle loss as the difference between washing loss and water-soluble fraction. Amino acid analysis was carried out in the samples and in the residues after 8 and 16 h of incubation in situ and degradation of individual amino acids was calculated for these incubation times. In vitro pepsin–pancreatin digestibility of CP (IPD) was determined in the samples as well as in the 8 and 16 h residues. Effective CP degradation for a rumen outflow rate of 8%/h (ED8) averaged 54.3% with a considerable variation among samples ranging from 44.3% to 62.7%. A multiple regression equation containing acid detergent insoluble N, total glucosinolates and petroleum ether extract as independent variables predicted ED8 with satisfying accuracy (R² = 0.74; RSD = 6.4%). Degradation of amino acids was different from that of CP for most amino acids studied, especially after 8 h of incubation. Compared with CP, degradation of essential amino acids was predominantly lower while degradation of non-essential amino acids was higher in most cases. However, for lysine and methionine no distinct difference with CP degradation was found. Degradation of individual amino acids was predicted from CP degradation with high accuracy using linear regression equations. Average IPD of RSM was 79.8 ± 2.6%. IPD was lower in the incubation residues and decreased with longer incubation time and increasing rumen degradation, respectively.     

Bias when predicting crude protein,dry matter digestibility and voluntary intake of tropical grasses by near-infrared reflectance

A study was made of the bias (non-random error) of regressions for predicting crude protein (CP) content, dry matter digestibility (DMD) in vivo and voluntary intake (VI) of forage from its near-infrared reflectance (NIRR) properties measured at 19 wavelengths. The regression was derived from 97 samples including six tropical grasses, leaf and stem fractions, pelleted and chopped forms and regrowths varying from 28 to 150 days.Bias associated with differences in feed type was proved to exist in regression equations for predicting nutritive value when it was shown that the residual errors of these regressions were significantly reduced by including the combined effects of grass species, fraction, form and age. Measures of the bias which might be expected were calculated for two contrasting situations. The internal measure of bias (IMB) was ‘estimated’ as a possible average bias of a feed type when predicting nutritive value for samples of similar types to those used when deriving the calibration equation, while the extrapolation measure of bias (EMB) was ‘estimated’ as that associated with prediction of the nutritive value for feed types not included in the calibration equation.Crude protein was estimated with a residual standard deviation (RSD) of ± 0.77% when regressed against the 19 reflectance values, but when information on grass species, parts and regrowth was also included in the regression the RSD was reduced to ± 0.46%. The maximum difference in the IMB between grass species was 0.80% crude protein, while for EMB it was 3.35% crude protein. When separated leaf and stem were considered the differences were larger.Dry matter digestibility was estimated with an RSD of ± 2.7% which decreased to ± 1.8% when grass species, age, form and study were taken into account. Grass species had only a small effect on IMB but the maximum difference for EMB between species reached 5.6%. The EMB indicated that the largest differences between deviations were associated with age of regrowth but this effect was absent with the IMB.Voluntary intake was estimated with an RSD of ± 7.2 g/kg W^0.75/day, which decreased to ± 2.5 g/kg W^0.75/day when grass species, form, part and age were taken into account. The largest bias was for pelleted and chopped forage with mean differences of 14.5 for IMB and 28.8 g/kg W^0.75/day for EMB, respectively.It was concluded that when nutritive value is predicted by NIRR the estimates may often be biased according to the grass species, plant part or physical form of the sample tested and that the pattern of bias may be complicated. In order to obtain accurate predictions from NIRR full account must be taken of this bias. This might be achieved by correcting the nutritive value estimates made from an NIRR regression, based on a large number of feed types, by addition of the bias associated with the feed type being estimated.     

Percentage digestible dry matter and crude protein in dried aquatic weeds

Percentage digestible dry matter (in vitro) and crude protein concentrations were determined for 40 species of aquatic weeds. Concentrations of digestible dry matter and crude protein in some aquatic weeds were comparable to those of conventional forage species.     

Degradability characteristics of dry matter and crude protein of forages in ruminants

Twelve corn silages, 22 grass silages and 14 grass hays, obtained from various farms located in the lower Fraser Valley region of British Columbia, and 16 alfalfa hays, grown primarily in the Columbia basin of central Washington State, were evaluated using both the rumen and the mobile nylon bag in situ techniques. Nylon bags containing each forage were incubated in duplicate for 0, 2, 4, 8, 12, 24, 48, 72, or 96 h in two of six non-lactating Holstein cows fitted with rumen and duodenal cannulae. All forage types were evaluated in terms of the following dry matter (DM) and crude protein (CP) digestion characteristics: soluble fraction A, degradable fraction B, degradation rate, lag phase, and effective degradability. The mobile nylon bag technique was used to determine intestinal disappearance of DM and CP from the forages following pre-incubation in the rumen for 12 h. Significant (P < 0.05) differences in degradation characteristics occurred within all forages with regard to the soluble and potentially degradable DM and CP fractions. Soluble CP content in the rumen varied from 44.08 to 75.37% and from 18.74 to 65.38% in the corn and grass silages, respectively, and from 48.27 to 75.43% and from 30.13 to 65.95% in the alfalfa and grass hays, respectively. Significant differences within each forage type were also observed for the degradable CP in fraction B: 10.89 to 45.28% for corn silage, 20.72 to 82.77% for grass silage, 16.67 to 44.88% for grass hay and 25.44 to 62.93% for alfalfa hays. Significant differences (P > 0.05) were observed in fractional rates of ruminal DM degradation of the grass hays and corn silages. Significant differences did exist in the fractional rates of ruminal CP degradation within all forage types with the exception of alfalfa hays. Effective degradabilities of DM and CP were also significantly different between samples of a particular forage type. The mobile nylon bag data indicated that approximately 20% of the original CP in the grass silage, grass hay and alfalfa hay samples disappeared in the intestine and that there was significant variation between individual samples. On average, in the corn silage samples more than 10% of the original nitrogenous material disappeared in the intestine. The results presented in this study clearly demonstrate that the use of tabulated values for describing individual batches of forages in terms of their degradability characteristics is inaccurate since they may not reflect the particular forage being used in the ration and thus may lead to errors in diet formulation.     

From protein catalogues towards targeted proteomics approaches in cereal grains

Due to their importance for human nutrition, the protein content of cereal grains has been a subject of intense study for over a century and cereal grains were not surprisingly one of the earliest subjects for 2D-gel-based proteome analysis. Over the last two decades, countless cereal grain proteomes, mostly derived using 2D-gel based technologies, have been described and hundreds of proteins identified. However, very little is still known about post-translational modifications, subcellular proteomes, and protein-protein interactions in cereal grains. Development of techniques for improved extraction, separation and identification of proteins and peptides is facilitating functional proteomics and analysis of sub-proteomes from small amounts of starting material, such as seed tissues. The combination of proteomics with structural and functional analysis is increasingly applied to target subsets of proteins. These “next-generation” proteomics studies will vastly increase our depth of knowledge about the processes controlling cereal grain development, nutritional and processing characteristics.     

In situ production of exopolysaccharides during Sourdough fermentation by cereal and intestinal isolates of lactic acid bacteria

EPS formed by lactobacilli in situ during sourdough fermentation may replace hydrocolloids currently used as texturizing, antistaling, or prebiotic additives in bread production. In this study, a screening of >100 strains of cereal-associated and intestinal lactic acid bacteria was performed for the production of exopolysaccharides (EPS) from sucrose. Fifteen strains produced fructan, and four strains produced glucan. It was remarkable that formation of glucan and fructan was most frequently found in intestinal isolates and strains of the species Lactobacillus reuteri, Lactobacillus pontis, and Lactobacillus frumenti from type II sourdoughs. By the use of PCR primers derived from conserved amino acid sequences of bacterial levansucrase genes, it was shown that 6 of the 15 fructan-producing lactobacilli and none of 20 glucan producers or EPS-negative strains carried a levansucrase gene. In sourdough fermentations, it was determined whether those strains producing EPS in MRS medium modified as described by Stolz et al. (37) and containing 100 g of sucrose liter(-1) as the sole source of carbon also produce the same EPS from sucrose during sourdough fermentation in the presence of 12% sucrose. For all six EPS-producing strains evaluated in sourdough fermentations, in situ production of EPS at levels ranging from 0.5 to 2 g/kg of flour was demonstrated. Production of EPS from sucrose is a metabolic activity that is widespread among sourdough lactic acid bacteria. Thus, the use of these organisms in bread production may allow the replacement of additives.     

Nylon capsule method and alfalfa hay crude protein digestibility evaluation

In a trial with two dairy cows we have determined crude protein total tract digestibility (TTDP_NC) by a new nylon capsule method. Nylon capsules were made of nylon cloth with 42 μm apertures. The capsule shape was lenticular, with 10 mm external diameter and 8 mm internal diameter. The capsules were loaded with two stainless steel balls of 149 mg total weight. The average weight of a sample (milled alfalfa hay) in one capsule was 12.9 mg. In each of the two periods 1260 capsules were inserted orally into each of the two cows. Mean capsule passage time (CPT) through the digestive tract was 36.1 h (s.e. 0.49). The total tract dry matter digestibility determined by the nylon capsule method (TTDM_NC) was significantly (P < 0.05) influenced by the time which the capsules spent in the digestive tract. When CPT was 25.4 h, TTDM_NC was 64.8%, while with CPT 50.4 h it was 70.3%. The mean value of TTDP_NC was 93.8%. A similar value, 92.3%, was obtained by calculation based on the values determined by the nylon bag and the mobile bag methods. The results have shown that it is possible to use the nylon capsule method for the determination of total tract digestibility of individual feed components in cattle.     

油菜地上部干物质分配与产量形成模拟模型

利用油菜器官生长与发育进程及环境因子之间的定量关系,构建了基于分配指数的油菜地上部器官干物质分配动态模拟模型.各器官干物质分配指数随着生理发育时间而变化,基因型、播期、氮素及水分水平影响各器官干物质在地上部分配的大小.其中,氮素营养水平对绿色叶片干物质分配影响最大,氮素营养水平越高,绿色叶片分配指数越大;播期影响角果分配指数,晚播的角果分配指数高于早播.模型引入氮素营养指数、水分及播期影响因子来定量油菜各器官在实际生产条件下的分配强度,同时考虑了品种遗传特性的影响.通过不同品种氮肥处理试验建立模型,利用不同品种播期试验资料对模型进行了初步检验,表明模型具有较好的预测性和适用性.     

Loading and bioavailability of iron in cereal grains

Cereal plants take up iron from the soil via a phytosiderophore-mediated chelation system. Following root absorption, iron is transported through the xylem and phloem of the plant with the help of a variety of efflux and influx transporters belonging to the Zrt Irt-like protein (ZIP) and yellow stripe-like (YSL) protein families. Iron-regulated transporter1, a member of the ZIP family, mobilises ferrous [Fe(II)] ions, while several YSL family members such as YSL2, YSL15 and YSL18 can transport both ferric [Fe(II)] and ferrous [F`III)] ions into developing grains via chelation with mugineic acid or its derivatives. The iron is accumulated largely in the outer aleurone layer and embryo of the grains, which are removed during milling, leaving behind consumable endosperm that contains a very low amount of iron. This review highlights the uptake, transport and loading mechanisms for iron in cereal grains and provides an overview of strategies adopted for developing highly iron-enriched grains.     

Regulation of aleurone development in cereal grains

The aleurone layer of cereal grains is important biologically as well as nutritionally and economically. Here, current knowledge on the regulation of aleurone development is reviewed. Recent reports suggest that the control of aleurone development is more complex than earlier models portrayed. Multiple levels of genetic regulation control aleurone cell fate, differentiation, and organization. The hormones auxin and cytokinin can also influence aleurone development. New technical advances promise to facilitate future progress.     

Effects of ensiling on in situ ruminal degradability and intestinal digestibility of corn forage

The effective degradability of dry matter (DM), crude protein (CP) and amino acids (AA), and the intestinal effective digestibility (IED) of DM and CP of a green forage corn (GC) and its silage (EC) were determined on freeze-dried samples using three rumen and duodenum cannulated wethers. Two rumen incubations with duplicate bags were performed for each feed. Rumen degradation was determined on one series of bags from each incubation. The other series was freeze-dried and used to determine IED using mobile nylon bags. Microbial contamination of rumen incubated residues (determined with ¹⁵N techniques) fitted exponential functions, which showed a greater microbial contribution in EC than in GC in the undegradable DM (18.6% vs. 13.5%) and CP (81.7% vs. 69.4%). Degradability was calculated considering the particle rumen outflow rate (k_p : 0.056/h) of the EC (ED_p) or additionally the rate of comminution and mixing (k_c : 0.130/h) of these particles (ED_cp). Ensiling increased ED_p (9.33%, p < 0.01) or ED_cp (5.30%, p = 0.062) of DM and was associated with losses of nitrogen and with large changes in the AA profile. It is necessary to correct the microbial contamination, because it represents 32.0% (GC) and 42.5% (EC) of the undegraded CP when using k_p and k_c . Ensiling caused higher degradabilities for some AA as well as large differences in the changes due to the rumen fermentation on the AA profile. However, it had only limited effects on the undegraded protein profile. Ensiling also reduced the IED of DM (23.3% vs. 14.6%; p = 0.057). In conclusion, results do not show losses of nutritive value by ensiling corn cut at vitreous grain stage.     

Processing cotton gin trash to enhance in vitro dry matter digestibility in reduced time

Cotton gin trash (CGT) in the raw form is poorly digested by ruminants due to lignocellulosic complexes. These structures must be broken down before adequate digestion can occur. This may be performed by physical and/or chemical means. Two methods for improving digestibility are particle size reduction and/or treatment with sodium hydroxide (NaOH). To evaluate the effectiveness of each method, three experiments were performed in which different CGT types were tested. Each type represented trash from a particular cleaning stage in the cotton ginning process. First, each type was ground with a knife-type grinding mill using screen sizes 0.5, 1.0, and 2.0 mm. For the second experiment, particle size was held constant at 2 mm, and all CGT types were treated with 4% and 6% NaOH (w/w) at room temperature. An agitation cycle of 5 min on and 10 min off was used, with the total mixing time being 4 h. Lastly, particle size and NaOH concentration were held constant, and treatments were performed at room temperature, 40 degrees C, and 50 degrees C. The total mixing times were 2 and 3 h for 50 and 40 degrees C, respectively. For all experiments two subsamples of each treatment were tested for in vitro dry matter digestibility (IVDMD). From grinding alone, digestibility increased as particle size decreased. Grinding to 0.5 mm resulted in an average IVDMD of 47.8% while grinding to 2.0 mm resulted in an average IVDMD of only 33.8%. Digestibility also improved with a greater NaOH concentration. An average in vitro digestibility of 70.5% was achieved with 6% NaOH (w/w) treatment, essentially doubling that of the raw CGT. Increasing the reaction temperature did not result in increased digestibility because the mixture dried out, with a consequent reduction in chemical distribution and uniformity in heat transfer. There are still chemical residues in the CGT, and elimination/reduction of these is an issue that needs to be addressed in further research.     

The nutritive value of concentrate feedstuffs for ruminant animals: Part I: In situ ruminal degradability of dry matter and organic matter

The aim of the study was to generate a database of ruminal degradability of dry matter (DM), and organic matter (OM) of different sources of concentrate ingredients (classified as protein, energy or protein+energy feeds) commonly offered to ruminants in European countries. The ruminal disappearance of DM and OM was measured using the in situ nylon bag technique, where the test feedstuffs were subject to ruminal incubation in four Friesian steers offered grass silage and concentrate. Disappearance of DM and OM from the test feeds from the rumen was measured at 0, 2, 4, 8, 14, 24 and 48 h. The exponential model of Ørskov and McDonald (1979) was used to calculate degradation kinetics. Test protein feeds were sunflower meal (SUN), rapeseed meal (RAP), soyabean meal (SBM) and cottonseed meal (CSM). Test energy feeds were palm kernel meal (PK), pollard (PO), barley (BA) and beet pulp (BP). Test protein+energy feeds were maize distillers grains (MDG), maize gluten feed (MGF), copra meal (CO) and malt combings (MC).

The effective degradability (degradability of feed, whilst considering rate of flow of feed from rumen to small intestine) of DM (EDDM) and OM (EDOM) in the protein feed SBM, where outflow rate k=0.02, was not influenced (P>0.05) by the sample of feed used. For the feeds classified as protein+energy feeds, the EDDM in MGF and MC were not affected (P>0.05) by the sample of feed for k=0.02. For the remainder of the concentrate feedstuffs used in this study, the sample of feed used had a pronounced effect on in situ degradability values. These data have shown that for the majority of feeds examined in this study, the different sources of any one feed are not equal in nutritive value and it is necessary to screen feeds for nutritive value before using them in ration formulation systems.     

Prediction of CP and starch concentrations in ruminal in situ studies and ruminal degradation of cereal grains using NIRS

Ruminal in situ incubations are widely used to assess the nutritional value of feedstuffs for ruminants. In in situ methods, feed samples are ruminally incubated in indigestible bags over a predefined timespan and the disappearance of nutrients from the bags is recorded. To describe the degradation of specific nutrients, information on the concentration of feed samples and undegraded feed after in situ incubation (‘bag residues’) is needed. For cereal and pea grains, CP and starch (ST) analyses are of interest. The numerous analyses of residues following ruminal incubation contribute greatly to the substantial investments in labour and money, and faster methods would be beneficial. Therefore, calibrations were developed to estimate CP and ST concentrations in grains and bag residues following in situ incubations by using their near-infrared spectra recorded from 680 to 2500 nm. The samples comprised rye, triticale, barley, wheat, and maize grains (20 genotypes each), and 15 durum wheat and 13 pea grains. In addition, residues after ruminal incubation were included (at least from four samples per species for various incubation times). To establish CP and ST calibrations, 620 and 610 samples (grains and bag residues after incubation, respectively) were chemically analysed for their CP and ST concentration. Calibrations using wavelengths from 1250 to 2450 nm and the first derivative of the spectra produced the best results (R²_Validation=0.99 for CP and ST; standard error of prediction=0.47 and 2.10% DM for CP and ST, respectively). Hence, CP and ST concentration in cereal grains and peas and their bag residues could be predicted with high precision by NIRS for use in in situ studies. No differences were found between the effective ruminal degradation calculated from NIRS estimations and those calculated from chemical analyses (P>0.70). Calibrations were also calculated to predict ruminal degradation kinetics of cereal grains from the spectra of ground grains. Estimation of the effective ruminal degradation of CP and ST from the near-infrared spectra of cereal grains showed promising results (R²>0.90), but the database needs to be extended to obtain more stable calibrations for routine use.     

A method using solubility to predict dry matter digestibility of cellulosic materials.

A rapid chemical procedure based on the solubility of a holocellulose sample in a system of dimethyl sulfoxide with paraformaldehyde has been developed to provide a laboratory method for predicting dry matter digestibility of cellulose containing samples. The amount of dry matter solubilized by the chemical procedure was closely correlated with anaerobic, in vitro, rumen fluid digestion and with digestibility as measured by aerobic Cellulomonas, sp. bacteria. The quantity of solvent and dissolving time had little effect on solubility over a wide range. The method is rapid, well suited for various cellulosic materials, and may be carried out with simple equipment and facilities.     

In situ visualization and effect of glycerol in lipase-catalyzed ethanolysis of rapeseed oil

Immobilized lipases can be used in biodiesel production to overcome many disadvantages of the conventional base-catalyzed process. However, the glycerol by-product poses a potential problem for the biocatalytic process as it is known to inhibit immobilized lipases, most likely by clogging of the catalyst particles. In this paper, this negative effect was further investigated and confirmed in ethanolysis of rapeseed oil. A dyeing method was developed for in situ visualization of glycerol in order to study its partitioning and accumulation during the ethanolysis reaction. The method was used to illustrate the interaction of glycerol with immobilized lipases and thus provided an aid for screening supports for lipase immobilization according to their interaction with glycerol. Glycerol was found to have great affinity for silica, less for polystyrene and no affinity for supports made from polymethylmethacrylate and polypropylene. It was also found that the immobilization of enzyme on the support influenced the adsorption of glycerol to the surface of the enzyme carrier.