Measurement of the postruminal digestibility of crude protein by the bag technique in cows

Adaptation of in vitro methodologies to estimate the intestinal digestion of lipids in ruminants

The objective of this study was to adapt existing in vitro methodologies to determine the extent of intestinal digestion of corn oil (CO), canola oil (CA), and beef tallow (BT) via manipulation of incubation length and concentrations of lipase, bile, and calcium within a buffer solution. Unless otherwise stated, 0.5 g of each lipid source were incubated separately and in triplicate, with triplicate batch culture runs for each treatment in 40 mL of 0.5 M KH2PO4 (pH = 7.6) for 24 h with pancreatin (8 g/L), bovine bile (2.5 g/L), and CaCl2 (10 mM). Individually, concentrations of pancreatin, bile, and CaCl2, as well as incubation length were tested. To examine the use of this assay to estimate in vitro total tract digestion, a KH2PO4 solution with concentrated amounts to reach the same final concentrations of pancreatin, bile, and Ca were used as the third step in a three-step total tract digestibility procedure. Free glycerol and free fatty acid (FFA) concentrations were measured using colorimetric assays as indicators of digestion. Data wereanalyzed as a completely randomized block design (block = run), using the Glimmix procedure of SAS. For each lipid source, free glycerol increased with increasing pancreatin; however, FFA was lowest at 0 g/L pancreatin but was similar at 6, 8, and 10 g/L. Both glycerol and FFA were greater for 2.5 and 5 g/L of bile than for 0 g/L for each lipid source. Calcium concentration did not affect glycerol or FFA for either CO or CA; however, glycerol and FFA for BT were greater when calcium was included at 5 and 10 mM than at 0 mM. For all fat sources, free glycerol and FFA increased after 1 h until 12 h, but did not increase from 12 to 24 h. When a concentrated mixture was used following fermentation and acidification steps, digestibility using FFA concentration increased as compared to just adding buffer; however, free glycerol concentration was indeterminable. Thus, free glycerol and FFA can be used as indicators of lipid digestion when a lipid source is incubated for at least 12 h in a buffer solution containing 8 g/L pancreatin, 2.5 g/L bile, and 5 mM Ca when only estimating in vitro intestinal digestion; however, when utilizing this assay in a three-step in vitro total tract digestibility procedure, only FFA can be used.

In vitro techniques to replace in vivo methods for estimating amino acid supply

Expressing the protein value of a food involves measurements of several of its characteristics. Many in vivo studies have shown, that the protein degradability in the rumen varies substantially both between and within foods and therefore estimation of protein degradability in the rumen is an important task in protein evaluation. The most common method used has been the in situ (in sacco, nylon bag) method but many in vitro methods have been introduced and are based on use of either buffer solubility, chemical methods, rumen fluid or enzymes. None of these in vitro methods has proven to be of general use. In further development of in vitro methods as well as the in situ method a major problem is lack of a set of samples with a ‘true’ in vivo degradability which can be used for calibration of alternative methods. Microbial protein synthesis in the rumen has to be related to food characteristics which can be analysed easily. In vitro methods which can predict organic matter digestibility in foods are available and can be used to predict microbial protein synthesis in the rumen. Intestinal digestibility of undegraded dietary protein varies substantially both between and within foods and easy methods to estimate intestinal digestibility are therefore essential. The mobile bag method is easy to use and seems to give reliable results on most foods but requires access to duodenal cannulated animals which prevents this method from being routine. Alternative in vitro methods have been developed but further research is required for validation of these methods on a wide range of foods before they can be accepted for general use.

Effect of diet forage to concentrate ratio on rumen degradability and post-ruminal availability of protein from fresh and dried lucerne

The ruminal degradation of dry matter (DM) and crude protein (CP) and the intestinal availability of CP of four lucerne samples were measured on two diets with lucerne hay to concentrate ratios of 2: 1 (diet F) and 1: 2 (diet C). Two samples of fresh lucerne (third cut) harvested after 2 (FL1) or 8 (FL2) weeks from the previous cut were used together with a sample of lucerne hay (LH) and another of dehydrated lucerne (DL). Rumen degradability, measured by the nylon bag technique, and rumen outflow rates were determined on three rumen cannulated wethers. Intestinal digestibility was determined by the mobile bag technique on three duodenal fistulated wethers. For CP, significantly lower values were observed with diet C than with diet F for the potentially degradable insoluble fraction (0·334 v. 0·397) and its degradation rate (0·093 v. 0·134 per h). As a consequence, the effective degradability was also lower with diet C (0·746 v. 0·821; P = 0·059). Effective degradability of DM was also apparently lower with diet C (0·596 v. 0·634). With both diets, the intestinal digestibility decreased in all the samples with increase of ruminal incubation time according to a simple exponential equation. The undegraded CP digested in the gut (Di) and therefore the effective intestinal digestibility (EID) were derived from this exponential function according to the rumen outflow of undegraded CP. Mean values of Di (expressed as proportion of food CP content) were respectively 0·091 and 0·142 for F and C diets and 0·084, 0·115, 0·116, and 0·152 for FL1, FL2, LH and DL samples. Lower rumen degradability was partially compensated for by higher Di values resulting in a close correlation between both parameters (r = –0·965; P 0·001). The change of the digestion site associated with the reduction of the effective degradability of CP produced also an increase in the undigested CP as a proportion of food CP. So, these values are respectively 0·087 and 0·112 for F and C diets and 0·053, 0·109, 0·096, and 0·141 for FL1, FL2, LH, and DL samples. No difference in EID between F and C diets was observed (0·529 v. 0·563). For samples, the only effect (P 0·05) was recorded between FL1 (0·618) and the other samples (0·509, 0·544 and 0·512 for FL2, LH, and DL, respectively).

Rumen Degradability and Small Intestinal Digestibility of the Amino Acids in Four Protein Supplements

The supplementation of livestock feed with animal protein is a present cause for public concern, and plant protein shortages have become increasingly prominent in China. This conflict may be resolved by fully utilizing currently available sources of plant protein. We estimated the rumen degradability and the small intestinal digestibility of the amino acids (AA) in rapeseed meal (RSM), soybean meal (SBM), sunflower seed meal (SFM) and sesame meal (SSM) using the mobile nylon bag method to determine the absorbable AA content of these protein supplements as a guide towards dietary formulations for the dairy industry. Overall, this study aimed to utilize protein supplements effectively to guide dietary formulations to increase milk yield and save plant protein resources. To this end, we studied four cows with a permanent rumen fistula and duodenal T-shape fistula in a 4×4 Latin square experimental design. The results showed that the total small intestine absorbable amino acids and small intestine absorbable essential amino acids were higher in the SBM (26.34% and 13.11% dry matter [DM], respectively) than in the SFM (13.97% and 6.89% DM, respectively). The small intestine absorbable Lys contents of the SFM, SSM, RSM and SBM were 0.86%, 0.88%, 1.43%, and 2.12% (DM basis), respectively, and the absorbable Met contents of these meals were 0.28%, 1.03%, 0.52%, and 0.47% (DM basis), respectively. Among the examined food sources, the milk protein score of the SBM (0.181) was highest followed by those of the RSM (0.136), SSM (0.108) and SFM (0.106). The absorbable amino acid contents of the protein supplements accurately reflected protein availability, which is an important indicator of the balance of feed formulation. Therefore, a database detailing the absorbable AA should be established.

Ruminal degradability and intestinal digestibility of individual amino acids in mixed diets with different crude protein levels measured by the modified in vitro three-step and mobile nylon bag technique

The ruminal degradability and intestinal digestibility of dry matter (DM), crude protein (CP) and amino acids (AA) in three total mixed rations with different CP levels were estimated using the modified in vitro three-step procedure (TSP) and mobile nylon bag (MNB) technique on growing lambs. The ruminal effective degradability of DM and CP did not respond with increasing dietary CP level. However, the intestinal digestibility of DM was significantly increased with increasing dietary CP level estimated by TSP (P < 0.05) or MNB method (P < 0.01). Intestinal digestibility coefficients of CP determined by TSP were lower than those of the MNB method. Histidine was extensively degraded by rumen micro-organisms, while tyrosine was the most anti-degradable AA among the samples. The ruminal AA degradability exhibited no significant differences except for threonine, tryptophan, alanine, aspartic acid and proline for the three diets. Similarly, only a few AAs (i.e. histidine, methionine, tryptophan, aspartic acid and cysteine in TSP; histidine, tryptophan, aspartic acid and serine in MNB) had significant differences in their intestinal digestibility; in addition, values of MNB were lower than that of the TSP method, indicating that intestinal digestibility of DM seems to be overestimated in TSP, while that of CP might be overestimated in the MNB method.

Measurement of the Intestinal Digestibility of Rumen Undegraded Protein Using Different Methods and Correlation Analysis

Four methods were adopted, including the mobile nylon bag (MNB) method, modified three-step in vitro (MTS) method, original three-step in vitro (OTS) method, and acid detergent insoluble nitrogen (ADIN) estimating method, to evaluate the intestinal digestibility of rumen undegradable protein (DRUP) of 10 types of concentrates and 7 types of roughages. After correlation analysis to determine the DRUP values using the MNB, MTS, OTS, and ADIN methods, the study aimed to find out appropriate methods to replace the MNB method due to its disadvantages such as high price, long time period, and use of a duodenal T-fistula. Three dairy cows with a permanent ruminal fistula and duodenal T-fistula were used in a single-factor experimental design. The results showed that the determined DRUP values using the MNB method for soybean meal, cottonseed meal, rapeseed meal, sunflower meal, corn germ meal, corn, rice bran, barley, wheat bran, corn fiber feed, Alfalfa (Zhao dong), Alfalfa (Long mu 801), Alfalfa (Long mu 803), grass (North), Grass (Inner Mongolia), corn silage and corn straw were 98.13%, 87.37%, 88.47%, 82.60%, 75.40%, 93.23%, 69.27%, 91.27%, 72.37%, 79.03%, 66.72%, 68.64%, 73.57%, 50.47%, 51.52%, 54.05%, and 43.84%, respectively. The coefficient of determination (R² = 0.964) of the results between the MTS method and the MNB method was higher than that (R² = 0.942) between the OTS method and the MNB method. The coefficient of determination of the DRUP values of the concentrates among the in vitro method (including the MTS and OTS methods) and the MNB method was higher than that of the roughage. There was a weak correlation between the determined DRUP values in concentrates obtained from the ADIN method and those from the MNB method, and there was a significant correlation (p<0.01) between the determined DRUP values of the roughage obtained from the MNB method and those obtained from ADIN method. The DRUP values were significantly correlated with the nutritional ingredients of the feeds. The regression equation was DRUP =100.5566+0.4169CP − 0.4344SP − 0.7102NDF − 0.7950EE (R² = 0.8668, p<0.01; CP, crude protein; SP, soluble protein; NDF, neutral detergent fiber; EE, ether extract). It was concluded that both the MTS method and the OTS may suitable to replace the MNB method for determining the DRUP values and the former method was more effective. Only the ADIN method could be used to predict the values of the roughages but conventional nutritional ingredients were available for all of the samples’ DRUP.

Digestion of feed amino acids in the rumen and small intestine of dairy cows measured with nylon-bag techniques

The disappearance of total N, non-protein-N and amino acid-N after washing, rumen incubation and intestinal passage of sugarbeet pulp, maize-gluten feed, maize feed meal, palm kernel meal, soyabean hulls, soyabean meal, grass silage, maize silage and concentrate was measured in four dairy cows using nylon-bag techniques. Disappearance of amino acid-N after washing varied between feedstuff's from 14 to 69% of feed amino acid-N, and was lower than disappearance of non-protein-N. For sugarbeet pulp, grass silage and maize silage, washing had a considerable effect on the amino acid profile. Disappearance of amino acid-N after rumen incubation was also lower than non-protein-N and varied between feedstuffs from 25 to 73% of feed amino acid-N. Rumen incubation had only a small effect on the amino acid profile of the residue after washing. Disappearance of amino acid-N in the intestine varied between feedstuffs from 70 to 99% of rumen undegraded amino acid-N, and was higher than the disappearance of non-protein-N. Intestinal incubation showed a considerable effect on the amino acid profile for all feedstuffs. It was concluded that protein that was assumed to escape rumen degradation and was absorbable in the intestine was higher in amino acids and methionine, and lower in non-amino acid-N and glutamic acid and proline compared with protein in the feedstuff.

Protein value for ruminants of a sample of whole cottonseed

The effective ruminal degradability (ED) of dry matter (DM), crude protein (CP) and amino acids, and the effective intestinal digestibility (IED) of DM and CP of a sample of whole cottonseed was measured using in situ and rumen outflow rate techniques in three wethers cannulated in the rumen and duodenum. The microbial contamination of rumen incubated residues was corrected by a continuous rumen infusion of15NH3as microbial marker and rumen solid associated bacteria as reference sample. Microbial contamination resulted in an overestimation of the undegradable fraction of DM (0·291v. 0·275;P<0·05) and CP (0·071v. 0·037;P<0·01) and a small underestimation of ED of DM (0·500v. 0·512;P=0·09) and CP (0·755v. 0·779;P=0·052). A proportion of 0·1 of the ruminal undegraded CP was of microbial origin and for essential amino acids this proportion varied from 0·042 to 0·150. Differences in ED between amino acids modified the amino acid profile, with an important reduction (0·2;P<0·01) in the proportion of lysine. Apparent intestinal digestibility of the insoluble fraction of this food, measured with the mobile nylon bag technique, showed large reductions (P<0·001) with the increase of the ruminal incubation time between 0 and 72 h: from 0·392 to 0·026 for DM and from 0·851 to 0·099 for CP. These evolutions fitted an exponential function with a previous lag. The IED was estimated either by integration of these equations and those describing the ruminal degradation and rumen outflow or by incubation through the intestines of a sample pooled to be representative of rumen flow of the undegraded food. The two methods gave similar values for both DM (0·222v. 0·203) and CP (0·659v. 0·658).

Determination of undegradable intake protein digestibility of forages using the mobile nylon bag technique

Two experiments were conducted using 2 ruminally and duodenally fistulated steers to determine the digestibility of undegradable intake protein (UIP) of smooth bromegrass (Bromis inermis), birdsfoot trefoil (Lotus coniculatus L.), and heat-treated alfalfa (Medicago sativa) using the mobile nylon bag technique. Undegradable intake protein was determined using neutral detergent insoluble CP at a single in situ incubation time point based on 75% of the total mean retention time estimated from IVDMD plus a 10-h passage lag. In Exp. 1, UIP (% DM) of smooth bromegrass in June and July were 1.82 and 1.71, respectively (P = 0.11). Undegradable intake protein (% DM) of birdsfoot trefoil increased from 1.30 in June to 1.94 in July (P < 0.01). Total tract indigestible protein of smooth brome-grass and birdsfoot trefoil increased in July (P < 0.05). Digestibility of UIP decreased in July for smooth brome-grass (P < 0.01) but tended to increase for birdsfoot trefoil (P = 0.07). In Exp. 2, alfalfa from plots fertilized with low (66 kg of N/ha) or high (200 kg of N/ha) amounts of N were dried to simulate 3 preservation methods: dehydrated (100 degrees C, 10 h), sun-cured (50 degrees C, 15 h), and lyophilized (-50 degrees C, 72 h) alfalfa. Undegradable intake protein (% DM) was estimated as in Exp. 1 and was 3.13, 2.10, and 1.84 for dehydrated, sun-cured, and lyophilized alfalfa, respectively. Total tract indigestible protein (% DM) was increased (P < 0.05) for dehydrated alfalfa (1.66) compared with sun-cured (1.54) or lyophilized (1.57) alfalfa. As a result of greater UIP flow to the lower tract, digestibility (%) of UIP was greater (P < 0.01) for dehydrated (46.4) than for sun-cured (25.6) or lyophilized (14.7) alfalfa. Heat-treated alfalfa samples increased net UIP absorption in the lower tract because 1.47, 0.56, and 0.27 percentage units of UIP (% DM) of dehydrated, sun-cured, and lyophilized alfalfa, respectively, disappeared. Overall, the digestibility of the UIP of these forages was low in the lower tract.

Digestion of feed amino acids in the rumen and intestine of steers measured using a mobile nylon bag technique

The disappearance of dry matter (DM), crude protein (CP), and amino acids (AA) in steers after rumen incubation and intestinal passage of alfalfa hay, barley hay, corn silage, barley grain, corn grain, wheat bran, meat meal, fish meal, cottonseed meal, and soybean meal were measured in 3 steers using a mobile nylon bag technique. Ruminal degradation of individual AA differed between feedstuffs. For barley hay and corn silage, the ruminal disappearance of total AA was higher and lower than the other feedstuffs, respectively. The intestinal digestibility of total AA in alfalfa hay was lower than the digestion of CP. The intestinal digestibility of Arg and His was higher than that of total AA in alfalfa hay, meat meal, cottonseed meal, soybean meal, barley hay, and wheat bran. In addition, the intestinal digestibility of Lys was higher than that of total AA in alfalfa hay, meat meal, cottonseed meal, soybean meal, barley hay, corn silage, and wheat bran. The intestinal disappearance of CP in most cases was higher than that of DM. The results indicated that feedstuffs with lower ruminal disappearance of DM, CP, total AA, essential AA, and nonessential AA generally had a higher intestinal disappearance, resulting in a relatively constant total tract disappearance. These results could be used to improve the current system of diet formulation in ruminants.

Concentrados protéicos para bovinos: 2. Digestão pós-ruminal da matéria seca e da proteína

O objetivo deste trabalho foi avaliar a digestão pós-ruminal de fontes protéicas. Utilizou-se a técnica de sacos de náilon móveis introduzidos no duodeno e colhidos nas fezes. Os alimentos introduzidos no intestino foram anteriormente incubados em sacos de náilon no rúmen ou foram separados das frações solúveis em água. O farelo de soja foi a fonte protéica de maior degradabilidade ruminal (73%) e altíssima digestibilidade intestinal (98%). O glúten de milho foi a fonte protéica menos degradada no rúmen (16%) e sua parcela sobrepassante foi altamente digerida no intestino (95%). Os farelos de algodão e de mamona mostraram características semelhantes com digestibilidade total da proteína de 95% e em torno de 65% de degradabilidade ruminal. O farelo de palmiste foi menos digerido (87% digestibilidade total quando incubado). Farinhas de origem animal foram menos digeridas no intestino e também no rúmen (fora o glúten), com digestibilidades totais de 75% para farinha de carne e ossos, 85% para farinha de penas e vísceras e farinha de peixe I, 67% para farinha de peixe II e apenas 46% para farinha de sangue.

Amino acid profile of escaped feed protein after rumen incubation and their intestinal digestibility

The crude protein content and amino acid profile of seven feedstuffs (linseed meal, maize gluten meal, rapeseed meal, rapeseed meal protected, soybean meal, fullfat soybean extruded and sunflower meal) were determined before and after ruminal incubation for 16 h in three bulls with large rumen cannulas. The intestinal disappearance of amino acids was measured using mobile bag technique. Ruminal incubation affected amino acid profile of all experimental feedstuffs. Crude protein degradation varied from 29.3% for maize gluten meal to 86.4% for rapeseed meal. A tendency towards increased disappearance was observed for glutamic acid, histidine, lysine and proline and decreased disappearance for branched-chain amino acids. The intestinal crude protein digestibility was higher than > 80%, except rapeseed meal (66.4%) and sunflower meal (77.8%). The least digestible individual amino acids were methionine and isoleucine in rapeseed meal, histidine and methionine in rapeseed meal protected and arginine in sunflower meal. In general, the lowest amino acid digestibilities were found in feedstuffs with the highest fibre content. The feedstuffs show that they have different potential for supplying of limiting amino acids. Of particular value are the feedstuffs with low crude protein degradability in the rumen and high intestinal digestibility of amino acids.

Effect of micronizing full fat canola seed on amino acid disappearance in the gastrointestinal tract of dairy cows

Ruminal and total tract digestion of the amino acids (AA) in full fat canola seed was studied in two in situ experiments with three nonlactating, ruminally and duodenally fistulated dairy cows. Whole, full fat canola seed was hand-cracked or micronized (an infrared heat treatment) for 90 s and then studied in that form or after grinding to pass a 1.25-mm sieve. In the first experiment, the four sample types were ruminally incubated in nylon bags for up to 96 h. In the second experiment, they were sealed in mobile nylon bags, incubated ruminally for 16 h, placed in acidified pepsin for 1 h, and then inserted into duodenal cannulas for passage through the intestine. Amino acids in the canola seed and in the residues from in situ incubations were analyzed by HPLC. Micronization reduced ruminal disappearance of total AA and essential AA from full fat canola seed. Degradation kinetics from Experiment 1 indicated reduced soluble fraction and increased slowly degradable fraction of both total AA and essential AA following micronization. Micronization reduced disappearances of total AA and essential AA from whole canola seed in the total digestive tract but did not affect total tract digestion of total AA or essential AA in ground seed. Intestinal disappearance of total AA and essential AA from both whole and ground full fat canola seed were increased by micronization. Micronizing canola seed may be of value in improving AA utilization in ruminants.

Ruminal and total plant cell-wall digestibility estimated by a combined in situ method utilizing mathematical models

Three ruminally and duodenally cannulated non-lactating Finnish Ayrshire cows were used to investigate ruminal and intestinal digestion of cell-wall carbohydrates by a combined in situ method. Five grasses cut at 10 d intervals were incubated in the rumen for 0, 6, 12, 24, 48, 72 and 96 h, and the undegraded residues were exposed to intestinal digestion. With advancing maturity of grass both the rate and extent of cell-wall digestion decreased. At early stages of growth the decreases were faster for the rate of digestion and at late stages of growth for the extent of digestion. Applying a passage rate of 0.02/h in one compartmental rumen model resulted in digestibility values markedly lower than typically observed in vivo. However, applying a rumen model incorporating a selective retention of particles and time-dependent release of particles from the non-escapable pool resulted in much higher digestibility values. Recovery of lignin after 96 h ruminal incubation with a subsequent mobile-bag incubation was very low (from 244 to 460 mg/g). Intestinal disappearance of neutral-detergent fibre (NDF) and hemicellulose decreased with advancing maturity of grass and with increasing length of preceding ruminal incubation period, i.e. with decreasing potential digestibility of the material. Disappearance of hemicellulose was much greater than that of cellulose for intact grasses but the difference diminished with increasing length of preceding rumen incubation period. On average, 195 mg/g of potentially digestible NDF disappeared from the mobile bags in the intestines. The post-ruminal digestion as a proportion of the total NDF digestibility varied between 0.034 and 0.058. Despite methodological problems both in ruminal in situ and intestinal mobile bag techniques, these methods can be used to investigate ruminal and intestinal cell-wall digestion and to partition cell-wall digestibility between ruminal and post-ruminal digestion providing that appropriate rumen models are used.

The role of the large intestine in post-ruminal digestion of feeds as measured by the mobile-bag method in cattle

To study the importance of site of recovery and other factors related to mobile-bag (MB) digestion values, two consecutive experiments in which diets were applied in a 3 x 3 Latin square design, were carried out with cannulated growing heifers. In Expt 1, several types of experimental feed were exposed to intestinal digestion in mobile bags made of two cloth types and filled with intact or rumen-undegradable (RUD) feed material to be recovered either from the ileum (IB) or faeces (FB). In Expt 2, mean retention time (MRT) of Yb-labelled digesta particles within the intestine and in vivo digestibility of diets were measured. With vegetable concentrates, FB resulted generally in slight overestimation of small-intestinal dry matter and N digestion, while with meat-and-bone meal no difference between FB and IB was found. The respective N digestibility of RUD late-cut silage was clearly underestimated as measured from FB. The disappearance of neutral-detergent fibre (NDF) of all feeds under test was higher from FB than from IB. It was not possible to isolate the influence of the large intestine on the MB values by changing bag cloth type. Irrespective of the longer retention time of bags and longer MRT of Yb in the intestine on a low as compared with a high level of feeding, only NDF disappearance of feeds increased due to lower feeding level. Altering the diet type to increase large-intestinal fermentation, as indicated in vivo, usually had no effect on the MB values. It is concluded that the site of collection of bags does not practically affect small-intestinal digestion values of feed N, unless the feed is rich in fibre.

Effects of extrusion of whole horse beans on protein digestion and amino acid absorption in dairy cows

Four lactating cows fitted with ruminal, duodenal, and ileal cannulas were used to determine the effects of extrusion of whole horse beans on ruminal CP degradation and absorption of AA from the small intestine. Diets contained 15% CP, of which 46% was provided by the raw or extruded whole horse beans. Spot samples of duodenal and ileal digesta were collected during a 72-h period. The markers Cr-EDTA, YbCl3, and purines were used for liquid, particulate, and bacteria, respectively. Extruded whole horse beans increased AA flow to the duodenum and disappearance in the small intestine. Diets containing extruded whole horse beans increased availability of total essential AA in the small intestine compared with diets containing raw whole horse beans.

Use of a combined synthetic fibre bag method to estimate the true total tract digestion of organic matter and nitrogen of hay and grass silage in cows

A 4 x 4 Latin square experiment was designed to determine and compare the total tract digestion of organic matter (OM) and nitrogen of hay and grass silage by combining the ruminal and intestinal digestion estimates obtained by the rumen bag and mobile bag methods. The diets were composed of forage alone or 30% forage and 70% barley. The rumen degradation (RD) was calculated using the degradation constants a, b, and c obtained to the forages, according to the equation RD = a+bc/(c+k). Intestinal digestion of escape feeds was estimated using the feed residues that resisted rumen degradation during 16 hours. For comparative purposes, the total tract digestion was also calculated based on the actual rumen degradation of forages during 16 hours rumen incubation. The effect of dietary interaction on the digestion of forages was assessed. Rumen degradation values obtained by 16 hours incubation did not provide sufficient basis to estimate reliably the total tract digestion by the combined bag method. Using calculated RD total tract digestion of OM of hay and grass silage were rather close to conventional in vivo digestion coefficient of respective feeds similar in chemical composition, when barley was not included in the diet. With hay, but not with grass silage, barley always markedly reduced the rumen degradation and total digestion of OM. Barley supplementation always increased the proportion of feed digested in the intestine. Nitrogen digestion was always higher with grass silage than with hay, and the combined bag method produced N digestion values 17.6-22.0%-units higher than those in the feed table. Barley supplementation did not affect the N digestion of the forages.(ABSTRACT TRUNCATED AT 250 WORDS)

[Postileal nutrient digestibility in cattle]

Four heifers of an average live weight of 301 kg supplied with ileocaecal re-entrant cannulae received rations consisting of 4 kg hay (variants A und B), 1 kg coarse wheat meal, 0.4 kg molasses, 100 g urea and 30 g mixed minerals per animal and day. After a 14-day preliminary feeding period the ileum digesta was quantitatively collected at the re-entrant cannula over 24 h. 10% of the digesta were used for analysis, the remainder was heated to 37 degrees C and returned. Under consideration of the digesta passage through the colon the 24-hour collection of faeces was started after a 6-hour delay after the first replacement of digesta. Losses of nutrients were calculated from the values analysed from digesta and faeces. No differences could be ascertained between the two hay variants. On an average of the two rations the nutrient losses of the scaffold substances-equivalent to the digestibility in the colon-showed the following values: crude fibre = 10.6%, NDF = 10.4%, ADF = 11.9% and hemicellulose = 7.4%. The losses of the other nutrients, corresponding to their apparent digestibility, had the following values: crude protein = 12.1%, crude fat = 10.7%, N-free extracts = 18.9%, ash = 31.2%, dry matter = 17.5%. The water balance showed that 8.2 l water of the 23.4 l supplied with the ileum digesta were excreted in faeces.

The effect of differing types of cloth and of contamination by non-feed nitrogen on intestinal digestion estimates using porous synthetic-fibre bags in a cow

The influence of free surface area and pore size of a synthetic-fibre bag, and flow of intestinal substances into the bag, on the intestinal digestion estimates by the nylon-bag method of dry matter (DM), neutral detergent fibre (NDF), nitrogen, NDF-N and feed 15N was studied using a non-lactating cow fed on hay supplemented with barley and oats at maintenance level. The bags containing 15N-labelled ground ryegrass (Lolium perenne), barley, barley straw or rapeseed (Brassica napus) straw were introduced into the duodenum through a T-shaped cannula and collected from the faeces. Also, the disappearance of N from the bag was related to the true intestinal N digestion by comparing it with the net loss between duodenum and faeces of 15N in ryegrass introduced into the duodenum in an aqueous suspension. It was noted that the bag cloth often significantly affected both disappearance values and the subsequent chemical composition of the residues. Re-analysing part of the data as a 2 x 2 factorial (free surface x pore size) suggested that free surface area was often more important than pore size as a determinant of both disappearance values and chemical composition. Lower apparent (Kjeldahl N) than true (15N) feed N disappearance from the bag suggested a notable proportion of non-feed N in the residues, especially with fibrous feeds with low N. With ryegrass, 15N net loss within the intestine was lower than 15N disappearance from the bags. It was concluded that disappearance of Kjeldahl N is an underestimate of feed N disappearance from bags, but may possibly be an overestimate of the true intestinal digestion of feed N.

In situ evaluation of the ruminal and intestinal digestibility of heat-treated whole cottonseeds

The effect of heating whole cottonseeds on the degradability of DM and CP in the rumen and the small intestine of lactating cows was determined in situ. Whole cottonseeds were heated for 1 or 2 h at 140, 160, or 180 degrees C prior to digestion. The degradation of DM and CP was determined in dacron bags suspended in the rumen for 3, 6, 9, 24, and 48 h. Bags incubated in the rumen for 24 h were introduced into the small intestine through a duodenal cannula and subsequently recovered in feces. The effective ruminal degradabilities of DM and of CP were evaluated, assuming a ruminal outflow rate of .08/h. Heating of whole cottonseeds decreased the degradability of DM and CP in the rumen with a corresponding increase in the amounts digested in the small intestine. The calculated temperature at which this effect was first observed was 130 degrees C. Following optimal heating amount of digestible CP reaching the small intestine more than doubled. The agreement between these findings and the results of previous in vivo experiments suggest that the dacron bag technique may reliably be used for determination of nutrient availability in the intestine.

Mobile nylon bag for estimating intestinal availability of rumen undegradable protein

The objective was to develop a method for estimating intestinal availability of rumen undegradable protein. One-gram samples of six feedstuffs were placed into small (3.5 X 5.5 cm) nylon bags (pore size 48 micron). Bags were heat sealed and ruminally incubated in a polyester mesh (lingerie) bag in quadruplicate for each of six time periods (0, 2, 4, 8, 12, 24 h). Two bags from each rumen incubation time were inserted into the small intestine via a duodenal cannula at the rate of one bag per 45 min. Bags were mechanically washed either upon removal from the rumen--for determination of rumen degradability, or when recovered from the feces--for estimation of intestinal availability. Dried bags plus contents were digested intact for nitrogen analysis. Rumen degradable protein and apparent intestinal availability of undegradable protein (based on 8 h of rumen incubation) for corn gluten meal, fish meal, meat and bone meal, soybean meal, canola meal, and alfalfa hay, respectively, were 11.8, 95.0; 28.5, 82.8; 46.7, 73.0; 55.1, 99.3; 69.7, 79.2; and 68.8, 71.2. Results support the use of this technique as a rapid method for estimating both ruminal degradability, and intestinal availability of rumen undegradable protein.