Rumen Escape Research Articles

Rumen escape protein in concentrate ingredients determined with the nylon bag and enzymatic techniques

Rumen escape protein (REP) was determined for 26 concentrate feed ingredients using the nylon bag technique and in vitro using a proteolytic enzyme preparation of Streptomyces griseus. In vitro, the samples were incubated for 0, 1, 6 and 24 h. The highest correlation was observed between percentage REP (%REP), determined with the nylon bag technique, and the in vitro undegradable fraction after 1 h of incubation (%U1) ( R 2=0.77). Longer incubation times weakened the relationship. %REP could be estimated from %U1 according to: % REP=−0.76 (±5.99)+0.81 (±0.09)×% U1 . The 0 h incubation, representing in vitro solubility, had a relationship ( R 2=0.67) with in situ %REP, suggesting that %REP is mainly determined by crude protein (CP) solubility and to a lesser extent by degradation.

Apparent ruminal degradation and rumen escape of soluble nitrogen fractions in grass and grass silage administered intraruminally to lactating dairy cows.

The main objective of this study was to investigate in vivo ruminal degradation and rumen escape of soluble N fractions in grass and grass silage. Soluble protein and long-chain peptides (PLP), small peptides (SP) and free AA (FAA) were obtained from fresh grass and grass silages fertilized with different levels of N. Soluble extracts from the forages were pulse dosed into the rumen of three cannulated lactating dairy cows, and a simple or complex model was used to examine the kinetics of the soluble N fractions in the rumen. When soluble extracts from silage were investigated, pulse dosages of total nonammonia N (NAN) were 21, 27, and 32 g, while for fresh grass only dosages of 20 g were ruminally administered. In the silage extracts, mean proportions of PLP-N, SP-N, and FAA-N in the NAN were 30, 52, and 18%, respectively, whereas in the fresh grass the corresponding values were 67, 20, and 13%. From silage extracts, all three soluble N fractions showed a linear decrease (P < 0.05) in degradation rate and an increase (P < 0.05) in ruminal escape with increasing dosage. In silage, mean degradation rates, parameterized from the complex model, were 230, 214, and 334%/h for PLP-N, SP-N, and FAA-N, respectively, and the ruminal escape was highest (P < 0.05) for SP-N (11.2% of dose) and lowest (P < 0.05) for FAA-N (5.0% of dose). No differences in degradation rate and ruminal escape between fresh grass and silage were observed. However, the proportion of N dose converted to ammonia was only 24% in the fresh grass, whereas for the silages a mean value of 76% was found. From this study, it is concluded that a significant amount of dietary soluble N escapes ruminal degradation, and thus contributes to the intestinal AA supply. Moreover, if the main aim is to study degradation kinetics of individual N fractions, a complex model should be used in the evaluation. This model can also be used to study ruminal synchronization of N and energy for microbial growth.

Effects of Spontaneous Heating on Estimates of Ruminal Nitrogen Degradation in Bermudagrass Hays from Two Harvests

Estimates of rumen degradable or escape N are an important component of current nutritional models for feeding livestock, but attempts to estimate these fractions for bermudagrass [Cynodon dactylon (L.) Pers.] have been limited, and the relationship between concentrations of these fractions and spontaneous heating during bale storage has not been evaluated. The objectives of this study were to (i) assess the relationship between rumen escape or degradable N and spontaneous heating in bermudagrass hays harvested from the same site during 1998 and 1999 and (ii) correlate estimates of rumen escape and degradable N with other measures of forage nutritive value that are evaluated commonly. A preparation of Streptomyces griseus protease was utilized in an in vitro laboratory procedure to quantify rumen degradable N in hays that heated spontaneously during storage in small haystacks. Maximum temperatures in these bales ranged from 37.1 to 69.8°C over 2 yr. Rumen escape N for 40 hays ranged from 407 to 613 g kg−1 N and increased linearly (P &lt; 0.05) with all indices of spontaneous heating in both 1998 and 1999; however, r2 statistics were highest for bales made in 1998 (r2 ≥ 0.588). Similar results were observed when ruminal escape N was expressed as a proportion of plant DM. Rumen degradable N expressed as a proportion of plant DM was related to indices of heating (P &lt; 0.0001) when harvest years were evaluated together, but the slopes were not significant (P &gt; 0.05) for specific harvest years.

Effect of source of betaine on growth performance and carcass traits in lambs

An experiment was conducted to determine the effect of the source of betaine and sex on growth performance and carcass characteristics of growing lambs. A factorial structure 3×2 with dietary betaine and sex as main effects were made. A total of 60 Manchego breed lambs with an initial weight of 13kg were randomly distributed into 12 pens. Weaned males and females were fed on a starter diet until 20kg live weight (LW) and then were changed to a finisher diets up to the slaughter live weight (approx. 28kg). Within each feeding period, starter and finisher diets containing 0 or 2gkg−1 betaine (betaine anhydrous or rumen escape betaine) were used to fed each group of male and female lambs. Effect of sex was observed on daily gain, feed conversion rate, fat thickness (FT), and carcass characteristics (p<0.001); faster growth and less lipids deposition were found in males versus females. No effect of source of betaine was found on growth performance and carcass traits in male lambs. Female takes 12 more days than males to reach the slaughter live weight and more lipid depositions was observed. Reduction in fat thickness, perirenal fat and intramuscular content of lipids were found in female lambs when they were fed the diet enriched in betaine anhydrous (p<0.05). Same effect for diet with rumen escape added betaine and control were observed in male and female lambs.

Ideal amino acid profiles as a basis for feed protein evaluation

The most important single factor affecting the efficiency of protein utilization is the profile of digestible essential amino acids entering the small intestine. Assuming a constant ideal amino acid profile of absorbed protein the requirements of all amino acids can be calculated when the requirement of one individual amino acid has been determined. In non-ruminants, the supply will be greatly influenced by the diet, but less so in ruminants due to the rumen microbial degradation of feed protein and synthesis of microbial protein with high biological value. However, the high-producing dairy cow requires a significant amount of rumen escape protein. Thus, the profile of the undegraded feed protein could influence the profile of the amino acids entering the small intestine to a point at which individual amino acids become limiting. For non-ruminants, lysine is usually the first limiting amino acid in feedstuffs. This has led to the general practice of expressing the requirements for all other essential amino acids relative to lysine. Alternatively, the amino acid requirements can be expressed relative to N. Then, dietary N required for synthesis of other N-compounds is also included. Moreover, the requirements of all amino acids can be calculated when the N requirement has been determined. However, this method cannot be used for ruminants, because the N requirement of rumen microbes may be higher than the requirement of the animal. In the future, computerised animal models based on scientifically correct feed evaluation systems offer the opportunity for securing optimal feeding of farm animals in relation to their ideal amino acid profile for all different purposes of production.

Nutritional value of feed grade chickpeas for ruminants and pigs

The feeding value of feed grade chickpeas (Kabuli and Desi type) for ruminants and pigs was determined in two studies. Two ruminally fistulated cows were used in the first study to determine the effects of moist heat treatment (127 °C for 10 min) on the ruminal protein degradability of feed grade chickpeas. Heat treatment reduced (P < 0.05) soluble crude protein and increased (P < 0.05) the amount of crude protein associated with neutral detergent fibre for both types of chickpeas. Ruminal degradability of crude protein for Kabuli and Desi chickpeas was reduced by 39 and 33% (P < 0.05) respectively as a result of heating. In the second study, 64 crossbred pigs were each assigned to one of four dietary treatments in a factorial (4 treatments × 2 sexes) design experiment. The experimental barley/wheat-based diets were supplemented with either soybean meal (control), Kabuli chickpeas (300 g kg−1), Desi chickpeas (300 g kg−1) or field peas (300 g kg−1). Dry matter and gross energy digestibility coefficients, determined using the indicator method, were lower (P < 0.05) for the Desi- than for the Kabuli-supplemented diet. However, no differences were observed in dry matter or gross energy digestibility between the Kabuli chickpea-supplemented diet and the control or the field pea-supplemented diet. Diets supplemented with chickpeas or field peas had a lower (P < 0.05) crude protein digestibility than the control diet. Pigs fed either of the chickpea-supplemented diets during the growing phase gained less (P < 0.05) than pigs fed the control diet. However, during the finishing phase and over the entire experiment, dietary treatment had no effect on pig performance. There were no significant differences in carcass traits between pigs fed any of the four diets. It was concluded that moist heat treatment is an effective method to increase the rumen escape protein value of chickpeas and that the inclusion of feed grade Kabuli or Desi chickpeas in finishing diets up 300 g kg−1 had no detrimental effects on pig performance. © 2000 Society of Chemical Industry

Influence of growing conditions on rumen escape protein and chemical composition in grass

The amount of rumen escape protein is commonly determined with the nylon bag technique. However, there is also an in vitro technique described using a protease of Streptomyces griseus (Aufrère et al., 1991; Cone et al., 1996), allowing systematical analysis of protein quality in a large number of samples. The aim of this study was to identify the influences of growing conditions on content of rumen escape protein in grass and grass silage and to investigate the relationships between rumen escape protein determined in vitro and in situ and chemical composition.

Effects of protein and energy supply on the growth and carcass composition of lambs from differing nutritional histories

Effects of dietary energy and protein supply on liveweight (LW) gain and gain of protein, fat and ash in the carcass, and weight and gain of non-carcass organs were determined in 118 weaned crossbred lambs from two nutritional histories at Camden, NSW in 1991. Half of the lambs were fed to achieve and maintain LW at 35 kg (LOW group) and half of the lambs were fed ad libitum until they attained 50 kg LW (HIGH group), during a preliminary period of 126 days. In the subsequent experimental period, lambs were allocated to treatments providing 500, 800, 1200 or 1500 g/day of pelleted diets (123 g crude protein, 10 MJ ME/kg dry matter). Diets at each intake contained either 0, 30, 60 or 90 g of formaldehyde-treated casein (rumen escape protein, REP). This resulted in an experiment comparing LOW and HIGH group lambs at four energy intakes, within which were four rates of inclusion of REP. During the 90-day experimental period, LOW group lambs had higher rates of gain of LW, carcass weight and all non-carcass components than did HIGH lambs (P&lt;0·001). At any rate of carcass gain, LOW lambs contained a significantly lower proportion of fat in carcass gain than did HIGH lambs (P&lt;0·05). After adjustment to a common carcass weight, the carcass of LOW lambs contained a significantly lower mass of fat than did that of HIGH lambs at slaughter (P&lt;0·05).Carcass fat gain in the experimental period was not affected by LW at the start of that period or by nutritional history once initial LW was accounted for as a covariate. Data were consistent with fat deposition being principally controlled by energy intake over the immediate pre-slaughter period. In contrast, responses to energy intake in the rate of gain of carcass muscles, ash, liver, head and feet and gut tissue were significantly greater in lambs of LOW compared to HIGH nutritional history. A significant component of this effect of nutritional history was attributable to LW differences between LOW and HIGH lambs; however, nutritional history still had a significant effect on these parameters once initial LW was accounted for as a covariate. Nutritional history may also have modified carcass composition by changing the partial efficiency of use of available energy for protein deposition without changing the partial energetic efficiency of fat deposition.

In situ disappearance of neutral detergent insoluble nitrogen from alfalfa and eastern gamagrass at three maturities.

In situ digestion kinetics of neutral detergent insoluble nitrogen (NDIN) from alfalfa (Medicago sativa L.) harvested at one-tenth bloom and eastern gamagrass (Tripsacum dactyloides L.) harvested at the boot (GGB), anthesis (GGA), and physiological maturity (GGM) stages of growth were determined with nonlinear regression techniques. Whole-plant tissue and associated leaf and stem fractions were incubated in the ventral rumen simultaneously. On a wholeplant basis, potential extents of degradation were particularly high (> or =904 g/kg NDIN) for GGB and GGA, relative to those of GGM and alfalfa (772 and 658 g/kg NDIN, respectively). For all plant parts, degradation rates of NDIN were faster (P<.05) for alfalfa than for all gamagrass forages. Degradation rate of NDIN did not differ (P>.05) across maturities for any gamagrass tissue type. These results indicate 1) that phenological development and lignification do not limit the rate of NDIN degradation in gamagrass forages but do markedly limit the potential extent of NDIN availability and 2) that most of the NDIN in these forages is potentially available in the rumen and can contribute to the ruminal N supply. Our secondary objective was to compare estimates of N escaping ruminal degradation that were determined on the basis of NDIN degradation kinetics (NDIN method) with those determined traditionally, on the basis of total residual N. The NDIN method mathematically eliminates all neutral detergent soluble N from consideration as part of the pool of dietary N potentially escaping the rumen intact. Estimates of rumen escape nitrogen determined on the basis of degradation rates of NDIN were consistently less than corresponding estimates that were determined on the basis of total residual N. When ruminal escape N that was determined with the NDIN method was regressed on corresponding estimates with the total residual N method, the slopes of the regression lines were .53 and .66 for assumed passage rates of .02 and .06 h(-1), respectively. For the forages evaluated in this study, these results indicate that neutral detergent soluble N may make important contributions to the pool of N escaping ruminal degradation.

Influence of supplemental protein quality on rumen fermentation, rumen microbial yield, forestomach digestion, and intestinal amino acid flow in late lactation Holstein cows

The quality of dietary protein for dairy cows is generally assessed based upon the proportion of it which is expected to degrade in the rumen (DIP) vs. that which is expected to escape the rumen undegraded (UIP). However characteristics of dietary proteins can impact the nutritional value of the DIP and UIP. Four lactating Holstein cows were fed a low protein (9.8% CP of DM) ration of 28.6% timothy silage, 27.2% whole crop barley silage, and 44.2% grain-based concentrate (DM basis). This was supplemented with 1.3 kg d−1 of ground barley with either no additional protein supplement, 1.11 kg d−1 of soybean meal, 0.67 kg d−1 of blood meal or 0.20 kg d−1 of urea. All cows were judged to have underperformed relative to expectations, with performance limited by supplies of DIP and/or UIP with all diets. Soybean meal supplementation substantially improved animal performance and measured parameters of N metabolism are consistent with a hypothesis that rumen bacterial growth and outflow, rumen escape of intact dietary protein, and the ability of animal metabolic processes to utilize absorbed energy yielding nutrients for productive purposes were all enhanced. Urea and blood meal supplementation both improved animal performance to a similar extent; although to a lesser degree than soybean meal. Measured parameters of N metabolism suggest that urea stimulated rumen bacterial growth and outflow leading to increased intestinal delivery of protein whereas blood meal supplementation enhanced intestinal delivery of protein due to its very high proportional escape from the forestomachs. Key words: Duodenum, amino acids, protein, protozoa, phosphatidylcholine

Prediction of the rumen fermentable organic matter content by an enzymatic method

In the Dutch protein evaluation system (Tammingaet al., 1994) microbial protein synthesized in the rumen is estimated from the fermentable organic-matter (FOM) content. The reference method to determine FOM is byin situincubations of food in the rumen of fistulated animals. However, this is a cumbersome, time-consuming and expensive procedure. In practice, FOM is estimated from the digestible organic-matter content (DOMD) corrected for crude fat (Cfat), rumen escape protein (EP) and starch (ES) and the fermentation products (FP), using tabular values. Apart from being indirect, this approach takes little or no account of the variability within foods. Although anin vitromethod based on rumen fluid may give a good prediction ofin situFOM for the majority of the foodstuffs (Coneet al., 1994), an enzymatic method is preferable for practical reasons. From the organic-matter (OM) degradation by a mixture of amylase and other carbohydrate degrading enzymes at 39°C during 0, 2, 6 and 24 h, Coneet al. (1996) obtained a moderate correlation within situFOM for 29 grass and grass silage samples (R2= 0.88; residual s.d. = 37 g/kg dry matter (DM)) and 80 samples of concentrates, maize and clover (R2= 0.77; residual s.d. = 42 g/kg DM). In this study a modified version of the enzymatic method of de Boeveret al. (1994), normally used to predict thein vivoOM digestibility and energy value of concentrates, was tested for its reliability to predictin situFOM of compound foods and forages.

Rumen Escape and Apparent Degradation of Amino Acids After Individual Intraruminal Administration to Cows

Apparent rumen degradation and escape of 18 amino acids (AA) after individual administration intraruminally were studied using two nonpregnant, nonlactating, rumen-cannulated cows fed a ration containing hay and concentrate twice daily. The pulse-dosages of AA were 75, 150, 300, and 600 mmol. Polyethylene glycol was used as the liquid marker.Rates of apparent degradation during the first 60min (initial degradation) varied markedly among the AA; rates were highest for Ser, Asn, Glu, and Gln and lowest for Tyr, Val, Arg, and His. At the 75-mmol dosage, which corresponded to an initial substrate concentration of about 1mM of rumen fluid, initial degradation varied between 95 and 40% of the dosage, depending on the AA. Rates, expressed as percentages of the dosage, decreased as dosages increased.During the first 8h after administration, escape of the AA increased from a mean of 9% at the lowest dosage to a mean of 21% at the highest dosage. At the highest dosage, Met caused a net increase in the concentration of 11 of the other AA in rumen fluid. Twelve of the AA administered caused a net increase in the concentration of Ala in rumen fluid.Methionine and Lys are among the AA considered to be limiting to milk yield. These AA showed relatively high rumen escape values and may be useful as feed supplements even in an unprotected form.

Potential of solubility, enzymatic methods and NIRS to predict in situ rumen escape protein

The percentage of feed protein escaping rumen degradation was measured by the in situ method (%EPsitu) for 29 compound feeds, untreated and formaldehyde-treated soyabean meal and 12 forages: 3 grass silages, 2 maize silages, fresh grass, grass hay, fodder beets, fresh potatoes, ensiled beet pulp, chopped ear-maize silage and brewers' grains. Loss of particles through bag pores was determined by the difference between the washable fraction (W) and the fraction soluble in borate-phosphate buffer at pH 6.7 (S). W - S was most pronounced for compound feeds (on average 14.4 percentage units), for brewers' grains and maize silages. A correction of %EPsitu, assuming that W - S degrades like the potentially degradable fraction, was not appropriate. Solubility in borate-phosphate buffer after 1 h, enzymic degradability by protease from Streptomyces griseus or ficin after 1, 6 and 24 h and near infrared reflectance spectroscopy (NIRS) (for compound feeds alone) were examined as a routine method to predict %EPsitu. With the buffer and S. griseus the effect of pH (6.7 vs. 8.0) and at pH 8.0 the effect of amount of substrate (500-mg sample vs. 20 mg N) were tested. With ficin, 500-mg samples were incubated at pH 6.7. Predictions were better when compound feeds and forages were considered separately. However, the best in vitro method was different for the 2 feed categories, being solubility in buffer for the compound feeds and enzymic degradation of a constant amount of protein with S. griseus at pH 8.0 for forages. NIRS showed potential to predict %EPsitu of compound feeds, but needs more reference samples. The Dutch feed tables appeared more accurate than the best in vitro method for compound feeds, but was too inaccurate for some forages like fodder beets, maize silage and ear-maize silage.

Interrelationships between amino acid and glucose metabolism in lambs of different dietary history supplemented with rumen escape protein

Changes in amino acid and glucose metabolism in response to increments of rumen escape protein (REP) were studied in groups of lambs of three differing dietary histories and consequent weights, but similar ages. Crossbred wether lambs (Merino × (Border Leicester × Merino)) were fed to obtain three distinct growth patterns. The LW group (n = 15) were offered a low quality roughage diet throughout the experiment. The MW group (n = 19) were offered a high quality mixed diet followed by the same low quality diet as LW lambs. The HW group (n = 8) were offered a high quality mixed diet throughout. All diets were offered once daily ad libitum. The LW, MW and HW groups had liveweights of 18, 32 and 41 kg respectively at the commencement of supplementation, and were 33±0·1 weeks of age. REP supplements (formaldehyde-treated casein) were offered at 0, 20, 40, 60 or 80 g/day to MW and LW lambs and at 0 or 40 g/day to HW lambs.REP increased basal digestible organic matter intake (DOMI), liveweight gain (LWG) and urinary N excretion and tended to increase N balance in LW and MW lambs. DOMI, N intake, N balance and LWG were all higher (P &lt; 0·05) in HW compared to MW and LW lambs. REP tended (P &lt; 0·10) to increase LWG in each dietary history group.Blood glucose concentration was higher (P &lt; 0·01) in HW than in other lambs but was not significantly altered by REP supplementation. Irreversible loss of glucose was greater (P &lt; 0·01) in HW lambs and increased (P &lt; 0·001) with REP for LW and MW lambs. REP increased (P &lt; 0·05) phenylalanine (Phe) concentration in blood, Phe flux and oxidation and whole body rates of protein synthesis and degradation. HW lambs had higher (P &lt; 0·05) values for all these parameters than did MW and LW lambs.REP increased (P &lt; 0·05) plasma concentrations of insulin-like growth factor-1, and plasma insulin increased (P &lt; 0·05) in MW but not in LW or HW lambs. REP had no effect on plasma growth hormone (GH) concentration. Plasma concentration of insulin was higher (P &lt; 0·05) in HW than in MW or LW lambs, while GH was not significantly affected by dietary history.The results show that supplementation of ruminant diets with REP increases the rate of flux and oxidation of amino acids, and the rate of glucose utilization. Amino acid supply appears to influence glucose utilization more through oxidation rate than supply, and this relationship is affected by previous dietary history (weight for age) and energy availability, either from the diet or from body stores.

A comparative study on amino acid availability of moist heated canola meal for poultry vs. ruminants

The objectives of this work were to measure the effect of moist heat treatment of canola meal (CM) on AA availabilities in poultry relative to ruminants, and to determine whether CM heated to increase rumen escape of protein could be used for poultry. Four groups of nine cockerels were randomly assigned to one of four treatments: untreated CM (control), CM moist heated (127°C) for 15 min, 45 min, and 90 min. Bioavailabilities of AA in CM for poultry were determined using the force-fed rooster technique. The resulting true available AA (TAAA) values were then compared with small intestinal AA disappearance values which were determined in steers. In poultry, 15 min heat treatment had no negative effects ( P > 0.05) on the TAAA values of all essential AA except methionine, lysine, and threonine which were reduced ( P < 0.05). Prolonged heat treatment (90 min) reduced ( P < 0.05) the TAAA values of all essential AA. In terms of amounts of available AA (g kg −1 DM CM), 15 min heat treatment did not influence ( P > 0.05) available methionine, threonine, phenylalanine, tryptophan and arginine, and increased ( P < 0.05) amounts of available leucine, isoleucine, histidine, and valine. Amount of available lysine was reduced (P < 0.05) by 11.8 g kg −1 initial lysine. Nylon bag results with steers indicated that 15 min heat treatment maximized the ( P < 0.05) small intestinal disappearance of all the individual essential AA and, also, increased amounts of available AA. Supplementation of the 15 min moist heated CM with lysine would be required for CM intended for poultry.

Prediction ofin situ Rumen Escape Protein fromin vitroIncubation with Protease fromStreptomyces griseus

Research was performed to determine in vitro the amount of rumen escape protein in mainly concentrate feedstuffs by incubation with a proteolytic enzyme preparation of Streptomyces griseus, with 24 feed samples with known in situ crude protein degradation characteristics. A close correlation (R 2 = 0.75) was found between the percentage of escape protein, calculated from the in situ and the in vitro methods. However, the percentage escape protein in situ could be estimated with a greater accuracy (R 2 = 0.80) using the undegraded fraction determined in vitro after 24 h incubation. Expressing escape protein as g kg -1 DM instead of a percentage, further improved the correlation with the amount of escape protein in situ (R 2 = 0.95). The amount of escape protein in situ could be estimated with similar accuracy from the undegraded crude protein fraction determined in vitro after 24 h incubation (R 2 = 0.92). Estimation of the amount of escape protein in situ did not improve with pre-incubation of the samples with amylase and carbohydrate degrading enzymes.

Protein and amino acid nutrition of lactating dairy cattle—today and tomorrow

The Cornell Net Carbohydrate and Protein System was used to (1) estimate absorbed amino acids provided by rumen escape protein and (2) formulate rations on the basis of amino acids. Forages, even those high in crude protein, only provide small amounts of rumen escape amino acids. Maize proteins are deficient in lysine. Oil seed proteins contain low levels of methionine. Animal and marine proteins, because of their high crude protein and low ruminal degradation, can be used to adjust the amino acid profile of absorbed protein, especially methionine (fish meal) and lysine (blood meal) Rations to support high levels of milk production need to contain protein sources with amino acid profiles that are complementary.

Rumen degradation and post-ruminal digestion of palm kernel by-products in dairy cows

Rumen degradation characteristics and digestion post-rumen were measured in seven (five expellers and two meals) samples of palm kernel by-products using four cannulated (rumen and distal duodenum) dairy cows and nylon bag techniques. The by-products were selected to provide variation in chemical composition and in vitro digestibility. All samples contained high levels of cell wall constituents (70–80% of the fat-free organic matter) and 16–22% protein. The rumen undegradable fraction of neutral detergent fibre (NDF) varied between 23 and 37%; degradation of the NDF fraction was preceded by a lag phase, which was longest in the meals. Rumen degradation of the protein fraction was slow, especially for two Nigerian samples. The meals displayed larger fractions of rumen undegradable protein than the expellers. This fraction was satisfactorily predicted by a univariate relationship with in vitro digestion of protein (pepsin). Variation in protein degradation could not be satisfactorily accounted for by laboratory analyses using fungal proteolytic enzymes alone. The estimated high level of rumen escape protein may be partly attributable to microbial contamination. Post-ruminal digestion of the escape protein varied between 83 and 92% and correlated strongly with in vitro (pepsin) protein digestibility. Calculations suggest a slow rate of outflow from the rumen of both cell wall and protein constituents in palm kernel by-products.

Effect of rumen escape amino acids and multiple TBA implants on feedlot performance of lightweight Holstein steer calves (1995)

Effect of rumen escape amino acids and multiple TBA implants on feedlot performance of lightweight Holstein steer calves (1995)

Effect of extruding on ruminal disappearance and lower gastrointestinal tract digestion of white lupin seeds

The effect of extruding white lupin (Lupinus albus 'Lublanc') seeds (WLS) at 110, 130, 150 or 180 °C on the in vitro solubility of crude protein (CP) and in sacco rumen degradation and intestinal digestion of rumen escape CP and fiber was determined. Rumen degradation was estimated by incubating nylon bags in the rumen of cows for 2, 4, 8, 16, 24 and 48 h. Extruding WLS at 110, 130, 150 and 180 °C reduced the CP-solubility by 32.8, 47.7, 58.4 and 67.5%, respectively. The effective ruminal degradabilities of CP, acid detergent fiber (ADF) and neutral detergent fiber (NDF) were evaluated assuming a ruminal outflow rate of 0.06 h−1. Heating WLS at 110, 130, 150 and 180 °C decreased the ruminal degradability of CP value: 89.8, 79.9, 65.1, 61.8 vs. 93.4% (raw), respectively; the corresponding values for ADF and NDF were: 38.4, 35.3, 34.2, 27.6 vs. 43.6% (raw) and 37.7, 33.1, 32.2, 26.5 vs. 39.4% (raw). Postruminal digestion was estimated using a sequence of ruminal in situ incubation for 4, 8 and 16 h, in vitro incubation in an acid-pepsin bath for 3 h and a mobile nylon bag technique distal to the abomasum. Extrusion of WLS decreased the degradability of CP, ADF and NDF in the rumen with a corresponding increase in the amounts digested in the postruminal sections; the whole-tract digestibility was generally unchanged. Therefore, the processing shifted the digestion of these components from rumen to the lower gastrointestinal tract. Key words: White lupin seed, in vitro solubility, rumen degradability, postruminal digestion, crude protein, detergent fiber