NDF Disappearance Research Articles

Effects of Buffer Additions on Fermentation of Dormant Range Grasses

Replicated two-stage in vitro studies were conducted to determine the effects of single amino acid or branched-chain volatile fatty acid buffer additions on in vitro dry matter disappearance, neutral detergent fiber disappearance, and fermentation kinetics of dormant range grasses. Substrates consisted of separate samples of 2 cool season mid-grasses, western wheatgrass (Agropyron smithii Rydb.) and Japanese brome (Bromus japonicus Thunb.), and a mixture of warm season shortgrasses, buffalograss (Bunchloe dactyloids [Nutt.] Engelm.), and blue grama (Bouteloua gracilis [H.B.K.] Lag. ex Steud.), hand clipped from standing forage in mid-March. Isonitrogenous treatments included buffer containing urea with or without amino acids, branched-chain volatile fatty acids, sodium sulfate, or starch. Urea increased (P < 0.05) in vitro dry matter disappearance and in vitro neutral detergent fiber disappearance of the cool season grasses over N free buffer. Methionine addition increased (P < 0.05) in vitro neutral detergent fiber disappearance and rate of fermentation of both cool season grasses and in vitro dry matter disappearance of Japanese brome over urea alone. Sodium sulfate increased (P < 0.05) in vitro neutral detergent fiber disappearance of Japanese brome compared to urea alone. None of the branched-chain volatile fatty acids tested increased dry matter disappearance, neutral detergent fiber disappearance, or rate of fermentation of the dormant range grasses. Addition of urea or amino acids did not increase in vitro dry matter disappearance or in vitro neutral detergent fiber disappearance of the shortgrass mixture. In vitro screening of amino acid and branched-chain volatile fatty acid buffer additions to dormant range grasses showed that methionine supplementation with urea offers the greatest potential, among the supplements evaluated, for improving digestibility and rate of fermentation of cool season grasses. None of the buffer supplements improved fermentation of the warm season grasses.

Rumen disappearance of organic matter, crude protein, crude fibre, ADF and NDF from grasses, white clover and grass-white clover mixture

Rumen disappearance of organic matter, crude protein, crude fibre, ADF and NDF from grasses, white clover and grass-white clover mixture

Rumen disappearance of organic matter, crude protein, crude fibre, ADF and NDF from grasses, white clover and grass-white clover mixture

Rumen disappearance of organic matter, crude protein, crude fibre, ADF and NDF from grasses, white clover and grass-white clover mixture

Effects of an Enzyme Addition on Corn Silage Fermentation

Whole plant corn silage was ensiled for 0, 2, 6, 14, 30, and 50 d in triplicate plastic silo bags, with or without addition of a commercial cellulase and xylanase enzyme mixture (230mL/ton). After each fermentation period, silage was removed and analyzed for DM, pH, water soluble carbohydrates (WSC), Total N, ADF, NDF, and lactic acid. Samples from 50 d silage bags were analyzed for in situ DM and NDF disappearance.Aerobic stability of silage was recorded upon opening 30 d silage bags. No differences were noted for pH, DM, or ammonia (percentage of total N). The WSC content (DM basis) was higher (P<.05) at 6 d for enzyme-treated silage (4.27 vs 3.91%). Increases in lactic acid levels for treated silage were noted after 2 d of fermentation, however this was significant only at 30 d (P<.10). Reductions in ADF and NDF concentrations were significant at 50 d for enzyme-treated silage (P<.10). No differences were observed for in situ disappearance of DM. After 48h of ruminal incubation, control silage had higher NDF disappearance. Following 3 d of silage exposure to air, temperature of enzyme-treated silage rose dramatically and declined to temperatures similar to the control at 5 d. Although silage was lower in ADF and NDF after 50 d of fermentation, these data suggest that an application of a commercial enzyme mixture to corn silage did not appreciably change silage fermentation or composition.

Ruminal characteristics, microbial populations, and digestive capabilities of newly weaned, stressed calves2

Eight ruminally fistulated steers, 7 to 8 mo old, were used in a completely randomized, 2 x 2 factorial experiment to determine the effects of energy density and protein source in receiving diets on in situ DM, NDF, and N disappearance, concentrations of ruminal bacteria, protozoa, ammonia, and pH. Two energy densities (1.80 and 1.48 Mcal/kg of NEm) and two protein sources (spray-dried blood meal [SDBM] and soybean meal [SBM]) were compared. Fistulated steers were weaned, transported by truck, and held in a sale barn before their arrival at the feedlot. On d 0 (day of arrival at the feedlot), DMI was 62% of DMI on d 7 after arrival. Overall, feeding a high-energy diet resulted in lower (P < .01) in situ DM disappearance (DMD) of orchardgrass than feeding a low-energy diet at both 24 and 48 h. In situ 24-h DMD averaged 46.6% on d-3 and 41.6% on d 0, whereas 48-h in situ DMD on d -3 and 0 averaged 58.2 and 58.6%, respectively, indicating the ruminal microbial population was not inhibited in its ability to digest available substrate. Additionally, there were no differences (P > .10) in 48-h in situ NDF disappearance between d -3 and 0 (58.8 vs 57.8%), respectively. No differences (P > .10) occurred in the concentration of total bacteria, or cellulolytic bacteria, due to feed and water deprivation. Concentration of total protozoa was lower (P < .05) on d 0 than at any other time. Entodinium averaged 72.5% of genera before weaning, and more than 90% of genera found on all treatments by d 21. Diplodinium and Epidinium percentages tended to decline after weaning. Isotricha concentrations were low and Dasytricha were eliminated after d 7. In conclusion, the concentration of ruminal bacteria and the ability to digest available substrate were not decreased immediately after weaning, trucking, and 24 h of feed and water deprivation.

Influence of yeast culture supplementation and advancing season on steers grazing mixed-grass prairie in the northern Great Plains: I. Dietary composition, intake, and in situ nutrient disappearance3

Twelve beef steers (368 +/- 25.3 kg) and four beef heifers (559 +/- 79.5 kg) fitted with ruminal cannulas were used to evaluate effects of yeast culture (YC) and advancing season on dietary chemical composition, intake, and in situ CP and NDF degradation. Treatments were control and YC supplementation (28.4 g.steer-1.d-1 dosed ruminally). Steers grazed from late June to early November 1991 on mixed-grass prairie. Experimental periods consisted of 10 d for adaptation and a 13-d collection phase. Forage samples collected from YC-supplemented steers had greater (P < .10) soluble N and in vitro OM disappearance than forage from controls throughout the grazing season. Organic matter intake was greater (P < .10) by YC-supplemented steers during June. Fecal output and OM intake increased (P < .10) from June to September. Increases (P < .10) in in situ NDF disappearance were noted at 8, 16, and 24 h in June, at 8, 48, and 72 h in July, and at 8 h in August for the YC treatment group. Supplemental YC did not affect (P > .10) rate or lag time of NDF disappearance. In situ CP disappearance (ISCPD) was greater (P < .10) at all times except 48 h in June, at 48 and 72 h in July, and at 0, 4, 8, and 12 h in August for YC-supplemented steers. Steers supplemented with YC had an increased extent (P < .10) of ISCPD in July and an increase in CP degradation rate in June; however, total CP degradation was greater (P < .10) during June for control than for YC steers.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of replacement of wheat bran by graded levels of molasses on digestion, degradation and digestion kinetics of fibre and rumen digesta pool size in crossbred ( Bos taurus × Bos indicus) steers fed native grass hay

This 4 × 4 Latin square experiment evaluated the effect of replacement of wheat bran by graded levels of sugar cane molasses on digestibility, degradation of fibre, digestion kinetics of fibre and rumen pool sizes. Four ruminally fistulated crossbred ( Bos taurus × Bos indicus) steers were given a basal diet of grass hay ad libitum and 4.0 kg dry matter (DM) of wheat bran day −1 (Diet M0). The other three diets consisted of replacement of wheat bran with 1.0 (Diet ML), 2.0 (Diet MM) or 3.0 (Diet MH) kg DM of molasses. Urea was used to make the three diets (ML, MM and MH) isonitrogenous with the basal diet (M0). Intake and digestibility of neutral detergent fibre (NDF) decreased from 4.65 to 3.31 and 0.65 to 0.55 (linear effect, P < 0.01) with increasing levels of molasses. Similarly, NDF digestion expressed as a proportion of potentially digestible NDF decreased linearly ( P < 0.01) when the level of molasses increased. The disappearance of hay DM from nylon bags decreased (significant linear effect after 48 h incubation period and onwards, P < 0.05) with increasing wheat bran substitution by molasses. The disappearance of NDF of hay from nylon bags decreased significantly only at 48 h (linear effect, P < 0.01) and at 96 h (quadratic effect, P < 0.05) when the amount of molasses increased. Although there were differences between diets in rumen pool sizes of DM, NDF and in digestion kinetics of NDF, these were not, in general, explained by polynomial orthogonal contrasts. Increasing the level of molasses caused a clear linear effect ( P < 0.01) only for rate of digestion ( k d) of NDF and true rate of digestion ( k dt) of NDF. There was also a quadratic effect ( P < 0.01) for rate of passage ( k p) of indigestible NDF, showing that diets ML and MM had greater rate of passage compared with the other two diets when the level of molasses was increased.

Effect of calcium salts of fatty acids on rumen function and the digestibility of rations by sheep

AbstractExperiments were conducted to determine the effects of supplementing chopped ryegrass hay with 0, 1.5, 3, 6 or 12% calcium salts of fatty acids (CaSFA; Megalac) on digestion in the rumen of cannulated cows and on nutrient digestibility by sheep. In‐situ ruminal disappearances of dry matter (DM) and cell wall fractions (acid detergent fibre, ADF, and neutral detergent fibre, NDF) were measured by the nylon bag technique. The DM, ADF and NDF disappearances were reduced for diets containing CaSFA at the 1.5, 3 or 6% levels after 48 h of rumen exposure. For diets containing 12% CaSFA, irrespective of the time of rumen incubation, DM disappearance was decreased, while ADF and NDF breakdown was improved. CaSFA supplementation did not influence invitro fermentation characteristics (pH, volatile fatty acid patterns). A digestibility experiment with six mature sheep showed no difference in nitrogen digestibility between unsupplemented and CaSFA‐supplemented diets. However, digestibilities of DM, ADF and NDF were higher relative to the basal for the 12% CaSFA: 63.1 versus 60.6%, 63.8 versus 58.7% and 67.4 versus 62.7%, respectively. Ether extract digestion was enhanced by increasing the level of CaSFA, the corresponding values being 49.1, 66.5, 78.6, 81.9 and 77.9% at 0, 1.5, 3, 6 and 12% CaSFA, respectively. Apparent digestibility of energy was higher for the 12% CaSFA than the control diet 68.8 versus 62.1%). Nitrogen and energy retention was improved due to the decreases in urine and faecal excretion, respectively.

Co-product fiber digestibility: kinetic and in vivo assessment

Nutrient digestion and kinetic characteristics of alfalfa hay, brewers grains, beet pulp, and cottonseed hulls were studied in two experiments. In the first experiment, these feedstuffs were fed with a mineral/vitamin supplement in a 4 x 4 Latin square to eight ewes to determine total tract digestibilities by 8-d total collection and rates of passage using Yb as a marker. In the second experiment samples of the same feedstuffs were incubated in situ in four ruminally fistulated steers in a 4 x 4 Latin square design to quantify ruminal disappearance of NDF and ADF. Three Dacron bags were placed in the rumen for each of six time periods: 6, 12, 24, 48, 72, and 96 h. Total tract digestibilities of DM ranged from 33% for cottonseed hulls to 78% for beet pulp. Digestibilities of NDF ranged from 32% for cottonseed hulls to 81% for beet pulp. Total tract retention times ranged from 74 h for beet pulp to 44 h for alfalfa. Retention time for alfalfa was lower (P < .05) than those for beet pulp or cottonseed hulls. Calculation of TDN values yielded values similar to those of NRC other than for cottonseed hulls, for which NRC values were 18 to 29% higher. Alfalfa hay and beet pulp were the feedstuffs with the most rapidly disappearing NDF, .124/h for alfalfa and .116/h for beet pulp, which were faster (P < .05) than those found in brewers grains and cottonseed hulls, .035 and .043/h, respectively. Potentially digestible NDF ranged from 55% for alfalfa hay to 94% for beet pulp.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of Enzyme-Inoculant Systems on Preservationand Nutritive Value of Haycrop and Corn Silages

Third-crop mixed grass-legume forage and corn were ensiled in 70-tonne bunker silos to evaluate the effects of a commercial carbohydrase enzyme-inoculant mixture (220 ml/tonne) and an experimental enzyme-inoculant mixture (264 ml/tonne) on silage fermentation and composition, ruminal degradation, and milk production. Twelve Jersey and 24 Holstein early lactation cows were fed one of four TMR at 32.5:32.5:35.0 haycrop silage:corn silage:concentrate (DM basis) containing a combination of treated and untreated silages from d 2 to 100 of lactation. Bunker silages were incubated twice in situ in fistulated cows in each dietary treatment to determine rates of DM and NDF degradation. Treatment of haycrop silage significantly reduced silage pH and acetic acid concentration and increased titratable acidity, lactic acid concentration, lactate: acetate ratio, and DM and NDF disappearances after 24h of ruminal incubation. Treated haycrop silage increased DMI:BW ratio and daily production of milk, milk protein, and SNF of early lactation cows. Application of the experimental mixture to corn silage did not change silage fermentation or composition, except that the concentration of NH3 was reduced. Enzyme-treated corn silage did not improve DMI and slightly reduced daily milk production in early lactation cows.

Effects of substituting feather meal for soybean meal on ruminal fiber fermentation and lamb and wool growth.

Our objective was to evaluate the effects of substituting feather meal (FM) for soybean meal (SBM) on ruminal fiber fermentation, lamb gain, blood metabolite profiles, and wool growth. A SBM supplement was formulated, and FM replaced either 33% (33FM), 66% (66FM), or 100% (FMS) of the SBM protein. Four ruminally cannulated wethers were used in a 4 x 4 Latin square design to study in situ ruminal digestion. Wethers were limit-fed barley straw and fed the supplements once daily. Ruminal NH3 N concentrations reflected a sampling time x protein source interaction (P < .01). Within sampling times, ruminal NH3 N concentrations decreased linearly (P < .05) as FM replaced soybean meal. Cubic (0 h; P < .10) and quadratic (24 h; P < .05) responses also were noted for ruminal NH3 N concentration. Substitution of FM for SBM had no effect (P > .10) on rate and extent of straw NDF disappearance. A 56-d feeding trial was conducted using 28 wether lambs (n = 7 per treatment; initial BW 32.3 kg). Wethers were individually fed chopped barley straw and one of the four supplements described previously. Linear increases (P < .05) in BW gain and serum total protein concentration were observed as FM replaced SBM. Wool fiber diameter and sulfur content did not differ (P > .10) among treatments. These data suggest that FM can be substituted for SBM in protein supplements fed to sheep consuming low-quality roughages at a maintenance level of ME intake.

Influence of methylamine on anaerobic rumen bacterial growth and plant fiber digestion

Anaerobic rumen bacteria were screened for growth inhibition by methylamine. Under nitrogen-limited growth conditions only Ruminobacter amylophilus, Prevotella ruminicola and Megasphaera elsdenii were significantly inhibited. Ruminobacter amylophilus was inhibited more than any other species. Inhibition of R. amylophilus growth occured at all increments in methylamine for all NH 4Cl concentrations tested (0·2–1·8 m m). Dimethylamine was less inhibitory, while trimethyl-, ethyl- and diethylamine were not inhibitory. When methylamine was added to in vitro mixed culture, ruminal fermentations containing alfalfa, neutral detergent fiber disappearance and ammonia production were not affected. This suggests that although methylamine may inhibit specific rumen bacteria, it does not alter overall mixed ruminal microorganism activities with alfalfa as a substrate.

Effect of ammonia treatment of barley straw on the dynamics of its degradation in the rumen

AbstractTwo experiments were designed to examine the effects of ammonia treatment of barley straw on rumen environmental conditions for fibre degradation, and to determine the effect of treatment on the soluble and insoluble fractions of straw. In experiment 1, rumen pH, and ammonia-nitrogen and volatile fatty acid concentrations in the rumen of sheep receiving untreated (US1) or ammonia-treated (TS1) straw were recorded. Also, both straws were incubated in the rumen of both groups of animals. There were no significant differences (P&amp;gt; 0·05) within rumen parameters, except for butyrate proportion, which was higher (P&amp;lt; 0·01) with TS1. Dry matter and neutraldetergent fibre disappearances of TS1 were higher (P&amp;lt; 0·001) than those of US1 at all the incubation times. Degradation of both straws in US1-fed sheep was not smaller, and in some periods of incubation was even greater, than in TS1-fed animals. In experiment 2, samples of untreated (US2) and treated (TS2) straw were incubated in wethers offered a mixture (50:50) of alfalfa hay and straw. Samples of US2 and TS2 were soaked in autoclaved rumen fluid to measure their solubility. It was clear that, although treatment increased the soluble fraction of US2 and TS2 by 52 and 65 g/kg respectively, from 0 to 72 h of incubation, increasing the differences between straws from 45 to 58 g/kg in that period, actual microbial action on the treated roughage was the more important factor, accounting for a difference between US2 and TS2 of 131 g/kg after 72 h incubation.

Influence of forbs and shrubs on ruminal fermentation and digesta kinetics in sheep fed a grass hay/straw diet

Four ruminally cannulated, Debouillet wethers were used in a 4×4 latin square experiment to evaluate the influence of a forb mix, a shrub mix and alfalfa (ALF) hay on ruminal fermentation characteristics and digesta kinetics of a basal grass hay/straw (GH/S; 1.04% N) diet. The grass hay was mostly blue grama (Bouteloua gracilis) mixed with barley (Hordeum vulgare) straw. Wethers were fed either the GH/S mix (70∶30), GH/S∶ALF (29∶58∶13), GH/S∶forbs (26∶54∶20), or GH/S∶shrubs (26∶54∶20). The forb component consisted of equal parts of scarlet globemallow (Sphaeralcea coccinea) and leatherleaf croton (Croton corymbulosus) while shrubs were composed of equal parts of fourwing saltbush (Atriplex canescens) and mountain mahogany (Cercocarpus montanus). Ruminal pH, ammonia-N, as well as total VFA concentrations and molar proportions of individual VFA did not differ among diets. Particulate passage rates tended (P>0.10) to be greater for diets containing ALF, forbs or shrubs (2.8, 2.9 and 2.8% h−1) than the GH/S diet (2.5% h−1). In situ DM and NDF disappearance of a GH/straw (50∶50) mix did not differ among treatments at most incubation times, except at 96 h when extent of both DM and NDF disappearance were greater (P<0.05) in sheep fed either forbs or shrubs than in those fed other diets.

Effects of pregnancy on digesta kinetics and ruminal fermentation in beef cows.

Four pregnant and four nonpregnant, ruminally cannulated beef cows were used to evaluate the effects of the last trimester of pregnancy on digesta kinetics and ruminal fermentation. Before breeding, cows were allotted randomly either to pregnant (PR) or to nonpregnant (NP) groups; PR cows were bred at the first estrus after synchronization. All cows were fed long-stem fescue hay at 15 g of DM/kg of BW based on BW 120 d before parturition of pregnant cows (average BW of 642 kg). Collection periods, each lasting 9 d, began at 96, 68, 41, and 10 +/- 1.3 d before parturition. Particulate passage rate was greater (P < .05) and retention times and gastrointestinal fill were less (P < .05) for PR than for NP cows. Apparent total tract DM digestion, rate and extent (96-h in situ incubation) of NDF disappearance, and ruminal fluid kinetics were not affected (P > .10) by pregnancy. A physiological state x sampling day interaction was noted (P < .05) for ruminal NH3 N, total VFA concentrations, and molar proportions of butyrate. Ruminal pH and individual VFA proportions, however, did not differ (P > .10) between PR and NP cows, except for valerate, which was less (P < .05) for PR than NP cows. Results suggest that in late pregnancy with restricted feeding, passage rate of particulates increases without substantial changes in fermentation or extent of digestion.

Supplemental methionine and time of supplementation effects on ruminal fermentation, digesta kinetics, and in situ dry matter and neutral detergent fiber disappearance in cattle.

Two experiments were conducted to study the effects of methionine supplementation on ruminal fermentation and digesta kinetics. In Exp. 1, nine ruminally cannulated beef heifers (average initial BW = 527 kg) in a crossover design were fed low-quality grass hay and cottonseed meal with or without 11.4 g of supplemental methionine (polysaccharide-coated). Particulate and fluid kinetics, rate of DM and NDF disappearance, ruminal VFA and NH3 N concentrations, and pH were not altered (P > .10) by supplemental methionine; however, ruminal purine concentration was greater (P < .05) in methionine-supplemented heifers than in unsupplemented heifers. In Exp. 2, 12 ruminally cannulated Holstein steers (average initial BW = 622 kg) grazing a fescue pasture were allotted to one of three groups: no supplemental methionine (CON) or 11.4 g of supplemental methionine fed at 0700 (AM) or at 1200 (PM). Forage intake, particulate kinetics, ruminal fluid kinetics, pH, VFA, and NH3 N concentrations were not altered (P > .10) by supplemental methionine or supplementation time. In situ rate of DM and NDF disappearance was greater (P < .05) in supplemented steers than in CON steers; AM steers exhibited faster (P < .05) rates than PM steers. Overall, methionine supplementation of low-quality forage increased ruminal purine concentration but did not alter in situ fermentation or digesta passage, whereas supplementation at 0700, but not at 1200, of steers grazing fescue forage increased rate of NDF fermentation.

Effects of forage species and particle size on bacterial cellulolytic activity and colonization in situ

Two ruminally cannulated Holstein heifers were used to evaluate effects of three forage species and two particle sizes in a 3 x 2 factorial arrangement on in situ fiber disappearance and carboxymethylcellulase activity (CMCase). A second objective was to compare CMCase and 15N as relative bacterial colonization markers. At time zero, 15N-enriched ammonium sulfate was dosed into the rumen. Residues in nylon bags incubated for 3, 6, 9, 12, 18, 24, 30, 36, 42, 48, 60, and 72 h were analyzed for NDF, ADF, CMCase, and 15N. Rates of NDF and ADF disappearance were faster (P < .05) for red clover (RC) than for gamagrass (GG) or orchardgrass (OG) and for forages ground to pass a 2-mm screen (P < .05) than for those ground to pass a 5-mm screen. Cumulative area under the curve (AUC) of CMCase activity was related to both NDF disappearance (r2 = .93) and 15N AUC (r2 = .99), indicating that CMCase can be used to estimate relative colonization of cellulolytic particle-associated bacteria (PAB). During the first 18 h of incubation, RC had greater (P < .05) CMCase and 15N enrichment of in situ residues than did OG or GG. The RC residues also had a greater (P < .05) ratio of CMCase activity:15N enrichment; this was presumed to indicate that, during this time, RC supported a greater total PAB population and had a greater proportion of cellulolytic PAB than did either GG or OG. Differences in the colonization rate of forage particles by cellulolytic PAB relative to total PAB may account for differences in rate of fiber digestion.

Intestinal supply of amino acids in steers fed ruminally degradable and undegradable crude protein sources alone and in combination2

The objective of this study was to examine the effect of combining ruminally degradable and undegradable CP sources on ruminal microbial protein synthesis and postruminal N and amino acid (AA) flows in steers. Six steers fitted with ruminal, duodenal, and ileal cannulas were fed diets containing corn silage and high-moisture corn supplemented with urea, soybean meal (SBM), dry corn gluten feed (DCGF), a combination of corn gluten meal and blood meal (CB), or SBM and DCGF in combination with CB. Estimated ruminal N escapes for SBM, DCGF, and CB were 32, 25, and 68%, respectively. Supplemental CP sources supplied 35 to 40% of diet CP (12.5% CP diets). Dry matter intake was adjusted to 2.3% of BW for each steer in each period. Total N flow at the duodenum decreased (P < .01) when the diet was supplemented with urea vs other proteins due to decreased (P < .01) flow of nonmicrobial N. However, microbial N and AA flows were greater (P < .05) for urea than for other protein supplements. Disappearance of OM and NDF in the stomach decreased (P < .07) or was numerically lower but nonmicrobial N at the duodenum increased (P < .08) as CB replaced SBM or DCGF in the diet. Protein source had little effect on ruminal fermentation characteristics except that ruminal ammonia N (NH3N) concentration was higher (P < .05) for urea than for other treatments. Total AA and essential AA flows to and disappearance from the small intestine increased (P < .06) as CB replaced DCGF. However, substituting CB for SBM had little effect on intestinal flows and disappearance of AA. These data suggest that source of ruminally degradable CP can influence the efficacy of feeding ruminally degradable and undegradable CP in combination. In general, source of supplemental CP had a greater effect on the quantity than on the profile of absorbable AA supplied to the duodenum.

Influence of Ruminally Dispensed Monensin and Forage Maturity on Intake and Digestion

Eight ruminally cannulated crossbred steers (average weight 336 kg) grazing native blue grama (Bouteloua gracilis [H.B.K.]) rangeland were used in a repeated measures design to evaluate effects of monensin ruminal delivery devices (MRDD) and forage phenology on ruminal digestion. Three periods were assessed: mid-August (Aug.), early October (Oct.), and mid-November (Nov.). One MRDD was placed in the reticulum of 4 steers via the ruminal cannula 21 days before each period. Intake was estimated using total fecal collections. Diet samples were collected using 3 esophageally fistulated steers. Ruminal fill was measured by ruminal evacuation; rate and extent of in situ ruminal neutral detergent fiber disappearance were estimated before ruminal evacuations. Ruminal passage rates, retention time, and apparent total tract organic matter digestibility were estimated using indigestible neutral detergent fiber. In vitro organic matter disappearance of esophageal masticate did not differ (P > .05) in Aug. and Oct. (average of 53.7%), but declined (P .10) by MRDD. In situ neutral detergent fiber disappearance at 96 hours was decreased (P < .10) by MRDD (68 vs 65% for control and MRDD, respectively). As the grazing season progressed, intake declined (P < .10), whereas ruminal fill and retention time increased (P < .05), and passage rate of indigestible neutral detergent fiber decreased (P < .05). At 48 hours in situ neutral detergent fiber was greatest (P < .05) in Aug. and least (P < .05) in Nov.

Computerized Monitoring of Gas Production to Measure Forage Digestion In Vitro

The techniques reported in this paper were developed to facilitate the study of the kinetics of forage digestion in vitro by measuring gas production. Fiber disappearance as a measure of the reaction rate has been replaced by the use of computerized pressure sensors to monitor the gaseous products (CO2, CH4) of microbial metabolism. The recording system described requires a computer, pressure sensors, an interface card, and appropriate software to monitor gas production continuously. Several variables, including sample size, inoculum size, vessel size, and type of pressure sensor, have been investigated to determine ranges within which gas production can be measured accurately, and the reproducibility of the results has been established. Because this technique uses small (100-mg) samples, a modified NDF method has been introduced that allows determination of extent of digestion at the end of an incubation in which gas production has been monitored. A strong linear relationship existed between NDF disappearance and gas production.