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PubMed1991

Effects of nitrogen fertilization and maturity of bromegrass on in situ ruminal digestion kinetics of fiber.

Four ruminally cannulated, nonlactating Holstein cows (593 kg) were fed bromegrass hay diets within a 4 X 4 Latin square. Treatments were arranged factorially and consisted of bromegrass fertilized with 0 or 89 kg N/ha and harvested in the late-boot or full-head stage of maturity. Total tract digestibility of DM (57.6 vs 51.1%), NDF (68.8 vs 63.0%), ADF (51.1 vs 46.0%) and cellulose (63.4 vs 53.5%) decreased with increasing maturity (P less than .05). These forages also were placed in dacron bags for determination of in situ digestion kinetics. Rate, extent of digestion, and lag times were determined for DM and fiber components using linear regression of log-transformed data or a nonlinear fitting procedure. Treatment effects generally were consistent between methods of calculating kinetic data; however, numerical results often differed greatly. Extents of in situ ruminal digestion (72 h residue) for NDF, hemicellulose and cellulose were lower (P less than .05) for full-head than for late-boot-stage bromegrass. Extent of digestion calculated using the nonlinear method followed similar trends. Nitrogen fertilization had no effect on extent or total tract digestibilities of fiber components of DM. In situ disappearance rates (calculated using both methods) for fiber fractions and DM generally were almost always affected less by maturity than by fertilization. Particles of N-fertilized bromegrass had more (P less than .05) bacterial N associated with them during the first 12 h in situ than did particles of unfertilized brome. Surface area equations based on lignification of NDF accurately estimated fiber digestion and suggested that lignification was the primary reason DM and NDF digestibilities decreased with advanced maturity. Due to the relatively low DM intakes of these diets (11 kg/d), rate of passage, not rate of digestion, was of principle importance in determining extent of digestion of these diets.

Animal Feed↗
PubMed1995

Influence of duodenal slaframine infusion on site of nutrient disappearance from the digestive tract of steers fed a high-concentrate diet.

The effect of duodenal slaframine (SF) infusion on site and extent of digestion was determined using four steers equipped with ruminal, duodenal, and ileal cannulas in a 4 x 4 Latin square. A 77% dry-rolled corn diet was provided in 12 equal portions daily at a DMI of 2.26% BW. Slaframine in a .9% saline excipient was infused into the duodenum every 12 h with total daily dose of 0, 30, 60, or 90 micrograms /kg of BW. Slaframine infusion had no effect on ruminal pH, ruminal NH3 N, or solids and liquids passage rate. Slaframine increased (linear, P < .10) total tract OM and starch disappearance and digestibility and tended to increase (linear, P = .14) total tract N digestibility. Ruminal starch disappearance tended to be decreased (quadratic, P = .16) by SF. Small intestinal OM digestibility was increased (linear, P < .10) but starch digestibility in the small intestine was not affected by SF. Increased total tract starch digestibility was caused by increased (quadratic, P < .10) starch fermentation in the large intestine. Ruminal feed N digestibility decreased at the intermediate doses of SF (quadratic, P < .10). Total N digestibility in the small intestine tended to be increased (cubic, P = .13) with 30 and 90 micrograms of SF/kg of BW. Decreased ruminal feed N digestion was compensated for by increased (quadratic, P < .10) small intestinal feed N disappearance for steers treated with intermediate doses of SF. The potential of SF to increase starch digestion in the rumen and small intestine seems to be limited.

Alkaloids↗
PubMed1996

Nutrient digestion by ileal cannulated dogs as affected by dietary fibers with various fermentation characteristics.

We studied the effects of dietary fibers with various fermentation characteristics on nutrient digestion at the distal ileum and in the total tract of dogs. The following high-protein (34%), high-fat (23%) diets were fed: 1) a control treatment (CON) with 0% supplemental fiber; 2) beet pulp (BP), 7.5%; 3) low-cellulose mixture (LCM), 2.5% cellulose + 5.0% pectin; 4) high-cellulose mixture (HCM), 5.0% cellulose + 2.5% pectin; or 5) Solka Floc (SF), 7.5% cellulose. Nutrient intakes by fiber-supplemented dogs were similar among treatment groups but greater (P < .05) than for dogs fed the control diet. Digestion of nutrients at the distal ileum was similar among groups except for fat: the dogs fed BP digested less fat than those fed the other sources of dietary fiber. Digestion of amino acids at the distal ileum was similar for all groups, except for lysine, which increased (P < .05) in digestibility as dietary cellulose concentration increased. Dogs consuming LCM had lower apparent ileal digestibility values for all nutrients, including most amino acids, than dogs consuming HCM or SF. Total tract digestion of DM and OM by dogs fed supplemental fiber was less (P < .05) than for dogs fed the control diet. The BP treatment was higher than other fiber treatments in total tract digestion of OM (P < .10) and total dietary fiber (P < .05). Total tract digestibilities of all nutrients exhibited either linear or quadratic responses to dietary cellulose concentrations. Apparent ileal and total tract nutrient digestion was influenced by the source of dietary fiber consumed.

Amino Acids↗
PubMed1997

Estimating endogenous amino acid flows at the terminal ileum and true ileal amino acid digestibilities in feedstuffs for growing pigs using the homoarginine method.

True ileal lysine digestibilities were determined using the homoarginine (HA) method in casein-, barley-, canola meal-, and barley-canola meal-based diets fed to growing pigs. Four Yorkshire barrows (25 to 49 kg BW) equipped with ileal T-cannulas were fed one of the diets according to a 4 x 4 Latin square design. All diets, except for the barley diet, were formulated to be similar in DE:CP ratio. Ileal digesta were collected continuously for 24 h on d 7 and 9 of each experimental period for determining apparent and true ileal digestibilities, respectively. True ileal lysine digestibility and endogenous flows were determined by feeding diets in which 50% of the protein-containing ingredients was guanidinated; the conversion of lysine to HA allows for direct determination of true lysine digestibilities. The apparent ileal CP and amino acid digestibilities were higher (P < .05) in the casein diet than in the barley, canola meal, and barley-canola meal diets. The CP digestibility was higher (P < .05) in the barley-canola meal diet than in the barley and canola meal diets. Endogenous lysine losses were influenced by diet (P < .05) and ranged between 586 and 1,429 mg/kg DM intake. True ileal lysine digestibilities in barley, canola meal, and barley-canola meal diets were similar (P > .05) and lower (P < .05) than in the casein diet. The true ileal amino acid digestibilities were estimated for other amino acids. Unlike apparent digestibilities, true digestibilities seemed additive in the barley-canola meal mixture.

Amino Acids↗
PubMed1999

Effect of fumaric acid and dietary buffering capacity on ileal and fecal amino acid digestibilities in early-weaned pigs.

Experiments were conducted to determine the effect of fumaric acid supplementation and buffering capacity of the diet on ileal and fecal digestibilities of CP, GE, and amino acids in early-weaned pigs. In two experiments, 12 pigs each were weaned at 14 d of age and fitted with a simple T-cannula at the distal ileum between 15 and 17 d of age. In both experiments, the pigs were fed four diets, based on wheat and soybean meal without (control) or with 1, 2, or 3% fumaric acid according to a balanced two-period change-over design. In Exp. 2, the buffering capacity of the diets was increased by supplementation of 3% sodium bicarbonate. The pigs were fed three times daily: equal amounts at 8-h intervals. The diets were supplied at a rate of 5% (wt/wt) of body weight. The inclusion of fumaric acid to the diet with a low buffering capacity increased (P < .05) the ileal digestibilities of CP, GE, and the majority of amino acids. The highest responses were found at an inclusion level of 2% fumaric acid. The improvements in apparent ileal amino acid digestibilities ranged from 4.9 to 12.8 percentage units. Supplementation of fumaric acid to a diet with a high buffering capacity led only to numerical increases in ileal digestibilities of CP, GE, and amino acids. In both studies, fumaric acid supplementation had no effect (P > .05) on the fecal digestibilities of CP, GE, and amino acids, except histidine. A high buffering capacity of the diet decreased the ileal amino acid digestibilities by 1 to 10 percentage units compared with diets with the low buffering capacities. In both experiments, ileal and fecal digestibilities were higher (P < .05) in Period 2 (on d 24 after weaning) than in Period 1 (on d 11 after weaning). A positive correlation (P < .05) between ileal digestibilities and fumaric acid supplementation to the diets with the low buffering capacities was observed in Period 1 (on d 11 after weaning), but not in Period 2 (on d 24 after weaning). No relationship (P > .05) between ileal digestibilities and fumaric acid supplementation to the diets with a high buffering capacity could be established. In conclusion, supplementation of fumaric acid to starter diets during the first 3 to 4 wk after weaning increases the ileal digestibilities of GE, CP, and amino acids.

Amino Acids↗
PubMed1999

Rate and extent of digestion of the ethanol-soluble and neutral detergent-insoluble fractions of corn grain.

The objectives of this study were to partition corn grain into three digestible fractions and to measure the rate of disappearance of these fractions in vitro. Seventeen corn grain samples with varied fiber concentrations were extracted with either 80% ethanol or neutral detergent to obtain estimates of the pool size and digestion kinetics of the A, B1, B2, and C fractions. The carbohydrate soluble in 80% ethanol averaged only 2.6+/-.3% of the DM, although 80% ethanol extracted 7.1+/-1.2% of DM of corn grain. The ethanol-soluble fraction of corn grain contained protein, ether-extractable compounds, and a small amount of ash in addition to carbohydrate. Because of this chemical heterogeneity and because of the small size of the ethanol-soluble fraction, it was not possible to determine the digestion rate of this fraction by measuring gas production. The NDF content of the corn grain was 10.6+/-.7% of DM and was highly digestible (94.6+/-1.4%). The digestible NDF contributed 9.5% of the total gas production from corn grain. Because the size, digestibility, and digestion rate of the digestible NDF fraction varied little among corn grain samples, it is not necessary to routinely analyze the digestion kinetics of the digestible NDF fraction of dried corn grain. An average gas production curve of this fraction can be used as a base to subtract from the total gas production curve to generate the gas production curve of the neutral detergent-soluble fraction for dried, ground corn grain samples.

Detergents↗
PubMed2002

Determination of true ileal amino acid digestibility and the endogenous amino acid outputs associated with barley samples for growing-finishing pigs by the regression analysis technique.

This study was conducted to determine true ileal AA digestibility coefficients and the endogenous AA outputs associated with barley samples for growing-finishing pigs using the regression analysis technique with dual digestibility markers. Six barrows, with 30.5 and 58.6 kg average initial and final BW, were fitted with a simple T-cannula at the distal ileum and fed six barley-based diets at close to ad libitum feed intake according to a 6 x 6 Latin square design. The six diets contained 97% of six barley samples varying from low to high in CP and AA contents (8.5, 9.2, 9.8, 11.5, 12.6, and 15.6% CP, respectively, on DM basis). The dietary NDF content ranged from 16.8 to 23.8% on DM basis. Chromic oxide (Cr2O3) and acid-insoluble ash (AIA) were used as digestibility markers. Each experimental period lasted 7 d. Ileal digesta were collected, at 2-h intervals, for a total of 24 h during d 6 and 7. There were linear relationships (P < 0.01) between dietary contents of apparent ileally digestible and total CP and AA as determined by using either Cr2O3 or AIA as a digestibility marker. The use of Cr2O3 vs AIA affected (P < 0.01) the determination of true ileal AA digestibility coefficients and the endogenous CP and AA outputs. However, there were no differences (P > 0.01) in the true ileal AA digestibility coefficients in barley samples between this study and the average values reported in the literature. The endogenous CP and AA outputs determined in this study were higher (P < 0.01) than reported values (35.1+/-3.0 vs 14.7+/-1.1 g CP/kg DMI). It is concluded that dual digestibility markers should be used to measure true ileal AA digestibility coefficients and endogenous AA outputs when dietary fiber content is high and the ileal digesta is collected through a simple T-cannula in the pig. True rather than apparent ileal AA digestibility coefficients determined in barley samples should be used in diet formulation for swine. The gastrointestinal endogenous AA secretion, recycling, and output losses are important in whole-body AA utilization and homeostasis, especially when fiber-enriched diets are fed to growing-finishing pigs.

Amino Acids↗
PubMed2004

Fat digestibility in Equus caballus follows increasing first-order kinetics.

The digestibility of ether extract varies greatly from forages to grains and further to added fats consisting mainly of triglycerides. This variation has been attributed to two main factors, the presence of nonhydrolyzable substances in the ether extract, especially in leafy foods, and the dilution of endogenous fecal fat. A compilation of results from 188 equine digestion balance observations on five basal feeds and 18 test feeds with added fats demonstrated a true digestibility of fat approaching 100% and an endogenous fecal fat of 0.22 g x d(-1) x kg BW(-1). The results revealed that nonhydrolyzable ether extract and endogenous fecal fat were insufficient to account for the difference between true digestibility and apparent digestibilities of ether extract in basal feeds and partial digestibilities of added fats in test feeds. A third possible contributing factor was demonstrated: an increasing first-order relationship between observed digestibilities (D, %) and the fat content of the feed (F, g/kg): D = 92.0 - 92.0e(-F/342). r2 = 0.81, P < 0.001. This equation indicates that 46% digestibility (half maximum) occurs at an ether extract or fat content of 24 g/kg, which is common in forages. It is consistent with fat digestibility or efficiency of absorption being a function of the rate of lipolysis, especially when residence time in the small intestine is limited. Consequently, we suggest that the kinetics of lipases, which are difficult to measure, may contribute to low digestibility when substrate concentration in the small intestine is low due to a low fat content in food. The status of vitamins A and E might be affected by low dietary fat contents and might be improved by fat supplementation.

Animal Feed↗
PubMed2005

Dry matter intake and digestion of alfalfa harvested at sunset and sunrise.

The preference exhibited by animals in selecting one feed over another is important only if the preferred diet is consumed daily in larger quantities, digested to a greater extent, or both. Six alfalfa (Medicago sativa L.) hays were harvested in pairs at sunset (PM) and sunrise (AM) on consecutive days at three harvest dates. A previous study of these hays demonstrated differences in ruminant preference favoring PM harvests. This study evaluated the effects of time of cutting and harvest date on voluntary DMI and nutrient digestibility. The hays were field-cured, baled, and chopped before evaluation for intake and digestibility. Studies were conducted for sheep (Ovis aries), goats (Capra hircus), and cattle (Bos taurus). Goats, but not steers or sheep, demonstrated differences in nutrient digestibility between PM- and AM-cut hays. Goats consumed more PM than AM hay (2.97 vs. 2.83 kg/100 kg of BW; P = 0.07) and digested it to a greater extent (0.710 vs. 0.696; P = 0.03), resulting in greater digestible DMI (2.11 vs. 1.97 kg/100 kg of BW; P = 0.03). Sheep consumed (mean = 2.52 kg/100 kg of BW; P = 0.59) and digested (mean = 0.681; P = 0.25) PM- and AM-cut hays similarly. Steers consumed larger quantities of PM-than AM-cut hay (2.90 vs. 2.62 kg/100 kg of BW; P = 0.11), but digestion did not differ with cutting time (mean = 0.660; P = 0.75). Difference values (composition of fed hay minus composition of orts) indicated that sheep and goats selected from the feed offered similarly, whereas steers selected differently. Difference values for CP averaged 94 and 101 g/kg for goats and sheep and 32 g/kg for steers (P < 0.01), and difference values for NDF averaged 185 and 196 g/kg for goats and sheep and 73 g/kg for steers (P <or= 0.01). Steer DMI and digestible DMI were associated with preference (r = +0.83, P <or= 0.05; and r = +0.89, P <or= 0.05) and with coordinates for preference criteria (dimension 1; r = +0.90, P <or= 0.05; and r = +0.89, P <or= 0.05) from a previous preference trial. Intake and digestion responses for goats and sheep showed no relationship with the previous preference trial measurements. For cattle and goats, the management strategy of mowing in the afternoon seems to take advantage of small, but influential diurnal changes in the soluble carbohydrate fraction and offers the potential to improve forage quality.

Animal Husbandry↗
PubMed1983

Influence of sodium bicarbonate and magnesium oxide on digestion and metabolism in yearling beef steers abruptly changed from high forage to high energy diets.

Eight rumen-cannulated steers (initial wt 330kg) were adapted to a mixed alfalfa-grass hay diet for 30 d and abruptly changed to complete mixed diets of corn silage, snapped ear corn and a corn-based supplement to determine the effects of buffers on diet adaptation, digestion and ruminal metabolism. The diets contained: 1) no buffer, 2) .5% magnesium oxide (MgO), 3) 1.0% sodium bicarbonate (NaHCO3) and 4) .5% MgO and 1.0% NaHCO3, as a percentage of diet dry matter (DM). Digestion, metabolism and ruminal characteristics were measured in each of 2 wk immediately after the diet change. The animals were then adapted to the mixed alfalfa-grass hay diet, re-randomized and assigned to the four diets, thus four steers consumed each diet. Intakes and digestibilities of DM were generally greater for the diets containing buffers. The most notable differences were a greater DM intake with added NaHCO3 and an improved DM digestibility with added MgO. The higher DM digestibility with MgO was apparently related to improved neutral detergent fiber (NDF) and starch digestion. Fecal pH was significantly increased with MgO addition. Because of the greater intake and digestibilities, the amount of DM, NDF, and starch digested tended to be greater for the buffered diets. There were no diet X week interactions for intake and digestibilities, thus the responses observed existed during both wk 1 and 2 after the change in diets. In general, intake and digestibilities were greater in wk 2 than in wk 1 for all diets.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Effect of sorghum grain variety and reconstitution on site and extent of starch and protein digestion in steers.

Hetero-yellow (HY), red (RED) and brown (BR, high tannin) sorghums were fed dry-rolled or reconstituted (RED and BR only) to evaluate the effect of variety and reconstitution on the site and extent of starch and protein digestion in steers fitted with ruminal, duodenal and ileal cannulae. Processed grains were incorporated into 88% sorghum (DM basis) diets fed at 2% of body weight in a 5 X 5 Latin square. Ruminal fermentation of organic matter, starch and protein tended to be lower for the dry-rolled RED than for either the dry-rolled HY or BR sorghum. Digestion of organic matter (OM) and starch in the small intestine was very low for dry-rolled sorghums. Total tract starch digestibility was lower for the dry-rolled RED sorghum (86.9%) than the BR (90.8%) and HY (91.4%). Nitrogen (N) digestibility ranged from 53.1% for the dry-rolled BR to 64.5% for the HY. Tannins were extensively (95.2%) degraded in the rumen, which may have enhanced fermentation of the BR sorghum. Reconstitution increased (P less than .05) total-tract starch digestion of the RED and tended to increase starch digestion of the BR as well. Total N flow to the duodenum tended to increase with reconstitution, with most of the increase being due to greater (P less than .05) microbial-N. Reconstitution also increased (P less than .05) total-tract N digestibility of the RED. The response to reconstitution for the RED sorghum appeared to be due primarily to an increase (P less than .10) in the extent of fermentation of organic matter and starch in the rumen. Reconstitution of BR, however, enhanced disappearance of starch from the small intestine. In both cases, most (97.3%) of the digestible starch of the reconstituted sorghums had disappeared before the terminal ileum. In contrast, 14.5% (621 g) of the digestible starch of dry-rolled RED disappeared in the large intestine. Sorghum grain variety and reconstitution appear to alter site and extent of starch and protein digestion, which may result in variable performance of cattle fed sorghum grain diets.

Animal Feed↗
PubMed1986

Influence of lignin on digestibility of forage cell wall material.

One-hundred-ninety-four grass samples, representing eight species, were used to determine the relationships of in vitro forage dry matter, cell wall, hemicellulose and cellulose digestibilities with lignin concentration. Linear regressions indicated that dry matter digestion was inhibited to a lesser degree (P less than .05) by lignin concentration than was cell wall digestion. Results for linear regressions of hemicellulose and cellulose digestibilities as functions of lignin concentration showed a greater (P less than .05) effect of lignin on cellulose digestion. Smooth bromegrass and switchgrass were collected at both Clay Center and Mead, NE; for all digestibility measures, the Clay Center samples gave stronger (P less than .05) negative correlations with lignin. A comparison of linear and curvilinear models indicated that, for all digestion measurements, the curvilinear model was a better (P less than .05) description of relationships with lignin concentration. For all digestibility measures, lignin's inhibiting effect declined at higher lignin concentrations. The curvilinear models did not show significant differences among the digestibility measures for effect of lignin. The demonstration that the forage digestibility response to lignin's inhibitory effect is curvilinear in nature suggests that the mechanism of lignin's inhibition is complex.

Animal Feed↗
PubMed1986

Evaluation of alfalfa-corn cob associative action. III. The effect of mechanically separated alfalfa fractions on intake, digestibility and ruminal characteristics of ammonia-treated corn cob diets fed to sheep.

The influence of mechanically separated alfalfa fractions on intake, digestibility and rate of ruminal passage was investigated using 48 lambs (32 kg) in a digestion trial. Whole plant pre-bloom alfalfa (25% crude protein) or fractions (presscake, dehydrated presscake, protein coagulum, dehydrated protein coagulum, whole juice or deproteinized juice) were added to a 3% ammonia (NH3)-treated corn cob negative control diet at levels equal to 20% wholeplant alfalfa dry matter (DM); eight treatments, six lambs/treatment. Ad libitum intake was greater (P less than .05) for alfalfa fiber (presscake) or juice supplemented diets compared with 20% direct cut alfalfa. Dry matter intake, digestibility of DM and cell walls, and rate of passage were highly correlated when diets were fed ad libitum. At equal DM intakes, dehydrated vs wet presscake increased (P less than .05) DM and cell wall digestibility. Heating of the protein may have reduced degradation rate and consequently a slower release of nutrients for microorganisms in the rumen. Whole vs deproteinized juice increased digestibility of cob DM (P = .11) and cell walls (P = .13), suggesting a response to level of degradable alpha-amino N. Whole and deproteinized juice increased cell wall digestibility compared with the negative control by 23.0 and 18.5 percentage units, respectively, suggesting that degradable alpha amino-N and cell solubles or other nutrients interacted to maximize microbial fiber digestion. Total and branch-chain volatile fatty acids measured at 6, 12 and 18 h post-feeding were highly correlated with nutrient digestibility. Ruminal NH3-N measured at 18 h was negatively correlated with dry matter (r = -.74) and cell wall (r = -.72) digestibility, showing that alfalfa supplies nutrients required by ruminal microorganisms for NH3 assimilation and fiber digestion. The mode of alfalfa associative action in high fiber diets is in supplying ruminal microorganisms with degradable protein and (or) other nutrients, rather than altering ruminal retention time.

Ammonia↗
PubMed1986

Effects of whole cottonseed, cottonseed oil or animal fat on digestibility of wheat straw diets by steers.

Two completely random digestion trials were conducted, each with 12 beef steers (325 kg initial weight), to measure changes in digestibilities of fat and of forage components when fat was added to diets containing 62 to 76% wheat straw. Trial 1 diets contained either no added fat or 6.3% added fat from whole cottonseed (30% of the diet), cottonseed oil or animal fat; diets were formulated to contain equal levels of cottonseed hulls and cottonseed meal. Trial 2 diets contained 0, 2, 4 or 8% added animal fat. In all forms and at all levels, added fat increased apparent digestibility of dietary lipid (P less than .05). However, estimated true digestibility of lipid decreased (from 94 to 71%) as added fat was increased from 0 to 8% (P less than .05). Up to 6.3% added fat increased digestible energy (DE) content of the diet. Fat additions of 2 and 4% increased daily DE intake (P less than .05) and did not depress digestibility of diet components (P greater than .05). Fat additions of 6.3% or greater, either as free fats or as whole cottonseed, reduced (P less than .05) mean acid detergent fiber digestibility from 40 to 28%. In addition to depressing fiber digestibility, 8% added fat reduced (P less than .05) digestibilities of dry matter (from 54 to 47%), organic matter (60 to 52%) and gross energy (60 to 51%). Oil fed as whole cottonseed caused digestibility depressions similar to free fat addition at the same level.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗
PubMed1988

Low-quality roughages in high-concentrate pelleted diets for sheep: digestion and metabolism characteristics as affected by corncob and(or) rice hull additions.

Two trials were conducted to determine effects of feeding corncobs, rice hulls or a combination of both on nutrient digestion and flow of digesta through the gastrointestinal tract of multiple-cannulated sheep (55-kg Rambouillet X Dorset rams; trial 1; 4 X 4 Latin square) as well as ruminal, digestive and metabolic characteristics of early-weaned lambs (24.1-kg crossbred rams; trial 2; randomized complete block design; 3 periods) fed pelleted 75% concentrate-25% roughage diets. In trial 1, apparent total tract dry matter (DM), organic matter (OM) and neutral detergent fiber (NDF) digestibilities decreased and N digestibility increased as percentage of dietary corncobs decreased and percentage of rice hulls increased. Site of NDF digestion appeared to shift from the upper to the lower digestive tract as percentage of corncobs decreased and percentage of rice hulls increased. In trial 2, apparent DM digestibility decreased as corncobs were replaced with rice hulls in the diet. Neutral detergent fiber digestibility was not affected by diet except in larger lambs at higher intakes, with NDF digestibility generally decreasing as percentage of dietary rice hulls increased. Nitrogen digestibility was not affected by replacing corncobs with rice hulls in the diet. Ruminal pH decreased as rice hulls replaced corncobs in the diet. These data are interpreted to indicate that rice hulls can be effectively substituted for corncobs in sheep diets when added at levels up to 25% of the total diet.

Animal Feed↗
PubMed2000

Effects of brown midrib 3 mutation in corn silage on productivity of dairy cows fed two concentrations of dietary neutral detergent fiber: 3. Digestibility and microbial efficiency.

The effects of digestibility of corn silage neutral detergent fiber (NDF) and dietary NDF content on ruminal digestion kinetics, site of nutrient digestion, and microbial N production efficiency were evaluated with eight multiparous high producing dairy cows in a duplicated 4 x 4 Latin square design with 21-d periods. Experimental diets contained corn silage from a brown midrib (bm3) hybrid or its isogenic normal control at two concentrations of dietary NDF (29 and 38%). The NDF digestibility estimated by a 30-h in vitro fermentation was higher for bm3 corn silage by 9.4 units (55.9 vs. 46.5%). Neither ruminal nor total tract NDF digestibility was affected by corn silage treatment. The bm3 corn silage diet decreased starch digestibility in the rumen and in the total tract, but increased postruminal starch digestibility compared with control diet. The bm3 corn silage diets increased microbial N flow to the duodenum and tended to decrease ruminal ammonia concentration. Microbial efficiency was greater for cows fed bm3 corn silage in spite of lower ruminal pH. Higher efficiency of microbial nitrogen production might be attributed to faster passage rate of NDF for cows fed bm3 corn silage compared with those fed control corn silage. Higher in vitro NDF digestibility might predict enhanced NDF fragility and ease of NDF hydrolysis in vivo. Enhanced in vitro NDF digestibility does not necessarily result in increased NDF digestibility either in the rumen or in the total tract, but possibly increases rate of passage and DMI, improving efficiency of microbial N production.

Animal Feed↗
PubMed2002

Effects of particle size of alfalfa-based dairy cow diets on site and extent of digestion.

Effects of ratio of alfalfa silage to alfalfa hay and forage particle size on nutrient intakes, site of digestion, rumen pools, and passage rate of ruminal contents were evaluated in a 4 x 4 Latin square design with a 2 x 2 factorial arrangement of treatments. The diets consisted of 60% barley-based concentrate and 40% forage made up either of 50:50 or 25:75 of alfalfa silage:alfalfa hay and alfalfa hay was either chopped or ground. Lactating dairy cows surgically fitted with ruminal and duodenal cannulas were used and offered ad libitum access to a total mixed ration. Intakes of nutrients were increased by increasing ratio of silage to hay but were not affected by particle size of forage. Change in ratio of silage to hay of diets did not affect site and extent of digestion. However, increased forage particle size of the diets improved digestibility of fiber and N in the total tract, and as well as digestibility of organic matter, starch, and acid detergent fiber in the intestine. There was a shift of starch digestion from the rumen to the intestine when forage particle size was increased, although total digestion of starch was not changed. Ruminal microbial protein synthesis and microbial efficiency also improved with increasing forage particle size. Cows fed ground hay versus chopped hay had significantly lower rumen wet mass regardless of the ratio of silage to hay. Reduced forage particle size also lowered ruminal nutrient pool size for cows fed the high silage diet. Ruminal passage rates of liquid and solid were decreased by reducing the ratio of silage to hay, and retention time of solids in the total tract was shortened by reducing forage particle size. These results indicate that manipulating ratio of silage to hay in the diets of dairy cows changed feed intake but had little effect on digestion. In contrast, increased forage particle size in dairy cow diets improved fiber digestion and microbial protein synthesis in the rumen, and shifted starch digestion from the rumen to the intestine. Dietary particle size, expressed as physically effective neutral detergent fiber, was a reliable indication of ruminal microbial protein synthesis and nutrient digestion.

Animal Nutritional Physiological Phenomena↗
PubMed2003

Effects of corn grain conservation method on ruminal digestion kinetics for lactating dairy cows at two dietary starch concentrations.

Effects of conservation method of corn grain and dietary starch concentration on ruminal digestion kinetics were evaluated. Eight ruminally and duodenally cannulated Holstein cows (55 +/- 15.9 days in milk; mean +/- SD) were used in a duplicated 4 x 4 Latin square design with a 2 x 2 factorial arrangement of treatments. Experimental diets contained either ground high moisture corn (HM) or dry ground corn (DG) at two dietary starch concentrations (32 vs. 21%). Mean particle size and dry-matter concentration of corn grain were 1,863 microm and 63.2%, and 885 microm and 89.7%, for HM and DG, respectively. Starch digestibility in the rumen was greater for HM treatments compared with DG treatments, but starch digestibility in the total tract was not affected by conservation method of corn grain because of compensatory digestion in the intestines. The difference in ruminal starch digestibility between HM and DG treatment was greater for high-starch diets (71.1 vs. 46.9%) compared with low-starch diets (58.5 vs. 45.9%). This interaction is attributed to a greater difference in first-order digestion rate of starch between HM and DG treatment in high-starch diets (28.2 vs. 14.6%/h) compared with low-starch diets (16.8 vs. 12.2%/h). This suggests that ruminal starch digestion is a second-order reaction limited by enzyme activities as well as substrate availability; ruminal contents of cows fed low-starch diets may have insufficient amylolytic activity for maximal starch digestion when readily fermentable starch is available. Rate of neutral detergent fiber digestion in the rumen was slower for high-starch diets and HM treatments compared with low-starch diets and DG treatments, respectively. Effects of corn grain conservation method on ruminal digestion kinetics are greatly altered by starch concentration of diets.

Amylases↗