Biomedical subjects

W Z Yang

Publications and source records attributed to W Z Yang.

At least 19 recordsLinked to original sources

PubMed2006

Effects of physically effective fiber on chewing activity and ruminal pH of dairy cows fed diets based on barley silage.

The objective of this study was to investigate the effects of physically effective neutral detergent fiber (peNDF) content of dairy cow diets containing barley silage as the sole forage source on feed intake, chewing activity, and ruminal pH. The experiment was designed as a replicated 3 x 3 Latin square using 6 lactating dairy cows with ruminal cannulas. Cows were offered 1 of 3 diets (high, medium, and low peNDF) obtained using barley silage that varied in particle length: long (theoretical cut length of 9.5 mm), medium (equal proportions of long and fine silages), and fine (theoretical cut length of 4.8 mm). The peNDF contents were determined using the Penn State Particle Separator and were 13.8, 11.8, and 10.5%, for the high, medium, and low diets, respectively. The physical effectiveness factors (defined as proportion retained on 19- and 8-mm screens) for the long and fine silages were 0.84 and 0.68, respectively. Increased forage particle size increased intake of peNDF but did not affect intake of DM and NDF. Ruminating and total chewing time were linearly increased with increasing dietary peNDF. Mean ruminal pH, area between the curve and a horizontal line drawn at pH 5.8 or 5.5, and time that pH was below 5.8 or 5.5 were not affected by peNDF content. Intake of peNDF was not correlated to any chewing activity but proportion of long particles on the 19-mm sieve tended to be correlated to ruminating chews (r = 0.36) and ruminating time (r = 0.36). These results indicate that increasing the peNDF content of diets increases chewing time. However, increased chewing time does not always improve ruminal pH status. Increasing chewing time and thus increasing salivary secretion may not fully overcome the effects of feed digestion and the production of fermentation acids that lower rumen pH. The results suggest that dietary peNDF and fermentable OM intake are critical in regulating rumen pH. Dietary particle size, expressed as peNDF, was a reliable indication of chewing activity.

Animals↗

PubMed2006

Physically effective fiber: method of determination and effects on chewing, ruminal acidosis, and digestion by dairy cows.

A study was conducted to investigate the effects of physically effective neutral detergent fiber (peNDF) content of dairy cow diets containing corn silage as the sole forage on intake, chewing, ruminal pH, microbial protein synthesis, digestibility, and milk production. A second objective was to compare current methods of measuring peNDF to determine the most suitable approach for use in ration formulation. The experiment was designed as a replicated 3 x 3 Latin square using 6 lactating dairy cows with ruminal cannulas. Diets varied in peNDF content (high, medium, and low) by altering the particle length of corn silage. The physical effectiveness factors (pef) and peNDF contents of the corn silage and diets were determined based on the original (19- and 8-mm sieves) and new Penn State Particle Separator (PSPS; 19-, 8-, and 1.18-mm sieves). A dry-sieving technique that measures the proportion of particles retained on a 1.18-mm sieve was also used. The new PSPS and the 1.18-mm sieve produced similar estimates of pef and peNDF of diets but gave higher values than the original PSPS. There was a much smaller range in pef of corn silage when 3 sieves, rather than 2, were used with the PSPS (range of 0.93 to 0.96 vs. 0.41 to 0.72, respectively). Consequently, increased forage particle length in the diets increased dietary peNDF content and its intake when using the original PSPS; however, the new PSPS and the 1.18-mm sieve failed to detect changes in dietary peNDF and peNDF intake. The peNDF values estimated based on fractional NDF rather than the total NDF content were higher, but the ranking of diets was not changed. Increased intake of peNDF linearly increased digestibility of CP and tended to linearly increase digestibility of fiber in the total tract. As a result, milk yield tended to linearly increase with no effect on milk composition. Ruminal microbial protein synthesis and microbial efficiency were higher with the medium peNDF than with the high or low peNDF diets. Total chewing time and ruminating time were linearly increased with increasing dietary peNDF, whereas influence of dietary peNDF on ruminal pH and fermentation was minimal. This study showed that increasing peNDF content of diets improved fiber digestion. Of the systems used to measure peNDF, the original PSPS provided a good description of dietary particle length and its effects on chewing time and rumen pH, whereas the new PSPS provided a more consistent chewing index, the ratio of total chewing activity to peNDF, across diets varying in chop length of corn silage.

Animal Nutritional Physiological Phenomena↗

PubMed2006

Increasing the physically effective fiber content of dairy cow diets may lower efficiency of feed use.

Barley silages varying in theoretical chop length were used to evaluate the effects of physically effective (pe) neutral detergent fiber (NDF) content of dairy cow diets on nutrient intakes, site and extent of digestion, microbial protein synthesis, and milk production. The experiment was designed as a replicated 3 x 3 Latin square using 6 lactating dairy cows with ruminal and duodenal cannulas. During each of 3 periods, cows were offered 1 of 3 diets (low, medium, and high peNDF) obtained using barley silage that varied in particle length: fine (theoretical chop length of 4.8 mm), medium (equal proportions of long and fine silages), and long (theoretical chop length of 9.5 mm). The peNDF contents were determined by multiplying the proportion (dry matter basis) of feed retained on the 2 screens (8 and 19 mm) of the Penn State Particle Separator by the NDF content of the diet, and were 10.5, 11.8, and 13.8% for the low, medium, and high diets, respectively. Increased forage particle length linearly increased intake of peNDF but intakes of dry matter, organic matter, starch, and N were highest for cows fed the medium peNDF diet. Digestibilities of organic matter, NDF, and acid detergent fiber in the total tract were linearly decreased with increasing dietary peNDF, although total digestibility of starch and N was not affected by the treatments. Nevertheless, decreased digestibility due to increased dietary peNDF did not reduce milk production or milk composition because the cows were in mid to late lactation. Ruminal microbial protein synthesis and microbial efficiency were numerically higher with the low peNDF than with the medium or high peNDF diets. These results indicate that increasing the peNDF content of a diet containing barley silage decreases fiber digestibility in the total tract and lowers microbial efficiency. Therefore, the benefits of increasing dietary particle size, expressed as peNDF, on reducing the risk of ruminal acidosis should be weighed against potentially negative effects on efficiency of feed use.

Animal Nutritional Physiological Phenomena↗

PubMed2005

Effects of physically effective fiber on digestion and milk production by dairy cows fed diets based on corn silage.

Effects of physically effective (pe) neutral detergent fiber (NDF) content of dairy cow diets on nutrient intakes, site and extent of digestion, microbial protein synthesis and milk production were evaluated in a double 3 x 3 Latin square design using 6 lactating dairy cows with ruminal and duodenal cannulas. During each of 3 periods, cows were offered 1 of 3 diets that were chemically similar but varied in peNDF content (high, medium, and low) by altering corn silage particle length. The peNDF contents were determined using the Penn State Particle Separator and were 11.5, 10.3, and 8.9%, for the high, medium, and low diets, respectively, and the physical effectiveness factors for the long, medium, and fine silages were 84.1, 72.6, and 67.2%, respectively. Increased forage particle length increased intake of peNDF but did not affect intakes of nutrients including dry matter, NDF, starch, and nitrogen. Except for starch, apparent digestibilities of nutrients in the total tract were linearly increased with increasing dietary peNDF. Fiber digestion was affected by dietary peNDF to a greater extent than were the other nutrients. However, increased digestibility due to increased dietary peNDF did not significantly improve milk production or milk composition. Increased dietary peNDF also increased numerically rumen microbial protein synthesis due to increased amount of organic matter fermented in the rumen. These results indicate that increasing the peNDF content of a corn silage based diet improves digestibility, especially digestibility of fiber, in the total tract. Dietary particle size, expressed as peNDF, is positively associated with nutrient digestibility when level of peNDF in the diet is low.

Animal Feed↗

PubMed2005

Effects of physically effective fiber on intake, chewing activity, and ruminal acidosis for dairy cows fed diets based on corn silage.

A study was conducted to investigate the effects of physically effective (pe) neutral detergent fiber (NDF) content of dairy cow diets containing corn silage as the sole forage type on feed intake, meal patterns, chewing activity, and rumen pH. The experiment was designed as a replicated 3 x 3 Latin square using 6 lactating dairy cows with ruminal cannulas. Diets were chemically similar but varied in peNDF content (high, medium, and low) by altering corn silage particle length. The physical effectiveness factors for the long (original), medium (rechopped once), and fine (rechopped twice) silages were determined using the Penn State Particle Separator and were 0.84, 0.73, and 0.67, respectively. The peNDF contents of the diets were 11.5, 10.3, and 8.9%, for the high, medium, and low diets, respectively. Increased forage particle length increased intake of peNDF but did not affect intake of DM or NDF. Number of chews (chews/d) and chewing time, including eating and ruminating time, were linearly increased with increasing dietary peNDF. Meal patterns were generally similar for all treatments, except that number of meals was quadratically increased with increasing dietary peNDF. Mean ruminal pH, area between the curve and a horizontal line at pH 5.8 or 5.5, and time that pH was below 5.8 or 5.5 were not affected by peNDF content. Dietary peNDF content was moderately correlated to number of chews during eating (r = 0.41) and to total chewing time (r = 0.37). The present study demonstrates that increasing the peNDF content of diets increased chewing time, but increased chewing time did not necessarily reduce ruminal acidosis. Models that predict rumen pH should include both peNDF and fermentable OM intake. Dietary particle size, expressed as peNDF, was a reliable indicator of chewing activity.

Animal Nutritional Physiological Phenomena↗

PubMed2004

Grain processing, forage-to-concentrate ratio, and forage length effects on ruminal nitrogen degradation and flows of amino acids to the duodenum.

The objectives of this study were to evaluate effects of dietary factors that alter ruminal fermentability on rumen N degradation, microbial protein synthesis, duodenal flows, and digestibility of amino acids (AA) in the intestines and the total tract. The experiment was a double 4 x 4 quasi-Latin square with a 2(3) factorial arrangement of treatments. The dietary factors were extent of barley grain processing, coarse (processing index; PI = 75.5%) or flat (PI = 60.2%); forage-to-concentrate (F:C) ratio, low (35:65) or high (55:45) on a DM basis; and forage particle length (FPL), long (7.59 mm) or short (6.08 mm). Eight lactating cows with ruminal and duodenal cannulas were offered ad libitum access to a total mixed diet. There were no significant interactions between dietary treatments for ruminal N degradation or its duodenal flow and digestibility in the intestines. Passage of microbial protein to the duodenum was improved with increased F:C ratio of the diet but was not affected by grain processing or FPL. Ruminal digestibility of N was increased with increased F:C ratio (49 vs. 60%) and with reduced FPL (59 vs. 50%). Increased grain processing improved N digestibility both in the intestine (15%) and in the total tract (8%). Reduction in the FPL of the diets reduced intestinal N digestion by 14% without affecting the N digestion in the total tract. Increased extent of grain processing tended to enhance duodenal flows of AA. In contrast, reducing FPL lowered flows of dietary AA to the duodenum because of lowered flows of feed plus endogenous N. Increased F:C ratio of the diet did not change the flow of total AA, but there was a reduced flow of dietary AA and increased flow of microbial AA. Flows of several individual AA were increased by feeding flatly rolled barley with limited effects of F:C ratio or FPL. An interaction between grain processing and FPL was detected for flows of some AA. Diets formulated with flatly rolled barley plus long FPL increased Arg, Thr, Asp, Glu, Ser, Tyr, and nonessential AA (NEAA) by more than 24%, compared with other combinations of grain processing and FPL. Digestibility of essential AA (EAA) in the intestine (68%) was higher than that of NEAA (63%), but digestion of total AA (65%) was similar to that of total N (66%). Digestibilities of individual AA in the intestine ranged from 46 to 77% and were generally improved with increased grain processing. However, effects of F:C ratio or FPL on digestion of AA were limited. These results indicate that manipulation of dairy cow diets can improve ruminal N degradation, microbial protein synthesis, flows of AA to the duodenum, and intestinal digestibility of AA. Combining dietary factors can be more beneficial than changing individual dietary factors for improving the delivery of AA to the small intestine.

Amino Acids↗

PubMed2004

Effects of mechanical processing on the nutritive value of barley silage for lactating dairy cows.

Mechanical processing of whole crop barley before ensiling may be useful for improving nutrient use by dairy cattle. The objective of this study was to assess the effects of feeding mechanically processed barley silage as the main forage source on lactational performance. Twenty-four Holstein cows, 16 primiparous (187 +/- 52 days in milk) and 8 multiparous (87 +/- 69 days in milk) cows, were used in a completely randomized design with a 2-wk covariate period and a 6-wk treatment period. The 2 treatments were: 1) total mixed ration (TMR) containing regular barley silage (RBS-TMR), and 2) TMR containing mechanically processed barley silage (MPBS-TMR). Barley silage and alfalfa hay supplied 41 and 5% of the dietary dry matter (DM), respectively. Intake, body weight, and milk production were measured during the covariate and treatment periods. In addition, 2 multiparous cows were used for in situ measurements of the ruminal DM and fiber degradation kinetics of the barley silages and TMR. Data were analyzed with repeated measurements using a mixed model that included the covariate adjustment. Feeding MPBS-TMR had no significant effects on DM intake (DMI; 21.7 kg/d), milk yield (33.9 kg/d), or milk composition, with only 4% FCM (fat-corrected milk) yield (29.7 vs. 31.7 kg/d) and milk fat concentration (3.30 vs. 3.57%) showing a numerical improvement. Apparent digestibilities of DM and nutrients were not affected by feeding MPBS-TMR, with the exception of starch digestibility, which tended to increase. Dairy efficiencies calculated as milk yield/DMI or FCM/DMI were not different between treatments. Body weight and body condition score were not affected by treatments. Effective ruminal degradability of DM was similar for both barley silages, indicating that when the silages were ground to remove the effects of mechanical processing, the potential digestion was similar. Mechanical processing of barley silage harvested at a mid-dough stage of maturity resulted in small improvements in its nutritive value for lactating dairy cows and had minor impact on digestibility and milk production.

Animal Feed↗

PubMed2003

Effects of enzyme supplementation of a total mixed ration on microbial fermentation in continuous culture, maintained at high and low pH.

A dual-flow continuous culture system was used to investigate the effects of pH and addition of an enzyme mixture to a total mixed ration (TMR) on fermentation, nutrient digestion, and microbial protein synthesis. A 4 x 4 Latin square design with a factorial arrangement of treatments was used, with four 9-d periods consisting of 6 d for adaptation and 3 d for measurements. Treatments were as follows: 1) high pH with control TMR, 2) high pH with TMR treated with enzyme, 3) low pH with control TMR, and 4) low pH with TMR treated with enzyme. Ranges of pH were 6.0 to 6.6 and 5.4 to 6.0 for high and low, respectively. Fermenters were fed twice daily a TMR consisting of 30% alfalfa hay, 30% corn silage, and 40% rolled corn (DM basis). The silage was milled fresh and the TMR was fed to the fermenters in fresh form (64% DM). The enzyme mixture was a commercial product of almost exclusive protease activity; it was applied daily to the fresh TMR and stored at 4 degrees C for at least 12 h before feeding. Degradability of OM, NDF, ADF, and cellulose was decreased (P < 0.05) by low pH. Hemicellulose and protein degradation were not affected by pH. Enzyme addition increased (P < 0.01) NDF degradability (by 43% and 25% at high and low pH, respectively), largely as a result of an increase in hemicellulose degradation (by 79% and 51% at high and low pH, respectively). This improvement was supported by an increase (P < 0.05) in the xylanase and cellulase activities in the liquid phase of the fermenter contents. Total VFA were decreased (P < 0.05) by low pH, but were not affected by enzyme addition. Total bacterial numbers were increased (P < 0.03) at low pH and tended (P < 0.13) to increase with enzyme addition. Cellulolytic bacteria in effluent fluid were decreased (P < 0.02) at low pH but were unaffected by enzyme addition. Despite a large increase (P < 0.001) in protease activity, protein degradation was only numerically increased by enzyme addition. Microbial protein synthesis was higher (P < 0.10) at high pH but was not affected by enzyme addition. Methane production, expressed as a proportion of total gases, was decreased (P < 0.001) at low pH but was not affected by enzyme addition. It is concluded that it is possible to adapt the continuous culture system to use fresh feeds instead of dried feeds. Overall, the results indicate that the enzyme product used in this study has a potential to increase fiber degradability without increasing methane production.

Animal Feed↗

PubMed2003

Effects of bacterial direct-fed microbials and yeast on site and extent of digestion, blood chemistry, and subclinical ruminal acidosis in feedlot cattle.

Two studies were conducted to determine whether a bacterial direct-fed microbial (DFM) alone or with yeast could minimize the risk of acidosis and improve feed utilization in feedlot cattle receiving high-concentrate diets. Eight ruminally cannulated steers, previously adapted to a high-concentrate diet, were used in crossover designs to study the effects of DFM on feed intake, ruminal pH, ruminal fermentation, blood characteristics, site and extent of digestion, and microbial protein synthesis. Steers were provided ad libitum access to a diet containing steam-rolled barley, barley silage, and a protein-mineral supplement (87, 8, and 5% on a DM basis, respectively). In Exp. 1, treatments were control vs. the lactic-acid producing bacterium Enterococcus faecium EF212 (EF; 6 x 10(9) cfu/d). In Exp. 2, treatments were control vs EF (6 x 10(9) cfu/d) and yeast (Saccharomyces cerevisiae; 6 x 10(9) cfu/d). Supplementing feedlot cattle diets with EF in Exp. 1 increased (P < 0.05) propionate and (P < 0.05) decreased butyrate concentrations, decreased the nadir of ruminal pH (P < 0.05), enhanced the flow of feed N (P < 0.10) to the duodenum but reduced that of microbial N (P < 0.10), reduced (P < 0.10) intestinal digestion of NDF, and increased (P < 0.10) fecal coliform numbers. Other than the increase in propionate concentrations that signify an increase in energy precursors for growth, the other metabolic changes were generally considered to be undesirable. In Exp. 2, providing EF together with yeast abolished most of these undesirable effects. Combining EF with yeast increased the DM digestion of corn grain incubated in sacco, but there were no effects on altering the site or extent of nutrient digestion. The diets used in this study were highly fermentable, and the incidence of subclinical ruminal acidosis, defined as steers with ruminal pH below 5.5 for prolonged periods of time, was high. Supplementing the diet with EF, with or without yeast, had limited effects on reducing ruminal acidosis. It seems that cattle adapted to high-grain diets are able to maintain relatively high feed intake and high fiber digestion despite low ruminal pH. The Enterococcus faecium bacterium and yeast used in this study were of limited value for feedlot cattle already adapted to high-grain diets.

Acidosis↗

PubMed2003

Effects of particle size of alfalfa-based dairy cow diets on chewing activity, ruminal fermentation, and milk production.

Effects offorage particle size measured as physically effective NDF and ratio of alfalfa silage to alfalfa hay of diets on feed intake, chewing activity, particle size reduction, salivary secretion, ruminal fermentation, and milk production of dairy cows were evaluated using 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, comprised either of 50:50 or 25:75 of alfalfa silage:alfalfa hay, and alfalfa hay was either chopped or ground. Various methods were used to determine physically effective NDF content of the diets. Cows surgically fitted with ruminal and duodenal cannulas were offered ad libitum access to these total mixed diets. The physically effective NDF content of the diets was significantly lower when measured using the Penn State Particle Separator than when measured based on particles retained on 1.18-mm screen. Intake of DM was increased by increasing the ratio of silage to hay but was not affected by physically effective NDF content of diets. Eating time (hours per day) was not affected by the physically effective NDF content of diets, although cows spent more time eating per unit of DM or NDF when consuming high versus low alfalfa hay diets. Ruminating time (hours per day) was increased with increased physically effective NDF content of the diets. Rumen pH was affected more by changing dietary particle size than altering the ratio of silage to hay. Feeding chopped hay instead of ground hay improved ruminal pH status: time during which ruminal pH was above 6.2 increased and time during which ruminal pH was below 5.8 decreased. Milk production was increased by feeding higher concentrations of alfalfa silage due to increased DM intake, but was not affected by dietary particle size. Feed particle size, expressed as mean particle length or physically effective NDF was moderately correlated with ruminating time but not with eating time. Although physically effective NDF and chewing time were not correlated to mean rumen pH, they were negatively correlated to the area between the curve and pH 5.8, indicating a positive effect on reducing the risk of acidosis. Milk fat content was correlated to rumen pH but not to physically effective NDF or chewing activity. These results indicate that increasing physically effective NDF content of the diets increased chewing activity and improved rumen pH status but had limited effect on milk production and milk fat content.

Animal Nutritional Physiological Phenomena↗

PubMed2002

Effect of a fibrolytic enzyme preparation from Trichoderma longibrachiatum on the rumen microbial population of dairy cows.

The effects of supplementing a dairy cow diet with incremental levels of a fibrolytic enzyme preparation (preparation B) from Trichoderma longibrachiatum on the rumen microbial population were investigated. Two cows fitted with rumen cannulae were each fed a diet containing barley-based concentrate (52%), maize silage (29%), and chopped alfalfa hay (19%), supplemented with 0, 1, 2, 5, or 10 L of preparation B per tonne of dry matter (DM). Preparation B stimulated numbers of total viable bacteria in a quadratic manner (P < 0.05), to approximately 230, 330, 390, and 250% at 1, 2, 5, and 10 L x t(-1) DM, respectively. Preparation B increased the numbers of cellobiose-utilizing (P < 0.01), xylanolytic (P < 0.05), and amylolytic bacteria (P < 0.05), but had no effect (P > 0.05) on numbers of cellulolytic bacteria. However, when bacterial numbers enumerated on each substrate were expressed as a proportion of total viable bacterial numbers, only cellobiose utilizers were stimulated, and this stimulation was limited to the 1 L x t(-1) DM level of preparation B (P < 0.05). The results of this study demonstrate that the inclusion of an exogenous fibrolytic enzyme preparation in dairy cow diets increased the numbers of rumen bacteria that utilize hemicelluloses and secondary products of cellulose digestion.

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↗

PubMed2001

Effect of dietary factors on distribution and chemical composition of liquid- or solid-associated bacterial populations in the rumen of dairy cows.

Effects of dietary factors including kernel thickness of processed barley grain, ratio of forage to concentrate, and forage particle length on chemical composition of bacteria, bacterial colonization of feed particles and distribution in the rumen, and duodenal flow of bacteria in dairy cows were evaluated. The experiment was designed as a double 4 x 4 quasi-Latin square with a 2 x 2 x 2 factorial arrangement of treatments using eight lactating cows with ruminal and duodenal cannulas. Barley grain was steam-rolled to two thicknesses: coarse (1.60 mm) or flat (1.36 mm); ratio of forage:concentrate was low (35:65) or high (55:45) (DM basis); and forage particle length was long (7.59 mm) or short (6.08 mm). Cows were offered ad libitum access to a total mixed diet. Chemical composition was different (P < 0.01) between liquid-associated bacteria (LAB) and solid-associated bacteria (SAB). Reduced barley thickness increased (P < 0.05) N content and 15N enrichment, but a high ratio of forage:concentrate decreased (P < 0.01) 15N enrichment of both the LAB and SAB. Significant differences between AA composition of the LAB and SAB were observed for 15 out of 17 AA studied. Bacterial colonization was linearly increased (P < 0.01) from about 5 to 70% as particle length of rumen contents was reduced from 3.35 mm to 0.15 mm (sieve size). The degree of colonization on each fraction of the rumen particulate matter was only affected (P < 0.10) by the ratio of forage:concentrate, with consistently higher (P < 0.10) bacterial colonization noted for high than for low forage:concentrate diets. Of the total bacterial mass within the rumen, less than 20% was associated with the liquid and over 70% was associated with the small particles that passed through the 0.6-mm sieve. Although the bacterial pool in the rumen was lower (P < 0.04) when flatly rolled barley rather than coarsely rolled barley was fed, bacterial flow to the duodenum was greater (P < 0.10) with increasing ratio offorage:concentrate. The present results confirm the differences of chemical composition and biomass for LAB and SAB. Manipulation of dietary factors such as ratio of forage:concentrate have the potential to alter bacterial colonization of rumen particles and the relative proportion of LAB to SAB, which were positively correlated to bacterial flow to the duodenum.

Amino Acids↗

PubMed2001

Resistance of feed enzymes to proteolytic inactivation by rumen microorganisms and gastrointestinal proteases.

Potential feed enzyme additives for ruminants were tested in vitro for their stability to ruminal microbial and gastrointestinal proteolysis. Four commercial preparations from Trichoderma longibrachiatum (A, B, C, and D) and one from an undisclosed source (E) were incubated up to 6 h with ruminal fluid taken from four lactating dairy cows before or 2 h after feeding. The stability of preparation B was also tested in the presence of pepsin at pH 3 and pancreatin at pH 7. Cellulase (EC 3.2.1.4), cellulose 1,4-beta-cellobiosidase (EC 3.2.1.91), beta-glucanase (EC 3.2.1.6), xylanase (EC 3.2.1.8), beta-glucosidase (EC 3.2.1.21), and beta-xylosidase (EC 3.2.1.37) activities were monitored throughout the incubations. Polysaccharidase activities of all enzyme preparations were remarkably stable in ruminal fluid taken after feeding. Ruminal fluid obtained before feeding inactivated the polysaccharidases in preparations B and D to a greater extent than ruminal fluid obtained after feeding. Cellulase and cellulose 1,4-beta-cellobiosidase activities were the least stable, declining (P < 0.05) by 35 and 60% for preparations B and D, respectively. Xylanase activity of preparation D decreased (P < 0.05) by up to 30% after 6 h of incubation, whereas beta-glucanase activity was not affected. The ability to degrade exogenous enzymes also differed among cows (P < 0.05). Pepsin and acid (pH 3.0) did not affect polysaccharidases in preparation B but decreased glycosidase activities by 10 to 15% (P < 0.05) after 1 h of incubation. Pancreatin, at the maximum concentration used, inactivated cellulase, cellulose 1,4-beta-cellobiosidase, and xylanase activities at a rate of 0.55, 1, and 0.45%/min, respectively. beta-Glucosidase and beta-xylosidase activities decreased by 1 and 0.75%/min, respectively. Partial proteolysis of cellulase, cellulose 1,4-beta-cellobiosidase, and xylanase by pancreatin produced a transient increase in activity. This twofold increase for cellulase and fourfold increase for cellulose 1,4-beta-cellobiosidase was directly proportional to pancreatin concentration. These results suggest that the enzyme feed additives tested were stable in the rumen of animals after feeding. Exogenous enzymes are likely to be more susceptible to the host gastrointestinal proteases in the abomasum and intestines than to ruminal proteases. However, exogenous polysaccharidases may survive for a considerable period of time in the small intestine and they probably maintain activity against target substrates in this environment.

Animal Feed↗

PubMed2001

Effects of barley grain processing on the site and extent of digestion of beef feedlot finishing diets.

Effects of extent of barley rolling on chewing activities, ruminal fermentation, and site and extent of digestion were evaluated for feedlot finishing cattle diets in a 4 x 4 Latin square design. Four Jersey steers (452 kg), cannulated in the rumen and duodenum, were used. Barley grain was temper-rolled to four extents: coarse, medium, medium-flat, and flat, which were expressed as processing index (PI, volume weight of barley after processing expressed as a percentage of its volume weight before processing, DM basis) and equivalent to 82, 75, 70, and 65%, respectively. Diets consisted of 9.7% barley silage, 86% temper-rolled barley, and 4.3% other ingredients (DM basis). Steers were offered ad libitum access to a total mixed ration once daily. Dry matter intake was not affected (P > 0.15) by PI of barley. Digestibility of OM in the rumen and in the total tract were numerically lower (P = 0.13) for steers fed coarsely rolled barley than for steers fed more extensively processed barley. Digestibility of starch in the total tract was linearly increased (P = 0.02) with grain processing, but NDF digestion was not affected by processing (P > 0.15). Digestibility of CP did not differ in the rumen but tended (P = 0.08) to increase in the total tract with increased processing of barley. Flow of microbial nitrogen to the duodenum was approximately one-third lower (linear effect, P = 0.06) for steers fed coarsely rolled barley than for steers fed further rolled barley. Increased grain processing tended to decrease (linear effect, P = 0.08) rumination time without affecting eating time. These results indicate that optimal degree of rolling for barley fed to feedlot cattle corresponded to a PI of 75% or lower. Coarsely rolled barley is not recommended because it resulted in the lowest digestibility and lowest microbial protein synthesis. Processing barley to attain a PI less than 75% resulted in marginal improvements in feed digestion, but rumination time decreased, which could lead to problems associated with acidosis if lower-fiber diets are used.

Animal Feed↗

PubMed2001

Effects of grain processing, forage to concentrate ratio, and forage particle size on rumen pH and digestion by dairy cows.

Dietary factors that alter the intake of effective fiber were evaluated for their effects on rumen fermentation, digestion, and milk production using a double 4 x 4 quasi-Latin square design with a 2(3) factorial arrangement of treatments. The dietary factors were extent of barley grain processing, coarse (1.60 mm) or flat (1.36 mm); forage-to-concentrate (F:C) ratio, low (35:65) or high (55:45) (dry matter basis); and forage particle length, long (7.59 mm) or short (6.08 mm). Eight lactating cows with ruminal and duodenal cannulas were offered ad libitum access to a total mixed diet and milked twice daily. Dry matter intake was increased by increasing the extent of grain processing. Mean rumen pH was lower for cows fed flatly rolled barley than for cows fed coarsely rolled barley, whereas F:C ratio or forage particle size had no effect on rumen pH. Rumen pH was not correlated with effective NDF intake but tended to be correlated with digestibility of starch in the rumen. Total tract digestibilities of dry matter, organic matter, starch, and neutral detergent fiber were increased by feeding flatly rolled barley or low F:C ratio diets. Milk yield and milk protein content were higher in cows fed flatly rolled barley or low F:C ratio diets. Milk fat content tended to increase with high F:C ratio or long forage particle length but was reduced by feeding flatly rolled barley. In this study, extent of grain processing and intake of ruminal available starch were the most influential factors affecting milk production. Reducing the ratio of F:C improved total digestion and actual milk production. Forage particle length had minimal impact on digestibility and milk production.

Ammonia↗

PubMed2001

Barley processing, forage:concentrate, and forage length effects on chewing and digesta passage in lactating cows.

Dietary factors that alter fermentability, NDF content, or particle size of the diet were evaluated for their effects on chewing behavior and distribution and passage of feed particles in the digestive tract of dairy cows. A double 4 x 4 quasi-Latin square design with a 2(3) factorial arrangement of treatments was used. The dietary factors were: extent of barley grain processing, coarse (1.60 mm) or flat (1.36 mm); forage-to-concentrate ratio (F:C), low (35:65) or high (55:45) (dry matter basis); and forage particle length, long (7.59 mm) or short (6.08 mm). Eight lactating cows with ruminal and duodenal cannulas were offered ad libitum access to total mixed diets. Chewing time, expressed as minutes per day or per kilogram of dry matter or neutral detergent fiber (NDF), was increased with high F:C diets due to increased eating and ruminating times but was decreased when expressed per kilogram of NDF intake from forage. The influence of forage particle length or grain processing on chewing activity was less pronounced than F:C ratio. Chewing activity was positively correlated to proportion of long forage particles in the diet but not to particle length of the diets. Influence of feed particle size on particle size distribution in different sites of the digestive tract was minimal. Particle size distributions of duodenal digesta and feces differed; the proportion of particles retained on the 3.35- or 1.18-mm screens was higher, but proportion of particles that passed through the 1.18-mm screen was lower in duodenal digesta than in feces. Relationships between chewing activities and ruminal pH or fractional passage rate of rumen contents were not significant. These results indicate that particle size of barley-based diets was not a reliable indicator of chewing activity. Forage particle size and NDF content of the diets were more reliable indicators of chewing activity than was the NDF content of forage. Fecal particle size was not an appropriate means of estimating the size of particles exiting the reticulorumen, at least for barley-based diets. Breakdown of coarse particles was necessary, but not a rate-limiting step for particles exiting the rumen. Passage rate of the rumen contents was affected by numerous factors including chewing activity.

Animal Feed↗

PubMed2000

Structural analysis of the transcriptional activation region on Fis: crystal structures of six Fis mutants with different activation properties.

The Fis protein regulates gene expression in Escherichia coli by activating or repressing transcription of a variety of genes. Fis can activate transcription when bound to DNA upstream of the RNA-polymerase-binding site, such as in the rrnB P1 promoter, or when bound to a site overlapping the -35 RNA polymerase binding site, such as in the proP P2 promoter. It has been suggested that transcriptional activation in both promoters results from interactions between specific amino acids within a turn connecting the B and C helices (the BC turn) in Fis and the C-terminal domain of the alpha-subunit of RNA polymerase (alphaCTD of RNAP). Here, crystal structures of six Fis BC turn mutants with different transcriptional activation properties, Q68A, R71Y, R71L, G72A, G72D and Q74A, were determined at 1.9 to 2.8 A resolution. Two of these mutants, R71Y and R71L, crystallized in unit cells which are different from that of wild-type Fis, and the structure of R71L offers the most complete Fis model to date in that the extended structure of the N-terminal region is revealed. The BC turn in all of these mutant structures remains in a nearly identical gamma gamma beta-turn conformation as present in wild-type Fis. Analyses of the molecular surfaces of the transactivation region of the mutants suggest that several residues in or near the BC turn, including Gln68, Arg71, Gly72 and Gln74, form a ridge that could contact the alphaCTD of RNAP on one side. The structures and biochemical properties of the mutants suggest that Arg71 is the most critical residue for contacting RNAP within this ridge and that the glycine at position 72 helps to stabilize the structure.

Amino Acid Substitution↗