Ruminal degradability of dry matter,crude protein,and amino acids in soybean meal,canola meal,corn, and wheat dried distillers grains

Different protein sources, such as canola meal (CM) or dried distillers grains (DDG), are currently used in dairy rations to replace soybean meal (SBM). However, little data exists comparing their rumen degradation in a single study. Therefore, the objective of this study was to compare the ruminal degradation of dry matter (DM), crude protein (CP), and AA of SBM, CM, high-protein corn DDG (HPDDG), and wheat DDG plus solubles (WDDGS). In situ studies were conducted with 4 rumen-fistulated lactating Holstein cows fed a diet containing 38% grass hay and 62% corn-based concentrate. Each protein source was incubated in the rumen of each cow in nylon bags for 0, 2, 4, 8, 16, 24, and 48 h to determine DM and CP rumen degradation kinetics, whereas additional bags were also incubated for 16 h to evaluate AA ruminal disappearance. Rumen DM and CP degradability was calculated from rumen-undegraded residues corrected or not for small particle loss. Data were fitted to an exponential model to estimate degradation parameters and effective degradability (ED) was calculated with a passage rate of 0.074 h⁻¹. The WDDGS and SBM had higher uncorrected ED (DM = 75.0 and 72.6%; CP = 84.8 and 66.0%, respectively) than CM and HPDDG (DM = 57.2 and 55.5%; CP = 59.3 and 48.2%, respectively), due to higher soluble fraction in WDDGS and a combination of higher potentially degradable fraction and rate of degradation in SBM. Correction for small particle loss from bags, higher for WDDGS than for the other protein sources, decreased estimated ED but did not alter feed ranking. The ruminal disappearance of AA after 16 h of incubation reflected the overall pattern of CP degradation between protein supplements, but the ruminal disappearance of individual AA differed between protein supplements. Overall, these results indicate that, in the current study, (1) SBM and WDDGS were more degradable in the rumen than CM and HPDDG, and (2) that small particle loss correction is relevant but does not alter this ranking.     

Mobile nylon bag for estimating intestinal availability of rumen undegradable protein

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

Investigating unsaturated fat, monensin, or bromoethanesulfonate in continuous cultures retaining ruminal protozoa. I. Fermentation, biohydrogenation, and microbial protein synthesis

Methane is an end product of ruminal fermentation that is energetically wasteful and contributes to global climate change. Bromoethanesulfonate, animal-vegetable fat, and monensin were compared with a control treatment to suppress different functional groups of ruminal prokaryotes in the presence or absence of protozoa to evaluate changes in fermentation, digestibility, and microbial N outflow. Four dual-flow continuous culture fermenter systems were used in 4 periods in a 4 × 4 Latin square design split into 2 subperiods. In subperiod 1, a multistage filter system (50-μm smallest pore size) retained most protozoa. At the start of subperiod 2, conventional filters (300-μm pore size) were substituted to efflux protozoa via filtrate pumps over 3 d; after a further 7 d of adaptation, the fermenters were sampled for 3 d. Treatments were retained during both subperiods. Flow of total N and digestibilities of NDF and OM were 18, 16, and 9% higher, respectively, for the defaunated subperiod but were not different among treatments. Ammonia concentration was 33% higher in the faunated fermenters but was not affected by treatment. Defaunation increased the flow of nonammonia N and bacterial N from the fermenters. Protozoal counts were not different among treatments, but bromoethanesulfonate increased the generation time from 43.2 to 55.6 h. Methanogenesis was unaffected by defaunation but tended to be increased by unsaturated fat. Defaunation did not affect total volatile fatty acid production but decreased the acetate:propionate ratio; monensin increased production of isovalerate and valerate. Biohydrogenation of unsaturated fatty acids was impaired in the defaunated fermenters because effluent flows of oleic, linoleic, and linolenic acids were 60, 77, and 69% higher, and the ratio of vaccenic acid:unsaturated FA ratio was decreased by 34% in the effluent. This ratio was increased in both subperiods with the added fat diet, indicating an accumulation of intermediates of biohydrogenation. However, the flow of 18:2 conjugated linoleic acid was unaffected by defaunation or by treatments other than added fat. The flows of trans-10, trans-11, and total trans-18:1 fatty acids were not affected by monensin or faunation status.     

Investigating unsaturated fat, monensin, or bromoethanesulfonate in continuous cultures retaining ruminal protozoa. II. Interaction of treatment and presence of protozoa on prokaryotic communities

Increasing the consistency of responses to reduce emissions of ruminal methane and nitrogenous wastes into the environment using microbial inhibitors requires an accurate assessment of microbial community profiles. In addition to direct inhibition of methanogens by feed additives, protozoa are often targeted for inhibition because their close physical association with endo- and ectosymbionts stimulates methanogenesis in the rumen. In this study, we first modified a continuous culture system to maintain a diverse protozoal population (faunated subperiod) and then selectively effluxed them without using any chemical agents (defaunated subperiod). In both subperiods, unsaturated fat (potentially inhibitory to ciliate protozoa, methanogens, and gram-positive bacteria), monensin (assumed to inhibit gram-positive bacteria), and bromoethanesulfonate (BES; a potent inhibitor of methanogens) were used to suppress the respective functional groups of microorganisms. Changes in microbial populations were determined using denaturing gradient gel electrophoresis, followed by cloning and DNA sequencing of the excised bands. Neither monensin nor unsaturated fat consistently affected methanogen populations under our conditions in either the faunated or defaunated subperiods. When BES was administered, bands presumptively linked to protozoa-associated methanogens in the faunated subperiod disappeared in the defaunated subperiod. However, there was no noticeable adaptation of the sensitive methanogens to BES. The effect of dietary treatments on bacterial populations in the fermenters was harder to ascertain because of the overriding period effect caused by a different inoculum in each period. Defaunation selectively decreased the intensity of bands associated with ruminococci and clostridia but seemed to increase some Butyrivibrio and related populations. Presence of protozoa influenced both bacterial and archaeal populations, probably by selective predation, competition for substrate, or through symbiotic interactions.     

Short communication: Effect of washing method,grinding size,and the determination of an indigestible fraction on in situ degradation of starch in mature corn grain

The objectives of this study were to determine (1) the effect of grinding size (1, 2, 4, and 6 mm) to determine effective ruminal disappearance (ERD); (2) the most adequate method to estimate the rapidly degradable fraction (A); (3) a time point to measure the indigestible fraction (C); and (4) the viability of using fewer time points to estimate starch fractional disappearance rate (k_d) of mature corn grain. Fraction A was determined by rinsing in a bucket or washing machine, rumen immersion followed by bucket or washing machine, and water immersion for 30 min followed by bucket or washing machine. Ruminal in situ incubations were performed at 48, 72, 96, and 120 h to determine fraction C, and at 0 (washing machine), 3, 6, 12, 18, 24, and 48 h to determine the kinetics of starch disappearance. Models were used with either 2 or 3 pools and k_d was determined by the linear slope of the log-transformed bag residues as a proportion of incubated samples over time. The ERD was calculated as A + B [k_d/(k_d + kp)], where kp is the ruminal fractional passage rate = 16.0% h^?1. Data were analyzed using PROC MIXED of SAS (SAS Institute Inc., Cary, NC) with the fixed effects of run (for fraction A analysis only) method (either washing or model), grinding size, and method by grinding size interaction, with cow as a random effect. Correlation between estimates calculated using all time points or combinations of 2 and 3 time points were determined using PROC CORR. Fraction A was reduced as grinding size increased, but was not altered by washing method. Samples ground at 6 mm had greater fraction C than other grinding sizes at 48, 72, or 96 h, but not at 120 h. Model affected the slowly degradable fraction (B) values solely, but the difference was minor (0.5 percentage units). Greater fractions B and C but reduced k_d and ERD were observed as grinding size increased. Based on correlation analysis the 2-pool model, incubation times of 0, 3, and 48 h were suitable to evaluate ruminal starch degradation kinetics in mature corn. Ruminal in situ incubation at 120 h highlighted the lack of a fraction C of starch (0.13% of starch). Washing method did not affect determination of fraction A of starch. Ruminal in situ incubations of 0, 3, and 48 h for starch degradation kinetics using a 2-pool model were adequate for mature ground corn, but 120 h of incubation is suggested to confirm the existence or absence of a fraction C. Grinding size affected starch degradation kinetics and fraction A determination.     

Estimation of the digestible energy of ruminant feedstuffs by the combined bag technique

The combined bag technique was used to estimate digestible energy of ruminant feedstuffs. Samples of corn, barley, and sorghum grains; soybean and sunflower meals; corn and wheat silages; and vetch and wheat hays were incubated in dacron bags in the rumens of dairy cattle for 3 to 72 h. Bags containing residues after 12 h of ruminal incubation were introduced into the duodenum and recovered from feces. Feeds and ruminal and intestinal residues were analyzed for dry matter (DM), organic matter (OM), crude protein (CP), neutral detergent fiber, and nonstructural carbohydrates. The effective ruminal degradability of OM was higher in grains (639 g/kg of DM) and in protein supplements (609 g/kg of DM) than in forages (373 g/kg of DM). For grains and forages, carbohydrates contributed most of the degradable OM in the rumen, but, in protein supplements, about 50% of the ruminally degradable OM originated from carbohydrate. For protein supplements, 54% of the OM that disappeared postruminally was CP, but, in the grains and forage ingredients, CP contributed less than 20% of the postruminal OM that disappeared. In grains and forages, 83% of total tract disappearance of OM was from carbohydrates. For protein supplements, CP contributed 50% to overall OM disappearance. The calculated energy equivalent of digested matter averaged among feeds was 4.71 kcal/g. A high correlation was found between digestible energy estimated by the combined bag technique and the respective National Research Council values. The combined bag technique is a useful tool for the estimation of digestible energy in feedstuffs.     

The effects of forage proportion and rapidly degradable dry matter from concentrate on ruminal digestion in dairy cows fed corn silage-based diets with fixed neutral detergent fiber and starch contents

This study investigated the effects of the forage-to-concentrate (F:C) ratio and the rate of ruminal degradation of carbohydrates from the concentrate on digestion in dairy cows fed corn silage-based diets. Six cows with ruminal cannulas were assigned to 6 treatments in a 6 × 6 Latin square. Treatments were arranged in a 3 × 2 factorial design. Three proportions of neutral detergent fiber from forage [FNDF; 7.6, 13.2, and 18.9% of dry matter (DM)] were obtained by modifying F:C (20:80, 35:65, and 50:50). These F:C were combined with concentrates with either high or low content of rapidly degradable carbohydrates. The dietary content of rapidly degradable carbohydrates from the concentrate was estimated from the DM disappearance of concentrate after 4 h of in sacco incubation (CRDM). Thus, 2 proportions of CRDM were tested (20 and 30% of DM). Wheat and corn grain were used as rapidly and slowly degradable starch sources, respectively. Soybean hulls and citrus pulp were used as slowly and rapidly degradable fiber sources, respectively. Concentrate composition was adjusted to maintain dietary starch and neutral detergent fiber contents at 35.9 and 28.9% of DM, respectively. There was no effect of the interaction between F:C and CRDM on DM intake (DMI), ruminal fermentation, chewing activity, and fibrolytic activity. When F:C decreased, DMI increased, the mean ruminal pH linearly decreased, and the pH range linearly increased from 0.95 to 1.27 pH unit. At the same time, the acetate-to-propionate ratio decreased linearly. Decreasing F:C linearly decreased the average time spent chewing per kilogram of DMI from 35.2 to 19.5 min/kg of DMI and decreased ruminal liquid outflow from 11.6 to 9.2 L/kg of DMI, suggesting a decrease in the salivary flow. Increasing CRDM decreased DMI and increased the time during which pH was below 6.0 (3.1 vs. 4.8 h), the pH range (0.90 vs. 1.33), and the initial rate of pH drop. It also increased the volatile fatty acid range (35 vs. 59 mM), thus suggesting an increased rate of fermentation. It also decreased the acetate-to-propionate ratio (2.9 vs. 1.8). Increasing CRDM barely affected the average time spent chewing per kilogram of DMI and the ruminal liquid outflow. These results suggest that rumen pH is controlled by different mechanisms when F:C is decreased or when CRDM is increased. Consequently, FNDF is a good predictor of the chewing time, whereas CRDM is a good predictor of the pH range and volatile fatty acid profiles. Finally, considering both FNDF and CRDM improves the prediction of mean pH.     

Shelf life of case-ready beef steaks (Semitendinosus muscle) stored in oxygen-depleted master bag system with oxygen scavengers and CO2/N2 modified atmosphere packaging

This study aims to evaluate the stability of beef from Semitendinosus muscle packaged in oxygen permeable wrapped-tray units and stored in a master bag system, with and without oxygen scavengers. Changes in the atmosphere composition, microbiological indexes, myoglobin forms and color parameters were monitored during the storage in master bag, blooming and display life. The presence of scavengers reduced rapidly the oxygen concentration and maintained it at values not detectable instrumentally. Within few days of storage in master bags, the resolution of the transient discoloration was completed and the meat quality was maintained over the anoxic storage. After the removal from master bags meat bloomed completely reaching OxyMb level and Chroma values higher than those on fresh meat at t₀. During 48 h of display life at 4 °C, quality attributes had a decay slower than samples stored traditionally in air. Without scavengers the oxygen caused the irreversible discoloration within 7 days, due to the formation of metmyoglobin on the surface.     

The effects of starch and rapidly degradable dry matter from concentrate on ruminal digestion in dairy cows fed corn silage-based diets with fixed forage proportion

This study investigated the effects of the type (starch vs. nonstarch) and rate of ruminal degradation of carbohydrates from the concentrate on digestion in dairy cows fed corn silage-based diets. Six ruminally cannulated cows were assigned to 6 treatments in a 6 × 6 Latin square design. Treatments were arranged in a 3 × 2 factorial design. Two starch levels [25 and 41% dry matter (DM) for low starch (LS) and high starch (HS) diets, respectively] were obtained by replacing starch-rich feedstuffs by nonstarch feedstuffs. These starch levels were combined with slowly, moderately, and rapidly rumen-degradable feedstuffs to obtain 3 levels of rapidly degradable carbohydrates from concentrate (18, 23, and 28% DM). These levels were estimated from the DM disappearance of concentrate after 4 h of in sacco incubation (CRDM). Wheat and corn grain were used as rapidly degradable and slowly degradable starch feedstuffs, respectively. Soybean hulls and citrus pulp were used as slowly degradable and rapidly degradable nonstarch feedstuffs, respectively. No interaction effect was found between dietary starch content and CRDM on pH range, volatile fatty acid (VFA) range, or VFA profile. Increasing CRDM led to a linear decrease in acetate-to-propionate ratio (from 2.7 to 2.1), and a linear increase in the pH and VFA ranges (from 0.86 to 1.12 pH units and from 34 to 56 mM, respectively). Feeding HS diets decreased acetate-to-propionate ratio (2.6 vs. 2.0) and increased pH range (0.89 vs. 1.04 pH units), but had no effect on VFA range. Increasing CRDM linearly decreased mean ruminal pH in LS diets but linearly increased mean ruminal pH in HS diets. Fibrolytic activity was unaffected in LS diets but decreased strongly in HS diets (from 62 to 50%). These findings suggest that pH regulation differs on a short-term and on a longer-term basis. In the short-term, increasing CRDM increased the rate of VFA production, which may have been partly buffered under LS diets due to the higher cation exchange capacity of nonstarch feedstuffs compared with starch-rich feedstuffs. In the longer term, feeding starch reduced fibrolytic activity, which may have led to lower total VFA production and higher mean pH. The results of this experiment clearly show that both fermentative characteristics of the concentrate and dietary starch content should be taken into account when formulating diets to prevent subacute ruminal acidosis and to predict VFA profile.     

Effectiveness of oxygen barrier oven bags in low temperature cooking on reduction of warmed-over flavor in beef roasts

A 3 × 3 × 2 factorial was utilized to determine if roast size (small, medium, large), cooking method (open-pan, oven bag, vacuum bag), and heating process (fresh, reheated) prevented warmed-over flavor (WOF) in beef clod roasts. Fresh vacuum bag and reheated open-pan roasts had higher cardboardy flavor scores compared with fresh open-pan roast scores. Reheated roasts in oven and vacuum bags did not differ from fresh roasts for cardboardy flavor. Brothy and fat intensity were increased in reheated roasts in oven and vacuum bags compared with fresh roasts in oven and vacuum bags. Differences in TBARS were found in the interaction of heating process and roast size with the fresh and reheated large, and reheated medium roasts having the lowest values. Based on TBARS data, to prevent WOF in reheated beef roasts, a larger size roast in a cooking bag is the most effective method.     

Comparison of the in situ and in vivo intestinal disappearance of ruminally protected methionine

We designed a switchback expriment to compare the intestinal disappearance of ruminally protected Met determined in situ or in vivo over three consecutive periods. Four nonlactating Holstein heifers (477+/-36 kg) with cannulae in the rumen, duodenum, and ileum were fed a diet based on timothy silage to meet requirements for maintenance (dry matter intake = 8.72+/-0.15 kg). A total of 16 bags, containing 1.5 g of ruminally protected Met, were incubated in the rumen (4.5 h) of each cow and transferred to an acid-pepsin solution to simulate the abomasum (2.5 h). Following each incubation, bags were recovered and three bags were dried at 55 degrees C and analyzed for Met. Remaining bags were introduced directly into the duodenal or ileal cannula for the in situ method, while for the in vivo method, the content of remaining bags was transferred into gelatin capsules before their introduction in the duodenal or ileal cannula. Spot samples of digesta were collected during a 96-h period, with Co-EDTA and Cr-mordanted fiber used as indigestible markers to estimate in vivo digestibility. The disappearance of Met in the small intestine determined in vivo tended to be higher than in situ (74.45 vs. 43.65+/-1.79%). Our results indicate that when used to assess intestinal availability of ruminally protected Met, the mobile nylon bag technique can underestimate the true bioavailability of Met.     

Technical note: A method to facilitate retrieval of polyester bags used in in sacco trials in ruminants

A method is described to facilitate the retrieval of polyester bags from ruminally cannulated cattle. The system consists of 2 major components, i) an accommodation vessel for multiple polyester bags in the form of an opaque nylon stocking, referred to as the “receptacle,” and ii) a shorter stocking, knotted with a loop on one end to attach to the receptacle, referred to as the “catcher.” The catcher is tied on the other end to the inside of the cannula plug. Sample bags are inserted in tandem into the receptacle, separated from each other by a tight knot. The receptacle is tied to the catcher and subsequently inserted into the rumen. Upon retrieval, receptacles are pulled out only far enough to expose the first bag to be removed. This procedure ensures easy bag retrieval without exposing the remaining bags (intended for further incubation) to air.     

Effects of Amount and Availability of Starch on Amylolytic Activity of Ruminal Solid-Associated Microorganisms

Three ruminally cannulated dry cows were used in an experiment designed as a Latin square to investigate the effects of amount and availability of starch on the amylolytic activity of ruminal solid-associated microorganisms (SAM). Animals were fed twice daily a diet (7 kg DM day^-1) consisting of wheat straw, cocksfoot hay and ground barley in the ratios 10: 90: 0, 10: 60: 30 and 10: 30: 60. Nylon bags containing rapidly (barley) or slowly (maize) degradable cereal grains were incubated in the rumen. Enzymes of the SAM were extracted from rumen contents and bag residues, and amylolytic (amylase and α-D -glucosidase) activities were measured. The in situ degradation of starch was determined. Increasing the level of barley in the diet induced a linear increase in amylase activity of SAM in the rumen contents. In the bags, amylase activity and starch degradation rate were not modified by supplementation. High activity was observed more rapidly in bags containing barley, where starch is rapidly available, than in bags containing maize, where starch is protected by a resistant endosperm. These results suggest that amylolytic activity of SAM may depend on the amount of starch available to microorganisms. © 1997 SCI.     

Effect of sodium bicarbonate on rate of passage and degradation of soybean meal in postpartum dairy cows

Effects of sodium bicarbonate on rate of passage and disappearance of soybean meal from the rumen were determined in a change-over experiment with eight cows. Experimental diets containing 50 or 60% roughage were fed over five 21-day periods with four cows per diet. Sodium bicarbonate at 1.0 and 2.5% (diet dry matter) were changed over in periods 2 and 4, whereas periods 1, 3, and 5 served as control. Rate of passage of soybean meal was measured with chromium-mordanted soybean meal and rate of disappearance by nylon bag technique. Effects of diet were similar for all responses. Response to the two percents of buffer was similar for dry matter intake, milk yield, milk fat, and protein. Percent buffer fed was associated positively with ruminal pH and with disappearance of nitrogen from nylon bags. The 0, 1, and 2.5% of buffer resulted in turnover rates of mordanted soybean meal of 8.22, 9.80, and 10.52%/h, but degradation of protein remained relatively constant at 36.0, 38.4, and 38.2%. The influence of rate of passage on ruminal degradability is discussed.     

Effects of fescue type and sampling date on the nitrogen disappearance kinetics of autumn-stockpiled tall fescue

Two tall fescue [Lolium arundinaceum (Schreb.) Darbysh] forages, one an experimental host plant/endophyte association containing a novel endophyte that produces low or nil concentrations of ergot alkaloids (HM4) and the other a typical association of Kentucky 31 tall fescue and the wild-type endophyte (Neotyphodium coenophialum; E+), were autumn-stockpiled following late-summer clipping and fertilization with 56 kg/ha of N to assess N partitioning and ruminal disappearance kinetics of N for these autumn-stockpiled tall fescue forages. Beginning on December 4, 2003, sixteen 361 ± 56.4-kg replacement dairy heifers were stratified by weight and breeding, and assigned to one of four 1.6-ha pastures (2 each of E+ and HM4) that were strip-grazed throughout the winter. Pastures were sampled before grazing was initiated (December 4), each time heifers were allowed access to a fresh pasture strip (December 26, January 15, and February 4), and when the study was terminated (February 26). Generally, fescue type and the fescue type × sampling date interaction exhibited only minor effects on total forage N, or partitioning of N within the cell solubles or the cell wall. For pregrazed forages, concentrations of N and N partitioned within the cell solubles both declined in a strongly linear relationship with sampling dates. In contrast, concentrations of cell-wall-associated N changed in erratic and often higher-ordered relationships with time, but the magnitude of these responses generally was limited. Unlike the partitioning of N within cell-wall and cell-soluble fractions, kinetic characteristics of ruminal N disappearance frequently exhibited interactions of fescue type and sampling date. For pregrazed forages, these included interactions for all response variables, and for postgrazed forages, fractions B and C, as well as rumen degradable protein. Ruminal disappearance rate for pregrazed E+ and HM4 exhibited quadratic (range = 0.057 to 0.082/h) and cubic (range = 0.057 to 0.075/h) relationships with time, respectively. For postgrazed E+ and HM4 forages, ruminal disappearance rate was unaffected (mean = 0.066/h) or only tended to be affected by sampling date (mean = 0.065/h), respectively. Concentrations of rumen degradable protein exhibited various curvilinear relationships with sampling dates, but disappearance was consistently extensive, and the overall range was relatively narrow (71.3 to 78.9% of N). These findings suggest that ruminal disappearance of N for autumn-stockpiled tall fescue forages remains extensive throughout the winter months and is only affected minimally by fescue type, sampling date, and grazing status.     

The effects of defaunation on the metabolism of lactic acid in the rumen

Two experiments examined the effects of defaunation on the ruminal metabolism of lactate. Three rumen-cannulated sheep given a diet of molassed sugar beet pulp and barley (80:20) were used to study the effects of defaunation (with manoxol-OT) on the metabolism of lactic acid produced endogenously from rumen fermentation. Defaunation increased mean ruminal concentrations of lactate from 3.4 mmol litre^?1 to 8.9 mmol litre^?1 but other rumen measurements remained virtually unchanged: pH, 6.3 and 6.3; molar proportions of acetic acid, 645 and 645 mmol mol^?1; propionic acid, 189 and 197 mmol mol^?1 and butyric acid 142 and 115 mmol mol^?1 for the faunated and defaunated states respectively. In a second experiment, two groups each of four rumen-cannulated sheep were used to study the effect of defaunation on the ruminal metabolism of added Na-D, L lactate. One group of four was defaunated using a rumen-washing technique whilst the other group of four remained faunated. The animals were given a diet of rolled barley and hay (60:40) and were given a series of intraruminal doses of Na-D, L lactate from 0 to 100 g day^?1, increasing by 20 g day^?1 every third day. Disappearance of added lactate was much more rapid in faunated animals: at the 100 g day^?1 dose rate, L-lactate concentrations had fallen from a peak of 6 g litre^?1 to >1 g litre^?1 after 3 h whereas in defaunated sheep the peak of 6.5 g litre^?1 was reduced to >1 g litre^?1 only after 7 h. In faunated animals lactate addition caused an increase in the ruminal concentration of total volatile fatty acids (VFA) from 147 to 217 mmol litre^?1 between the zero and 100 g day^?1 dose rates, accompanied by an increase in the molar proportion of propionic acid from 190 to 320 mmol mol^?1. However, in defaunated animals there was only a small increase in total VFA concentrations from 94 to 106 mmol ml^?1 with no change in the molar proportion of propionic acid and a small increase in butryric acid from 140 to 180 mmol mol^?1.     

Effect of lactic acid bacteria inoculants on in vitro digestibility of wheat and corn silages

The aim of the study was to determine the effect of 10 sources of lactic acid bacteria (LAB) on dry matter digestibility (DM-D) and neutral detergent fiber digestibility (NDF-D), in various combinations with starch, in vitro. The soluble starch represented a concentrate feed, whereas silage represented feeding only roughage. The DM-D and NDF-D were determined after 24 and 48 h of incubation to represent effective (24 h) and potential (48 h) digestibility. Addition of LAB was both by direct application of the inoculants to rumen fluid (directly fed microbials) and by the use of preinoculated silages. For each feed combination, tubes without added LAB served as controls. The results indicate that, overall, some LAB inoculants applied at ensiling or added directly to the rumen fluid had the potential to increase the DM-D and NDF-D. The major significant inoculant effect on NDF-D was obtained after 24 h of incubation, whereas the effect after 48 h was mainly nonsignificant. The effective inoculants seemed to minimize the inhibitory effect of the starch on NDF-D within 24 h, perhaps by competition with lactate-producing rumen microorganisms.     

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

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

Technical note: assessment of recovery site of mobile nylon bags for measuring ileal digestibility of starch in dairy cows

The objective of this study was to evaluate recovery site of mobile nylon bags for measuring ileal digestibility of ruminally undegraded starch in dairy cows. Eight feed samples of untreated and treated concentrates were examined. Three lactating cows equipped with rumen fistula and duodenal and ileal cannulas were used in the experiment. The mobile nylon bags containing intact feeds or residues after a 12-h ruminal incubation were pretreated using a 2-step procedure to simulate abomasal digestion before insertion through the duodenal cannula. To assess the effect of hindgut fermentation on starch digestibility, approximately half of the bags were collected from the ileum and half from the feces. The results indicate that feed samples should be preincubated in rumen before insertion into duodenum, and that samples with relatively high fractions of rumen-undigestible starch should be collected from the ileum instead of from feces.