Effects of urea and sodium bicarbonate supplementation of a high-fiber diet on nutrient digestion and ruminal characteristics of defaunated sheep.

Five sheep (average BW 48 kg) with ruminal, duodenal, and ileal cannulas were fed 63% roughage: 37% concentrate diets (CP = 14.5%) in a 5 x 5 Latin square design to study effects of urea and sodium bicarbonate supplementation on nutrient digestion and ruminal characteristics of defaunated sheep. Diets were fed twice daily (DMI = 1,076 g/d). Defaunation was accomplished with 25-ml doses of alkanate 3SL3/sheep daily for 3 d. Control sheep were faunated (Treatment 1) and fed soybean meal as the major N supplement. Remaining sheep were maintained defaunated and fed either the same diet as Treatment 1 (Treatment 2), Treatment 1 with urea replacing 30% of the soybean meal N (Treatment 3), or Treatment 1 with 2% sodium bicarbonate in the diet (Treatment 4). Treatment 5 was a combination of Treatments 3 and 4. Compared with the faunated control, defaunation decreased (P less than .05) total tract DM, OM, NDF, ADF, and CP digestibilities (71.5 vs 69.4, 73.8 vs 71.7, 64.6 vs 61.4, 58.7 vs 55.8, and 74.2 vs 70.6%, respectively) and average (2 to 12 h postfeeding) ruminal fluid ammonia (23.5 vs 13.7 mg/dl) and isobutyrate (.9 vs .7 mM) concentrations. However, defaunation increased (P less than .05) linoleic and linolenic acid flows (.58 vs .45 g C18:2/d; .17 vs .14 g C18:3/d) to and disappearance (.50 vs .39 g C18:2/d; .14 vs .11 g C18:3/d) from the small intestine. Urea supplementation increased (P less than .05) total tract DM (70.2 vs 68.6%) and OM (72.3 vs 71.0%) digestibilities of defaunated sheep but lowered (P less than .05) ruminal fluid isobutyrate concentration (.6 vs .8 mM). Sodium bicarbonate supplementation increased (P less than .05) ruminal fluid pH (6.4 vs 6.2), isobutyrate concentration (.75 vs .60 mM), total tract ADF digestibility (57.6 vs 54.2%), and ruminal NDF (41.6 vs 28.5%), ADF (36.6 vs 22.8%), and CP (-5.5 vs -26.8%) digestibilities in defaunated sheep. Dietary supplementation of urea or sodium bicarbonate increased nutrient digestion by defaunated sheep.     

Comparison of various amino acids for estimation of microbial nitrogen in digesta

Methods of estimating microbial N in digesta were compared, and two simplified methods were described for separation of diaminopimelic acid (DAP) from methionine in acid hydrolysates of biological samples using an automated amino acid analyzer. Recoveries of DAP when added to bacterial, abomasal and feed samples were 92 to 98%. All samples analyzed (bacteria, protozoa and several feedstuffs) contained detectable DAP (or another amino acid with similar elution time). Apparent DAP-N (percentage of total sample N) in feeds ranged from 12 to 78% of bacterial DAP-N concentration. These values are greater than can be accounted for by bacterial contamination. Correction for apparent dietary DAP was appropriate when using this microbial marker. Reasonable estimation of bacterial N was made in abomasal digesta of steers fed high-grain diets using DAP, lysine or combinations of DAP and leucine or lysine and leucine. There was excellent agreement among these marker methods in ranking dietary treatment regimens with respect to bacterial N present in the abomasum. The use of leucine alone, or the combination of DAP and lysine, gave nonrealistic values. Two-amino-ethylphosphonic acid (AEP) was not detected in acid hydrolysates of mixed ruminal protozoa or abomasal digesta. Two other ninhydrin-reactive compounds with elution times close to AEP were detected in all samples analyzed, which may have been identified as AEP in other studies. It was concluded that corrected DAP and lysine were the best estimates of bacterial N and AEP was precluded as a marker of protozoal N.     

N tau-methylhistidine--feed and duodenal content and ruminal degradation

N tau-methylhistidine (NMH) concentrations were determined in acid hydrolysates of 12 common feedstuffs for ruminants, and duodenal digesta from steers fed alfalfa haylage and high-moisture corn. For six species of grass hays, NMH concentrations ranged from nondetectable (ND; less than .1 nmol/g dry matter) to .6 nmol/g dry matter. Two legume hays had NMH concentrations of .9 and 2.0 nmol/g dry matter, respectively. For corn silage, high-moisture corn, beet pulp and soybean meal, NMH concentrations were 1.3, 1.1, 1.5 and 2.2 nmol/g dry matter, respectively. Duodenal digesta NMH concentrations ranged from ND to 1.2 nmol/g dry matter. When pure NMH (1 mM) was incubated with rumen fluid in vitro for 8 h, only 14% was degraded while leucine (1 mM) was totally degraded. From the feedstuffs used in this study, results show that exogenous (dietary) NMH is not a concern in skeletal muscle protein turnover studies in cattle using urinary NMH excretion because it can be calculated that potential NMH intake from the preceding feedstuffs would be less than 1% of normal urinary excretion and that ruminal microbes are not a potential source of NMH. NMH was resistant to in vitro ruminal degradation. The in vitro ruminal NMH degradation results suggest that when feedstuffs containing at least 15 nmol/g dry matter are fed (far greater than values observed in this study) a significant proportion of urinary NMH would arise directly from exogenous sources and would invalidate the use of this technique in assessing protein turnover in cattle.     

Effects of protozoa on bacterial nitrogen recycling in the rumen

The effects of protozoa on ruminal NH3-N kinetics and bacterial N recycling were measured in five sheep (57.6+/-7.1 kg BW, x +/- SD) with ruminal and duodenal cannulas in naturally faunated, defaunated, and refaunated periods. The sheep were fed a diet of 239 g of alfalfa haylage and 814 g of barley concentrate per day (DM basis) divided into 12 equal portions and allocated at 2-h intervals. A pulse dose of 300 mg of 15N as [15N]NH4Cl was administered into the rumen (on d 1 and 15) and 300 mg of 15N as [15N]urea was administered intravenously to the blood (d 8). Enrichment of 15N was measured in ruminal NH3-N, bacterial N, and plasma urea N over a period of 35 h. Total collection of urine was made for 5 d and analyzed for purine derivatives to calculate the flow of microbial N. Ruminal parameters and nutrient digestibilities were also measured. Sheep were defaunated using a rumen washing procedure 50 d prior to measurements in the defaunated period. Sheep were refaunated with ruminal contents from a faunated sheep receiving the same diet. Measurements began 26 d following refaunation, at which time protozoal numbers had returned to those in the originally faunated sheep. Data reported in parentheses are for faunated, defaunated, and refaunated sheep, respectively. Total culturable and cellulolytic bacterial numbers were unaffected by defaunation, but there was an increase in flow of microbial N from the rumen (10.8, 17.3, and 11.1 g N/d; P < .05) in the defaunated period. Flux, irreversible loss, and intraruminal recycling of NH3-N and recycling of NH3-N from plasma urea N were not affected by defaunation. Defaunation had no effect on reducing the absolute amount (13.8, 10.0, and 11.3 g N/d; P > .20) of bacterial N recycling and the percentage of N flux through the bacterial N pool. Total-tract digestion was reduced in defaunated compared with faunated sheep by 8, 17, 15, and 32% for OM, N, NDF, and ADF, respectively. In conclusion, defaunation improved ruminal N metabolism through the enhancement of bacterial protein synthesis, and improvement in the flow of microbial protein to the host animal.     

Comparative characterization of reticular and duodenal digesta and possibilities of estimating microbial outflow from the rumen based on reticular sampling in dairy cows

The objective of this experiment was to investigate the possibility of estimating the outflow of nutrients and microbial protein from the rumen based on sampling reticular contents as an alternative to duodenal sampling. Microbial protein flow estimates were also compared with a third method based on sampling of ruminal contents. Reticular and duodenal digesta and ruminal contents were recovered from 4 cows used in a 4 x 4 Latin square design experiment, in which the ruminal effects of 4 exogenous enzyme preparations were studied. Large and small particulate and fluid markers were used to estimate digesta flow in a triple-marker model; 15N was used as a microbial marker. Reticular and duodenal digesta were segregated into small and large particles (SP and LP, respectively) and a fluid phase, and ruminal digesta was segregated into particulate and fluid phases. Compared with digesta recovered at the duodenum, reticular digesta had lower OM and greater NDF contents. The proportion of microbial N was notably greater in the fluid phase of reticular digesta. Ruminal outflow of DM and OM was greater (by 17 and 28%) and that of NDF was lower (by 14%) when estimated from duodenal compared with reticular samples. There was no difference in the estimated flow of starch and nonammonia and microbial N between the reticular and duodenal techniques. Microbial N flow estimated based on ruminal sampling was similar to those based on duodenal and reticular sampling. The ruminal method, however, grossly overestimated flow of DM, OM, and NDF. This study supports the concept that microbial protein outflow from the rumen can be measured based on sampling of ruminal or reticular digesta. The reticular sampling technique can also provide reliable estimates for ruminal digestibility of OM, N, and fiber fractions. These findings need to be confirmed in experiments with basal diets varying in structure and forage-to-concentrate ratios.     

Effects of protozoa on the antioxidant activity in the ruminal fluid and blood plasma of cattle

The objective of this study was to investigate the antioxidant status in ruminal fluid and blood plasma among three faunated and two defaunated (protozoa‐free) cattle (average bodyweight of 225 kg), fed hay plus concentrate. The extra cellular antioxidant activity of the mixed protozoa and bacteria suspensions were also studied in vitro. The antioxidant activity was detected by means of the free radical scavenging ability. The activity (units/microbial nitrogen) of the protozoal suspension increased from 59 (0 h) to 318 (18 h), and decreased to 40 (24 h) during incubation. The activity of the bacterial suspension also increased from 111 (0 h) to 644 (18 h), and decreased to 533 (24 h). The antioxidant activity (units/mL, U/mL) in the ruminal fluid of faunated (ranging from 116 to 254) and defaunated (ranging from 66 to 110) cattle was increased after 2 h and decreased after 5 h of feeding, being significantly higher in the faunated cattle. The antioxidant activity of blood plasma (U/mL) ranged from 248 to 316 in the faunated and 121–170 in the defaunated cattle during 0–5 h after feeding, being significantly higher in the faunated cattle. Therefore, defaunation possibly causes a decrease in the antioxidant level in the ruminal fluid, and may impair the health and performance of ruminants through an oxidant–antioxidant imbalance.     

Effects of Sapindus saponaria fruits on ruminal fermentation and duodenal nitrogen flow of sheep fed a tropical grass diet with and without legume

Six adult African-type hair sheep (BW = 40.3 +/- 6.3 kg) fitted with ruminal and duodenal cannulas were subjected to four treatments. Sheep were offered basal diets at a rate of 80 g of DM/kg of metabolic BW (equivalent to ad libitum access) consisting either of a low-quality grass hay (Brachiaria dictyoneura, 3.7% CP, DM basis) alone or in combination with a forage legume (Cratylia argentea, 18.6% CP, DM basis) in a 3:1 ratio (DM basis). In addition, 0 or 8 g of DM of Sapindus saponaria fruits (12.0% crude saponins, DM basis) per kilogram of metabolic BW was administered intraruminally. Supplementation of C. argentea increased intakes of OM (+21%; P < 0.01) and CP (+130%; P < 0.001), as well as ruminal fluid ammonia N concentrations (from 2.40 to 8.43 mg/dL; P < 0.001). Apparent OM and N digestibilities were not affected by legume addition, but ADF digestibility decreased by 10% (P < 0.01). Total ruminal VFA concentration was unchanged, but acetate:propionate was lower (P < 0.01) and isobutyrate proportion was greater (P < 0.001) with the legume addition. Legume supplementation increased duodenal flows of total N (+56%; P < 0.001), nonammonia N (+52%; P < 0.001), ruminal escape N (+80%; P < 0.001), and microbial N (+28%; P < 0.05). Microbial efficiency was not affected by legume addition. Supplementation of S. saponaria increased (P < 0.05) dietary OM intake by 14%, but had no effect on CP intake and ruminal fluid ammonia concentration or on OM and N digestion. Digestibility of ADF was decreased (P < 0.01) by 10% with S. saponaria as was acetate:propionate (P < 0.001) and the isobutyrate proportion (P < 0.001). Ruminal protozoa counts increased (P < 0.01) by 67% with S. saponaria. Duodenal N flows were not significantly affected by S. saponaria supplementation, except for microbial N flow (+34%; P < 0.01). Microbial efficiency was greater (P < 0.05) by 63% with the addition of S. saponaria. Few interactions between legume and S. saponaria supplementation were observed. The NDF digestibility was decreased with S. saponaria in the grass-alone diet, but not in the legume-supplemented diet (interaction; P < 0.05). Interactions were absent in ruminal fermentation measures and duodenal N flow, indicating that effects were additive. Results suggest that, even when not decreasing ruminal protozoa count, supplementation of S. saponaria fruits is a beneficial way to improve ruminal VFA profile, microbial efficiency, and duodenal flow of microbial protein in sheep fed tropical grass-alone or grass-legume diets.     

Effects of bentonite on wool growth and nitrogen metabolism in fauna-free and faunated sheep.

Two experiments were carried out with sheep that originated from a fauna-free flock and were fed a soybean meal-corn silage diet with or without a bentonite supplement. One-half of the sheep fed each diet in each experiment were faunated with a mixed population of ruminal protozoa, whereas the other half of the sheep remained fauna-free until the end of both experiments. Wool growth and daily gain were measured in Exp. 1. (eight rams per treatment), which lasted 110 d, and the metabolic effects in the rumen and intestinal tract of protozoa and dietary bentonite supplement were tested with cannulated wethers (four wethers per treatment) in Exp. 2. The results of Exp. 1 showed decreased wool growth (P less than .05) due to the presence of protozoa in the rumen. Dietary supplementation with bentonite partly offset the decreased wool growth in sheep with protozoa, but there were no effects of dietary bentonite and no protozoa x bentonite interaction (P greater than .05). Daily gain was decreased by the dietary bentonite (P less than .05) supplement but was not affected (P greater than .05) by the ruminal presence of protozoa. In Exp. 2, protozoa increased (P less than .01) the ruminal concentrations of ammonia and decreased (P less than .05) the acetic:propionic acid molar ratio. Fractionation of N in the duodenal digesta flowing from the stomach to the small intestine showed that protozoa decreased (P less than .05) the flow of nonammonia N and bacterial N, and there was a protozoa x bentonite interaction for these effects (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Ruminal fermentation and duodenal flow following progressive inoculations of fauna-free wethers with major individual species of ciliate protozoa or total fauna

Naturally fauna-free (FF) wethers, equipped with ruminal and duodenal cannulas, were used in two groups of eight (Group A) and seven (Group B) animals in six consecutive experimental periods, each lasting for 28 d. The objective was to measure ruminal fermentation traits, and flows of nonammonia nitrogen (NAN), total amino acid (TAA), and bacterial nitrogen (BN) from the stomach after inoculation with individual ciliate protozoa species in each period. The wethers in both groups were fed a diet based on corn silage, haylage, and soybean meal, and they remained FF during the first period. At the beginning of each other period, the wethers were progressively inoculated intraruminally with one individual major species of ruminal ciliate protozoa or total fauna (TF). Thus, Group A was progressively inoculated (+) with Dasytricha ruminantium (DS), Polyplastron multivesiculatum (PP), Isotricha intestinalis (IS), Entodinium caudatum (EN) and TF-type A. Also, Group B was progressively inoculated (+) with IS, DS, Epidinium ecaudatum (EP), Eudiplodinium maggi (EU), and EN. Duodenal digesta and ruminal fluid were collected and sampled in each period on d 26 and 28, respectively, and subjected to chemical analyses. A significantly higher (P < .05) pH (6.4) in ruminal fluid of the Group A wethers was obtained when each DS, DS+PP, DS-PP-IS+EN, and TF population was present in the rumen than when the wethers were FF (6.2). In the Group B wethers, pH (6.1) was lower (P < .05) for the population of IS-DS-EP+EU than for other populations (6.2 to 6.3). The concentration of total VFA in ruminal fluid was higher (P < .05) in the Group B wethers when IS, IS+DS, or IS-DS+EP populations were present in the rumen than when the wethers were FF. The flow of NAN, TAA, and BN from the stomach to the intestinal tract was generally lower for different protozoa populations than for the FF period. Largest decreases (P < .05) in the flow of NAN, TAA, and BN occurred when EN was added into the rumen of wethers in the A and B groups, which already contained populations of DS-PP+IS and IS-DS-EP+EU, respectively. Holotrich protozoa had very little effect on the protein metabolism in the rumen, but cellulolytic protozoa (PP, EP, and EU) and EN decreased the efficiency of protein utilization by the ruminant host.     

The biohydrogenation of linoleamide in vitro and its effects on linoleic acid concentration in duodenal contents of sheep

Previous studies showed that oleamide was protected from ruminal biohydrogenation and increased 18:1(n-9) concentration in milk when fed to lactating dairy cows. To appraise whether this protection extended to linoleamide, a rumen in vitro experiment was conducted to determine biohydrogenation of linoleamide followed by two sheep experiments to evaluate whether linoleamide could increase 18:2 (n-6) concentration in duodenal contents. Treatments for the in vitro and sheep studies consisted of three diets containing no added lipid (control), linoleic acid, or linoleamide. Lipids were added at 10% (DM basis) of the in vitro substrate (ground grass hay). The three substrates were incubated with mixed ruminal microbes in triplicate, and 5 mL of culture contents was taken at 0, 24, and 48 h for analysis of 18:2 (n-6) concentration by gas chromatography. The concentrations of 18:2 (n-6) (corrected for 18:2 (n-6) in the control cultures) at 0, 24, and 48 h were 2.51, 0.38, and 0.11 mg/5 mL for the linoleic acid cultures compared to 2.10, 1.35, and 1.08 mg/5 mL for the linoleamide cultures. Compared to linoleic acid, the cultures containing linoleamide had higher 18:1 (n-9) and lower concentrations of biohydrogenation products including trans-18:1 and 18:0. Three sheep with duodenal cannulas were fed the three diets in two separate 3 x 3 Latin squares each with 2-wk periods. The two squares only differed in the amount of added lipid (1.5 vs 5% of the ration DM). When the lipids were added at 1.5% of the ration DM, they had little effect on duodenal 18:2 (n-6) concentration (2.8, 3.6, and 4.3 mg/g DM for the control, linoleic acid, and linoleamide treatments, respectively). At 5% of the ration DM, both lipid supplements increased duodenal 18:2 (n-6) concentration over the control diet with a greater response observed for linoleamide (2.5, 12.2, and 16.8 mg/g DM for the control, linoleic acid, and linoleamide treatments, respectively). This study demonstrates reduced biohydrogenation of linoleamide based on its ability to maintain a higher concentration of 18:2 (n-6) in ruminal cultures and in duodenal contents of sheep compared to free linoleic acid.     

Effects of defaunation on in situ dry matter and nitrogen disappearance in steers and growth of lambs.

Trials were conducted to determine effects of defaunation procedures on protozoal concentrations and in situ nutrient disappearance in steers and to determine effects of defaunation and supplemental protein source on performance of lambs. Four ruminally cannulated steers were isolated from other ruminants and fed a dehydrated alfalfa-cracked corn diet for three periods with four replicates (steers) per period. Treatments were as follows: 1) control (no defaunation), 2) dosing fasted steers for two consecutive days with 40 g dioctyl sulfosuccinate (DSS) and 3) daily feeding of 40 g DSS to defaunated, nonfasted steers. Ten days post-dosing with DSS (treatment 2), three steers were free of protozoa but one steer still had a ruminal concentration of .6 x 10(4) protozoa/ml. Compared to steers prior to defaunation, treating steers for 2 d with DSS decreased (P less than .05) both in situ soybean meal (SBM) N disappearance at 3, 6 and 9 h of incubation and in situ orchardgrass DM disappearance at 24 h of incubation. Feeding 40 g of DSS daily for 10 d was not successful in maintaining the rumen free of protozoa. Thirty crossbred Targhee lambs (avg wt, 25 kg) were defaunated with DSS and allotted by BW and sex to five treatments: 1) defaunated, fish meal supplemented at 9.5% dietary CP (FM-9.5% CP), 2) defaunated, SBM-9.5% CP, 3) refaunated, FM-9.5% CP, 4) refaunated, SBM-9.5% CP and 5) refaunated SBM-12% CP. Defaunated lambs remained free of protozoa during the 56-d performance trial that was initiated 24 d after the defaunation procedure.(ABSTRACT TRUNCATED AT 250 WORDS)     

Postprandial trends in estimated ruminal digesta polysaccharides and their relation to changes in bacterial groups and ruminal fluid characteristics

In a diurnal study, feedstuff and digesta polysaccharides, ruminal bacterial carbohydrate-fermenting groups, and selected ruminal fluid characteristics (ruminal pH, ammonia and volatile fatty acids) were measured in ruminal-cannulated Holstein steers fed high- or low-forage diets at maintenance level intake once daily. A procedure for the sequential extraction of soluble sugar, starch, pectin, hemicellulose and cellulose from feedstuffs was developed to measure these carbohydrates in dietary and ruminal digesta samples. Recovery of dry matter (determined chemically) using this scheme was 60 to 70%. Data were obtained within the ranges of those in the literature for similar feedstuffs and(or) by similar methods. Dietary analysis by the sequential method yielded total recovery across all carbohydrate fractions of 87 and 81% for the high- and low-forage diets, respectively, and similar recoveries were obtained for the digesta samples. Analytical variation was small (less than or equal to 15% CV), which permitted comparison of the carbohydrate profiles of the digesta over time. From these values, total ruminal digesta polysaccharide content was calculated and, when plotted over time, indicated that the disappearance per fraction corresponded with theoretical curves for ruminal fermentation of major feedstuff components. The postprandial variation within the bacterial population carbohydrate-fermenting groups was small, but changes were consistent with digesta component fermentation. Xylan- and cellulose-fermenting groups followed a pattern compatible with the disappearance of these polysaccharides from the rumen. In contrast, soluble sugar-fermenting groups predominated at all times despite the rapid rise and fall of these components in the digesta. Ruminal fluid pH, ammonia and total carbohydrate supported the digesta and bacterial trends observed. The data are interpreted to suggest that once daily maintenance feeding of high- or low- forage diets permits detection of digesta sugar and polysaccharide changes, supports a relatively stable microbial population while specific groups increase and decrease with the availability of substrate, and results in few differences in ruminal fluid traits.     

Site of 3-methylindole and indole absorption in steers after ruminal administration of L-tryptophan

To determine the site of 3-methylindole (3MI) and indole absorption in cattle after ruminal administration of L-tryptophan (TRP), 4 Holstein steers were given 0.4 g of TRP/kg of body weight directly into the rumen through ruminal cannulas. Chromium EDTA and ruthenium phenanthroline were added to feedings of orchard grass hay twice a day for measurement of fluid and particulate flow to the duodenum, respectively. Passage of 3MI and indole (products of ruminal fermentation of TRP) to the duodenum was determined by the products of digesta flow rate and concentration in duodenal contents. Ruminal fluid, duodenal contents, and jugular blood were sampled at postdosing hours (PDH) 0, 6, 12, 18, 24, 36, and 72 for analysis of 3MI, indole, and digesta flow markers. Ruminal, duodenal, and jugular plasma concentrations of 3MI and indole peaked at PDH 12 to 24 at 152.4 and 25.9; 15.5 and 1.0; and 8.7 and 2.2 mg/L, respectively. Most 3MI and indole reaching the duodenum were associated with the particulate phase of the digesta. On a molar basis, total passage of 3MI to the duodenum during 72 hours amounted to 1.0% of the TRP dose for 3MI and 0.1% of the TRP dose for indole. Absorption of 3MI and indole in these steers was almost entirely proximal to the duodenum.     

奶牛常用饲料干物质和淀粉瘤胃降解规律的研究

以3头安装有永久性瘤胃瘘管的泌乳前期荷斯坦奶牛为试验动物，在精粗比为55：45的日粮条件下，采用Insacco法测定了奶牛常用饲料瘤胃内干物质和淀粉的降解规律。试验结果表明。不同饲料干物质和淀粉的降解率不同。能量饲料中，麸皮干物质和淀粉的瘤胃降解率高于玉米：蛋白质饲料中，干物质和淀粉的降解率由高到低顺序依次是豆粕〉胡麻饼〉棉粕：常用粗料中，玉米青贮干物质和淀粉的降解率均高于青干草。     

Effects of defaunation and various nitrogen supplementation regimens on microbial numbers and activity in the rumen of sheep

Five sheep (average BW 62 kg) were fed 65% roughage: 35% concentrate diets (CP = 15%) in a 5 x 5 Latin square design to study the effects of combinations of defaunation and N supplements (soybean meal [SBM], corn gluten meal [CGM], blood meal [BM], urea, and casein) differing in ruminal degradation on ruminal microbial numbers and activity. Diets were fed twice daily (DM intake 1,759 g/d). Defaunation was accomplished with doses of 30 ml of alkanate 3SL3.sheep-1.d-1 for 3 d with 2 d of fasting. Treatment 1 (control) involved feeding faunated sheep a diet in which the supplemental N was 67% SBM N and 33% urea N. Treatment 2 involved feeding defaunated sheep the same diet as the control. Treatments 3, 4, and 5 involved feeding defaunated sheep diets in which the supplemental N source was either 67% CGM-BM N (CGM and BM combined on a 1:1 N ratio): 33% urea N, or 33% CGM-BM N:67% urea N or 33% CGM-BM N:33% urea N:33% casein N, respectively. Compared with the faunated control, defaunation (Treatments 2, 3, 4, and 5) increased (P less than .05) total direct counts of ruminal bacteria (2.7 vs 1.3 x 10(11)/ml), fungal zoospores (2.8 vs 1.4 x 10(5)/ml), and ruminal microbial protease activity (1.4 vs 1.0 mg azocasein/[ml ruminal fluid.h]). Defaunation did not have a consistent effect on ruminal microbial deaminase activity. Compared with the control, defaunation resulted in lower (P less than .05) total perchloric acid-soluble amino N in ruminal fluid at 4 and 10 h after the morning feeding. Defaunation did not decrease (P greater than .05) total free amino acid concentrations in ruminal fluid, but it altered the profile of free amino acids. Although defaunation increased (P less than .05) ruminal bacterial numbers, no increases in total microbial CP or OM concentrations in ruminal contents were observed.     

Effect of presence of rumen protozoa on degradation of cell wall constituents in gastrointestinal tract of cattle

The cell wall constituents of feces from three faunated and three defaunated (without ruminal ciliate protozoa) cattle fed on a Sudangrass hay and concentrate mixture (8:5) were analyzed. There was little difference in digestibility of dry matter between the faunated and defaunated cattle. Analysis of the fecal sugar residues revealed that the digestibilities of arabinose and galactose, derived from pectic and hemicellulosic substances located within the compound middle lamella, were higher in the defaunated cattle than the faunated cattle (P < 0.05), whereas the digestibilities of glucose and xylose, derived mainly from cellulose and xylan, were unchanged by the removal of protozoa. The digestibility of lignin was not different between the faunated and defaunated cattle, but those of mannose and p‐coumaric acid were lower in the defaunated than in the faunated animals (P < 0.05). The ratio of primary cell wall to secondary cell wall in fecal plant materials was lower for the defaunated than for the faunated cattle. The results in this study suggested that the defaunation enhanced the microbial degradation of the thin cell walls, but depressed the degradation of developed cell walls.     

Effect of dietary protein level on nitrogen metabolism in the growing bovine: II. Diffusion into and utilization of endogenous urea nitrogen in the rumen

Six Angus heifer calves (234 kg) were assigned to either a high (HP; 126.1 g N/d) or low (LP; 66.5 g N/d) protein intake to evaluate ruminal criteria associated with movement of blood urea-N (BUN)-derived NH3-N from the rumen wall into interior ruminal digesta. Calves received 4.8 kg DM/d of diets containing 30% cottonseed hulls and 70% cornsoybean meal in equal portions at 4-h intervals. Following single i.v. injections of 15N-urea, ruminal fluid was collected serially for 4 h postinjection from digesta located adjacent to the rumen wall (wall-proximate digesta; WPD) and from the center of the rumen digesta mass after manual agitation (center mixed digesta; CMD). Mean ruminal NH3-N (RAN) concentrations were higher (P less than .05) for HP than for LP, but were not affected (P greater than .05) by digesta sampling site. Ruminal urease activity was higher (P less than .05) for LP than for HP and tended (P = .14) to be higher for WPD than for CMD. Area under the 15N enrichment curve (AUC) ratios between sampling sites (WPD/CMD x 100) for RAN were greater (P less than .05) for LP than for HP. However, AUC ratios for bacterial N were not affected (P greater than .05) by protein level. Whereas BUN-derived 15NH3 appeared to thoroughly equilibrate with RAN in interior ruminal digesta with HP, there appeared to be a declining enrichment gradient for RAN from the rumen wall to the interior ruminal digesta with LP. Data are interpreted to suggest that bacteria at or near the rumen wall may preferentially utilize some BUN-derived NH3-N entering through the rumen wall in calves fed LP diets.     

Manipulation of nitrogen digestion by sheep using defaunation and various nitrogen supplementation regimens

Five ruminally, duodenally, and ileally cannulated sheep (average BW 62 kg) were fed 65% roughage: 35% concentrate diets (CP = 15%) in a 5 x 5 Latin square design to study the applicability of using a combination of defaunation with N supplements (soybean meal [SBM], corn gluten meal [CGM], blood meal [BM], urea, and casein) with different extents of ruminal degradation to manipulate microbial protein synthesis and amount of ruminal escape protein. Diets were fed twice daily (1,759 g DM/d). Defaunation was accomplished with 30-ml doses of alkanate 3SL3 (active ingredient: sodium lauryl diethoxy sulfate)/sheep daily for 3 d with 2 d of fasting. Treatment 1 (control) involved feeding faunated sheep a diet in which the supplemental N (45% of total dietary N) was 67% SBM N and 33% urea N. Treatment 2 involved feeding defaunated sheep the same diet as the control. Treatments 3, 4, and 5 involved feeding defaunated sheep diets in which the supplemental N source was either 67% CGM-BM (1:1 N ratio) N:33% urea N, or 33% CGM-BM N:67% urea N or 33% CGM-BM N:33% urea N:33% casein N, respectively. Compared with the faunated control, defaunation decreased (P less than .05) ruminal ammonia concentration (19 vs 26 mg/dl) and increased (P less than .05) CP flow to the duodenum (253 vs 214 g/d) due to a trend for increases in both bacterial (BCP) and nonbacterial (NBCP) CP flows.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ruminal ciliated protozoa in cattle fed finishing diets with or without supplemental fat

Ruminal samples were collected at slaughter from 364 unfasted steers fed different finishing diets to obtain information on numbers and species distribution of ciliated protozoa in feedlot cattle. Total numbers of protozoa averaged 1.59 X 10(5)/g of ruminal contents. A total of 47 steers (12.9%) were defaunated, but 4.1% of the steers possessed numbers of protozoa greater than 10(6)/g. Entodinium species did not always dominate the protozoan populations; 41 faunated steers (11.2%) were devoid of entodinia, and 79 additional steers (21.7%) possessed populations dominated (greater than 50%) by other genera. Isotricha was the most commonly occurring genus supplanting Entodinium, but Polyplastron and Epidinium were frequently present in high concentrations. Tallow and soybean soapstock supplementation reduced (P less than .05) numbers of protozoa in steers consuming wheat diets. However, yellow grease supplementation did not affect numbers of protozoa in steers fed either sorghum or corn diets. Average ruminal pH was 6.20 on the wheat diet, 6.05 on the corn diet, and 5.69 and 6.23 for the two sorghum diets, respectively. We found no correlation between ruminal pH and numbers of protozoa on any diet. The presence of relatively high protozoan concentrations and few defaunated animals in feedlot cattle necessitates reevaluation of the role that ciliated protozoa play in ruminal metabolism of animals fed processed, high-concentrate diets.     

Intraruminal supplementation with increasing levels of exogenous polysaccharide-degrading enzymes: effects on nutrient digestion in cattle fed a barley grain diet

The effects of supplying increasing ruminal doses of exogenous polysaccharide-degrading enzymes (EPDE) on rumen fermentation and nutrient digestion were studied using eight ruminally cannulated heifers, four of which were also duodenally cannulated, in a replicated Latin square. The heifers were fed a diet of 85.5% rolled barley grain and 14% barley silage (DM basis), and once daily they were given intraruminal doses of 0 (Control), 100, 200, or 400 g of a preparation containing polysaccharide-degrading enzymes. Enzyme treatment decreased ruminal pH (linear, P<.001) and increased ammonia N (quadratic, P<.001) concentration. The ruminally soluble fraction and effective degradability of feed DM in situ were increased (quadratic response, P<.001) by enzyme treatment. Ruminal administration of EPDE increased ruminal fluid carboxymethylcellulase and xylanase activities linearly (P<.001) and beta-glucanase activity quadratically (P<.01), decreased (quadratic response, P<.05) ruminal fluid viscosity, and did not affect (P>.05) ruminal fluid amylase activity. Elevated levels of fibrolytic activities in the rumen resulted in increased (quadratic, P<.001) carboxymethylcellulase, xylanase, and beta-glucanase (P<.01) activities in duodenal digesta. Duodenal amylase activity and reducing sugar concentration were also increased (quadratic responses, P<.001 and P<.05, respectively) by EPDE. Xylanase activity of fecal DM was increased linearly (P<.05) with increasing ruminal EPDE levels. Apparent digestibilities of DM, crude protein, and NDF were not affected by EPDE supplementation. Enzyme treatment did not affect (P>.05) urinary excretion of allantoin and uric acid, or concentrations of glucose and urea in blood.