Actinobacillus succinogenes sp. nov., a novel succinic-acid-producing strain from the bovine rumen.
Strain 130ZT was isolated from the bovine rumen. It is a facultatively anaerobic, pleomorphic, Gram-negative rod. It exhibits a 'Morse code' form of morphology, which is characteristic of the genus Actinobacillus. Strain 130ZT is a capnophilic, osmotolerant succinogen that utilizes a broad range of sugars. It accumulates high concentrations of succinic acid (> 70 g l-1). Strain 130ZT is positive for catalase, oxidase, alkaline phosphatase and beta-galactosidase, but does not produce indole or urease. Acid but no gas is produced from D-glucose and D-fructose. 16S rRNA sequence analysis places strain 130ZT within the family Pasteurellaceae; the most closely related members of the family Pasteurellaceae have 16S rRNA similarities of 95.5% or less with strain 130ZT. Strain 130ZT was compared with Actinobacillus lignieresii and the related Bisgaard Taxa 6 and 10. Based upon morphological and biochemical properties, strain 130ZT is most similar to members of the genus Actinobacillus within the family Pasteurellaceae. It is proposed that strain 130ZT be classified as a new species, Actinobacillus succinogenes. The type strain of Actinobacillus succinogenes sp. nov. is ATCC 55618T. (+info)
A cold-active glucanase from the ruminal bacterium Fibrobacter succinogenes S85.
We previously characterized two endoglucanases, CelG and EGD, from the mesophilic ruminal anaerobe Fibrobacter succinogenes S85. Further comparative experiments have shown that CelG is a cold-active enzyme whose catalytic properties are superior to those of several other intensively studied cold-active enzymes. It has a lower temperature optimum, of 25 degrees C, and retains about 70% of its maximum activity at 0 degrees C, while EGD has a temperature optimum of 35 degrees C and retains only about 18% of its maximal activity at 0 degrees C. When assayed at 4 degrees C, CelG exhibits a 33-fold-higher kcat value and a 73-fold-higher physiological efficiency (kcat/Km) than EGD. CelG has a low thermal stability, as indicated by the effect of temperature on its activity and secondary structure. The presence of small amino acids around the putative catalytic residues may add to the flexibility of the enzyme, thereby increasing its activity at cold temperatures. Its activity is modulated by sodium chloride, with an increase of over 1.8-fold at an ionic strength of 0.03. Possible explanations for the presence of a cold-active enzyme in a mesophile are that cold-active enzymes are more broadly distributed than previously expected, that lateral transfer of the gene from a psychrophile occurred, or that F. succinogenes originated from the marine environment. (+info)
Processing, mixing, and particle size reduction of forages for dairy cattle.
Adequate forage amounts in both physical and chemical forms are necessary for proper ruminal function in dairy cows. Under conditions in which total amounts of forage or particle size of the forage are reduced, cows spend less time ruminating and have a decreased amount of buoyant digesta in the rumen. These factors reduce saliva production and allow ruminal pH to fall, depressing activity of cellulolytic bacteria and causing a prolonged period of low ruminal pH. Insufficient particle size of the diet decreases the ruminal acetate-to-propionate ratio and reduces ruminal pH. The mean particle size of the diet, the variation in particle size, and the amount of chemical fiber (i.e., NDF or ADF) are all nutritionally important for dairy cows. Defining amounts and physical characteristics of fiber is important in balancing dairy cattle diets. Because particle size plays such an important role in digestion and animal performance, it must be an important consideration from harvest through feeding. Forages should not be reduced in particle size beyond what is necessary to achieve minimal storage losses and what can be accommodated by existing equipment. Forage and total mixed ration (TMR) particle sizes are potentially reduced in size by all phases of harvesting, storing, taking out of storage, mixing, and delivery of feed to the dairy cow. Mixing feed causes a reduction in size of all feed particles and is directly related to TMR mixing time; field studies show that the longest particles (>27 mm) may be reduced in size by 50%. Forage and TMR particle size as fed to the cows should be periodically monitored to maintain adequate nutrition for the dairy cow. (+info)
Ruminally undegraded intake protein in sheep fed low-quality forage: effect on weight, growth, cell proliferation, and morphology of visceral organs.
To determine the influence of increasing levels of supplemental ruminally undegraded intake protein (UIP) on visceral organ weights, growth, cell proliferation, and morphology, 20 mature ewes of mixed breeding were fed a 6.55% CP grass hay:straw mixture (40:60) and assigned to one of four supplemental treatments. Supplements were control (no supplement) and low, medium, and high levels of UIP. After 42 to 46 d on treatment, ewes were infused i.v. with 5-bromo-2-deoxy-uridine (BrdU, a thymidine analog used to provide an index of the rate of intestinal cell proliferation) and slaughtered 1 h later. Visceral organs were weighed, and subsamples were obtained to evaluate visceral DNA, RNA, and protein contents (frozen samples) as well as intestinal morphology (fixed samples). Final BW; eviscerated BW (EBW); total visceral weight; and liver fresh, dry, and dry fat-free weights were increased (P<.10) in protein-supplemented ewes compared with controls, but were not influenced by increasing levels of UIP. Tissue weights of duodenum, jejunum, ileum, cecum, and colon were not greatly influenced by treatment. There were no differences among treatments in intestinal DNA and protein concentrations and the ratios RNA:DNA and protein:DNA. Jejunal RNA concentration and content was increased (P<.10) in low compared with medium and high treatments. Jejunal RNA content also was decreased (P<.10) in high compared with the medium UIP treatment. Liver RNA and protein contents were increased (P<.10) with protein supplementation. In contrast, contents of RNA, DNA, and protein in duodenum, ileum, cecum, and colon were not influenced by treatment. In addition, neither the rate of intestinal proliferation (BrdU labeling) nor intestinal morphology (crypt depth, villus length, or villus width) were affected by treatment. These data indicate that the influence of protein supplementation on visceral growth involves primarily the liver and not the intestines. These data also indicate that visceral growth, except in jejunum, are not altered by differing levels of UIP supplementation. (+info)
Fermentation substrate and dilution rate interact to affect microbial growth and efficiency.
The effect of dilution rate (D) on carbohydrate, fibrous and nonfibrous, and protein fermentation by ruminal microorganisms was studied using a single-effluent continuous-culture system. The diets of fibrous carbohydrate, nonfibrous carbohydrate, or protein were formulated with soybean hulls (FC), ground corn (NFC), or isolated soy protein (PR) as the primary ingredient, respectively. Six dilution rates (.025, .050, .075, .10, .15, and .20/h of fermenter volume) were used. Digestibilities of DM, OM, and CP for the three diets and of NDF and ADF for the FC diet decreased (P<.001) as D increased, although the response of the digestibility to D varied with diet. Increasing D resulted in an increase in pH (P<.001) and a decrease (P<.001) in ammonia concentration. Daily volatile fatty acid production increased (quadratic; P<.01) for the FC and NFC diets, but decreased (quadratic; P<.001) for the PR diet. Increasing D quadratically increased (P<.001) the molar percentage of acetate and propionate, but quadratically decreased (P<.001) butyrate and valerate for the FC and NFC diets. For the PR diet, the molar percentage of propionate and valerate increased (quadratic; P<.01), whereas acetate and butyrate decreased (linear; P<.001) in response to increasing D. Molar percentage of isobutyrate and isovalerate decreased (P<.01) with increasing D for all three diets. As D increased, daily microbial N production showed quadratic responses with maximum values achieved at .126, .143, and .187/h D for the FC, NFC, and PR diet, respectively. There was a positive correlation between microbial growth efficiency (MOEFF) and D. A quadratic model fit the data of MOEFF as affected by D, and maximum MOEFF of 37.3, 59.6, and 71.4 g of bacterial N/kg OM truly fermented were calculated to be achieved at .177, .314, and .207/h D for the FC, NFC, and PR diet, respectively. Dilution rate significantly influenced the ruminal microbial fermentation of fibrous and nonfibrous carbohydrates and proteins, and was positively related to microbial yield and growth efficiency. In addition, microbial nitrogen composition, and therefore efficiency, was affected by substrate fermented. (+info)
Relationship between ruminal starch degradation and the physical characteristics of corn grain.
The objectives of this study were to determine the range of variation in the rate and extent of in situ ruminal starch degradation of 14 corns differing in vitreousness and to predict ruminal starch degradability by physical characteristics of corn grains. This study was conducted with eight dent and six flint corns. Ruminal starch degradability was determined by an in situ technique on 3-mm ground grains. Physical characteristics of corn grain were measured: hardness by grinding energy and particle size distribution, apparent and true densities, and specific surface area. Ruminal DM and starch degradabilities averaged 50 and 55.1% and varied from 39.7 to 71.5% and from 40.6 to 77.6%, respectively. Ruminal starch degradability averaged 61.9 and 46.2% in dent and flint types, respectively. The proportion of coarse particles (61.9 vs. 69.6% for dent and flint, respectively), the apparent density (1.29 vs. 1.36 g/cm3 for dent and flint, respectively), and the specific surface area (.13 vs. .07 m2/g for dent and flint, respectively) varied with the vitreousness. Ruminal starch degradability could be predicted accurately by vitreousness (r2 = .89) or by the combination of apparent density and 1,000-grain weight (R2 = .91), a measurement faster than the vitreousness determination. (+info)
Nutrient-specific preferences by lambs conditioned with intraruminal infusions of starch, casein, and water.
We hypothesized that lambs discriminate between postingestive effects of energy and protein and associate those effects with a food's flavor to modify food choices. Based on this hypothesis, we predicted that 1) lambs would acquire a preference for a poorly nutritious food (grape pomace) eaten during intraruminal infusions of energy (starch) or protein (casein) and that 2) shortly after an intraruminal infusion of energy or protein (preload), lambs would decrease their preferences for foods previously conditioned with starch or casein, respectively. Thirty lambs were allotted to three groups and conditioned as follows. On d 1, lambs in each group received grape pomace containing a different flavor and water was infused into their rumens as they ate the pomace. On d 2, the flavors were switched so each group received a new flavor and a suspension of starch (10% of the DE required per day) replaced the water infusion. On d 3, the flavors were switched again, and a suspension of casein (2.7 to 5.4% of the CP required per day) replaced the starch infusion. Conditioning was repeated during four consecutive trials. Lambs in Trial 1 had a basal diet of alfalfa pellets (e.g., free access from 1200 to 1700) and 400 g of rolled barley. Lambs in Trials 2, 3, and 4 received a restricted amount of alfalfa pellets (990 g/d) as their basal diet. After conditioning, all animals received an infusion of water, and, 30 min later, they were offered a choice of the three flavors previously paired with water, starch, or casein. On the ensuing days, the choice was repeated, but starch, casein, and barley replaced the water preload. The nutrient density of the infused preloads was increased during consecutive trials. Lambs preferred the flavors paired with starch > water > casein during Trial 1 (P < .05) and the flavors paired with starch > casein > water during Trials 2 (P < .05), 3 (P < .001), and 4 (P < .001). Preloads of casein decreased preferences for flavors previously paired with casein (P < .10 [Trial 2]; P < .001 [Trial 3], and increased preferences for flavors paired with starch (P < .05 [Trial 2]; P < .001 [Trial 3]). Preloads of energy (barley) had the opposite effect (P < .05 [Trial 3]). These results indicate that lambs discriminated between the postingestive effects of starch and casein and associated the effects with specific external cues (i.e., added flavors) to regulate macronutrient ingestion. (+info)
Degradation of two protein sources at three solids retention times in continuous culture.
Effects of solids retention times (SRT) of 10, 20, and 30 h on protein degradation and microbial metabolism were studied in continuous cultures of ruminal contents. Liquid dilution rate was constant across all retention times at .12 h(-1) (8.3 h mean retention time). Two semipurified diets that contained either soybean meal (SBM) or alfalfa hay (ALFH) as the sole nitrogen source were provided in amounts that decreased as SRT was increased. Digestion coefficients for DM, NDF, and ADF increased with increasing SRT. Digestion coefficients for nonstructural carbohydrates were higher in the SBM diet than in the ALFH diet but were not affected by SRT. Protein degradation in the ALFH diet averaged 51% and was unaffected by retention time. In the SBM diet, digestion of protein was 77, 78, and 96% at 10-, 20-, and 30-h retention times, respectively. Microbial efficiency decreased with increasing SRT and was greater for the SBM than for the ALFH diet. Efficiencies ranged from 30.6 to 35.7 and 20.8 to 29.2 g of N/kg of digested DM for the SBM and ALFH diets, respectively, as SRT decreased from 30 to 10 h. The diaminopimelic acid content of the microbes increased as SRT increased, indicating that changes in microbial species occurred owing to passage rates. From these results, we concluded that the digestibility decreases associated with increased ruminal turnover rates may be less for nonstructural carbohydrates and protein than for the fiber fractions. (+info)