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PubMed2025

PMkbase (version 1.0): an interactive web-based tool for tracking bacterial metabolic traits using phenotype microarrays made interoperable with sequence information and visualizing/processing PM data.

Bacteria showcase remarkable metabolic diversity and traits, even among strains of the same species. In recent years, a large number of bacterial genomes have been sequenced, leading to the elucidation and documentation of genomic differences and commonalities across and within species. Genome-scale metabolic reconstructions, which are often defined and curated using data from phenotype microarrays, elucidate the differences in metabolic traits resulting from genomic diversity. These microarrays measure cellular respiration on a variety of carbon, nitrogen, phosphorus, and sulfur sources and various stressors and inhibitors over a period of time to determine the metabolic activity of a given strain. Despite their popularity in measuring bacterial metabolic activity and traits, no public databases that allow researchers to warehouse, access, and analyze this information currently exist. Additionally, there are no publicly available tools that allow researchers to view the variance of these metabolic traits across bacterial strains. To address this need, we present Phenotype Microarray Knowledgebase (PMkbase [version 1.0], https://pmkbase.com/), an interactive database that acts as a repository of phenotype microarray (PM) data with integrated sequence information. Binarized activity calls, along with associated kinetic parameters, are made for all metabolic substrates and inhibitors. Users can upload their own data for analysis and visualization and to perform quality checks on their experiments. PMkbase will address an unmet need to track and view bacterial metabolic traits and provide researchers with valuable information to develop metabolic models, enrich pangenomic analyses, and design new experiments.IMPORTANCEBacterial species can be differentiated by their metabolic profiles or the type of nutrients they consume. Interestingly, strains within the same species also display differences in nutrient consumption. Phenotype microarrays are a high-throughput, widely used technology to measure which substrates can be metabolized by various microbial strains and the extent to which inhibitors can affect it. Despite their widespread use, public databases to parse and access this data type at scale do not exist. PMkbase, which contains 9,024 data points for nitrogen substrate utilization, 41,664 data points for carbon substrate utilization, 8,448 data points for phosphorus/sulfur substrate utilization, and 27,264 data points on various antibiotics across three species (Escherichia coli, Pseudomonas putida, and Staphylococcus aureus), has been developed to allow researchers to freely access PM data, along with enriching the data with sequence information.

Bacteria↗
PubMed1999

Effect of dietary high- and low-methylated citrus pectin on the activity of the ileal microflora and morphology of the small intestinal wall of broiler chicks.

1. A study was conducted with broiler chicks to evaluate the effects of dietary high-methylated citrus pectin (HMC) or low-methylated citrus pectin (LMC) on the performance, nutrient digestibility, morphology of the small intestinal wall and ileal microbial activity. 2. Both pectin products were tested at a dietary content of 30 g/kg using a diet based on maize and soya flour. 3. Inclusion of HMC in the diet depressed weight gain and food utilization significantly. With a dietary addition of LMC there were only small decreases in weight gain and food utilisation. 4. Digestibility of dry matter, organic matter, crude fat, starch and amino acids, nitrogen retention and metabolisable energy value were reduced significantly when HMC was added to the diet. The addition of LMC to the diet reduced fat and ash digestibility and metabolisable energy value significantly. 5. Inclusion of LMC in the diet increased ileal viscosity marginally, whilst HMC had such an effect that the supernatant could not be extracted. Microbial activity in the ileum, particularly that of Enterococci, Bacteroidaceae, Clostridia and E. coli, was increased significantly with dietary addition of HMC. Inclusion of LMC in the diet did not greatly affect microbial activity as only the number of Clostridia was increased. 6. The addition of HMC to the diet markedly affected the morphology of the intestinal wall and significantly increased the number of goblet cells per 100 villus cells and the sucrase isomaltase activity was increased significantly. However, the morphology of the intestinal wall was hardly affected by LMC, whereas the number of goblet cells per 100 villi cells was significantly increased. 7. Results of the present study indicate that the inclusion of water-soluble pectins in diets of chicks changes ileal microbial activity and the morphology of the small intestinal wall. The magnitude of these changes depends on the degree of methylation of the pectins.

Animals↗
PubMed1991

Rumen digestive physiology and microbial ecology.

The rumen is a dynamic, continuous fermentation compartment that provides a suitable environment for a variety of species of anaerobic bacteria, protozoa, and fungi. These microorganisms have a complex series of interactions with the feeds supplied to the host, with some using particulate matter as both sources of nutrients and sites of sequestration to avoid being washed from the rumen by the rapid flow of fluids. Because of the ability to use soluble nutrients and to reproduce rapidly, other microbes associate primarily with the liquid phase of the rumen contents. Due to the metabolic activity of all microbial populations, feeds are converted to microbial matter and fermentation end products, which serve as nutrients for the ruminant. Optimum feed utilization by ruminants is dependent on achieving maximum rumen fermentation and flow of microbial protein to the duodenum. At this time, it is clear that the major nutrients required by the microbial populations include both fibrous and nonfibrous sources of carbohydrates and nitrogen in the form of ammonia, amino acids, and peptides. In spite of five decades of research, the exact quantities and sources of these nutrients that will result in optimum rumen fermentation rates and microbial yields are only partially known.

Animals↗
PubMed1997

Microbial Utilization of Free and Clay-Bound Insecticidal Toxins from Bacillus thuringiensis and Their Retention of Insecticidal Activity after Incubation with Microbes.

The insecticidal toxins produced by Bacillus thuringiensis subspp. kurstaki and tenebrionis were resistant when bound on clays, but not when free, to utilization by pure and mixed cultures of microbes as sources of carbon and carbon plus nitrogen, and their availability as a nitrogen source was reduced. The bound toxins retained insecticidal activity both before and after exposure to microbes or pronase. The insecticidal activity of the toxins persisted for 40 days (the longest time evaluated) in nonsterile soil continuously maintained at the -33-kPa water tension and room temperature, alternately air dried and rewetted to the -33-kPa water tension, or alternately frozen and thawed, although alternate drying and wetting reduced the activity.

Journal Article↗
PubMed1976

Coffee grounds. I. Effects of coffee grounds on ration digestibility and diuresis in cattle, on in vitro rumen fermentation, and on rat growth.

Holstein steers were used to compare rations in which coffee grounds replaced grain at rates of 0, 5, 10, or 20%. The coffee grounds analyzed (%) dry matter 91.1, protein 11.8, fat 23.1, fiber 42.5, ash .7, and caffeine .13. Digestibility coefficients for dry matter, crude protein, and energy decreased, and ether extract increased progressively as concentrations of coffee grounds in the ration were increased. There was a significant decrease in nitrogen retention and utilization when the rations contained 10 or 20% coffee grounds. Coffee grounds depressed feed intake, increased urinary output, and increased water intake (based on dry matter intake). Coffee grounds caused diuresis and renal, urethral, and bladder irritation. Adding coffee grounds up to 35% of the substrate did not depress rumen microbial fermentation, as measured by in vitro gas production. Weight gain of rats fed rations containing 22.5% untreated coffee grounds was reduced significantly. Water extraction removed some undersirable factors in coffee grounds for rats, and ether extraction removed most of them. Incremental additions of coffee oil (1, 3, or 5%) to the basal diet resulted in incremental decreases in rat weight gain.

Animal Feed↗
PubMed2002

Analysis of river pollution data from low-flow period by means of multivariate techniques: a case study from the oil-shale industry region, northeastern Estonia.

The oil-shale industry has created serious pollution problems in northeastern Estonia. Untreated, phenol-rich leachate from semi-coke mounds formed as a by-product of oil-shale processing is discharged into the Baltic Sea via channels and rivers. An exploratory analysis of water chemical and microbiological data sets from the low-flow period was carried out using different multivariate analysis techniques. Principal component analysis allowed us to distinguish different locations in the river system. The riverine microbial community response to water chemical parameters was assessed by co-inertia analysis. Water pH, COD and total nitrogen were negatively related to the number of biodegradative bacteria, while oxygen concentration promoted the abundance of these bacteria. The results demonstrate the utility of multivariate statistical techniques as tools for estimating the magnitude and extent of pollution based on river water chemical and microbiological parameters. An evaluation of river chemical and microbiological data suggests that the ambient natural attenuation mechanisms only partly eliminate pollutants from river water, and that a sufficient reduction of more recalcitrant compounds could be achieved through the reduction of wastewater discharge from the oil-shale chemical industry into the rivers.

Biodegradation, Environmental↗
PubMed1992

Mineralization of glucose and lignocellulose by four arctic freshwater sediments in response to nutrient enrichment.

Microbial biomass and activity were examined in four different arctic sediments: littoral lake sediment and profundal lake sediment from Toolik Lake, Alaska, thaw pond sediment, and eroding river bank peat. The thaw pond sediment had the largest viable microbial biomass, while the profundal sediment had the smallest. Rates of glucose or acetate incorporation into lipids, glucose mineralization, and lignocellulose mineralization (all normalized per unit of biomass) were highest in the river peat sample, however. The kinetics of glucose mineralization in the profundal sediment were very different from those in the other three samples: although the initial rate of mineralization was five times lower than that in the peat and two times lower than that in the littoral and thaw pond sediments, the maximum amount of 14CO2 evolved from [14C]glucose eventually equaled that in the peat and exceeded that in the littoral and thaw pond sediments by 2.0 and 3.5 times, respectively. Carex aquatilis [14C-cellulose]- and [14C-lignin]lignocellulose mineralization rates in the profundal sediment equaled or exceeded those in the littoral sediment after 16 and 46 days, but the pattern of nutrient limitation differed: the profundal sediment was the only one sampled that exhibited nitrogen limitation, while the other three sediments appeared to be limited primarily by phosphorus. The addition of nitrogen and phosphorus together had no cumulative effects on lignocellulose mineralization. When the rates of mineralization or incorporation of glucose are compared with those of lignocellulose, the results of this study indicate that profundal sediment communities may be better able to utilize the more recalcitrant substrates relative to the labile substrates than microbial communities from sediments rich in detritus and standing macrophytes.

Acetates↗
PubMed2002

Form of rumen-degradable carbohydrate and nitrogen on microbial protein synthesis and protein efficiency of dairy cows.

Sixteen multiparous lactating Holstein cows (four with rumen cannulae) were fed diets varying in the content and form of ruminally degradable carbohydrates and N to examine dietary effects on microbial protein synthesis (MPS) and whole animal N efficiency, and to evaluate the use of a model based on milk urea N (MUN) for predicting urinary N excretion and N utilization efficiency (NUE). A replicated Latin square design (consisting of diet and experimental period) was employed. The four diets consisted of two low protein diets with either 20% ground corn (diet LP) or 13.5% ground corn plus 3% sucrose (diet LP sucrose) and two high protein diets with 13.5% corn and 3% sucrose with either urea (diet HP urea) or soybean meal (diet HP SBM) as supplemental rumen-degradable protein sources. The intakes of dry matter and N were increased by increasing dietary crude protein (CP) level. However, the yields of milk and milk protein were not affected by CP level. Yield of microbial protein was reduced by sucrose and increased by CP level. There were no differences between urea and SBM supplementation on DM intake, milk yield, or MPS. Mean urinary N excretion for all cows (252 g/d) was underestimated by 55 g/d or overestimated by 25 or 33 g/d using alternative equations based on MUN. Subsequently, NUE (mean = 22.4%) was underestimated by 7.5, 3.2, or 2.9%, using a previously published set of equations. Urinary N excretion and NUE could be predicted within 10 and 14% of observed values, respectively, using a set of equations incorporating MUN. Therefore, MUN appears to be a useful tool to help assess N losses from lactating cows.

Ammonia↗
PubMed2006

Growth inhibition by nitrocompounds of selected uric acid-utilizing microorganisms isolated from poultry manure.

The overall objective of this study was to evaluate the potential ability of nitrocompounds to reduce ammonia volatilization by inhibiting uric acid-utilizing microorganisms. Experiment I was conducted to evaluate the effects of nitrocompounds on the growth of uric acid-utilizing microorganisms isolated from poultry manure during six-hour incubation. There were five treatments: (1) control, (2) 50 mM nitroethane, (3) 50 mM nitroethanol, (4) 50 mM nitropropanol, and (5) 50 mM nitropropionic acid. Optical density values of nitrocompounds were significantly lower than that of control at two, four, and six hours. Plate counts of uric acid-utilizing microorganisms after six-hour incubation exhibited that nitrocompounds greatly reduced the growth of these microorganisms except for the nitroethane (P < 0.05). The nitropropanol and nitropropionic acid treatments showed significantly higher inhibitory effects compared to the nitroethanol. Experiments II and III were conducted to evaluate inhibitory effects of nitrocompounds on growth of uric acid-utilizing microorganisms compared to non-nitrocompounds such as ethanol, propanol, and propionic acid. Experiments II and III consisted of seven treatments: (1) control, (2) nitroethanol, (3) nitropropanol, (4) nitropropionic acid, (5) ethanol, (6) propanol, and (7) propionic acid. The incubation times of Experiments II and III were 6 and 24 h, respectively. The nitrocompounds were significantly more successful in inhibiting growth of uric acid-utilizing microorganisms compared to those non-nitrocompounds. These results suggest that nitrocompounds exhibit potential to reduce ammonia volatilization in poultry manure by inhibiting growth of uric acid-utilizing microorganisms.

Air Pollutants↗
PubMed2003

Mycelial colonization by bradyrhizobia and azorhizobia.

This study examines mycelial colonization of common soil fungi by bradyrhizobia and an azorhizobial strain, resulting in the forming of biofilms. The effects of the fungal exudates on a bradyrhizobial strain have also been investigated. Bradyrhizobia gradually colonized the mycelia for about 18 days, after which the biofilm structures collapsed with the release of the rhizobial cell clusters to the culture medium. The azorhizobial strain showed differential colonization of the mycelia. In general, there were no considerable mycotoxin effects of the fungal exudates on the bradyrhizobial strain used, instead the rhizobial strain utilized the exudates as a source of nutrition. This study indicates that the present microbial association with biofilm formation has important implications in the survival of rhizobia under adverse soil conditions devoid of vegetation. Further, it could have developed an as yet unidentified nitrogen fixing system that could have contributed to the nitrogen economy of soils.

Rhizobium↗
PubMed1999

Effects of type of carbohydrate supplementation to lush pasture on microbial fermentation in continuous culture.

Eight single-flow continuous culture fermenters were used to study the effects of the type of energy source on ruminal N utilization from high quality pasture. The four dietary treatments included high quality grass and legume pasture alone (50:50; wt/wt), pasture plus soybean hulls, pasture plus beet pulp, and pasture plus corn. Diets supplemented with additional sources of energy (soybean hulls, beet pulp, and corn) were isocaloric but differed in the type and rate of carbohydrate fermentation. Energy supplements constituted 45% of the total dietary dry matter and were fed twice daily at 12-h intervals in place of pasture, which is characteristic of grain feeding at milking when animals are in a grazing situation. Energy supplementation reduced pH, NH3 N flow, and NH3 N concentration and increased bacterial N flow (as a percentage of N intake). The supplementation of corn and soybean hulls resulted in the highest microbial N flow (as a percentage of N intake). Corn had a tendency to reduce fiber digestion because of excessively low NH3 N concentrations. Beet pulp was similar to corn in that it decreased NH3 N concentrations. Supplementation of soybean hulls resulted in a more synchronized fermentation, greater volatile fatty acid production, and greater fiber digestion. Nitrogen utilization by microbes was maximized by supplementation with soybean hulls or corn twice a day. With diets based on pasture, it may be more important to improve bacterial N flow and bacterial utilization of N than to maximize the efficiency of bacterial protein synthesis because better utilization of N by ruminal microorganisms results in higher bacterial N flow and higher fiber digestion.

Ammonia↗
PubMed1995

The influence of dietary fibre on protein digestion and utilization in monogastrics.

Current knowledge of the effects of dietary fibre and associated components on protein digestibility and utilization are discussed. Based on the literature it could be shown that the implications and mechanisms behind the effect of soluble and insoluble dietary fibre on protein digestibility and utilization are quite different. Insoluble dietary fibre will increase faecal bulk and faecal nitrogen excretion is primarily due to and increased excretion of cell wall bound protein. Contrary to this, soluble dietary fibre increase faecal bulk and faecal nitrogen due to an increased excretion of microbial nitrogen. A matter of controversy is the influence of dietary fibre on endogenous nitrogen excretion and factors affecting the losses of nitrogen in this way. It is not known if fibre acts as a secretogogue.

Animals↗
PubMed1986

Optimized batch fermentation of cheese whey-supplemented feedlot waste filtrate to produce a nitrogen-rich feed supplement for ruminants.

An optimized batch fermentation process for the conversion of cattle feedlot waste filtrate, supplemented with cheese whey, into a nitrogenous feed supplement for ruminants is described. Feedlot waste filtrate supplemented with cheese whey (5 g of whey per 100 ml) was fermented by the indigenous microbial flora in the feedlot waste filtrate. Ammonium hydroxide was added to the fermentation not only to maintain a constant pH but also to produce ammonium salts of organic acids, which have been shown to be valuable as nitrogenous feed supplements for ruminants. The utilization of substrate carbohydrate at pH 7.0 and 43 degrees C was >94% within 8 h, and the crude protein (total N x 6.25) content of the product was 70 to 78% (dry weight basis). About 66 to 69% of the crude protein was in the form of ammonia nitrogen. Lactate and acetate were the predominant acids during the first 6 to 8 h of fermentation, but after 24 h, appreciable levels of propionate and butyrate were also present. The rate of fermentation and the crude protein content of the product were optimal at pH 7.0 and decreased at a lower pH. For example, fermentation did not go to completion even after 24 h at pH 4.5. Fermentation proceeded optimally at 43 degrees C, less so at 37 degrees C, and considerably more slowly at 23 and 50 degrees C. Concentrations of up to 15 g of cheese whey per 100 ml of feedlot waste filtrate were fermented efficiently. Fermentation of feedlot waste filtrate obtained from animals fed low silage-high grain, high silage-low grain, or dairy rations resulted in similar products in terms of total nitrogen and organic acid composition.

Journal Article↗
PubMed2004

Effect of dietary crude protein level and degradability on ruminal fermentation and nitrogen utilization in lactating dairy cows.

The objectives of this experiment were to investigate the effects of two ruminally degradable protein (RDP) levels in diets containing similar ruminally undegradable protein (RUP) and metabolizable protein (MP) concentrations on ruminal fermentation, digestibility, and transfer of ruminal ammonia N into milk protein in dairy cows. Four ruminally and duodenally cannulated Holstein cows were allocated to two dietary treatments in a crossover design. The diets (adequate RDP [ARDP] and high RDP [HRDP]), had similar concentrations of RUP and MP, but differed in CP/RDP content. Ruminal ammonia was labeled with 15N and secretion of tracer in milk protein was determined for a period of 120 h. Ammonia concentration in the rumen tended to be greater (P = 0.06) with HRDP than with ARDP. Microbial N flow to the duodenum, ruminal digestibility of dietary nutrients, DMI, milk yield, fat content, and protein content and yield were not statistically different between diets. There was a tendency (P = 0.07) for increased urinary N excretion, and blood plasma and milk urea N concentrations were greater (P = 0.002 and P = 0.01, respectively) with HRDP compared with ARDP. Milk N efficiency was decreased (P = 0.01) by the HRDP diet. The cumulative secretion of ammonia 15N into milk protein, as a proportion of 15N dosed intraruminally, was greater (P = 0.003) with ARDP than with HRDP. The proportions of bacterial protein originating from ammonia N and milk protein originating from bacterial or ammonia N averaged 43, 61, and 26% and were not affected by diet. This experiment indicated that excess RDP in the diet of lactating dairy cows could not be efficiently utilized for microbial protein synthesis and was largely lost through urinary N excretion. At a similar MP supply, increased CP or RDP concentration of the diet would result in decreased efficiency of conversion of dietary N into milk protein and less efficient use of ruminal ammonia N for milk protein syntheses.

Ammonia↗
PubMed2003

An in vitro evaluation of some unconventional ruminant feeds in terms of the organic matter digestibility, energy and microbial biomass.

In vitro organic matter apparent digestibility (IVOMAD), true digestibility (IVOMTD), metabolizable energy (ME), net energy lactation (NEL), microbial nitrogen (MN) and synthesis of microbial biomass (MBM) were estimated to predict the nutritive values of some agricultural by-products, drought-tolerant range plants and browses. The relationships between in vitro gas production (GP), and true or apparent digestibility. MN and MBM were studied utilizing an in vitro incubation technique. The values of IVOMAD, IVOMTD, ME, NEL, GP, MBM and MN varied with the studied experimental materials. The true fermentation of the outside part of Atriplex leucoclada produced a higher volume of gas than the middle or the inside parts, and this was associated with an increase in the values of IVOMAD, IVOMTD, ME and NEL. However, screening off the wood from olive cake to obtain olive cake pulp increased the IVOMAD, IVOMTD, ME, NEL and the volume of gas production from the true fermented material. One ml of gas was generated from the true degradation of 5 mg of wheat straw, Moringa oleifera, Alhagi camelorum, Eucaliptus camaldulensis and A. leucoclada, from 11 mg of Prosopsis stephaniana and olive cake pulp, and from 20 mg of olive cake or olive cake wood. The amount of MN or MBM produced from 100 mg of truly fermented organic matter depended on the kind of the fermented material and amounted to 0.7-2.9 mg or 8-34 mg, respectively. Crude fibre was negatively correlated to IVOMAD, IVOMTD, ME and NEL. Gas production was positively correlated to IVOMAD and IVOMTD but negatively correlated to MBM and MN.

Animal Feed↗
PubMed1989

Isolation of microorganisms capable of degrading isoquinoline under aerobic conditions.

Isoquinoline-degrading microbial cultures were isolated from oil- and creosote-contaminated soils. The establishment of initial enrichment cultures required the use of emulsified isoquinoline. Once growth on isoquinoline was established, isoquinoline emulsification was no longer required for utilization of isoquinoline as the sole source of carbon and nitrogen by these cultures. An isoquinoline-degrading Acinetobacter strain was isolated from one of the enrichment cultures. The degradation of isoquinoline was accompanied by the accumulation of a red cell-associated pigment and of 1-hydroxyisoquinoline, which was further degraded to unknown intermediary ring-cleavage products and carbon dioxide.

Acinetobacter↗
PubMed2001

High levels of nitric oxide production decrease early but increase late survival of Brucella abortus in macrophages.

Nitric oxide (NO), produced by the iNOS protein, is known as a defense mechanism against various pathogens and an apoptotic inducer of cells. Apoptosis can also be a host protective mechanism against intracellular bacteria. The intracellular survival of Brucella abortus in RAW264.7 macrophages was examined under conditions of the apoptotic inducer, NO. Since B. abortus does not induce high output of NO, Escherichia coli LPS and IFN-gamma, as potential therapeutic modalities, were added to increase the expression of iNOS, and thus NO. Using 10 ng/ml E. coli LPS and 25 U/ml IFN-gamma, nitrite production was as high as 140 microM by 72 h. However, when macrophages were infected with B. abortus, the nitrite concentration was 60 microM after 72 h post infection, greater than a two-fold decrease. The number of surviving bacteria decreased, from 6 to 24 h, in the presence of nitrite accumulation. In the absence of B. abortus there was an increase in apoptotic cells at 72 h with high nitrite accumulation. In contrast, the number of macrophage apoptotic bodies decreased in the presence of B. abortus. The data suggest that: (i) NO accelerates the killing of intracellular B. abortus, but not to completion during the first 24 h of infection; (ii) B. abortus can prevent apoptosis as an advantage for bacterial survival inside macrophages and (iii) surviving intracellular bacteria then replicate steadily after 24 h. B. abortus probably expresses genes that counteract the effect of a high NO environment or activates genes to utilize NO as a nitrogen source, as the Brucella genome codes for nitric and nitrous oxide reductase genes.

Animals↗
PubMed1999

Effect of replacing alfalfa silage with high moisture corn on ruminal protein synthesis estimated from excretion of total purine derivatives.

Twenty-four multiparous dairy cows (eight with ruminal cannulae) were blocked by days in milk and assigned to six balanced 4 x 4 Latin squares with 21-d periods. The four diets, formulated from alfalfa silage plus a concentrate mix based on ground high moisture ear corn, contained (dry matter basis): 1) 20% concentrate, 80% alfalfa silage (24% nonfiber carbohydrate; NFC), 2) 35% concentrate, 65% alfalfa silage (30% NFC), 3) 50% concentrate, 50% alfalfa silage (37% NFC), or 4) 65% concentrate, 35% alfalfa silage (43% NFC). Soybean meal and urea were added to make diets isonitrogenous with equal nonprotein nitrogen (NPN) (43% of total N). Total urine was collected with indwelling Folley catheters for 24 h during each period. There was no effect of diet on urinary creatinine excretion (average 29 mg/kg of BW/d). There were quadratic effects of diet on total urinary ecretion of allantoin, uric acid, and purine derivatives (allantoin plus uric acid), and on ruminal synthesis of microbial N estimated from purine derivatives; maxima occurred at about 35% dietary NFC. Urinary excretion also was estimated with spot urine samples from creatinine concentration and the mean daily creatinine excretion. Daily excretion of allantoin, uric acid, and purine derivatives estimated from spot urine sampling followed the same pattern as that observed with total collection; differences between measured and estimated urine volume were significant only for 35% dietary concentrate. Spot urine sampling appeared to yield satisfactory estimates of purine derivative excretion. Maximal urea N excretion was estimated to occur at about 31% dietary NFC. Milk allantoin secretion increased linearly with concentrate and accounted for 4 to 6% of the total purine derivative excretion. Microbial yield was maximal at 35% dietary NFC, suggesting that this was the optimal level for utilization of dietary NPN from alfalfa silage and other sources.

Allantoin↗