Why do many ruminal bacteria die and lyse so quickly?

Reevaluating human-microbiota symbiosis: Strain-level insights and evolutionary perspectives across animal species

The prevailing consensus in scientific literature underscores the mutualistic bond between the microbiota and the human host, suggesting a finely tuned coevolutionary partnership that enhances the fitness of both parties. This symbiotic relationship has been extensively studied, with certain bacterial attributes being construed as hallmarks of natural selection favoring the benefit of the human host. Some scholars go as far as equating the intricate interplay between humans and their intestinal microbiota to that of endosymbiotic relationships, even conceptualizing microbiota as an integral human organ. However, amidst the prevailing narrative of bacterial species being categorized as beneficial or detrimental to human health, a critical oversight often emerges - the inherent functional diversity within bacterial strains. Such reductionist perspectives risk oversimplifying the complex dynamics at play within the microbiome. Recent genomic analysis at the strain level is highly limited, which is surprising given that strain information provides critical data about selective pressures in the intestine. These pressures appear to focus more on the well-being of bacteria rather than human health. Connected to this is the extent to which animals depend on metabolic activity from intestinal bacteria, which varies widely across species. While omnivores like humans exhibit lower dependency, certain herbivores rely entirely on bacterial activity and have developed specialized compartments to house these bacteria.

Review: Biological consequences of the inhibition of rumen methanogenesis

Decreasing enteric CH4 emissions from ruminants is important for containing global warming to 1.5 °C and avoid the worst consequences of climate change. However, the objective of mitigating enteric CH4 emissions is difficult to reconcile with the forecasted increase in production of ruminant meat and milk, unless CH4 production per animal and per kilogram of animal product are decreased substantially. Chemical compound 3-nitrooxypropanol and bromoform-containing red algae Asparagopsis are currently the most potent inhibitors of rumen methanogenesis, but their average efficacy would have to be increased to mitigate enteric CH4 emissions to contain global warming to 1.5 °C, if the demand for ruminant products increases as predicted. We propose that it may be possible to enhance the efficacy of inhibitors of methanogenesis through understanding the mechanisms that cause variation in their efficacy across studies. We also propose that a more thorough understanding of the effects of inhibiting methanogenesis on rumen and postabsorptive metabolism may help improve feed efficiency and cost-effectiveness as co-benefits of the methanogenesis inhibition intervention. For enhancing efficacy, we examine herein how different inhibitors of methanogenesis affect the composition of the rumen microbial community and discuss some mechanisms that may explain dissimilar sensitivities among methanogens to different types of inhibitors. For improving feed efficiency and cost-effectiveness, we discuss the consequences of inhibiting methanogenesis on rumen fermentation, and how changes in rumen fermentation can in turn affect postabsorptive metabolism and animal performance. The objectives of this review are to identify knowledge gaps of the consequences of inhibiting methanogenesis on rumen microbiology and rumen and postabsorptive metabolism, propose research to address those knowledge gaps and discuss the implications that this research can have for the efficacy and adoption of inhibitors of methanogenesis. Depending on its outcomes, research on the microbiological, biochemical, and metabolic consequences of the inhibition of rumen methanogenesis could help the adoption of feed additives inhibitors of methanogenesis to mitigate enteric CH4 emissions from ruminants to ameliorate climate change.

Microbial Populations in Ruminal Liquid Samples from Beefmaster Steers at Both Extremes of RFI Values

The gut microbiota is involved in the productivity of beef cattle, but the impact of different analysis strategies on microbial composition is unclear. Ruminal samples were obtained from Beefmaster steers (n = 10) at both extremes of residual feed intake (RFI) values (5 with the lowest and 5 with the highest RFI) from two consecutive days. Samples were processed using two different DNA extraction methods. The V3 and V4 regions of the 16S rRNA gene were amplified using PCR and sequenced with a MiSeq instrument (Illumina). We analyzed 1.6 million 16S sequences from all 40 samples (10 steers, 2 time points, and 2 extraction methods). The abundance of most microbes was significantly different between DNA extraction methods but not between high-efficiency (LRFI) and low-efficiency (HRFI) animals. Exceptions include the genus Succiniclasticum (lower in LRFI, p = 0.0011), and others. Diversity measures and functional predictions were also mostly affected by DNA extraction methods, but some pathways showed significant differences between RFI levels (e.g., methylglyoxal degradation, higher in LRFI, p = 0.006). The results suggest that the abundance of some ruminal microbes is associated with feed efficiency and serves as a cautionary tale for the interpretation of results obtained with a single DNA extraction method.

High-Grain Diet Feeding Altered Blood Metabolites, Rumen Microbiome, and Metabolomics of Yaks

Currently, information available on the comprehensive changes in the rumen bacteria and metabolites of yaks fed high-grain diets is limited. This study aimed to investigate the effects of high-grain diet feeding on the blood metabolites, rumen microbiome, and metabolomics of yaks by using 16S rDNA gene sequencing and liquid chromatography–mass spectrometry (LC/MS). Here, fourteen healthy male yaks (body weight, 249.61 ± 8.13 kg) were randomly assigned to two different diets: a hay diet (0% grain, CON, n = 7), or a high-grain diet (70% grain, HG, n = 7). At the 74th day of treatment, blood and ruminal fluid samples were collected for the blood metabolites, rumen microbiome, and metabolomics analyses. The HG diet increased lipopolysaccharides (LPS), aspartate aminotransferase (AST), gamma-glutamyltransferase (GGT), haptoglobin (HPT), serum amyloid-A (SAA), interleukin-1β (IL1-β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) serum concentrations (p < 0.05). Compared with the CON diet, the HG diet decreased rumen pH (p < 0.05), and increased total volatile fatty acids concentration, and proportion of butyrate (p < 0.05). The relative abundance of Firmicutes and Saccharibacteria were higher (p < 0.05), while Bacteroidetes was lower (p < 0.05) in the HG group than those in the CON group. At the genus level, the relative abundance of Christensenelaceae_R-7_group, Ruminococcaceae_NK4A214_group, Lachnospiraceae_NK3A20_group, and Acetitomaculum were higher than in those in the HG diet (p < 0.05). Compared with the CON group, the HG diet increased the concentrations of biogenic amines (histamine, tyramine, and putrescine), common amino acids (phenylalanine, threonine, serine, etc.), and arachidonic acid (prostaglandin H2, prostaglandin E2, 12(S)-HPETE, etc.). Collectively, these findings demonstrate that the HG diet altered the microbiota and metabolites, as well as potentially damaged their rumen health and induced inflammation in yaks.

Profiles of Odd- and Branched-Chain Fatty Acids and Their Correlations With Rumen Fermentation Parameters, Microbial Protein Synthesis, and Bacterial Populations Based on Pure Carbohydrate Incubation in vitro

The objectives of this study were to evaluate changes in profiles of odd- and branched-chain fatty acids (OBCFA), including pentadecanoic acid (C15:0), 13-methyltetradecanoic acid (iso-C15:0), 12-methyltetradecanoic acid (anteiso-C15:0), 14-methylpentadecanoic acid (iso-C16:0), heptadecanoic acid (C17:0), 15-methylhexadecanoic acid (iso-C17:0), and 14-methylhexadecanoic acid (anteiso-C17:0) during in vitro fermentation of pure carbohydrates mixtures in the buffer-rumen fluid. The second objective was to correlate the changes in the OBCFA profile to the corresponding changes in ruminal fermentation parameters, microbial crude protein (MCP) synthesis, and bacterial populations. Five pure carbohydrates mixtures containing different cellulose: starch (C:S) ratios, i.e., 0:100, 25:75, 50:50, 75:25, and 100:0, were incubated for 6, 12, 18, and 24 h in vitro. The results showed that there was significant interaction (P < 0.05) between C:S and incubation time for changes in all OBCFA profiles, except iso-C17:0. The highest concentration of total OBCFA (3.94 mg/g dry matter; DM) was observed in the residues after 24 h of fermentation when the C:S was 0:100, while the lowest concentration of OBCFA (1.65 mg/g DM) was produced after 6 h of incubation when the C:S was 50:50. The correlation analysis revealed that the concentration of iso-C16:0 might be a potential marker for the estimation of total volatile fatty acids (ρ = 0.78) and MCP synthesis (ρ = 0.82) in the rumen. Compared to starch degrading bacteria, cellulolytic bacteria had stronger correlations with OBCFA concentrations, and the strongest correlation was found between the population of Ruminococcus flavefaciens with C15:0 concentration (ρ = 0.70). Notably, this is the first paper reporting relationship between OBCFA with rumen fermentation products and microbial protein synthesis based on fermentation of pure carbohydrates mixtures in vitro, and thus avoid confounding interference from dietary protein and fat presence in the in vivo studies. However, more in-depth experiments are needed to substantiate the current findings.

No hints at glyphosate-induced ruminal dysbiosis in cows

Glyphosate-based herbicides are among the most used non-selective herbicides worldwide and inhibit synthesis of aromatic amino acids in plants, bacteria, and fungi. Given the broad usage, controversies concerning potential effects of glyphosate on health and especially on gut microbiomes arose. For cattle, it has been proposed based on in vitro data that glyphosate has detrimental effects on the ruminal microbiome, which manifest as a specific inhibition of bacteria involved in fiber degradation and as an enrichment of specific pathogens. In the present study, glyphosate effects on the ruminal microbiome were analyzed in vivo using glyphosate contaminated feedstuffs with strong differences in dietary fiber and dietary energy content in order to reproduce the proposed detrimental glyphosate effects on the rumen microbiome. While significant impact of dietary factors on the ruminal microbiome and its products are pointed out, no adverse glyphosate effects on ruminal microbiome composition, diversity, and microbial metabolites are observed.

Abomasal infusion of ground corn and ammonium chloride in early-lactating Holstein-Friesian dairy cows to induce hindgut and metabolic acidosis

Next to rumen acidosis, other forms of acidosis may also affect lactational performance of cows. Therefore, the effects of hindgut acidosis, induced via abomasal infusion of ground corn, and metabolic acidosis, induced via abomasal infusion of NH₄Cl, were studied in cows in early lactation. Observations were made on intake and digestibility of nutrients, lactation performance, energy and N partitioning, blood acid-base status, and rumen and hindgut fermentation characteristics. In a 6 × 6 Latin square design, 6 rumen-fistulated, second-lactation Holstein-Friesian dairy cows (48 ± 17 d in milk) were subjected to 5 d of continuous abomasal infusions of water as control, or solutions of 2.5 mol of NH₄Cl/d, 5.0 mol of NH₄Cl/d, 3.0 kg of ground corn/d, or the combination of ground corn with either of the 2 NH₄Cl levels, followed by 2 d of rest. Treatment solutions were administered via peristaltic pumps through infusion lines attached to the rumen cannula plug and an abomasal infusion line with a flexible disk (equipped with holes to allow digesta passage) to secure its placement through the sulcus omasi. A total mixed ration consisting of 70% grass silage and 30% concentrate (on dry matter basis) was fed at 95% of ad libitum intake of individual cows. The experiment was conducted in climate respiration chambers to determine feed intake, lactation performance, and energy and N balance. Abomasal infusion of NH₄Cl affected the acid-base status of the cows, but more strongly when in combination with abomasal infusion of ground corn. Metabolic acidosis (defined as a blood pH < 7.40, blood HCO₃ concentration < 25.0 mmol/L, and a negative base excess) was observed with 5.0 mol of NH₄Cl/d, 3.0 kg of ground corn/d + 2.5 mol of NH₄Cl/d, and 3.0 kg of ground corn/d + 5.0 mol of NH₄Cl/d. Metabolic acidosis was associated with decreased milk lactose content, metabolic body weight, energy retained as protein, and fecal N excretion, and increased urine N excretion, and tended to decrease intake of nutrients. Digestibility of several nutrients increased with 5.0 mol of NH₄Cl/d, likely as a result of decreased intake. Abomasal ground corn infusion resulted in hindgut acidosis, where fecal pH decreased from 6.86 without ground corn to 6.00 with ground corn, regardless of NH₄Cl level. The decrease in fecal pH was likely the result of increased hindgut fermentation, evidenced by increased fecal volatile fatty acid concentrations. Hindgut acidosis was associated with decreased digestibility of nutrients, except for starch, which increased, and crude fat, which was not affected. No systemic inflammatory response was observed, suggesting that the hindgut epithelium was not severely affected by the more acidic conditions or barrier damage. Abomasal infusion of ground corn increased milk yield, milk protein and lactose yield, fecal N excretion, N use efficiency, and total energy retained as well as energy retained in fat, and reduced milk fat content and urine N excretion.

High Rumen-Degradable Starch Diet Promotes Hepatic Lipolysis and Disrupts Enterohepatic Circulation of Bile Acids in Dairy Goats

BACKGROUND

High rumen-degradable starch (RDS) diets decrease milk fat. The increase of LPS in plasma associated with increased RDS impairs liver function, immune response and lipid metabolism, which depress the precursors for milk fat.

OBJECTIVE

This study investigated the mechanism of depression of milk fat precursors in the liver and small intestine of dairy goats fed different RDS diets.

METHOD

Eighteen Guanzhong lactating goats (second lactation, 45.8 ± 1.54 kg) and 6 ruminally cannulated dairy goats (aged 2-3 y, 54.0 ± 2.40 kg) were fed 3 different diets with low dietary RDS concentrations of 20.52% (LRDS), medium RDS of 22.15% (MRDS), and high RDS of 24.88% (HRDS) for 36 and 21 d, respectively, in experiments 1 and 2. The liver metabolites and jejunal microbiota in experiment 1 and LPS concentrations in rumen fluid and plasma in experiment 2 were measured. One-way ANOVA was used to analyze the biochemical parameters and mRNA or protein expression. The MIXED procedure was used to analyze LPS concentrations.

RESULTS

In experiment 1, the HRDS diet showed increased activity of alkaline phosphatase (27.4 to 41.4 U/L) in plasma (P < 0.05) compared with LRDS treatment. The HRDS diet significantly increased the hepatic concentrations of l-carnitine (129%), l-palmitoylcarnitine (306%), taurochenodeoxycholate (856%), and taurodeoxycholic acid (588%) in liver (variable importance in the projection > 1, P < 0.10) compared with the LRDS treatment. Goats fed the HRDS diet had 33.6% greater liver protein expression of carnitine palmitoyltransferase-1 (P < 0.05), and greater relative abundance of Firmicutes and Ruminococcus 2 in the jejunal content (linear discriminant analysis > 2.0, P < 0.05) than did goats fed LRDS diet. In experiment 2, goats fed the HRDS diet had greater LPS concentrations in rumen fluid (7.57 to 13.6 kEU/mL) and plasma (0.037 to 0.179 EU/mL) (P < 0.05) than did goats fed LRDS diet.

CONCLUSIONS

Feeding the HRDS diet promoted hepatic lipid β-oxidation and disrupted phospholipid and bile acids metabolisms in liver, thereby reducing the supply of lipogenic precursors to the mammary gland in dairy goats.

Rumen Virus Populations: Technological Advances Enhancing Current Understanding

The rumen contains a multi-kingdom, commensal microbiome, including protozoa, bacteria, archaea, fungi and viruses, which enables ruminant herbivores to ferment and utilize plant feedstuffs that would be otherwise indigestible. Within the rumen, virus populations are diverse and highly abundant, often out-numbering the microbial populations that they both predate on and co-exist with. To date the research effort devoted to understanding rumen-associated viral populations has been considerably less than that given to the other microbial populations, yet their contribution to maintaining microbial population balance, intra-ruminal microbial lysis, fiber breakdown, nutrient cycling and genetic transfer may be highly significant. This review follows the technological advances which have contributed to our current understanding of rumen viruses and drawing on knowledge from other environmental and animal-associated microbiomes, describes the known and potential roles and impacts viruses have on rumen function and speculates on the future directions of rumen viral research.

Effects of Different Concentrate Feed Proportions on Ruminal Ph Parameters, Duodenal Nutrient Flows and Efficiency of Microbial Crude Protein Synthesis in Dairy Cows During Early Lactation

The aim of the study was to examine different pH parameters, such as variations throughout the day, depending on differing concentrate feed proportions. Moreover, special attention was payed to individual variation in microbial efficiencies (microbial crude protein/fermented organic matter) and their relation to ruminal pH, nutrient flows and digestibilities. For this, cows were grouped according to microbial efficiency (more, n = 5, vs. less efficient cows, n = 4). After calving, thirteen ruminally cannulated pluriparous cows, including nine duodenally cannulated animals, were divided into groups offered rations with a lower (35% on dry matter basis, n = 7) or a higher (60% on dry matter basis, n = 6) concentrate feed proportion. Ruminal pH parameters were assessed continuously by using intraruminal probes. Nutrient flows, nutrient digestibility and microbial efficiency were determined for duodenally cannulated cows. For most ruminal pH parameters it seemed that individual variability was higher than the treatment effect. However, a positive relationship between actual concentrate intake and diurnal pH fluctuations was found. Besides, the effect of individually different microbial efficiencies was assessed. Again, there were no group differences for pH parameters. However, nutrient flows were significantly higher in more efficient cows, whereas digestibilities were lower in in more efficient cows.

Carbohydrate Transport by Group Translocation: The Bacterial Phosphoenolpyruvate: Sugar Phosphotransferase System

The Bacterial Phosphoenolpyruvate (PEP) : Sugar Phosphotransferase System (PTS) mediates the uptake and phosphorylation of carbohydrates, and controls the carbon- and nitrogen metabolism in response to the availability of sugars. PTS occur in eubacteria and in a few archaebacteria but not in animals and plants. All PTS comprise two cytoplasmic phosphotransferase proteins (EI and HPr) and a species-dependent, variable number of sugar-specific enzyme II complexes (IIA, IIB, IIC, IID). EI and HPr transfer phosphorylgroups from PEP to the IIA units. Cytoplasmic IIA and IIB units sequentially transfer phosphates to the sugar, which is transported by the IIC and IICIID integral membrane protein complexes. Phosphorylation by IIB and translocation by IIC(IID) are tightly coupled. The IIC(IID) sugar transporters of the PTS are in the focus of this review. There are four structurally different PTS transporter superfamilies (glucose, glucitol, ascorbate, mannose) . Crystal structures are available for transporters of two superfamilies: bcIIC^mal (MalT, 5IWS, 6BVG) and bcIIC^chb (ChbC, 3QNQ) of B. subtilis from the glucose family, and IIC^asc (UlaA, 4RP9, 5ZOV) of E. coli from the ascorbate superfamily . They are homodimers and each protomer has an independent transport pathway which functions by an elevator-type alternating-access mechanism. bcIIC^mal and bcIIC^chb have the same fold, IIC^asc has a completely different fold. Biochemical and biophysical data accumulated in the past with the transporters for mannitol (IICBA^mtl) and glucose (IICB^glc) are reviewed and discussed in the context of the bcIIC^mal crystal structures. The transporters of the mannose superfamily are dimers of protomers consisting of a IIC and a IID protein chain. The crystal structure is not known and the topology difficult to predict. Biochemical data indicate that the IICIID complex employs a different transport mechanism . Species specific IICIID serve as a gateway for the penetration of bacteriophage lambda DNA across, and insertion of class IIa bacteriocins into the inner membrane. PTS transporters are inserted into the membrane by SecYEG translocon and have specific lipid requirements. Immunoelectron- and fluorescence microscopy indicate a non-random distribution and supramolecular complexes of PTS proteins.

Do more mechanistic models increase accuracy of prediction of metabolisable protein supply in ruminants?

Ruminal microbes partially degrade dietary protein and synthesise microbial protein, which, along with undegraded true protein, contributes to metabolisable protein for the animal. Rumen models have been developed over the past several decades in an effort to better predict metabolisable protein supply for ration formulation for ruminants. These models have both empirical and mechanistic components. Separation of dietary protein into fractions that include non-protein nitrogen, true protein and unavailable protein has been a fundamental element of these models. Ruminal degradation of one or more true protein fractions is then estimated on the basis of the kinetics of digestion and passage. Some models use the same method to predict substrate supply for microbial protein production. Although mechanistic models have been extensively used in diet-formulation programs worldwide, their ability to improve accuracy of prediction of metabolisable protein over simpler empirical models is questionable. This article will address the potential of mechanistic models to better predict metabolisable protein supply in ruminants as well as their limitations.

In vitro investigation of the ruminal digestion kinetics of different nitrogen fractions of 15N-labelled timothy forage

An in vitro method based on ¹⁵N-labelled forage nitrogen (N) was developed to study ruminal N metabolism of soluble N (SN), insoluble N (ISN) and neutral detergent insoluble N (NDIN) fractions of timothy forage. Timothy grass was grown on replicated experimental plots with one plot receiving ¹⁵N-labelled and the other unlabelled N fertilizer. Harvested grass was preserved as dried grass or as formic acid treated or untreated silage. The intact forages and their corresponding N fractions were incubated in buffered rumen fluid in vitro to determine degradation parameters based on the ¹⁵N fluxes between labelled feed N and ammonia N pools. A high percentage (25–38%) of ¹⁵N-labelled ammonia disappeared from ammonia N pool during the first 15 min of incubation. Microbial uptake of dried grass SN fraction was higher than of silage SN fractions. Fractional degradation rates of SN from formic acid treated silage, untreated silage and dried grass during the first 6 hours of incubation were 0.145, 0.125 and 0.115 /h, respectively. By the end of the incubation period (28 h), 69, 66 and 43%, of the SN fraction of formic acid treated silage, untreated silage and dried grass, respectively were recovered as ammonia. The percentage of ISN fractions degraded to ammonia N were 9, 34 and 27%, respectively. Based on the changes in ¹⁵N-labelled ammonia N pool in blank incubation and appearance of ¹⁵N to ammonia N pool from ¹⁵N-labelled NDIN fractions, it was estimated that a significant portion of microbial lysis occurred when incubations were carried out for longer than 20 hours. With dried grass the contribution of ammonia N for microbial N synthesis was greater than with silages. Use of ¹⁵N-labelled forages together with this in vitro method is a promising technique for determining soluble N degradation parameters, but it requires further development to be used for determining degradation parameters of insoluble N fractions and work with whole feeds.

Review: Enhancing gastrointestinal health in dairy cows

Due to their high energy requirements, high-yielding dairy cows receive high-grain diets. This commonly jeopardises their gastrointestinal health by causing subacute ruminal acidosis (SARA) and hindgut acidosis. These disorders can disrupt nutrient utilisations, impair the functionalities of gastrointestinal microbiota, and reduce the absorptive and barrier capacities of gastrointestinal epithelia. They can also trigger inflammatory responses. The symptoms of SARA are not only due to a depressed rumen pH. Hence, the diagnosis of this disorder based solely on reticulo-rumen pH values is inaccurate. An accurate diagnosis requires a combination of clinical examinations of cows, including blood, milk, urine and faeces parameters, as well as analyses of herd management and feed quality, including the dietary contents of NDF, starch and physical effective NDF. Grain-induced SARA increases acidity and shifts availabilities of substrates for microorganisms in the reticulo-rumen and hindgut and can result in a dysbiotic microbiota that are characterised by low richness, diversity and functionality. Also, amylolytic microorganisms become more dominant at the expense of proteolytic and fibrolytic ones. Opportunistic microorganisms can take advantage of newly available niches, which, combined with reduced functionalities of epithelia, can contribute to an overall reduction in nutrient utilisation and increasing endotoxins and pathogens in digesta and faeces. The reduced barrier function of epithelia increases translocation of these endotoxins and other immunogenic compounds out of the digestive tract, which may be the cause of inflammations. This needs to be confirmed by determining the toxicity of these compounds. Cows differ in their susceptibility to poor gastrointestinal health, due to variations in genetics, feeding history, diet adaptation, gastrointestinal microbiota, metabolic adaptation, stress and infections. These differences may also offer opportunities for the management of gastrointestinal health. Strategies to prevent SARA include balancing the diet for physical effective fibre, non-fibre carbohydrates and starch, managing the different fractions of non-fibre carbohydrates, and consideration of the type and processing of grain and forage digestibility. Gastrointestinal health disorders due to high grain feeding may be attenuated by a variety of feed supplements and additives, including buffers, antibiotics, probiotics/direct fed microbials and yeast products. However, the efficacy of strategies to prevent these disorders must be improved. This requires a better understanding of the mechanisms through which these strategies affect the functionality of gastrointestinal microbiota and epithelia, and the immunity, inflammation and 'gastrointestinal-health robustness' of cows. More representative models to induce SARA are also needed.

Estimates of diet selection in cattle grazing cornstalk residues by measurement of chemical composition and near infrared reflectance spectroscopy of diet samples collected by ruminal evacuation

Six ruminally cannulated cows (570 ± 73 kg) fed corn residues were placed in a 6 × 6 Latin square to evaluate predictions of diet composition from ruminally collected diet samples. After complete ruminal evacuation, cows were fed 1-kg meals (dry matter [DM]-basis) containing different combinations of cornstalk and leaf and husk (LH) residues in ratios of 0:100, 20:80, 40:60, 60:40, 80:20, and 100:0. Diet samples from each meal were collected by removal of ruminal contents after 1-h and were either unrinsed, hand-rinsed or machine-rinsed to evaluate effects of endogenous compounds on predictions of diet composition. Diet samples were analyzed for neutral (NDF) and acid (ADF) detergent fiber, acid detergent insoluble ash (ADIA), acid detergent lignin (ADL), crude protein (CP), and near infrared reflectance spectroscopy (NIRS) to calculate diet composition. Rinsing type increased NDF and ADF content and decreased ADIA and CP content of diet samples (P < 0.01). Rinsing tended to increase (P < 0.06) ADL content of diet samples. Differences in concentration between cornstalk and LH residues within each chemical component were standardized by calculating a coefficient of variation (CV). Accuracy and precision of estimates of diet composition were analyzed by regressing predicted diet composition and known diet composition. Predictions of diet composition were improved by increasing differences in concentration of chemical components between cornstalk and LH residues up to a CV of 22.6 ± 5.4%. Predictions of diet composition from unrinsed ADIA and machine-rinsed NIRS had the greatest accuracy (slope = 0.98 and 0.95, respectively) and large coefficients of determination (r2 = 0.86 and 0.74, respectively). Subsequently, a field study (Exp. 2) was performed to evaluate predictions of diet composition in cattle (646 ± 89 kg) grazing corn residue. Five cows were placed in 1 of 10 paddocks and allowed to graze continuously or to strip-graze corn residues. Predictions of diet composition from ADIA, ADL, and NIRS did not differ (P = 0.99), and estimates of cornstalk intake tended to be greater (P = 0.09) in strip-grazed compared to continuously grazed cows. These data indicate that diet composition can be predicted by chemical components or NIRS by ruminal collection of diet samples among cattle grazing corn residues.

Effect of storage temperature on Streptococcus mutans viability

Abstract Introduction Proper storage conditions and maintenance of viable biological material plays an important role in microbiological research, allowing for the opportunity to conduct future studies. Objective To evaluate the viability of Streptococcus mutans strains that were previously grown and stored under different temperatures for approximately eight years. Material and method In this study, we evaluated 393 bacterial isolates that were stored in a freezer at -80°C (G1) and 200 isolates stored in a freezer at -20°C (G2). Aliquots of each sample were plated on blood agar and mitis-salivarius bacitracin sucrose agar-solidified medium. After incubating under microaerophilic conditions in an incubator at 37°C for 72 hours, the presence, morphology and purity of bacterial growth was observed. The data were analyzed by means of descriptive statistics. Result Microbial viability was observed in almost all samples (99.7%) in G1, whereas all isolates stored at -20°C were considered inviable. Conclusion The viability of S. mutans is influenced by the storage temperature of the samples, and the strains remain viable when stored under ideal temperature conditions (-80°C), even when stored for a long period of time.

Auto Poisoning of the Respiratory Chain by a Quorum-Sensing-Regulated Molecule Favors Biofilm Formation and Antibiotic Tolerance

Bacterial programmed cell death and quorum sensing are direct examples of prokaryote group behaviors, wherein cells coordinate their actions to function cooperatively like one organism for the benefit of the whole culture. We demonstrate here that 2-n-heptyl-4-hydroxyquinoline-N-oxide (HQNO), a Pseudomonas aeruginosa quorum-sensing-regulated low-molecular-weight excreted molecule, triggers autolysis by self-perturbing the electron transfer reactions of the cytochrome bc1 complex. HQNO induces specific self-poisoning by disrupting the flow of electrons through the respiratory chain at the cytochrome bc1 complex, causing a leak of reducing equivalents to O2 whereby electrons that would normally be passed to cytochrome c are donated directly to O2. The subsequent mass production of reactive oxygen species (ROS) reduces membrane potential and disrupts membrane integrity, causing bacterial cell autolysis and DNA release. DNA subsequently promotes biofilm formation and increases antibiotic tolerance to beta-lactams, suggesting that HQNO-dependent cell autolysis is advantageous to the bacterial populations. These data identify both a new programmed cell death system and a novel role for HQNO as a critical inducer of biofilm formation and antibiotic tolerance. This newly identified pathway suggests intriguing mechanistic similarities with the initial mitochondrial-mediated steps of eukaryotic apoptosis.

Influence of Substrates on the Surface Characteristics and Membrane Proteome of Fibrobacter succinogenes S85

Although Fibrobacter succinogenes S85 is one of the most proficient cellulose degrading bacteria among all mesophilic organisms in the rumen of herbivores, the molecular mechanism behind cellulose degradation by this bacterium is not fully elucidated. Previous studies have indicated that cell surface proteins might play a role in adhesion to and subsequent degradation of cellulose in this bacterium. It has also been suggested that cellulose degradation machinery on the surface may be selectively expressed in response to the presence of cellulose. Based on the genome sequence, several models of cellulose degradation have been suggested. The aim of this study is to evaluate the role of the cell envelope proteins in adhesion to cellulose and to gain a better understanding of the subsequent cellulose degradation mechanism in this bacterium. Comparative analysis of the surface (exposed outer membrane) chemistry of the cells grown in glucose, acid-swollen cellulose and microcrystalline cellulose using physico-chemical characterisation techniques such as electrophoretic mobility analysis, microbial adhesion to hydrocarbons assay and Fourier transform infra-red spectroscopy, suggest that adhesion to cellulose is a consequence of an increase in protein display and a concomitant reduction in the cell surface polysaccharides in the presence of cellulose. In order to gain further understanding of the molecular mechanism of cellulose degradation in this bacterium, the cell envelope-associated proteins were enriched using affinity purification and identified by tandem mass spectrometry. In total, 185 cell envelope-associated proteins were confidently identified. Of these, 25 proteins are predicted to be involved in cellulose adhesion and degradation, and 43 proteins are involved in solute transport and energy generation. Our results supports the model that cellulose degradation in F. succinogenes occurs at the outer membrane with active transport of cellodextrins across for further metabolism of cellodextrins to glucose in the periplasmic space and inner cytoplasmic membrane.

Maximizing efficiency of rumen microbial protein production

Rumen microbes produce cellular protein inefficiently partly because they do not direct all ATP toward growth. They direct some ATP toward maintenance functions, as long-recognized, but they also direct ATP toward reserve carbohydrate synthesis and energy spilling (futile cycles that dissipate heat). Rumen microbes expend ATP by vacillating between (1) accumulation of reserve carbohydrate after feeding (during carbohydrate excess) and (2) mobilization of that carbohydrate thereafter (during carbohydrate limitation). Protozoa account for most accumulation of reserve carbohydrate, and in competition experiments, protozoa accumulated nearly 35-fold more reserve carbohydrate than bacteria. Some pure cultures of bacteria spill energy, but only recently have mixed rumen communities been recognized as capable of the same. When these communities were dosed glucose in vitro, energy spilling could account for nearly 40% of heat production. We suspect that cycling of glycogen (a major reserve carbohydrate) is a major mechanism of spilling; such cycling has already been observed in single-species cultures of protozoa and bacteria. Interconversions of short-chain fatty acids (SCFA) may also expend ATP and depress efficiency of microbial protein production. These interconversions may involve extensive cycling of intermediates, such as cycling of acetate during butyrate production in certain butyrivibrios. We speculate this cycling may expend ATP directly or indirectly. By further quantifying the impact of reserve carbohydrate accumulation, energy spilling, and SCFA interconversions on growth efficiency, we can improve prediction of microbial protein production and guide efforts to improve efficiency of microbial protein production in the rumen.

Saccharomyces cerevisiae live culture affects rapidly fermentable carbohydrates fermentation profile in precision-fed dairy heifers

Lascano, G. J., Heinrichs, A. J. and Tricarico, J. M. 2015. Saccharomyces cerevisiae live culture affects rapidly fermentable carbohydrates fermentation profile in precision-fed dairy heifers. Can. J. Anim. Sci. 95: 117–127. The experimental objective was to determine the dose effect of live yeast culture (YC) on rumen fermentation profiles and microbial total cell concentrations in precision-fed dairy heifers exposed to different rapidly fermented carbohydrates diets. A split-plot design with starch level as the whole plot and YC dose as sub-plot was administered in a four-period (21 d) 4×4 Latin square balanced for carryover effects. Eight Holstein heifers were allocated to two starch treatments (28% starch: HS; 17% starch: LS) and to a sequence of YC doses (0, 10, 30, and 50 g d−1). Total volatile fatty acid concentration was not different among YC doses or starch level, but molar proportions of propionate, isobutyrate, and isovalerate were higher for HS than for LS. Mean ruminal ammonia concentration was increased in HS-fed heifers. Heifers fed HS had an increased number of viable, non-viable, and total fluid-associated bacteria, particle-associated bacteria, and total bacteria. Increasing YC dose linearly beyond 10 g d−1 decreased viable and total fluid-associated bacteria. The effects of various YC doses on ruminal fermentation products, pH, and microbial total cell concentrations indicate diet dependency between source of readily available carbohydrates and YC addition in dairy heifers.

Processamento do milho para vacas leiteiras em pastejo

Doze vacas lactantes Holandês-Gir (1/2), em sistema de pasto rotativo de Panicum maximumcv. Mombaça, foram suplementadas com concentrados contendo milho seco finamente moído (MM), milho expandido (ME), milho floculado a vapor (MF) ou milho moído reidratado e ensilado (MU). O delineamento experimental adotado foi o de quadrado latino 4 x 4, com três repetições. O consumo de pasto foi maior quando as vacas foram suplementadas com MF, o que se refletiu em maior consumo de MS, PB, FDN para o mesmo tratamento. A digestibilidade aparente da MS foi maior para as dietas de MF e MM. A digestibilidade aparente da FDN foi menor para MU. A produção e composição do leite das vacas não diferiram entre os tratamentos, entretanto a eficiência alimentar foi menor para MF.

Effects of feeding increasing proportions of corn grain on concentration of lipopolysaccharide in the rumen fluid and the subsequent alterations in immune responses in goats

This study was conducted to investigate the effects of feeding increasing proportions of corn grain on concentration of lipopolysaccharide (LPS) in the rumen fluid and the subsequent alterations in immune responses as reflected by plasma concentrations of serum amyloid A (SAA) and haptoglobin (Hp) in goats. Nine goats were assigned to three diets (0%, 25%, and 50% corn grain) in a 3 ×3 Latin square experimental design. The results showed that as the proportion of dietary corn increased, the ruminal pH decreased (p< 0.001), and the concentrations of propionate (p<0.001), butyrate (p<0.001), lactic acid (p = 0.013) and total volatile fatty acid (p = 0.031) elevated and the ruminal LPS level increased (p<0.001). As the proportion of dietary corn increased, the concentration of SAA increased (p = 0.013). LPS was detectable in the blood of individual goats fed 25% and 50% corn. A real-time PCR analysis showed that the copy number of phylum Bacteroidetes (p<0.001) was reduced (4.61×10⁹copies/mL to 1.48×10⁹copies/mL) by the increasing dietary corn, and a correlation analysis revealed a significant negative correlation between the number of Bacteroidetes and rumen LPS levels. Collectively, these results indicated that feeding goats high proportions (50%) of corn grain decreased the ruminal pH, increased LPS in the rumen fluid and tended to stimulate an inflammatory response.

Grain-rich diets differently alter ruminal and colonic abundance of microbial populations and lipopolysaccharide in goats

High grain feeding has been associated with ruminal pH depression and microbial dysbiosis in cattle. Yet, the impact of high grain feeding on the caprine rumen and hindgut microbial community and lipopolysaccharide (LPS) release is largely unknown. Therefore, the objective was to investigate the effect of increasing dietary levels of barley grain on the microbial composition and LPS concentrations in the rumen and colon of goats. Effects were compared with respect to the responses of ruminal and colonic pH and short-chain fatty acid (SCFA) generation. Growing goats (n = 5-6) were fed diets containing 0, 30, or 60% coarsely ground barley grain for 6 weeks. Ruminal ciliate protozoa were counted with Bürker counting chamber, and quantitative PCR was used to compare bacterial populations. Increasing dietary grain level linearly increased (P < 0.05) ruminal numbers of entodiniomorphids. With the 60% grain diet, there was a reduction in ruminal abundance of the genus Prevotella and Fibrobacter succinogenes, whereas the ruminal abundance of Lactobacillus spp. increased compared to the 0 and 30% grain diets (P < 0.05). In the colon, abundance of the genus Prevotella and F. succinogenes increased (P < 0.05) in goats fed the 60% grain diet compared to those fed the other diets. Colonic abundance of Clostridium cluster I was related to the presence of grain in the diet. Ruminal LPS concentration decreased (P < 0.05) in response to the 60% grain diet, whereas its colonic concentration increased in response to the same diet (P < 0.05). Present results provide first insight on the adaptive response of rumen protozoa and rumen and colonic bacterial populations to increasing dietary levels of grain in goats. Although luminal pH largely affects microbial populations, fermentable substrate flow to the caprine hindgut may have played a greater role for colonic bacterial populations in the present study.

Gene sets for utilization of primary and secondary nutrition supplies in the distal gut of endangered Iberian lynx

Recent studies have indicated the existence of an extensive trans-genomic trans-mural co-metabolism between gut microbes and animal hosts that is diet-, host phylogeny- and provenance-influenced. Here, we analyzed the biodiversity at the level of small subunit rRNA gene sequence and the metabolic composition of 18 Mbp of consensus metagenome sequences and activity characteristics of bacterial intra-cellular extracts, in wild Iberian lynx (Lynx pardinus) fecal samples. Bacterial signatures (14.43% of all of the Firmicutes reads and 6.36% of total reads) related to the uncultured anaerobic commensals Anaeroplasma spp., which are typically found in ovine and bovine rumen, were first identified. The lynx gut was further characterized by an over-representation of ‘presumptive’ aquaporin aqpZ genes and genes encoding ‘active’ lysosomal-like digestive enzymes that are possibly needed to acquire glycerol, sugars and amino acids from glycoproteins, glyco(amino)lipids, glyco(amino)glycans and nucleoside diphosphate sugars. Lynx gut was highly enriched (28% of the total glycosidases) in genes encoding α-amylase and related enzymes, although it exhibited low rate of enzymatic activity indicative of starch degradation. The preponderance of β-xylosidase activity in protein extracts further suggests lynx gut microbes being most active for the metabolism of β-xylose containing plant N-glycans, although β-xylosidases sequences constituted only 1.5% of total glycosidases. These collective and unique bacterial, genetic and enzymatic activity signatures suggest that the wild lynx gut microbiota not only harbors gene sets underpinning sugar uptake from primary animal tissues (with the monotypic dietary profile of the wild lynx consisting of 80–100% wild rabbits) but also for the hydrolysis of prey-derived plant biomass. Although, the present investigation corresponds to a single sample and some of the statements should be considered qualitative, the data most likely suggests a tighter, more coordinated and complex evolutionary and nutritional ecology scenario of carnivore gut microbial communities than has been previously assumed.

Diet-induced bacterial immunogens in the gastrointestinal tract of dairy cows: impacts on immunity and metabolism

Dairy cows are often fed high grain diets to meet the energy demand for high milk production or simply due to a lack of forages at times. As a result, ruminal acidosis, especially subacute ruminal acidosis (SARA), occurs frequently in practical dairy production. When SARA occurs, bacterial endotoxin (or lipopolysaccharide, LPS) is released in the rumen and the large intestine in a large amount. Many other bacterial immunogens may also be released in the digestive tract following feeding dairy cows diets containing high proportions of grain. LPS can be translocated into the bloodstream across the epithelium of the digestive tract, especially the lower tract, due to possible alterations of permeability and injuries of the epithelial tissue. As a result, the concentration of blood LPS increases. Immune responses are subsequently caused by circulating LPS, and the systemic effects include increases in concentrations of neutrophils and the acute phase proteins such as serum amyloid-A (SAA), haptoglobin (Hp), LPS binding protein (LBP), and C-reactive protein (CRP) in blood. Entry of LPS into blood can also result in metabolic alterations. Blood glucose and nonesterified fatty acid concentrations are enhanced accompanying an increase of blood LPS after increasing the amount of grain in the diet, which adversely affects feed intake of dairy cows. As the proportions of grain in the diet increase, patterns of plasma β-hydoxybutyric acid, cholesterol, and minerals (Ca, Fe, and Zn) are also perturbed. The bacterial immunogens can also lead to reduced supply of nutrients for synthesis of milk components and depressed functions of the epithelial cells in the mammary gland. The immune responses and metabolic alterations caused by circulating bacterial immunogens will exert an effect on milk production. It has been demonstrated that increases in concentrations of ruminal LPS and plasma acute phase proteins (CRP, SAA, and LBP) are associated with declines in milk fat content, milk fat yield, 3.5% fat-corrected milk yield, as well as milk energy efficiency.

Dasytricha dominance in Surti buffalo rumen revealed by 18S rRNA sequences and real-time PCR assay

The genetic diversity of protozoa in Surti buffalo rumen was studied by amplified ribosomal DNA restriction analysis, 18S rDNA sequence homology and phylogenetic and Real-time PCR analysis methods. Three animals were fed diet comprised green fodder Napier bajra 21 (Pennisetum purpureum), mature pasture grass (Dicanthium annulatum) and concentrate mixture (20% crude protein, 65% total digestible nutrients). A protozoa-specific primer (P-SSU-342f) and a eukarya-specific primer (Medlin B) were used to amplify a 1,360 bp fragment of DNA encoding protozoal small subunit (SSU) ribosomal RNA from rumen fluid. A total of 91 clones were examined and identified 14 different 18S RNA sequences based on PCR-RFLP pattern. These 14 phylotypes were distributed into four genera-based 18S rDNA database sequences and identified as Dasytricha (57 clones), Isotricha (14 clones), Ostracodinium (11 clones) and Polyplastron (9 clones). Phylogenetic analyses were also used to infer the makeup of protozoa communities in the rumen of Surti buffalo. Out of 14 sequences, 8 sequences (69 clones) clustered with the Dasytricha ruminantium-like clone and 4 sequences (13 clones) were also phylogenetically placed with the Isotricha prostoma-like clone. Moreover, 2 phylotypes (9 clones) were related to Polyplastron multivesiculatum-like clone. In addition, the number of 18S rDNA gene copies of Dasytricha ruminantium (0.05% to ciliate protozoa) was higher than Entodinium sp. (2.0 × 10(5) vs. 1.3 × 10(4)) in per ml ruminal fluid.

Assessment of protozoa in Yunnan Yellow cattle rumen based on the 18S rRNA sequences

Library of ruminal protozoal 18S rRNA of Yunnan Yellow Cattle has been constructed in the present study. Phylogenic analysis of sequences was meanwhile employed to reveal the diversity of protozoa in the rumen of Yunnan Yellow Cattle. One Yellow Cattle was fed malt meal (YCRPB) and the other was fed wheat straw (YCRPS). A protozoa-specific primer (P-SSU-342f) and a eukarya-specific primer (Medlin B) were used to amplify a 1,360-bp fragment of DNA encoding protozoal small subunit (SSU) ribosomal RNA from rumen fluid. The results showed as follows: A total of 121 clones were obtained and fell into four genera identified as Entodinium (66.9%), Dasytricha (5.8%), Isotricha (9.1%), and Diplodinium (18.2%). Within the genus Entidinium, 48 of the YCRPB sequences and 33 of the YCRPS sequences clustered with the Entodinium caudatum. 7 of the YCRPB sequences were phylogenetically placed within the genus Dasytricha. 11 of the YCRPB sequences were related with high confidence to Isotricha intestinalis. 22 of the YCRPS sequences were phylogenetically placed within the genus Diplodinium. The predominant protozoal genus identified in the rumen fluid belonged to the Entodinium group, and the divergences between two cattle may due to diet and individual differences.

Nutrient demand interacts with forage family to affect nitrogen digestion and utilization responses in dairy cows

The effect of preliminary feed intake on responses to diets containing alfalfa silage or orchardgrass silage was evaluated using 8 ruminally and duodenally cannulated Holstein cows in a crossover design experiment with a 14-d preliminary period and two 15-d treatment periods. Responses measured were intake, digestion, and utilization of N. Cows were 139 +/- 83 (mean +/- standard deviation) days in milk at the beginning of the preliminary period. During the 14-d preliminary period, 3.5% fat-corrected milk yield ranged from 23.9 to 47.6 kg/d (mean = 36.9 kg/d) and preliminary voluntary dry matter intake (pVDMI) ranged from 14.2 to 21.3 kg/d (mean = 18.6 kg/d). Treatments were a diet with alfalfa silage as the sole forage (AL) and a diet with orchardgrass silage as the sole forage (OG). Alfalfa silage contained 20.5% crude protein (CP; dry matter basis) and orchardgrass silage contained 20.4% CP; AL contained 18.3% CP and 5.6% estimated rumen-undegraded CP, and OG contained 18.8% CP and 6.3% estimated rumen-undegraded CP. Mean N intake was similar between treatments, ruminal N digestibility was greater for AL (30.4%) than for OG (17.7%), and whole-tract N digestibility did not differ between treatments. Intake and duodenal flow of N depended on a treatment x pVDMI interaction; both N intake and duodenal flow increased more for AL than for OG as pVDMI increased. Duodenal flow of microbial N and the efficiency of microbial N production from OM also depended on a treatment x pVDMI interaction in a manner similar to N intake and duodenal flow. However, treatment x pVDMI interactions also indicate that as pVDMI increased and N intake increased for AL compared with OG, a decreasing proportion of the additional N consumed from AL was digested and used for increased milk protein production or body tissue gain. Therefore, when feeding less-filling diets, such as those containing large proportions of legume forage, to high-producing cows, reducing dietary N concentration could increase the efficiency of N utilization and reduce the extent to which greater DMI leads to greater N excretion.

Quantitative analysis of cellulose degradation and growth of cellulolytic bacteria in the rumen

Ruminant animals digest cellulose via a symbiotic relationship with ruminal microorganisms. Because feedstuffs only remain in the rumen for a short time, the rate of cellulose digestion must be very rapid. This speed is facilitated by rumination, a process that returns food to the mouth to be rechewed. By decreasing particle size, the cellulose surface area can be increased by up to 10(6)-fold. The amount of cellulose digested is then a function of two competing rates, namely the digestion rate (K(d)) and the rate of passage of solids from the rumen (K(p)). Estimation of bacterial growth on cellulose is complicated by several factors: (1) energy must be expended for maintenance and growth of the cells, (2) only adherent cells are capable of degrading cellulose and (3) adherent cells can provide nonadherent cells with cellodextrins. Additionally, when ruminants are fed large amounts of cereal grain along with fiber, ruminal pH can decrease to a point where cellulolytic bacteria no longer grow. A dynamic model based on STELLA software is presented. This model evaluates all of the major aspects of ruminal cellulose degradation: (1) ingestion, digestion and passage of feed particles, (2) maintenance and growth of cellulolytic bacteria and (3) pH effects.

The bacteriophages in human- and animal body-associated microbial communities

Felix d'Herelle first demonstrated, about 90 years ago, the presence of bacteriophages in human and animal body microbiota. Our comprehension of the impact of naturally occurring bacteriophages on symbiotic bacteria, and of their role in general homeostasis of macro-organism, nevertheless remains quite fragmentary. Analysis of data in various human- and animal body-associated microbial systems on phage occurrence, diversity, host specificity and dynamics, as well as host occurrence, specificity and dynamics, suggests that mechanisms which stabilize phage-bacteria coexistence are not identical for either different species or different body sites. Regulation by phage infection instead probably depends on specific physical, chemical and biological conditions, e.g. pH, nutrient densities, host prevalence, relation to mucosa and other surfaces and presence of phage inhibiting substances. In some animal species intestinal bacteriophages thus appear to exert significant selective pressure over at least some resident bacterial populations, resulting in phages playing important roles in the self-regulation of these microbial systems while at the same time contributing to maintenance of bacterial diversity (i.e. 'killing the winner'). Emerging data additionally suggest that bacteriophage particles could play roles in regulating the immune reactions of the macro-organism. Alternatively, for many systems links between phages and community characteristics have not been established.

Repeated ruminal acidosis challenges in lactating dairy cows at high and low risk for developing acidosis: ruminal pH

The primary objective of this experiment was to determine whether lactating dairy cows that are at high (HR) or low (LR) risk for experiencing ruminal acidosis, because of their diet and stage of lactation, differ in their response to an acidosis challenge. A secondary objective was to determine whether the severity of acidosis changes with repeated challenges. The experiment was a completely randomized design with 2 groups (risk scenarios, HR vs. LR) and 3 periods corresponding to 3 repeated acidosis challenges. Eight lactating ruminally cannulated cows were assigned to 1 of 2 groups: HR, early lactation cows fed a 45% forage diet, or LR, midlactation cows fed a 60% forage diet. Cows were exposed to 3 acidosis challenges, each separated by 14 d. The challenge consisted of restricting total mixed rations to 50% of ad libitum intake for 24 h, followed by a 1-h meal of 4 kg of ground barley-wheat before allocating the total mixed rations. Ruminal pH was measured continuously for 9 of the 14 d each period using an indwelling system. Subacute acidosis (SARA) was described at 2 thresholds: pH <5.8 and pH <5.5. As expected, HR cows had lower ruminal pH profiles (curves) compared with LR cows: mean pH (5.81 vs. 6.21) and nadir pH (5.13 vs. 5.53). The HR cows also experienced SARA to a greater extent than LR cows during the experiment (pH <5.8, 10.6 vs. 3.5 h/d; pH <5.5, 5.9 vs. 1.6 h/d). The pH profiles of cows in both risk categories decreased with each challenge period; mean pH was 6.13, 6.03, 5.77, and nadir pH was 5.52, 5.34, and 5.14 in periods 1, 2, and 3, respectively. The challenges caused a similar decrease in pH for cows in both risk categories, but because the HR cows had a lower baseline pH, they experienced more severe SARA with each subsequent challenge. Feed restriction the day before administering the acidosis challenge caused ruminal pH to gradually increase. On the challenge day, the entire grain allotment was consumed by all cows in period 1, six cows in period 2, and only 3 cows in period 3. The pH plummeted immediately after each grain challenge. Ruminal pH remained very low during the first day after the challenge for all cows, but LR cows began their recovery more quickly than HR cows. Regardless of risk category, with each successive challenge, the pH decrease on the challenge day was more severe: nadir pH on the challenge day was 5.19, 5.07, and 4.90 and duration of SARA (pH <5.8) was 12.2, 13.4, and 15.8 h/d in periods 1, 2, and 3. This study indicates that cows become more prone to acidosis over time even though they decrease intake of the challenge grain to avoid acidosis. The severity of each subsequent bout of acidosis increases, especially for cows fed diets low in physically effective fiber and at high acidosis risk. Therefore, a bout of acidosis that occurs due to improper feed delivery or poor diet formulation can have long-term consequences on cow health and productivity.

Corn Grain Endosperm Type and Brown Midrib 3 Corn Silage: Ruminal Fermentation and N Partitioning in Lactating Cows

Interactions of endosperm type of corn grain and the brown midrib 3 mutation (bm3) in corn silage on ruminal fermentation and microbial efficiency of lactating dairy cows were evaluated. Eight ruminally and duodenally cannulated cows (72 +/- 8 d in milk; mean +/- SD) were used in a duplicated 4 x 4 Latin square design experiment with a 2 x 2 factorial arrangement of treatments. Treatments were corn grain endosperm type (floury or vitreous) and corn silage type (bm3 or isogenic normal). Diets contained 26% neutral detergent fiber and 30% starch. Increasing ruminal starch digestibility by replacing vitreous corn grain with floury grain reduced mean and minimum ruminal pH. Brown midrib 3 corn silage reduced mean and minimum ruminal pH and increased total volatile fatty acid concentration. Ruminal pH was positively associated with rate of valerate absorption. Although floury endosperm reduced acetate:propionate ratio in both control and bm3 corn silage diets, it had a greater effect on reducing acetate:propionate ratio for control silage compared with bm3 corn silage. Nonammonia N flow to the duodenum did not differ among treatments and no effects of treatment were detected for microbial N and nonammonia, nonmicrobial N flow. Although treatment effects on ruminal fermentation and ruminal pH were observed, few interactions of treatment were detected and treatments did not affect flow of N fractions to the intestines.

Sources of Variation in Rates of in Vitro Ruminal Protein Degradation

Rates and extents of ruminal protein degradation for casein, solvent soybean meal (SSBM), expeller soybean meal (ESBM), and alfalfa hay were estimated from net appearance of NH3 and total amino acids in in vitro media containing 1 mM hydrazine and 30 mg/L of chloramphenicol. Protein was added at 0.13 mg of N/mL of medium, and incubations were conducted for 4 to 6 h, usually with hourly sampling. Inocula were obtained from ruminally cannulated donor cows fed diets of grass silage or alfalfa and corn silages plus concentrates. Preincubation or dialysis of inocula was used to suppress background NH3 and total amino acids; however, preincubation yielded more rapid degradation rates for casein and SSBM and was used in subsequent incubations. Preincubation with added vitamins, VFA, hemin, or N did not alter protein degradation. Protein degradation rates estimated for SSBM, ESBM, and alfalfa were not different when computed from total N release or N release in NH3 plus total amino acids, regardless of whether amino acids were quantified using ninhydrin colorimetry or o-phthalaldehyde fluorescence. Accounting for the release of peptide-N also did not affect estimated degradation. However, casein degradation rates were more rapid when using total N release or accounting for peptide-N, indicating significant accumulation of small peptides during its breakdown. Rates also were more rapid with inocula from lactating cows versus nonlactating cows with lower feed intake. Protein degradation rates were different due to time after feeding: casein rate was more rapid, but SSBM and ESBM rates were slower with inocula obtained after feeding. Several characteristics of ruminal inoculum that influenced breakdown of the rapidly degraded protein casein did not appear to have direct effects on degradation of protein in soybean meal.

Pelleted Beet Pulp Substituted for High-Moisture Corn: 3. Effects on Ruminal Fermentation, pH, and Microbial Protein Efficiency in Lactating Dairy Cows

The effects of increasing concentrations of dried, pelleted beet pulp substituted for high-moisture corn on ruminal fermentation, pH, and microbial efficiency were evaluated using eight ruminally and duodenally cannulated multiparous Holstein cows in a duplicated 4 x 4 Latin square design with 21-d periods. Cows were 79 +/- 17 (mean +/- SD) DIM at the beginning of the experiment. Experimental diets with 40% forage (corn silage and alfalfa silage) and 60% concentrate contained 0, 6.1, 12.1, or 24.3% beet pulp substituted for high-moisture corn on a DM basis. Diet concentrations of NDF and starch were 24.3 and 34.6% (0% beet pulp), 26.2 and 30.5% (6% beet pulp), 28.0, and 26.5% (12% beet pulp), and 31.6 and 18.4% (24% beet pulp), respectively. Substituting beet pulp for corn did not affect daily mean or minimum ruminal pH but tended to reduce pH range. Ruminal acetate:propionate responded in a positive exponential relationship to added beet pulp. Rate of valerate absorption from the rumen was not affected by treatment. Substituting beet pulp for corn up to 24% of diet DM did not affect efficiency of ruminal microbial protein production, expressed as microbial N flow to the duodenum as a percentage of OM truly digested in the rumen. Microbial efficiency was not correlated to mean pH or daily minimum pH. While microbial efficiency was not directly related to concentration of beet pulp fed, it was positively correlated with passage rate of particulate matter, as represented by starch and indigestible NDF, probably due to reduced turnover of microbial protein in the rumen.

The bacteriophages of ruminal prevotellas

Rumen bacteriophage-lyzed bacterial strains of the genus Prevotella were isolated and preliminarily characterized. The strain TCl-1 the species P. bryantii was the only prevotella strain successfully infected with filter sterilized rumen fluid from a black-and-white Holstein cow. Two types of plaques were observed, both rather small and turbid. Preliminary electron microscopy observation showed that several morphologically different bacteriophages were present in these plaques. The plaque eluates were further used for the infection of other prevotella strains. The plaques produced by the bacteriophages were observed with two strains, i.e. P. bryantii B(1)4 and P. brevis GA33. The bacteriophages from both strains were examined by transmission electron microscopy and several morphologically different bacteriophages were observed, among others also a large virion with an icosahedral head with the diameter of approximately 120 nm. The bacteriophage was identified in plaques of bacterial cells of the strain GA33 and has an approximately 800 nm long helical tail, which places it among the largest ruminal bacteriophages described to date. Other bacteriophages from the same indicator strain as well as from P. bryantii B(1)4 strain were smaller and tail structures were not observed in all of them.

Effect of a controlled-release urea supplementation on feed intake, digestibility, nitrogen balance and ruminal kinetics of sheep fed low quality tropical forage

Four ruminally cannulated crossbred sheep (25+/-3.4kg BW) were divided into a 4x4 Latin square design to measure the effects of controlled-release urea supplement (CRUS). The basal diet consisted of 60% sugar cane tops (Saccharum officinarum), 30% full plant corn stubble (Zea mays), and 10% King grass (Pennisetum purpureum). Feed intake, digestibility, N balance and in situ ruminal kinetics were studied with four diets, D1 (control), D2, D3 and D4, which included the ratios of 100:0%, 90:10%, 80:20% or 70:30% of basal diet with CRUS. Results showed DMI differences (P<0.05) for D4 (822g per day) versus D1, D2 and D3 (580, 659 and 700g per day, respectively). N retention increased (P<0.05) for D4 (35.69g per day) versus D1, D2 and D3 (9.29, 6.85 and 19.10g per day, respectively). In vivo N digestibility was greater (P<0.05) in D4 (79.63%) than in D1 (57.57%). In vivo digestibility of DM, OM, GE, cellulose and hemicellulose was similar among the four groups. Digestibility of cell walls in D4 was higher (P<0.05) at 74.06% versus 67.78% in D1. In situ DM digestibility showed differences (P<0.05) among all diets at 9, 12, 24 and 48h of incubation. Potentially digestible fiber, 52.61%, was higher (P<0.05) in D4 versus 31.00% in D1. Indigestible fiber, 35.29%, was lowest (P<0.05) in D4 compared to 81.51% in D1. Digestion rate constant (k(d)) was different (P<0.05) between the experimental diets and control. Passage constant (k(p)) was different (P<0.05) between all diets (0.036/h in D4 to 0.081/h in D1). True digestibility was higher (P<0.05) in D4 (44.64%) compared to D1 (19.55%), but in D2 (24.54%) and D3 (28.22%) there was no difference. Cellulose in situ digestion rate, the potentially digestible fiber, was higher (P<0.05) in D3 (42.74%) as compared to D1 (22.50%). Time of disappearance of cellulose in D4 (14.79h) was less (P<0.05) than in D1 (24.03h), however there was no difference between D1 and D2. Hemicellulose in situ digestion was different (P<0.05) between D3 (45.48%) and D1 (23.61%). Digestion rate was higher (P<0.05) between D3 and D4 as compared to D1. Passage rate was different (P<0.05) between D4 (0.033/h) and D1 (0.018/h). True digestibility in D3 (34.84%) and D4 (34.62%) was higher (P<0.05) than that in D1 (20.06%) and D2 (25.86%). Half-time disappearance (t(1/2)) for hemicellulose was higher (P<0.05) in D1 (62.36h) than in D3 (28.00h) and D4 (20.64h). This study demonstrated that low quality forages at 70% of the total diet can be efficiently utilized by sheep when controlled-release urea supplementation is 30% of the feeding regime.

Effect of a controlled-release urea supplement on rumen fermentation in sheep fed a diet of sugar cane tops (Saccharum officinarum), corn stubble (Zea mays) and King grass (Pennisetum purpureum)

Four cannulated sheep were used to study ruminal fermentation of a diet consisting of 60% sugar cane tops (Saccharum officinarum), 30% corn stubble (Zea mays), 10% King grass (Pennisetum purpureum) and 0% (control), 10, 20 or 30% controlled-release urea supplement (CRUS) (diets 1, 2, 3 and 4, respectively). Average ruminal pH did not differ among diets (P>0.05), but during the first 6h of sampling tended to be higher for CRUS diets. Ammonia concentrations were higher (P<0.01) in all treatments over controls, indicating microbial protein generation. Acetic acid production (mM/1) decreased (P<0.05), propionic acid increased (P<0.05), while butyric acid production did not differ among CRUS diets and controls (P>0.05). Total amounts of ruminal VFA were lowest (P<0.01) in controls, while CRUS diets produced more of these energy sources. Supplementation of the high fiber diets with 10, 20 or 30% CRUS increasingly improved rumen fermentation, ammonia supply and VFA production. The results show that low quality forages (up to 70% DMI) can be used efficiently by sheep when conditions for ruminal microorganism are improved with a controlled-release urea supplement.

Performance of dairy cattle fed citrus pulp or corn products as sources of neutral detergent-soluble carbohydrates

The effects of modifying the dietary profile of neutral detergent-soluble carbohydrates (NDSC) on milk production and rumen fermentation were determined. Corn silage and alfalfa hay-based diets were formulated to contain 40% calculated NDSC supplied primarily by dried citrus pulp as a source of neutral detergent-soluble fiber (NDSF), or corn products as sources of starch. Diets were compared within cow with reversal experiments with two periods. In experiment 1, 11 multiparous Holstein cows including three ruminally cannulated animals were individually fed diets containing 23.6% citrus pulp (diet CPD) or 25.3% corn hominy (diet HD) on a dry matter basis. In experiment 2, 184 animals fed as two groups received diets containing 20.5% citrus pulp (diet CPD) or 19.5% cornmeal (diet CMD). Diets CPD provided more dietary NDSF and HD and CMD more starch. In experiment 1, cows fed HD had a greater milk protein percentage (+0.12%), and tended to yield more milk protein (0.08 kg/d) than cows fed CPD. Although ruminal H+ concentrations did not differ between diets, diet x time postfeeding interactions were significant. Ruminal organic acid concentrations did not differ between diets. In experiment 2, cows fed CMD yielded more milk (3.9 kg/d), 3.5% fat- and protein-corrected milk (2.6 kg/d), fat (0.05 kg/d), and protein (0.08 kg/d), whereas cows fed CPD produced greater concentrations of fat (+0.18%), and milk urea nitrogen (0.76 mg/dl). Modifying the proportions of NDSC in the diet can alter milk production and composition, the pattern of ruminal fermentation, and N utilization in dairy cows.