Measurement of Elastase and Cysteine Proteinases in Synovial Fluid of Patients with Rheumatoid Arthritis, Sero-Negative Spondylarthropathies, and Osteoarthritis

Synovial fluid samples were collected from 45 patients with rheumatoid arthritis, spondylarthropathy, or osteoarthritis, to study their content of elastase (EC 3.4.21.37) and of cysteine proteinases (EC 3.4.22.1, 3.4.22.15). We measured both elastase complexed with alpha 1-proteinase inhibitor and elastase activity toward the substrate L-pyroglutamyl-L-prolyl-L-valine-p-nitroanilide. Cysteine proteinase activities were measured with the substrates N-benzyloxycarbonyl-L-phenylalanyl-L-arginine-7-amido-4-methylcoumarin (Z-Phe-Arg-AMC) and Z-Arg-Arg-AMC and the inhibitor E-64 [L-trans-epoxysuccinyl-leucyl-amido-(4-guanidino)-butane]. In all these enzyme assays, higher median values were obtained in inflammatory arthropathies than in osteoarthritis. The concentration of the elastase-alpha 1-proteinase inhibitor complex and of elastase and cysteine proteinase activities were statistically higher in patients with rheumatoid arthritis than in patients with osteoarthritis. The difference in results between patients with spondylarthropathy and patients with osteoarthritis was statistically significant only for the elastase-alpha 1-proteinase inhibitor complex. The median values of the complex and of both enzyme activities were higher in patients with rheumatoid arthritis than in patients with spondylarthropathy; however, the difference was statistically significant only for the cysteine proteinase activity measured with Z-Arg-Arg-AMC substrate. These results suggest that both elastase and cysteine proteinases, which are increased in patients with inflammatory arthritis, are involved in cartilage degradation in these arthropathies.

Tau deletion promotes brain insulin resistance

The molecular pathways underlying tau pathology-induced synaptic/cognitive deficits and neurodegeneration are poorly understood. One prevalent hypothesis is that hyperphosphorylation, misfolding, and fibrillization of tau impair synaptic plasticity and cause degeneration. However, tau pathology may also result in the loss of specific physiological tau functions, which are largely unknown but could contribute to neuronal dysfunction. In the present study, we uncovered a novel function of tau in its ability to regulate brain insulin signaling. We found that tau deletion leads to an impaired hippocampal response to insulin, caused by altered IRS-1 and PTEN (phosphatase and tensin homologue on chromosome 10) activities. Our data also demonstrate that tau knockout mice exhibit an impaired hypothalamic anorexigenic effect of insulin that is associated with energy metabolism alterations. Consistently, we found that tau haplotypes are associated with glycemic traits in humans. The present data have far-reaching clinical implications and raise the hypothesis that pathophysiological tau loss-of-function favors brain insulin resistance, which is instrumental for cognitive and metabolic impairments in Alzheimer's disease patients.

Hippocampal T cell infiltration promotes neuroinflammation and cognitive decline in a mouse model of tauopathy

Alzheimer's disease is characterized by the combined presence of amyloid plaques and tau pathology, the latter being correlated with the progression of clinical symptoms. Neuroinflammatory changes are thought to be major contributors to Alzheimer's disease pathophysiology, even if their precise role still remains largely debated. Notably, to what extent immune responses contribute to cognitive impairments promoted by tau pathology remains poorly understood. To address this question, we took advantage of the THY-Tau22 mouse model that progressively develops hippocampal tau pathology paralleling cognitive deficits and reappraised the interrelationship between tau pathology and brain immune responses. In addition to conventional astroglial and microglial responses, we identified a CD8-positive T cell infiltration in the hippocampus of tau transgenic mice associated with an early chemokine response, notably involving CCL3. Interestingly, CD8-positive lymphocyte infiltration was also observed in the cortex of patients exhibiting frontemporal dementia with P301L tau mutation. To gain insights into the functional involvement of T cell infiltration in the pathophysiological development of tauopathy in THY-Tau22 mice, we chronically depleted T cells using anti-CD3 antibody. Such anti-CD3 treatment prevented hippocampal T cell infiltration in tau transgenic animals and reverted spatial memory deficits, in absence of tau pathology modulation. Altogether, these data support an instrumental role of hippocampal T cell infiltration in tau-driven pathophysiology and cognitive impairments in Alzheimer's disease and other tauopathies.

Rescue of impaired late-phase long-term depression in a tau transgenic mouse model

Cognitive decline, the hallmark of Alzheimer's disease, and accompanying neuropsychiatric symptoms share dysfunctions of synaptic processes as a common cellular pathomechanism. Long-term potentiation has proven to be a sensitive tool for the "diagnosis" of such synaptic dysfunctions. Much less, however, is known about how long-term depression (LTD), an alternative mechanism for the storage of memory, is affected by Alzheimer's disease progression. Here, we demonstrate that impaired late LTD (>3 hours) in THY-Tau22 mice can be rescued by either inhibition of glycogen synthase kinase-3 (GSK3β) activity or by application of the protein-phosphatase 2A agonist selenate. In line with these findings, we observed increased phosphorylation of GSK3β at Y216 and reduced total phosphatase activity in biochemical assays of hippocampal tissue of THY-Tau22 mice. Interestingly, LTD induction and pharmacologic inhibition of GSK3β appeared to downregulate GSK3ß activity via a marked upregulation of phosphorylation at the inhibitory Ser9 residue. Our results point to alterations in phosphorylation and/or dephosphorylation homeostasis as key mechanisms underlying the deficits in LTD and hippocampus-dependent learning found in THY-Tau22 mice.

Meat quality, fatty acid composition and flavour analysis in Belgian retail beef

The objective of this study was to evaluate the differences in biochemical, sensorial and quality characteristics of retail beef in Belgium. Four types of beef (Belgian Blue double-muscled, Limousin, Irish and Argentine) and two different muscles (longissimus lumborum and semimembranosus) were bought at the retail level and compared with regard to colour, shear force, collagen content, fatty acid analysis, taste panel evaluation as well as flavour analysis. Belgian Blue and Limousin beef had a paler colour, lower collagen and intramuscular fat contents. Fatty acid profiles were significantly different between the four types, with significantly higher PUFA/SFA and n-6/n-3 ratios for Belgiam Blue and Limousin beef compared to Argentine and Irish beef. There were significant differences between the meat types for taste panel tenderness and shear force, however both measurements did not fully correspond. Flavour analysis by gas chromatography-mass spectrometry as well as sensory analysis demonstrated that Irish and Argentine beef had a higher flavour intensity related to higher contents of volatile compounds. Differences in tenderness and flavour between the meat types were probably affected by differences in ageing time, related to import vs local production of meat.

Detrimental effects of diet-induced obesity on τ pathology are independent of insulin resistance in τ transgenic mice

The τ pathology found in Alzheimer disease (AD) is crucial in cognitive decline. Midlife development of obesity, a major risk factor of insulin resistance and type 2 diabetes, increases the risk of dementia and AD later in life. The impact of obesity on AD risk has been suggested to be related to central insulin resistance, secondary to peripheral insulin resistance. The effects of diet-induced obesity (DIO) on τ pathology remain unknown. In this study, we evaluated effects of a high-fat diet, given at an early pathological stage, in the THY-Tau22 transgenic mouse model of progressive AD-like τ pathology. We found that early and progressive obesity potentiated spatial learning deficits as well as hippocampal τ pathology at a later stage. Surprisingly, THY-Tau22 mice did not exhibit peripheral insulin resistance. Further, pathological worsening occurred while hippocampal insulin signaling was upregulated. Together, our data demonstrate that DIO worsens τ phosphorylation and learning abilities in τ transgenic mice independently from peripheral/central insulin resistance.

NMDA receptor dysfunction contributes to impaired brain-derived neurotrophic factor-induced facilitation of hippocampal synaptic transmission in a Tau transgenic model

While the spatiotemporal development of Tau pathology has been correlated with occurrence of cognitive deficits in Alzheimer's patients, mechanisms underlying these deficits remain unclear. Both brain-derived neurotrophic factor (BDNF) and its tyrosine kinase receptor TrkB play a critical role in hippocampus-dependent synaptic plasticity and memory. When applied on hippocampal slices, BDNF is able to enhance AMPA receptor-dependent hippocampal basal synaptic transmission through a mechanism involving TrkB and N-methyl-d-Aspartate receptors (NMDAR). Using THY-Tau22 transgenic mice, we demonstrated that hippocampal Tau pathology is associated with loss of synaptic enhancement normally induced by exogenous BDNF. This defective response was concomitant to significant memory impairments. We show here that loss of BDNF response was due to impaired NMDAR function. Indeed, we observed a significant reduction of NMDA-induced field excitatory postsynaptic potential depression in the hippocampus of Tau mice together with a reduced phosphorylation of NR2B at the Y1472, known to be critical for NMDAR function. Interestingly, we found that both NR2B and Src, one of the NR2B main kinases, interact with Tau and are mislocalized to the insoluble protein fraction rich in pathological Tau species. Defective response to BDNF was thus likely related to abnormal interaction of Src and NR2B with Tau in THY-Tau22 animals. These are the first data demonstrating a relationship between Tau pathology and synaptic effects of BDNF and supporting a contribution of defective BDNF response and impaired NMDAR function to the cognitive deficits associated with Tauopathies.

Effect of rate of pH decline on muscle enzyme activities in two pig lines

Muscle enzyme activities were measured in m. transversus abdominis (TA) samples of two pig lines, differing in stress sensitivity and in breeding objectives. Animals of line one were stress sensitive and selected for a high carcass lean content (LEAN), those of line two were homozygous stress resistant and selected for maximum live weight gain (GROWTH). Muscle samples of 16 pigs per line were excised at 1 h and sampled at 3 h post mortem. Boars, gilts and barrows were almost equally represented. Pigs of line GROWTH had a higher fat and lean tissue gain (P<0.01) and a lower carcass lean content (P<0.001) than those of line LEAN. Lower activities of μ-calpain, m-calpain, pyroglutamyl aminopeptidase I, acid lipase and neutral phospholipase were measured in TA muscle samples of line LEAN compared with line GROWTH (P<0.05). Activities of dipeptidyl peptidase IV and acid phospholipase tended to be somewhat lower for line LEAN, whereas activities of calpastatin, cathepsin (B+L) and cathepsin D were not different. Sex-class effects were analogous to line effects. Significant correlation coefficients between activities of several enzymes and pH values 1 h post mortem, both within and across lines, suggest that lower enzyme activities are a consequence of a more pronounced denaturation due to a faster post mortem pH decline.

Beneficial effects of exercise in a transgenic mouse model of Alzheimer's disease-like Tau pathology

Tau pathology is encountered in many neurodegenerative disorders known as tauopathies, including Alzheimer's disease. Physical activity is a lifestyle factor affecting processes crucial for memory and synaptic plasticity. Whether long-term voluntary exercise has an impact on Tau pathology and its pathophysiological consequences is currently unknown. To address this question, we investigated the effects of long-term voluntary exercise in the THY-Tau22 transgenic model of Alzheimer's disease-like Tau pathology, characterized by the progressive development of Tau pathology, cholinergic alterations and subsequent memory impairments. Three-month-old THY-Tau22 mice and wild-type littermates were assigned to standard housing or housing supplemented with a running wheel. After 9 months of exercise, mice were evaluated for memory performance and examined for hippocampal Tau pathology, cholinergic defects, inflammation and genes related to cholesterol metabolism. Exercise prevented memory alterations in THY-Tau22 mice. This was accompanied by a decrease in hippocampal Tau pathology and a prevention of the loss of expression of choline acetyltransferase within the medial septum. Whereas the expression of most cholesterol-related genes remained unchanged in the hippocampus of running THY-Tau22 mice, we observed a significant upregulation in mRNA levels of NPC1 and NPC2, genes involved in cholesterol trafficking from the lysosomes. Our data support the view that long-term voluntary physical exercise is an effective strategy capable of mitigating Tau pathology and its pathophysiological consequences.

Early Tau pathology involving the septo-hippocampal pathway in a Tau transgenic model: relevance to Alzheimer's disease

Alzheimer's disease is a neurodegenerative disorder characterized by amyloid deposits and neurofibrillary tangles. Cholinergic dysfunction is also a main pathological feature of the disease. Nevertheless, the links between cholinergic dysfunction and neuropathological hallmarks of Alzheimer's are still unknown. In the present study, we aimed to further investigate Tau aggregation in cholinergic systems, in a Tau transgenic mouse model. THY-Tau22 mice have recently been described as a novel model of Alzheimer-like Tau pathology without motor deficits. This strain presents an age-dependent development of Tau pathology leading to synaptic dysfunctions as well as learning and memory impairments. In the present work, we observed that Tau pathology differentially affects cerebral structures. Interestingly, early Tau pathology was observed in both hippocampus and basal forebrain. Moreover, some morphological as well as functional alterations of the septohippocampal pathway suggest a disconnection between these two key brain regions in Alzheimer's disease. Finally, these data suggest that Tau pathology may participate in cholinergic degeneration.

Dietary n-3 fatty acids have suppressive effects on mucin upregulation in mice infected with Pseudomonas aeruginosa

Background

Mucin hypersecretion and mucus plugging in the airways are characteristic features of chronic respiratory diseases like cystic fibrosis (CF) and contribute to morbidity and mortality. In CF, Pseudomonas aeruginosa superinfections in the lung exacerbate inflammation and alter mucus properties. There is increasing evidence that n-3 polyunsaturated fatty acids (PUFAs) exhibit anti-inflammatory properties in many inflammatory diseases while n-6 PUFA arachidonic acid (AA) favors inflammatory mediators such as eicosanoids prostaglandin E2 (PGE2) and leukotriene B4 (LTB4) that may enhance inflammatory reactions. This suggests that n-3 PUFAs may have a protective effect against mucus over-production in airway diseases. Therefore, we hypothesized that n-3 PUFAs may downregulate mucins expression.

Methods

We designed an absolute real-time PCR assay to assess the effect of a 5-week diet enriched either with n-3 or n-6 PUFAs on the expression of large mucins in the lungs of mice infected by P. aeruginosa.

Results

Dietary fatty acids did not influence mucin gene expression in healthy mice. Lung infection induced an increase of the secreted gel-forming mucin Muc5b and a decrease of the membrane bound mucin Muc4. These deregulations are modulated by dietary fatty acids with a suppressive effect of n-3 PUFAs on mucin (increase of Muc5b from 19-fold up to 3.6 × 10⁵-fold for the n-3 PUFAs treated group and the control groups, respectively, 4 days post-infection and decrease of Muc4 from 15-fold up to 3.2 × 10⁴-fold for the control and the n-3 PUFAs treated groups, respectively, 4 days post-infection).

Conclusion

Our data suggest that n-3 PUFAs enriched diet represents an inexpensive strategy to prevent or treat mucin overproduction in pulmonary bacterial colonization.

Milk Odd- and Branched-Chain Fatty Acids in Relation to the Rumen Fermentation Pattern

The objectives of this study were 1) to determine whether a relationship exists between molar proportions of volatile fatty acids in the rumen and milk odd-and branched-chain fatty acid concentrations (i.e., iso C13:0, anteiso C13:0, iso C14:0, C15:0, iso C15:0, anteiso C15:0, iso C16:0, C17:0, iso C17:0, anteiso C17:0, and cis-9 C17:1); and 2) to evaluate the accuracy of prediction of the latter equations using an independent data set. For development of the regression equations, individual cow data from 10 feeding experiments with rumen-fistulated dairy cows were used, resulting in a data set of 148 observations. Milk odd- and branched-chain fatty acids were closely related to the molar proportions of acetate (SE = 15.3 mmol/mol), propionate (SE = 14.7 mmol/mol), and butyrate (SE = 9.2 mmol/mol). These regression equations were further validated using data from the literature (n = 14). Evaluation of these prediction equations using the independent data set resulted in a root mean square prediction error of 3.0, 9.0, and 8.9% of the observed mean for acetate, propionate, and butyrate, respectively. In addition, less then 5% of the mean square prediction error was due to line bias. This suggests that the currently developed prediction equations based on milk odd- and branched-chain fatty acids show potential to predict molar proportions of individual volatile fatty acids in the rumen.

Effect of Forage:Concentrate Ratio on Fatty Acid Composition of Rumen Bacteria Isolated From Ruminal and Duodenal Digesta

Four dairy cows were used to examine the effect of the dietary forage:concentrate ratio [35:65, 50:50, 65:35, and 80:20 on a dry matter (DM) basis] on the fatty acid composition of rumen bacteria isolated from the liquid (LAB) and solid (SAB) phase of the rumen and duodenal digesta. Rumen contents were sampled 4 h after the morning feeding. Solid and liquid phases were separated from rumen contents and duodenal bacteria from a composite duodenal sample by differential centrifugation. Total fatty acid content in bacterial DM was 1.6 to 2.8 times higher in SAB compared with LAB, and increased with dietary concentrate. In combination with published reports, the data show that bacterial fatty acid content and composition is closely related to dietary fatty acids except for C18:2n-6 and C18:3n-3. A decrease in forage:concentrate ratio increased bacterial concentration of trans-10 C18:1, and this increase was 3.4 times higher in LAB compared with SAB. Analysis of odd- and branched-chain fatty acids showed large differences between SAB and LAB, which probably reflected a difference in species composition. The variation in odd- and branched-chain fatty acids between SAB and LAB was used to estimate their relative proportions in duodenal bacteria by means of linear programming, and showed an increased proportion of SAB from 64.7 to 74.8% with increasing forage:concentrate ratio. In addition, increasing the proportion of dietary forage was closely related to the proportion of anteiso C15:0 in total odd- and branched-chain fatty acids (r(pearson) = -0.771). The bacterial concentration of iso C17:0 closely reflected the bacterial growth rate as shown by the relation with cytosine:N (r(pearson) = -0.729). These strong relationships suggest that odd- and branched-chain fatty acids might be used as tool to evaluate nutrient supply to rumen bacteria.

Use of Odd and Branched-Chain Fatty Acids in Rumen Contents and Milk as a Potential Microbial Marker

The objectives of this study were: 1) to determine if a correlation exists between rumen odd and branched-chain fatty acids (OBCFA, i.e., C(15:0), iso C(15:0), anteiso C(15:0), C(17:0), iso C(17:0), anteiso C(17:0), and C(17:1)), uracil, and purine bases (PB), 2) to evaluate the potential of milk OBCFA secretion to predict duodenal flow of microbial protein in lactating cows, 3) to evaluate the accuracy of the latter prediction equations using an independent data set, and 4) to determine whether these predictions were more accurate than predictions based on dry matter intake (DMI) and dietary characteristics. In the first experiment, 4 lactating dairy cows arranged in a 4 x 4 Latin square were offered diets based on grass silages of different botanical composition and a standard concentrate. The relationship between rumen pool size of OBCFA and microbial matter was investigated. Rumen pool size of microbial matter (g), determined 4, 12, and 17 h after feeding, using uracil and PB as microbial markers, was closely related to OBCFA (g) [r(2) = 0.716, root mean square error (RMSE) = 4.45]. To correct for differences in marker concentrations among strains of rumen microbes, C(17:0) was included in the regression equations, resulting in an increased predictive power (r(2) = 0.780, RMSE = 3.92). The relationship between microbial flow to the duodenum and milk OBCFA yield was evaluated in a second experiment with lactating dairy cows offered diets based on grass silage and concentrates differing in starch source. Similar to observations in the rumen, milk OBCFA yield was closely related to microbial flow to the duodenum (RMSE = 4.28), but predictive power of equations did not increase when straight-chain C(17)-fatty acids were included in the regression equations (RMSE = 4.92). Evaluation of the current prediction equations with 3 independent datasets resulted in a root mean square prediction error of 20.5 and 13.4% of the observed mean for equations based on milk secretion of total OBCFA and straight-chain C(17)-fatty acids, respectively. Comparison of the accuracy of the latter equations with 2 previously published equations based on DMI and dietary characteristics suggest the former to be more accurate. This first evaluation suggests that milk OBCFA could be used as a marker for duodenal flow of microbial matter, especially when accurate measurements of DMI are not available.

Rumen odd and branched chain fatty acids in relation to in vitro rumen volatile fatty acid productions and dietary characteristics of incubated substrates

A first aim of this batch in vitro experiment (21 h) was to use changes in odd and branched chain fatty acid (OBCFA) patterns to suggest shifts in microbial populations, associated with four types of incubated whole dairy cow diets. Principal component analysis suggested higher dietary starch increased the proportion of C15:0 and C17:0, whereas increased neutral detergent fibre content was positively related to anteiso C15:0 concentrations, which is in agreement with the importance of these fatty acids in respectively amylolytic and cellulolytic bacteria. A second aim of the experiment was to relate rumen volatile fatty acid proportions to OBCFA by principal component regression and to compare these relations with predictions based on diet proximate composition. The R2 values achieved for the regressions between acetate, propionate and butyrate, and OBCFA were 79.6%, 86.6% and 84.9% respectively. Moreover, in the current study, predictions of the rumen fermentation pattern showed higher R2 (p < 0.01) when based on OBCFA compared with proximate feed composition. If relations persist in vivo, there could be scope for milk OBCFA to predict the supply of specific rumen nutrients.

Nutritive value and qualitative assessment of secondary compounds in seeds of eight tropical browse, shrub and pulse legumes

Seeds of four tropical multipurpose trees (Albizia saman, Albizia lebbeck, Albizia rhizonse, Leucaena leucocephala), two shrubs (Tephrosia candida, Tephrosia bracteolata) and two pulse legume (Lablab purpureus, Canavalia ensiformis) were chemically analysed for dry matter (DM), ash, crude protein (CP), neutral detergent fibre (NDF) and ether extract (EE). Qualitative evaluation of secondary metabolites (saponins, phenols, steroids, and alkaloids) was elucidated. The DM, ash, CP, NDF and EE ranged between 88.9-93.6 %, 3.0-5.4 %, 24.8-38.2 %, 22.1-46.9 % and 2.0-17.0 % respectively. All seed species contained at least one group of secondary plant metabolites and steroids were common to all except C. ensiformis that was not implicated for any. A. lebbeck and A. rhizonse showed low saponin content. Indications for water soluble tannins were reported for L. leucocephala while the two species of Tephrosia contained flavonoids or condensed tannins. The study suggested the potentials of the legumes seed species as a feed source for ruminants.

Effects of freezing and drying grass products prior to fatty acid extraction on grass fatty acid and lipid class composition--a technical note

Grass and grass silage represent a rich and natural source of omega-3 polyunsaturated fatty acids, in particular linolenic acid, for ruminants. Recent research, focusing on improving the content of these beneficial fatty acids in grass, requires storage of the forage samples prior to analysis. In this study, we evaluated whether conservation of fresh grass and grass silage by freezing (1 and 4 weeks,--18 degrees C) and/or drying (24h, 50 degrees C) affected its fatty acid content and induced shifts between lipid classes. FA were extracted using chloroform/methanol (2/1, v/v) and triacylglycerols (TAG), free fatty acids (FFA) and polar lipids (PL) were separated by thin layer chromatography. Fatty methyl esters (FAME) were identified by gas chromatography. Loss of thawing liquor might provoke a dramatic decrease in extractable lipid after frozen storage of both grass and grass silage. Morever, after frozen storage, fatty acids in grass but not in grass silage seem subjected to a higher rate o f lipolysis and oxidation, as suggested by increased quantities of FFA (3.1, 7.6, 8.4 % of total FAME) and reduced proportions of poly-unsaturated fatty acids (79.5, 73.6 and 74.1 % of total FAME) when analysing fresh grass samples directly or after 1 and 4 weeks of frozen storage, respectively. Drying of fresh grass did not provoke changes in FA composition, but distribution of FA over lipid classes was significantly altered, with an increase in TAG (5.1 to 17.9 % of total FAME) and FFA (2.4 to 14.9 % of total FAME) and lower proportions of PL (90.7 to 55.7 % of total FAME).

Effect of N fertilisation rate, energy supplementation and supplementation strategy on efficiency of N utilisation in the sheep rumen

The effect of nitrogen (N) fertilisation (200 vs. 400 kg N ha-1 year-1) of pasture cut in the beginning (end of May) and the end (end of August) of the grazing season and of simultaneous or separated feeding of maize and grass (400 kg N ha-1 year-1) on efficiency of N utilisation in the rumen has been studied using four rumen cannulated wethers. Doubling N fertiliser rate increased grass CP production by about 60%, but induced extensive excess of rumen degradable N, reflected in high urinary urea excretion (rpearson = 0.747). The latter was lower (74% at the maximum) when feeding less fertilised or older grass or when supplementing with maize silage. Although simultaneous feeding of maize silage with grass changed patterns of rumen ammonia concentrations, no change in urinary excretion of purine derivatives was observed. Hence, faecal or urinary N excretion was unaffected by the supplementation strategy. Microbial growth efficiency was estimated from urinary excretion of purine derivatives and fermented OM. The latter was calculated from total rumen CH4 production, based on rumen fermentation stoichiometry and taking into account proportional concentrations of individual volatile fatty acids. Higher levels of intake tended to improve rumen microbial growth efficiency slightly (rpearson = 0.406), which, however, could not compensate for the reduced effective rumen DM degradability (rpearson = -0.442). The latter was apparently associated with a partial shift of the fermentation from the rumen to the hindgut, as suggested from the negative correlation (rpearson = -0.745) between faecal RNA concentrations and rumen effective degradability.

Methane emissions from the rumen of sheep fed a mixed grass-clover pasture at two fertilisation rates in early and late season

In vivo CH4 production from four rumen-fistulated sheep fed fresh ryegrass-white clover (Lolium perenne – Trifolium repens) diets ad libitum was monitored using C2H6 as a tracer gas. Treatments comprised mixed pastures at two different fertilisation rates (0 vs. 150 kg N ha–1 yr–1) and at two periods in the growing season (early, June–July vs. late, August–September). Higher crude protein (CP) [22.5% dry matter (DM)] in late vs. early season (13% DM) was associated with increased importance of protein fermentation, as suggested by higher rumen concentrations of iso-acids [3.7 ± 1.0 vs. 2.4 ± 0.9% total volatile fatty acids (VFA)]. However, rumen CH4 production (25.8 ± 5.0 L kg–1 DMI) was not affected, probably because of compensatory seasonal changes in the chemical composition of the pasture, su0 as reduced water-soluble carbohydrates (WSC) (13.0 ± 2.6 vs. 4.9 ± 1.4% DM) or increased neutral detergent fibre (NDF) (48.5 ± 6.1 vs. 57.4 ± 4.6% DM). Although clover saponins might have a defaunation and CH4 inhibitory effect, considerable seasonal or fertiliser-induced changes in clover proportion did not affect rumen protozoal concentrations (8.8 ± 1.6 ×105 mL–1 rumen contents, early season), rumen methanogenesis or microbial growth as suggested from urinary excretion of purine derivatives (6.7 ± 1.7 mmol d–1). In contrast, however, a clear animal effect was found: on average, one animal produced less CH4 than the three others (20.3 vs. 27.6 L kg–1 DMI). Key words: Ryegrass, clover, N fertilisation, season, rumen, methane Mbanzamihigo, L., Fievez, V., da Costa Gomez, C., Piattoni, F., Carlier, L. et Demeyer, D. 2002. Les émissions

Effect of level and origin of rumen degradable nitrogen on rumen microbial growth and nitrogen utilisation efficiency of animals fed maize silage at maintenance

Isoenergetic maize silage diets, fed at maintenance to 24 suckling cows (Exp. 1) and to 3 (Exp. 2) or 4 (Exp. 3) rumen fistulated sheep, were compared with a urea and controlled release NPN diet (Exps. 1 and 2) and with a protein-N supplemented diet (Exp. 3). Supplementation increased blood urea concentrations (44.7 +/- 22.3 vs. 97.6 +/- 23.7 mg urea-N x L(-1)) (Exp. 1) and renal urea excretion (2.5 +/- 1.1 vs. 7.6 +/- 1.8 g urea-N x d(-1)) (Exps. 2 and 3), whereas blood allantoin concentrations (286.7 +/- 77.0 micromol x L(-1)) (Exp. 1) and renal excretion of purine derivatives (357.6 +/- 90.7 mg purine-N x d(-1)) (Exps. 2 and 3) were not affected, indicating additional N supplementation did not improve rumen microbial growth. However, some deficiency of rumen degradable N might occur in non supplemented diets as suggested by the reduced rumen NH3-N and RNA concentrations (868 +/- 270 vs. 1466 +/- 466 mg RNA x kg(-1) rumen contents).

Extractibility of the protein and peptide fraction for different types of dry fermented sausages in relation to GPC-analysis

The use of GPC (gel filtration chromatography) for investigating the proteolysis during fermentation and ripening of dry fermented sausages (Northern and Mediterranean type) and the choice of a suitable extraction solvent for this technique was evaluated. Solvents in a wide range of acidity were used in this experiment (pH 0.5-13). A calculation of the percentage extracted nitrogencompounds for each solvent and a comparison of the GPC-profile for each extract select the HCl-dilutions with a pH 1 to 3 as the most suitable extraction solvent. Although very basic solvents extract most of the protein and peptide fraction, they lead to some degradation of the proteins and peptides and are not reliable. Clear differences between the GPC-profiles for both types of sausages were not observed.

Analysis of fatty acid isomers in ruminant tissues by silver thin layer chromatography followed by gas chromatography

A method for the analysis of trans fatty acids is described in this paper. Separation of trans isomers from the corresponding cis was based on the different facility with which the double bonds in the alkyl chains of both types of fatty acids form polar complexes with silver, and it was carried out by Thin Layer Chromatography (TLC), using silver nitrate impregnated plates. Further separation, identification and quantification of the individual C18:1 isomers, analysed as methyl esters, was carried out by Gas Chromatography (GC). The determination of the content of the isomer t11-C18:1 in ruminant tissues can contribute to try to elucidate the metabolic pathway formation of conjugated linoleic acid (CLA), shown as a fatty acid of beneficial health effects. Furthermore, the analysis of trans fatty acids in other dietary foods seems to be interesting due to their influence on the modification of the serum lipids profile and the role of this type of compounds in human health.

Age and incubation time effects on in vitro caecal fermentation pattern in rabbits before and after weaning

The caecal fermentation pattern was studied in four litters of rabbits. Rabbits were sequentially slaughtered at the age of 4 (before weaning), 6, 8 and 11 weeks. Their caecal contents were analyzed and incubated in vitro at 39 degrees C for 6 and 12 h. Net productions of short-chain fatty acids (SCFA), hydrogen and methane were determined. The average caecal weight increased three-times within two weeks after weaning, from 31.4 to 93.7 g. At the end of the experiment, the caecal weight was on average 134.4 g. A large variability of the SCFA concentration observed before weaning decreased after weaning. Measurements of caecal metabolite profiles and results of in vitro experiments indicated a certain decrease of propionate in favour of butyrate, associated with the weaning. The establishment of methanogens in rabbits was slow. Methanogenesis started in one out of four rabbits at the age of 6 weeks. Five weeks later, one of four rabbits still did not produce methane. The hydrogen recovery decreased between the 4th and the 6th week of age, due to the increase of the butyrate/propionate ratio. After the 6th week, the hydrogen recovery increased with age, apparently because of the increase in methane production. Hydrogen recovery tended to increase during incubation, suggesting a decrease of reductive acetogenesis. This increase was observed both in methanogenic and non-methanogenic rabbit caecal cultures. In former cultures, the ratio CH4/SCFA rose with time of incubation.

Targets and procedures for altering ruminant meat and milk lipids

Beef and dairy products suffer from a negative health image, related to the nature of their lipid fraction. Rumen lipid metabolism involves the presence of saturated lipids in ruminant tissues. Lipolysis, fatty acid biohydrogenation and formation of microbial fatty acids in the rumen and their effects on rumen outflow of fatty acids are discussed. Special emphasis is given to the formation of trans-fatty acids and the possibilities of decreasing biohydrogenation. Small differences in intestinal digestibilities of fatty acids are mentioned, followed by a discussion on transfer of absorbed fatty acids into milk and adipose tissue lipids. The preferential retention of polyunsaturated fatty acids as well as the balance between synthesis and incorporation of fatty acids in tissues is described. Dietary means for the modification of milk fat are listed, with special emphasis on the possibilities for enrichment in polyunsaturated fatty acids and the presence of conjugated linoleic acids. A description of the nature and development of fat depots in beef cattle is followed by a discussion of breed, conformation and feed effects on adipose tissue distribution and fatty acid composition. Special emphasis is given to the very lean Belgian Blue double-muscled breed. The review ends with a consideration of the limits to the modification of ruminant fats, involving considerations of consumer acceptance as well as animal welfare and environmental effects.