Rowett Research Institute

About: Rowett Research Institute is a based out in . It is known for research contribution in the topics: Rumen & Population. The organization has 2986 authors who have published 4459 publications receiving 239472 citations.

The route of absorbed nitrogen into milk protein

Abstract: A database reviewing the metabolism of nitrogen (N) compounds from absorption to milk has been compiled from 14 published and unpublished studies (33 treatments) that measured the net flux of N compounds across the splanchnic tissues in dairy cows. Apparent N digestibility averaged 0·65, with this then partitioned between 0·34 excreted in urine and 0·31 secreted as milk.Nitrogen metabolites are absorbed from the lumen of the gut into the portal vein, mainly as free amino acids (AA) and ammonia; these represented 0·58 and 0·57 of digested N, respectively. All of the ammonia absorbed was removed by the liver with, as a result, a net splanchnic flux of zero. Detoxification of ammonia by the liver and catabolism of AA results in production of urea as an end-product. Hepatic ureagenesis is a major cross-road in terms of whole body N exchange, being the equivalent of 0·81 of digested N. Therefore, salvage of a considerable part of this ureagenesis is needed to support milk protein synthesis. This salvage occurs via transfer of urea from the blood circulation into the lumen of the gut. On average, 0·47 of hepatic ureagenesis was returned to the gut via the portal-drained viscera (equivalent to 0·34 of digested N) with 0·56 of this then used for anabolic purposes e.g. as precursor N for microbial protein synthesis. On average, 0·65 of estimated digestible AA was recovered in the portal vein. This loss (0·35) is due to oxidation of certain AA across the gut wall and non-absorption of endogenous secretions. The magnitude of this loss is not uniform among AA and varies between less than 0·05 for histidine to more than 0·90 for some non-essential AA, such as glutamine.A second database (six studies, 14 treatments) was constructed to further examine the subsequent fate of absorbed essential AA. When all AA are aggregated, the liver removed, on average, 0·45 of portal absorption but this value hides the considerable variation between individual AA. Simplistically, the AA behave as two major groups: one group undergoes very little hepatic removal and includes the branched-chain AA and lysine. For the second group, removal varies between 0·35 and 0·50 of portal absorption, and includes histidine, methionine and phenylalanine. For both groups, however, the efficiency of transfer of absorbed AA into milk protein decreases with increasing supply of protein. This loss of efficiency is linked directly with increased hepatic removal of AA from the second group and, probably, increased catabolism by peripheral tissues, including the mammary gland, of AA from the first group. Therefore, we must stop using fixed factors of conversion of digestible AA to milk in our predictive schemes and acknowledge that metabolism of AA between delivery from the duodenum and conversion to milk protein will vary with nutrient supply. New information evolving from re-analysis of the literature and recent studies will allow better models to be devised for the prediction of nutrient-based responses by the lactating cow. Consideration of biological efficiency, rather than maximal milk yield, will lead to systems that are economically more sensible for the farmer and that have better environmental impacts.

Flagellin Suppresses Epithelial Apoptosis and Limits Disease during Enteric Infection

Abstract: Flagellin, the primary component of bacterial flagella, is a potent activator of toll-like receptor 5 (TLR5) signaling and is a major proinflammatory determinant of enteropathogenic Salmonella. In accordance with this, we report here that aflagellate Salmonella mutants are impaired in their ability to up-regulate proinflammatory and anti-apoptotic effector molecules in murine models of salmonellosis and that these mutants elicit markedly reduced early mucosal inflammation relative to their isogenic parent strains. Conversely, aflagellate bacteria were more potent activators of epithelial caspases and subsequent apoptosis. These phenomena correlated with a delayed but markedly exacerbated mucosal inflammation at the later stages of infection as well as elevated extra-intestinal and systemic bacterial load, culminating in a more severe clinical outcome. Systemic administration of exogenous flagellin primarily reversed the deleterious effects of in vivo Salmonella infection. These observations indicate that in Salmonella infection, flagellin plays a dominant role in activation of not only innate immunity but also anti-apoptotic processes in epithelial cells. These latter TLR-mediated responses that delay epithelial apoptosis may be as critical to mucosal defense as the classic acute inflammatory response. This notion is consistent with the emerging paradigm that specific TLR ligands may have a fundamental cytoprotective effect during inflammatory stress.

Estimation of the relative abundance of different Bacteroides and Prevotella ribotypes in gut samples by restriction enzyme profiling of PCR-amplified 16S rRNA gene sequences

Abstract: We describe an approach for determining the genetic composition of Bacteroides and Prevotella populations in gut contents based on selective amplification of 16S rRNA gene sequences (rDNA) followed by cleavage of the amplified material with restriction enzymes. The relative contributions of different ribotypes to total Bacteroides and Prevotella 16S rDNA are estimated after end labelling of one of the PCR primers, and the contribution of Bacteroides and Prevotella sequences to total eubacterial 16S rDNA is estimated by measuring the binding of oligonucleotide probes to amplified DNA. Bacteroides and Prevotella 16S rDNA accounted for between 12 and 62% of total eubacterial 16S rDNA in samples of ruminal contents from six sheep and a cow. Ribotypes 4, 5, 6, and 7, which include most cultivated rumen Prevotella strains, together accounted for between 20 and 86% of the total amplified Bacteroides and Prevotella rDNA in these samples. The most abundant Bacteroides or Prevotella ribotype in four animals, however, was ribotype 8, for which there is only one known cultured isolate, while ribotypes 1 and 2, which include many colonic Bacteroides spp., were the most abundant in two animals. This indicates that some abundant Bacteroides and Prevotella groups in the rumen are underrepresented among cultured rumen Prevotella isolates. The approach described here provides a rapid, convenient, and widely applicable method for comparing the genotypic composition of bacterial populations in gut samples. Methods for enumerating gut bacteria that are based on cultivation, isolation, and biochemical testing are generally laborious and do not guarantee recovery of the less easily cultivated species. This is a particular problem for obligately anaerobic bacteria, which make up the great majority of organisms present in densely populated gut habitats such as the rumen and hind gut (13, 31). For this reason, there has been increasing interest in the rapid enumeration of microbial groupings by analysis of nucleic acids extracted from gut samples. Probing of extracted RNA with radiolabelled or fluorescently labelled oligonucleotide probes has been used in several studies (6, 14, 20, 30) but relies on developing panels of probes for different groups from available sequence data. Sequencing of random PCR-amplified 16S rRNA gene (rDNA) clones has provided valuable information on total eubacterial diversity for human fecal microflora (37). However, more rapid approaches to the study of diversity that allow the examination of large numbers of samples are required, and a semiquantitative PCR detection approach based on serial dilution has been reported for some of the predominant gut anaerobes (35). The approach we take here is to perform selective PCR amplification of 16S rRNA genes from the gram-negative anaerobic genera Bacteroides and Prevotella by using DNA extracted from gut samples and then to estimate the genotypic composition of samples from restriction enzyme cleavage patterns (restriction fragment length polymorphism [RFLP]) of the amplified DNA (PCR-RFLP). 16S rDNA PCR-RFLP approaches have proved valuable for typing isolated bacterial strains (see, e.g., refer

Dynamics of upward and downward N2O and CO2 fluxes in ploughed or no-tilled soils in relation to water-filled pore space, compaction and crop presence

Abstract: Sharp peaks in nitrous oxide (N2O) fluxes under no-tillage in wet conditions appear to be related to near surface soil and crop cover conditions. Here we explored some of the factors influencing tillage effects on short-term variations in gas flux so that we could learn about the mechanisms involved. Field investigations revealed that a cumulative emission of 13 kg N2O–N ha−1 over a 12-week period was possible under no-tillage for spring barley. We investigated how reducing crop cover and changing the structural arrangement of the water-filled pore space (WFPS) by short-term laboratory compaction influenced N2O and carbon dioxide (CO2) fluxes in upward and downward directions in core samples from tilled and untilled soil. Increasing the downward flux of N2O within a soil profile by changing soil or moisture conditions may increase the likelihood of its further reduction to N2 or dissolution. We took undisturbed cores from 3 to 8 cm depth, equilibrated them to −1 or −6 kPa matric potential, incubated them and measured N2O and CO2 fluxes from the upper and lower surfaces in a purpose-designed apparatus before and after compaction in an uniaxial tester. We also measured WFPS, air permeability, bulk density and air-filled porosity before and after compaction. Spring barley was tested in 1999 and winter barley in 2000. Fluxes of N2O were from 1.5 to 35 times higher from no-tilled than ploughed even where the soil was of similar bulk density. Reduction of the crop cover increased CO2 flux and could reduce N2O flux. The effects of structural changes induced by laboratory compaction on the fluxes of N2O and CO2 were not influenced greatly by the tillage and crop cover treatments. Fluxes from the upper surfaces of cores (corresponding to 3 cm soil depth, upwards direction) could be up to ∼100 times greater (N2O) or ∼8 times (CO2) than from the lower surfaces (8 cm depth, downwards direction). These differences between surfaces were greatest when N2O fluxes were very high in no-tilled soil (4.2 mg N2O–N m−2 h−1) as occurred when WFPS exceeded 80% or became blocked with water, an effect that was increased by our compaction treatment. In general N2O fluxes increased with WFPS. The production and emission of N2O were strongly influenced by the soil physical environment, the magnitude of the water-filled pore space and continuity of the air-filled pore space in particular, produced in no-till versus plough cultivation.

The effect of dietary molybdenum and iron on copper status, puberty, fertility and oestrous cycles in cattle

Abstract: Two experiments were conducted to examine the effects of supplementation of a control diet of barley grain and barley straw containing 4 mg copper (Cu)/kg dry matter (D.M.) either with 5 mg molybdenum (Mo)/kg D.M. or with 500 or 800 mg iron (Fe)/kg D.M. on puberty, fertility and oestrous cycles of cattle. Puberty occurred normally in control, Fesupplemented and control animals on a restricted intake whereas it was delayed by 12 and 8 weeks respectively by Mo supplementation. This effect of Mo was not due to the low Cu status since this was equally low in the Fe-supplemented animals, nor was it due to the reduced growth rate since puberty occurred normally in control animals that had a similar live-weight gain. A significant reduction in the pulsatile release of luteinizing hormone was observed within 11 weeks of the Mo supplementation and before any of the other clinical signs were evident, suggesting that Mo may be affecting puberty by altering the release of luteinizing hormone either directly or indirectly.Mo supplementation significantly reduced the percentage conception rate to 12–33% compared with 57–80% in control and Fe-supplemented animals. This effect was not dependent on the rate of live-weight gain which was standardized across the different treatments at approximately 0·6 kg/day. Within 12 weeks of the replacement of dietary Fe by Mo a lower conception rate occurred; replacing dietary Mo by Fe led to a normal conception rate within 12 weeks without any accompanying changes in Cu status or in the rate of live-weight gain. The plasma Mo concentrations, however, changed significantly during these alterations in dietary supplementation. The pre-ovulatory peak height of luteinizing hormone was significantly lower in animals on the Mo-supplemented diet compared with control and Fe-supplemented animals, but the administration of LHRH did not alter the conception rate.More Mo-supplemented animals failed to ovulate following prostaglandin induced synchronization in comparison with the other treatments, and by the 84th week a significantly greater number of Mo-supplemented animals (12/18) had become anoestrous compared with the other groups (2/30). Cu repletion of these anoestrous Mo animals for a period of 20 weeks did not result in resumption of normal oestrous cycles, but ovulation and oestrus were induced by progesterone and LHRH treatment. Results in the latter part of the study indicated that Mo caused superovulation.These data show that Mo supplementation delayed the onset of puberty, decreased the conception rate and caused anovulation and anoestrus in cattle without accompanying changes in Cu status or in live-weight gain. It is suggested that these effects of Mo are associated with a decreased release of luteinizing hormone that might be due to an altered ovarian steroid secretion.