In situ caecal degradation of roughages in horses Degradação cecal in situ de alimentos volumosos em equinos

The present study was carried out to evaluate the in situ degradation of dry matter (DM), neutral detergent fiber (NDF) and crude protein (CP) in roughages by the in situ caecal digestion technique in horses. The roughages evaluated were: Lucerne hay (Medicago sativa), peanut (Arachis pintoi cv. Amarillo), desmodio(Desmodium ovalifolium), stylo (Stylosanthes guianensis cv. Mineirão), pigeon pea (Cajanus cajan), lime-yellow pea (Macrotyloma axillare) and coastcross hay (Cynodon dactylon cv. coastcross). The assay was conducted in a complete randomized design with seven roughages and three replications. One mare with a cannula fitted in the caecum was used, fed diet consisting of coastcross hay (80%) and concentrate (20%) at 2.0% BW, four times a day. Nylon 6.5 × 20 cm bags were used with 45 &#956;/pore, containing 5.2 g DM/bag, inserting 3 or 4 bags in the caecum at the times of 2, 4, 6, 8, 12, 24 and 48 hours incubation. The caecum in situ degradability parameters of nutrients were obtained by Ørskov model. The DM degradability parameters of all the roughages were significant. There was no fit to the model for pigeon pea for CP and NDF and desmodio. Peanut, stylo and lime-yellow pea presented larger potentially degradable DM with values of 53, 46.5 and 40%, respectively, and higher values for the soluble fraction of 20, 21, 28.6%, with high degradability rates of 10.36, 20.26 and 14.8% h-1. Higher NDF degradation rates were observed in these foodstuffs with values of 9.1 and 11.3, 11.2% h-1, high potentially degradable fraction with values of 55, 51.8 and 47.2%, and greater CP degradation at 48 hours with values of 87, 95, and 94.8%. Peanut, stylo and lime-yellow pea presented potential for use in horses diets.<br>Objetivou-se avaliar a degradação da matéria seca (MS), fibra em detergente neutro (FDN) e proteína bruta de alimentos volumosos pela técnica da digestão cecal in situ em equinos. Avaliaram-se as forrageiras: feno de alfafa (Medicago sativa), amendoim forrageiro (Arachis pintoi cv. Amarillo), desmódio (Desmodium ovalifolium), estilosantes (Stylosanthes guianensis cv. Mineirão), guandu (Cajanus cajan), macrotiloma (Macrotyloma axillare) e feno de coastcross (Cynodon dactylon cv. coastcross). O ensaio teve duração de 35 dias e foi realizado em delineamento inteiramente casualizado com sete alimentos e três repetições. Utilizou-se uma égua fistulada no ceco, alimentada com dieta composta por feno de coastcross (80%) e concentrado (20%), fornecida quatro vezes ao dia em quantidade equivalente a 2% do peso vivo. No ceco, foram inseridos 3 a 4 sacos de náilon de porosidade 45 &#956; de 6,5 × 20 cm, contendo 5,2 g de MS/saco, nos tempos de 2, 4, 6, 8, 12, 24 e 48 horas de incubação. Os parâmetros de degradação da MS de todos os volumosos foram significativos. Não houve ajuste no modelo de degradação da PB e FDN do guandu. O amendoim, estilosantes e macrotiloma apresentaram maior fração potencialmente degradável da MS, com valores de 53, 46,5 e 40%, respectivamente, e os maiores valores da fração solúvel de 20, 21, 28,6%, além de elevadas taxas de degradação (10,36, 20,26 e 14,8%h-1). Nestes alimentos, também foram observadas as maiores taxas de degradação da FDN (9,1 e 11,3, 11,2%h-1), das frações potencialmente degradáveis (55, 51,8 e 47,2%) e as mais altas taxas de degradação da PB em 48 horas de incubação (87, 95, 94,8%, respectivamente). O amendoim forrageiro, o estilosantes e o macrotiloma apresentam potencial de uso nas dietas para equinos

Overview of physics results from MAST towards ITER/DEMO and the MAST Upgrade

New diagnostic, modelling and plant capability on the Mega Ampère Spherical Tokamak (MAST) have delivered important results in key areas for ITER/DEMO and the upcoming MAST Upgrade, a step towards future ST devices on the path to fusion currently under procurement. Micro-stability analysis of the pedestal highlights the potential roles of micro-tearing modes and kinetic ballooning modes for the pedestal formation. Mitigation of edge localized modes (ELM) using resonant magnetic perturbation has been demonstrated for toroidal mode numbers n = 3, 4, 6 with an ELM frequency increase by up to a factor of 9, compatible with pellet fuelling. The peak heat flux of mitigated and natural ELMs follows the same linear trend with ELM energy loss and the first ELM-resolved T i measurements in the divertor region are shown. Measurements of flow shear and turbulence dynamics during L–H transitions show filaments erupting from the plasma edge whilst the full flow shear is still present. Off-axis neutral beam injection helps to strongly reduce the redistribution of fast-ions due to fishbone modes when compared to on-axis injection. Low- k ion-scale turbulence has been measured in L-mode and compared to global gyro-kinetic simulations. A statistical analysis of principal turbulence time scales shows them to be of comparable magnitude and reasonably correlated with turbulence decorrelation time. T e inside the island of a neoclassical tearing mode allow the analysis of the island evolution without assuming specific models for the heat flux. Other results include the discrepancy of the current profile evolution during the current ramp-up with solutions of the poloidal field diffusion equation, studies of the anomalous Doppler resonance compressional Alfvén eigenmodes, disruption mitigation studies and modelling of the new divertor design for MAST Upgrade. The novel 3D electron Bernstein synthetic imaging shows promising first data sensitive to the edge current profile and flows

Overview of physics results from MAST

Major developments on the Mega Amp Spherical Tokamak (MAST) have enabled important advances in support of ITER and the physics basis of a spherical tokamak (ST) based component test facility (CTF), as well as providing new insight into underlying tokamak physics. For example, L-H transition studies benefit from high spatial and temporal resolution measurements of pedestal profile evolution (temperature, density and radial electric field) and in support of pedestal stability studies the edge current density profile has been inferred from motional Stark effect measurements. The influence of the q-profile and E x B flow shear on transport has been studied in MAST and equilibrium flow shear has been included in gyro-kinetic codes, improving comparisons with the experimental data. H-modes exhibit a weaker q and stronger collisionality dependence of heat diffusivity than implied by IPB98(gamma, 2) scaling, which may have important implications for the design of an ST-based CTF. ELM mitigation, an important issue for ITER, has been demonstrated by applying resonant magnetic perturbations (RMPs) using both internal and external coils, but full stabilization of type-I ELMs has not been observed. Modelling shows the importance of including the plasma response to the RMP fields. MAST plasmas with q &amp;gt; 1 and weak central magnetic shear regularly exhibit a long-lived saturated ideal internal mode. Measured plasma braking in the presence of this mode compares well with neo-classical toroidal viscosity theory. In support of basic physics understanding, high resolution Thomson scattering measurements are providing new insight into sawtooth crash dynamics and neo-classical tearing mode critical island widths. Retarding field analyser measurements show elevated ion temperatures in the scrape-off layer of L-mode plasmas and, in the presence of type-I ELMs, ions with energy greater than 500 eV are detected 20 cm outside the separatrix. Disruption mitigation by massive gas injection has reduced divertor heat loads by up to 70%

Overview of new MAST physics in anticipation of first results from MAST Upgrade

The mega amp spherical tokamak (MAST) was a low aspect ratio device (R/a  =  0.85/0.65 ~ 1.3) with similar poloidal cross-section to other medium-size tokamaks. The physics programme concentrates on addressing key physics issues for the operation of ITER, design of DEMO and future spherical tokamaks by utilising high resolution diagnostic measurements closely coupled with theory and modelling to significantly advance our understanding. An empirical scaling of the energy confinement time that favours higher power, lower collisionality devices is consistent with gyrokinetic modelling of electron scale turbulence. Measurements of ion scale turbulence with beam emission spectroscopy and gyrokinetic modelling in up-down symmetric plasmas find that the symmetry of the turbulence is broken by flow shear. Near the non-linear stability threshold, flow shear tilts the density fluctuation correlation function and skews the fluctuation amplitude distribution. Results from fast particle physics studies include the observation that sawteeth are found to redistribute passing and trapped fast particles injected from neutral beam injectors in equal measure, suggesting that resonances between the m  =  1 perturbation and the fast ion orbits may be playing a dominant role in the fast ion transport. Measured D–D fusion products from a neutron camera and a charged fusion product detector are 40% lower than predictions from TRANSP/NUBEAM, highlighting possible deficiencies in the guiding centre approximation. Modelling of fast ion losses in the presence of resonant magnetic perturbations (RMPs) can reproduce trends observed in experiments when the plasma response and charge-exchange losses are accounted for. Measurements with a neutral particle analyser during merging-compression start-up indicate the acceleration of ions and electrons. Transport at the plasma edge has been improved through reciprocating probe measurements that have characterised a geodesic acoustic mode at the edge of an ohmic L-mode plasma and particle-in-cell modelling has improved the interpretation of plasma potential estimates from ball-pen probes. The application of RMPs leads to a reduction in particle confinement in L-mode and H-mode and an increase in the core ionization source. The ejection of secondary filaments following type-I ELMs correlates with interactions with surfaces near the X-point. Simulations of the interaction between pairs of filaments in the scrape-off layer suggest this results in modest changes to their velocity, and in most cases can be treated as moving independently. A stochastic model of scrape-off layer profile formation based on the superposition of non-interacting filaments is in good agreement with measured time-average profiles. Transport in the divertor has been improved through fast camera imaging, indicating the presence of a quiescent region devoid of filament near the X-point, extending from the separatrix to ψ n ~ 1.02. Simulations of turbulent transport in the divertor show that the angle between the divertor leg on the curvature vector strongly influences transport into the private flux region via the interchange mechanism. Coherence imaging measurements show counter-streaming flows of impurities due to gas puffing increasing the pressure on field lines where the gas is ionised. MAST Upgrade is based on the original MAST device, with substantially improved capabilities to operate with a Super-X divertor to test extended divertor leg concepts. SOLPS-ITER modelling predicts the detachment threshold will be reduced by more than a factor of 2, in terms of upstream density, in the Super-X compared with a conventional configuration and that the radiation front movement is passively stabilised before it reaches the X-point. 1D fluid modelling reveals the key role of momentum and power loss mechanisms in governing detachment onset and evolution. Analytic modelling indicates that long legs placed at large major radius, or equivalently low at the target compared with the X-point are more amenable to external control. With MAST Upgrade experiments expected in 2019, a thorough characterisation of the sources of the intrinsic error field has been carried out and a mitigation strategy developed

Overview of physics results from MAST

Major developments on the Mega Amp Spherical Tokamak (MAST) have enabled important advances in support of ITER and the physics basis of a spherical tokamak (ST) based component test facility (CTF), as well as providing new insight into underlying tokamak physics. For example, L-H transition studies benefit from high spatial and temporal resolution measurements of pedestal profile evolution (temperature, density and radial electric field) and in support of pedestal stability studies the edge current density profile has been inferred from motional Stark effect measurements. The influence of the q-profile and E x B flow shear on transport has been studied in MAST and equilibrium flow shear has been included in gyro-kinetic codes, improving comparisons with the experimental data. H-modes exhibit a weaker q and stronger collisionality dependence of heat diffusivity than implied by IPB98(gamma, 2) scaling, which may have important implications for the design of an ST-based CTF. ELM mitigation, an important issue for ITER, has been demonstrated by applying resonant magnetic perturbations (RMPs) using both internal and external coils, but full stabilization of type-I ELMs has not been observed. Modelling shows the importance of including the plasma response to the RMP fields. MAST plasmas with q > 1 and weak central magnetic shear regularly exhibit a long-lived saturated ideal internal mode. Measured plasma braking in the presence of this mode compares well with neo-classical toroidal viscosity theory. In support of basic physics understanding, high resolution Thomson scattering measurements are providing new insight into sawtooth crash dynamics and neo-classical tearing mode critical island widths. Retarding field analyser measurements show elevated ion temperatures in the scrape-off layer of L-mode plasmas and, in the presence of type-I ELMs, ions with energy greater than 500 eV are detected 20 cm outside the separatrix. Disruption mitigation by massive gas injection has reduced divertor heat loads by up to 70%