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Weathered rockfill materials, characterized by a mixture of soil matrix and rock aggregates, are widely distributed in mountainous areas. These soils are frequently used for subgrade or riprap in engineering practice, and the mobilized shear strength is crucial for analyzing the displacement and stability of these geo-structures. A series of direct shear tests are performed on a gap-graded soil with a full range of coarse fraction. The behavior of gap-graded soils is analyzed, and a simple model is proposed for the evolution of mobilized stress ratio during direct shearing process based on mixture theory. The change of inter-aggregate configuration is incorporated by introducing a structure variable which increases with coarse fraction and decreases approximately linearly with the overall horizontal shear strain in double logarithmic plot. It reasonably reflects a gradually transformation from a matrix-sustained structure into an aggregate-sustained one with the increase of coarse fraction. The model has four parameters, and at least two direct shear tests need to be done for the calibration. Validation of the model is done by using the test data in this work and those from the literature.

In this paper, a new spectral variables selection method, induced mutation genetic algorithm (IMGA), is proposed for near-infrared (NIR) spectroscopy. Based on the idea of genetic algorithm (GA), the IMGA greatly simplifies the process of biological evolution, which not only inherits the advantages of global optimization of the GA, but also effectively improves the convergence speed. In this study, the IMGA is applied to the selection of characteristic spectral variables for green tea origin identification. After five times of genetic evolutions, 11 characteristic spectral variables are selected from 156 spectral variables. Based on the 11 characteristic spectral variables, the classification model is built by partial least squares (PLS), and both the sensitivity and specificity of classification model are raised to 1 for prediction set. The overall results indicate that the IMGA can be well applied to the selection of characteristic spectral variables and effectively improve the prediction accuracy and calculation speed of the near-infrared model.

Naturally formed soils (e.g., residual soils and deposit clays) usually show an absent range of particle size. Frequently used by geotechnical communities worldwide, such gap-graded soils can be simplified as binary mixtures composed of fine soil matrix and coarse rock aggregates. In this study, an elastoplastic model is proposed for gap-graded soils based on a volume average scheme and homogenization theory. The proposed model incorporates a structural variable to account for the evolution of the inter-granular skeleton of rock aggregates. The model is then implemented in a numerical code by the linearized integration technique proposed by Bardet and Choucair (1991). It is shown that the model can predict a wide range of variations of the overall shear responses with the increase in volume fraction of rock aggregates. An isotropic loading induces a nonuniform stress distribution in gap-graded soils, where the stress in the soil matrix is lower than that of the rock aggregates. The stress path of the matrix is approximately parallel with that of the rock aggregates during triaxial shear loading. The proposed model contains only one additional structure parameter compared with the generalized modified Cam clay model, which can be easily calibrated from the data of a conventional triaxial compression tests. Comparison between our model predictions and the experimental data from literature indicates that the propose model can well reproduce the mechanical responses of gap-graded soils within a wide range fraction of rock aggregates.

A new simple classification modeling procedure, multi-wavelength statistical discriminant analysis (MW-SDA), is proposed for the identification of Shandong green tea origins coupled with near-infrared (NIR) spectroscopy. After smoothing and first derivative preprocessing, seven characteristic wavelengths (CW) were selected by enlarging the detailed information of preprocessed spectra. Then, for each characteristic wavelength, a classification threshold is calculated according to the differences in absorbance value, which can best separate the spectra for different origins. Based on the seven CWs and corresponding thresholds, seven classifiers were obtained, which form the classification model. The performance of the calibration model was evaluated according to sensitivity, specificity, and classification accuracy. Analysis results indicated that MW-SDA can be used well to build classification models. The predicted precision of the last model in prediction set was: sensitivity = 1, specificity = 0.967, and accuracy = 98.3%.

Weathered gap-graded soils are a common geological body in mountainous regions, and they are widely used as construction materials. The shear strength is the controlling parameter for the d...

Clayey/silty sands are widespread as naturally sedimentary soils such as marine deposits in estuaries and offshore locations. They belong to a unique class of gap-graded soils featuring a d...

In open-pit coal mining, the excavated clayey cover is dumped without any compaction to form a landfill with a relatively open structure. In this type of material, water flowing through the landfills prefers the inter-lump voids, which have a permeability significantly higher than the clay lumps. With increasing time, the lumps in the upper layer may be partially transformed into a reconstituted soil, occupying the inter-lump voids with consequent decrease in permeability of the landfill. In the study presented here, a consolidation model is proposed based on the double porosity concept and the homogenisation theory. The analysis follows these steps: step 1, a representative volume of lumpy composite soils is divided into four parts and the governing differential equations are formulated based on conservation of mass; step 2, the inter-lump porosity for the lumpy composite structure is formulated as a function of the overall porosity and the porosity of its constituents; step 3, to account for stress (strain) concentrations within the lumpy composite material, a homogenisation relation is used based on analysis of the soil structure; step 4, the hydraulic conductivities of the inter-lump material (lumps) and intra-lump material (reconstituted soil) are approximated by the same set of parameters; step 5, for the lumpy soil, a new relationship between the strains and the absolute velocities of the solid skeleton is proposed, which eliminates the influence of the rigid displacement of the lumps. The model simulations are compared with experimental data, indicating that the proposed model can well represent the consolidation curves of the lumpy composite soil observed in the laboratory.

In this paper, the compression behavior of sand-marine clay mixtures was investigated, both experimentally and theoretically. The test data reveal that the Normal Compression Line of a sand-clay mixture depends on both the sand fraction and the initial water content of the clay matrix. The local stress in the clay matrix σ ′ c is approximately close to the overall stress of the sand-clay mixture σ′ for a sand mass fraction of 20%. The stress ratio, σ′ c / σ′ , falls significantly with increasing overall stress for a sand fraction of 60%, which may be attributed to the formation of clay bridges between adjacent sand particles. A compression model was formulated within the homogenization framework. First, a homogenization equation was proposed, which gives a relationship between the overall stiffness E and that of the clay matrix Ec . Then, a model parameter ξ was incorporated considering the sensitivity of the structure parameter on the volume fraction of the clay matrix. Finally, a simple compression model with three model parameters was formulated using the tangent stiffness. Comparisons between the experimental data and simulations reveal that the proposed model can well represent the compression curves of the sand-marine clay mixtures observed in the laboratory.

Fresh lumpy soils from open-pit mining have a relatively open structure, which transforms gradually into a lumpy composite structure due to weathering factors. The resulting lumpy composite soils consist of natural stiff lumps and a reconstituted soil within the inter-lumps space. The stress and strain distributions are not uniform, since there is a significant difference of the stiffnesses for these two constitutes. The lumpy soils with a composite structure are investigated in this paper, both experimentally and theoretically. First, the volume of the lumpy composite soil is divided into separate parts and the evolution of the volume fraction of the lumps is considered. A nonlinear Hvorslev surface considering soil structure is proposed for the lumps on the dry side of the critical state and evaluated based on laboratory data. Finally, a simple model for the lumpy soils is proposed within a homogenization framework. Comparisons between the experimental data and simulations reveal that the proposed model can well represent the stress–strain and volume deformation behavior observed in the laboratory.

Clay mixture is a waste material in open pit mining from the excavation of various soil layers. In the present study, a general constitutive framework is proposed for the prediction of compressibility of remolded clay mixtures. First, the resulting structure of a clay mixture is simplified as a composite structure, in which the elements of the constituents are randomly distributed in a representative elementary volume. Afterwards, the initial water contents of the constituents are estimated based on a simplified model for the undrained shear strength of the clay mixture. Then, the representative elementary volume of the mixed soil is divided into separate individual parts and the volume fractions of the constituents are formulated as functions of the overall porosity and those of the constituents. Finally, a homogenization law is proposed based on the analysis of the randomly arranged structure together with a simple compression model for clay mixtures. Parameters required by the model correspond only to the constituents, which are simple to calibrate based on standard laboratory tests. By making comparisons of the predictions with test data, it is shown that the proposed model can well represent the compression behavior of the clay mixtures.

The deposition of excavated natural soils, e.g. in open pit mines or during land reclamation, produces in general lumpy soils with multimodal pore sizes. The mechanical behaviour of such soils is determined by interaction between the firm to stiff lumps and the soft to liquid soil material in the macrovoids between the lumps. The initial skeleton composed of lumps resembles a coarse grained soil. However, contrary to mineral grains, the macrograins (lumps) are not incompressible and time-independent. Due to rising overburden during the subsequent deposition of the excavated soil, a time-dependent deformation of the lumps takes place, being accompanied by a softening of the lumps’ surface. The space between the lumps, originally occupied by air, becomes gradually filled with that soft material. A constitutive description of the lumpy soils should take into account all the mentioned effects. In this paper, main ideas and fundamentals for the constitutive modelling of the relevant phases of lumpy soils are outlined. With help of a homogenization method, a material model suitable for practical applications can be obtained.

The pore water dissipation of sand–clay mixtures is significantly affected by the sand fraction due to nonuniform stress distribution. On the basis of the elastic visco-plastic modeling con...

Landfills consisting of waste natural lumpy soils from open-pit mining are being deposited. The shear strength of excavated lumpy soils is important for designing the landfills. To this end...

The clayfills are being produced in open-pit mining. The stress state in the stiff lumps of the clayfills is significantly lower than in situ level. As a result, their current states lie on the dry side of the critical state. The linear Hvorslev surface is widely used due to its simplicity and capability to model the limit stress condition of soils on the dry side. However, it may overestimate the strength at very low stress level. For this purpose, a series of drained triaxial tests were performed on a silty clay at very small stress levels. The failure points of the tested soil confirm a nonlinear relationship in $$p^{\prime }$$ –q plane on the dry side of the critical state. The degree of nonlinearity increases after being normalized by the Hvorslev equivalent pressure, which can be well modeled by a nonlinear power law criterion proposed by Atkinson (Geotechnique 57(2):127–135, 2007). Based on the test data and the critical state concept, a new failure line is proposed with help of the equivalent Hvorslev pressure. The nonlinear Hvorslev surface is then incorporated into an elastoplastic model and a hypoplastic model. Comparisons between the experimental data and simulations reveal that the proposed models can well represent the behavior observed in the laboratory.

The lumpy soil is a by product of the open-pit mining. A composite-lumpy material (in which, the lumps are randomly distributed in the reconstituted soil) is being created due to the degradation of the initial granular structure. In the present study, the compression and failure behaviour of an artificial lumpy material with randomly distributed inclusions are investigated using the finite element method. The computation results show that the stress ratio, defined as the ratio of the volume average stress between the lumps and the reconstituted soil within the inter-lump voids, is significantly affected by both the volume fraction and the preconsolidation pressure of the lumps under an isotropic compression path, while the volume fraction of the lumps plays a minor role under a triaxial compression path. Based on the simulation results, a homogenization law was proposed utilizing the secant stiffnesses.

Sandstone usually disintegrates into gap-graded granular materials with a matrix-sustained structure due to weathering factors. This paper presents an investigation on the small strain stiffness of this type of granular materials based on Discrete Element Method (DEM) simulations. Our numerical results indicate the percentage of sliding contact is negligibly small within the small strain range, and the small strain stiffness of fines is well consistent with the widely recognized Hardin’s equation. Both findings confirm the validity of DEM simulations on the study of small strain response of granular materials. The simulation results are further analyzed based on mixture theory. A structure variable is introduced to correlate with the evolution of inter-aggregates structure. This variable is found to increase with the volume fraction of coarse aggregates but is rather independent of the confining stress and the initial void ratio of the fine matrix. Based on the insights drawn from DEM simulations, a homogenization equation is proposed for the small strain stiffness of gap-graded granular soils to reproduce the small strain stiffness of gap-gaped materials observed in our numerical simulations and is further validated by laboratory test data from the literature. The equation can be conveniently incorporated into classical elastoplastic models to model gap-graded granular materials.

Warm laser shock peening (WLSP) is a thermomechanical strengthening technique with tempering treatment during laser shock peening (LSP) to optimize the mechanical properties of a metallic material. In WLSP, processing temperature plays a key role in regulating the final product’s mechanical properties. In this work, Ti6Al4V titanium alloy is used to evaluate effect of temperature on mechanical properties during warm laser shock peening. The compressive residual stress (CRS) generated by WLSP at different temperature was measured by X-ray diffraction (XRD) and the surface hardness was investigated to reveal the surface strength features under different heat treatments as well. It was found that regardless of which temperature applied during the WLSP process, the treated specimens all displayed high-amplitude CRS on the surface or in depth, but the surface peak CRS decreases gradually as temperature increases. Specially, when the WLP temperature exceeded 250°C, the decreasing slope raised. The CRS affected width increased first, and then decreased with the increases of temperature. The maximum CRS affected width was about 6.25 mm, appearing at a temperature of 250 °C. For the affected depth of CRS, firstly, as the temperature increases from 20 to 250 °C, the thickness of affected layer rises with temperature. However, when the temperature exceeds 300°C, the affected depth of CRS sharply declines. In addition, the WLSP technology could improve the hardness of Ti6Al4V titanium alloy from 389 HV at room temperature to 418 HV at 350 °C

Laboratory tests on sand–marine clay mixtures reveal that the effect of sand mass fraction on the overall consolidation behavior is negligible for a sand mass fraction of 20% or less. Furth...

Lumpy soils are inhomogeneous materials which can be encountered in land reclamation and open pit mining. The lumps are randomly distributed in the reconstituted soil but on a mesoscale their configuration can be expressed by two simplified configurations of both constituents. In order to investigate the behaviour of these two basic configurations, isotropically consolidated drained triaxial shear tests were performed on artificially prepared specimens with parallel and series structures. The laboratory tests show that the failure plane of the series specimens is located in the constituent with the lower strength; the specimens with the parallel structure have a failure plane which crosses both constituents. As a result, the shear strength of the series specimens is only slightly higher than that of the constituent with the lower strength and the strength of the parallel specimens lies between those of the constituents. Furthermore, the maximum volumetric strain of the series specimens is lower than that ...

Clay mixtures are a by-product from open pit mining during the excavation of various soil layers. The mechanical behaviour of landfills composed of these clay mixtures is complex. In the present study, two clays were used to produce soil mixtures artificially in the laboratory. The physical properties, compression behaviour and remoulded undrained shear strength of the resulting materials were investigated. The test results show that the actual measured values of the liquid limit were close to the expected theoretical value (the constituents are supposed to contribute proportionally to their amounts), but there was a non-negligible difference in the plasticity indices. The constants of intrinsic compressibility are affected by both the initial void ratio and the liquid limit. The remoulded shear strength of the clay mixtures can be also normalised with the liquid limit or the consistency index.

Metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) has been identified as a potential cancer biomarker, yet the mechanism by which it influences the development of cancer remains unknown. In this study, we aimed to correlate MALAT1 expression with pathological features and prognosis in cancer patients. Several databases were searched using combinations of keywords relating to MALAT1 and cancer. After selection of relevant cohort studies according to strict criteria, a meta-analysis was conducted. Twelve studies were analyzed, involving 958 cancer patients. Elevated MALAT1 expression was associated with poor prognosis and larger tumors [prognosis: hazard ratio = 3.11, 95% confidence interval (CI) = 1.98-4.23, P = 0.000; tumor size: odds ratio (OR) = 0.40, 95%CI = 0.21-0.74, P = 0.003]. However, no connection with histological grade, T-stage, lymph node (LN) metastasis, or distant metastasis was established (all P0.05). A correlation between increased expression and poor prognosis was observed in the large and small sample-size subgroups (all P0.05), as was a relationship with large tumor size (OR = 0.30, 95%CI = 0.13-0.71, P = 0.006). Expression was correlated with T-stage and distant metastasis in the small sample-size subgroup (all P0.05), but no association was detected regarding histological grade, LN metastasis in either subgroup (all P0.05). Our findings demonstrate that elevated MALAT1 expression correlates with large tumor size, advanced tumor stage, and poor prognosis, and might therefore be utilized to evaluate clinical pathological features and prognostic out come for cancer patients.

For the excavated clayey cover of a coal seam in open-pit mining, the shear strength is the most important issue after its deposition in landfills. For this purpose, an artificial lumpy material was investigated in this paper. A transition form between a reconstituted soil and natural lumpy soil governs the mechanics of the soils artificially deposited after the excavation. This paper presents triaxial and oedometer tests (including K0 and isotropic consolidation tests conducted in triaxial cell) both on an artificial lumpy soil and its corresponding reconstituted form. Compression, permeability and strength of lumpy materials have been evaluated. When normalized by Hvorslev pressure, the shear strength of both lumpy materials and reconstituted soil lies on unique lines, with strength parameters of the lumpy materials lower than that of the reconstituted soil. Both the consolidation and triaxial test results indicate that the reconstituted soil, which exists in the inter-lump voids, plays a crucial role in the behaviour of lumpy materials.

Digestible (DE), metabolizable (ME), and net (NE) energy values of seven diets were measured in castrated male pigs of 45 (Stage 1), 100 (Stage 2), or 150 (Stage 3) kg BW. Diets were prepared from a basal diet supplemented with cornstarch, or sucrose, or a protein mixture (referred to here as protein), or rapeseed oil, or a mixture of fibrous ingredients (referred to as fiber), or rapeseed oil+fiber. Diets were fed at similar levels (x maintenance) at the three stages. Heat production at different feeding levels, as measured by indirect calorimetry, allowed calculation of energy retained by each pig (equal to ME intake minus heat production) and an estimate of fasting heat production of all pigs (360 kcal/kg BW.42). Net energy intake was then calculated for each pig as retained energy plus 360 x BW.42. The amounts of DE digested before the end of the ileum (DEi) and in the hindgut (DEh) were measured. Formulation of diets allowed calculation of energy values of the ingredients added to the basal diet. Digestibility and metabolizability of diets increased significantly from Stages 1 to 3, with higher variations for low-energy diets. The NE:ME ratio (k, %) and dietary NE content were not affected (P > .05) by stage of growth. On average, k was 75%, with higher values for diets containing rapeseed oil or starch (77%) and lower estimates for the fiber diet (72%). As a consequence, k was approximately 90, 82, 80, 72, and 60% for rapeseed oil, cornstarch, sucrose, protein, and fiber, respectively. These values are consistent with the lower k value for ME from DEh (57 vs 78% for DEi). Present data confirm that the hierarchy between feeds is dependent on the energy system (DE vs ME vs NE) and that the NE concept is superior in predicting the "true" energy value. The present results combined with previous ones show that, under practical conditions, the same NE prediction equations based on digestible nutrient contents, or preferably DE or ME contents, can be applied at all stages of growth in pigs. However, attention should be paid to factors such as BW or feeding level that affect digestibility and metabolizability of feeds markedly. The effects are the most important for ingredients.

Digestible (DE), metabolizable (ME), and net (NE) energy values of 61 diets were measured in 45-kg growing Large White boars. Net energy was calculated as energy retained at an average ME intake equivalent to 540 kcal/kg BW.60 plus fasting heat production estimated from data of the present experiment as 179 kcal/kg BW.60. Retained energy was measured as the difference between ME intake and heat production obtained in respiration chambers. The amounts of DE digested before the end of the ileum (DEi) and in the hindgut (DEh) were also measured for each diet. Regression equations for predicting dietary NE content from digestible nutrient levels or from DE or ME and chemical characteristics or from chemical composition only were calculated. Efficiencies of utilization of ME for NE (k, %) were also obtained. The mean k value for the 61 diets was 74% (range: 69 to 77). Digestible nutrients were used differently for NE: k values varied from approximately 60% for digestible CP or digestible cell wall fractions to 82% for starch and 90% for digestible ether extract. Accordingly, k for ME associated with DEh was lower than ME from DEi (58 vs 76%). Equations for predicting NE content are proposed. Their applicability, the comparison with other available NE prediction equations, and the effects of energy system on diet formulation are discussed.

Heat production (HP; indirect calorimetry) of six Large White castrated sows (mean BW 208 kg) kept individually in metabolism cages at 24°C and fed once a day (d) at about maintenance energy level (415 kJ ME/kg BW 0.75 ) and their physical activity (standing versus lying) were recorded continuously over 24 h after a meal. Each measurement lasted 5 consecutive days and was repeated 8–10 times for each sow over 9 months. HP related to activity (AHP) was calculated according to a statistical model in which HP was a function of time after the meal and standing activity. Resting heat production (RHP) corresponded to the difference between HP and AHP. HP and AHP averaged 402 kJ kg BW −0.75 d −1 and 14.9 kJ/min (or 0.26 kJ kg BW −0.75 min −1 ), respectively. Mean duration of daily activity was 241 min. AHP was then equivalent to 62 kJ kg BW −0.75 d −1 or 15% of HP. Consequently, RHP averaged 340 kJ kg BW −0.75 d −1 . Minimum RHP (23 h after the meal) was 290 kg BW −0.75 d −1 . These values were significantly different between sows. Meal duration averaged 14 min. Variations in activity, total HP and RHP over the day are presented. The mean increment of HP related to food intake represented about 15% of ME supply. Compared to other species, the energy requirement for standing activity in pigs is distinctly higher.

Metal-semiconductor-metal ultraviolet photodetectors were fabricated by using the sputtered Ga-doped ZnO (GZO) thin films on sapphire substrate as an active layer. Current-voltage (I-V) and opto-electrical characteristics of the devices were investigated. It is found that the peak optical responsivity of the devices can be significantly improved by selecting appropriate thermal annealing temperature, i.e., from 12.0 A/W (annealed at 500 °C) and 54.0 A/W (700 °C). Furthermore, dark current of the devices drops by two orders of magnitude after annealing process. The significant improvement in performance of the device is ascribed to the removal of massive defect centers of the GZO thin films and increase of Schottky barrier height between the GZO and metal electrodes after thermal annealing at appropriate temperatures.

Digestible (DE), metabolizable (ME), and net (NE) energy values of seven diets were measured in castrated male pigs of 45 (Stage 1), 100 (Stage 2), or 150 (Stage 3) kg BW. Diets were prepared from a basal diet supplemented with cornstarch, or sucrose, or a protein mixture (referred to here as protein), or rapeseed oil, or a mixture of fibrous ingredients (referred to as fiber), or rapeseed oil+fiber. Diets were fed at similar levels (x maintenance) at the three stages. Heat production at different feeding levels, as measured by indirect calorimetry, allowed calculation of energy retained by each pig (equal to ME intake minus heat production) and an estimate of fasting heat production of all pigs (360 kcal/kg BW.42). Net energy intake was then calculated for each pig as retained energy plus 360 x BW.42. The amounts of DE digested before the end of the ileum (DEi) and in the hindgut (DEh) were measured. Formulation of diets allowed calculation of energy values of the ingredients added to the basal diet. Digestibility and metabolizability of diets increased significantly from Stages 1 to 3, with higher variations for low-energy diets. The NE:ME ratio (k, %) and dietary NE content were not affected (P.05) by stage of growth. On average, k was 75%, with higher values for diets containing rapeseed oil or starch (77%) and lower estimates for the fiber diet (72%). As a consequence, k was approximately 90, 82, 80, 72, and 60% for rapeseed oil, cornstarch, sucrose, protein, and fiber, respectively. These values are consistent with the lower k value for ME from DEh (57 vs 78% for DEi). Present data confirm that the hierarchy between feeds is dependent on the energy system (DE vs ME vs NE) and that the NE concept is superior in predicting the "true" energy value. The present results combined with previous ones show that, under practical conditions, the same NE prediction equations based on digestible nutrient contents, or preferably DE or ME contents, can be applied at all stages of growth in pigs. However, attention should be paid to factors such as BW or feeding level that affect digestibility and metabolizability of feeds markedly. The effects are the most important for ingredients.

Digestible (DE), metabolizable (ME), and net (NE) energy values of 61 diets were measured in 45-kg growing Large White boars. Net energy was calculated as energy retained at an average ME intake equivalent to 540 kcal/kg BW.60 plus fasting heat production estimated from data of the present experiment as 179 kcal/kg BW.60. Retained energy was measured as the difference between ME intake and heat production obtained in respiration chambers. The amounts of DE digested before the end of the ileum (DEi) and in the hindgut (DEh) were also measured for each diet. Regression equations for predicting dietary NE content from digestible nutrient levels or from DE or ME and chemical characteristics or from chemical composition only were calculated. Efficiencies of utilization of ME for NE (k, %) were also obtained. The mean k value for the 61 diets was 74% (range: 69 to 77). Digestible nutrients were used differently for NE: k values varied from approximately 60% for digestible CP or digestible cell wall fractions to 82% for starch and 90% for digestible ether extract. Accordingly, k for ME associated with DEh was lower than ME from DEi (58 vs 76%). Equations for predicting NE content are proposed. Their applicability, the comparison with other available NE prediction equations, and the effects of energy system on diet formulation are discussed.

Six diets prepared from a basal diet and either 30% corn starch or 20% sucrose or 8% rapeseed oil or 30% of a mixture of fibre-rich ingredients or 8% rapeseed oil and 30% of fibre-rich ingredients (diet 6) were fed to 45 (stage 1), 100 (stage 2) and 150 (stage 3) kg body weight pigs in order to quantify the effect of body size on digestibility of feeds. Digestibility of energy and nutrients and urinary and methane energy losses were measured for diets and calculated (by the difference method) for corn starch, sucrose, rapeseed oil and fibrous ingredients. Animals were fed close to ad libitum. Digestibility coefficients (DC) of nutrients and energy of diets were significantly higher at stage 2 than at stage 1. The improvement was small between stage 2 and stage 3. On average for the six diets, the DC of energy was 82.6, 85.0 and 85.8% at stages 1, 2 and 3, respectively. However, the variation in digestibility of diets with body weight was greater when dietary cell wall content was increased. The effect of body weight on energy value of diets estimated from DE measurements was attenuated by higher methane (0.5, 0.7 and 0.8% of DE intake at stages 1, 2 and 3, respectively) and urinary energy losses in heavier pigs. As a consequence of changes in DE values of diets with body weight, DE values of sucrose, rapeseed oil and fibrous ingredients were higher in heavier pigs. In 100 kg pigs, the DE content of corn starch, sucrose, rapeseed oil and fibrous ingredients averaged 17.7, 16.1, 37.7 and 8.7 MJ per kg dry matter, respectively. Results obtained on diet 6 indicate no evidence of digestive interaction between fat and fibre.

The contribution of hindgut to digestion of energy and nutrients was measured at three body weights (BW) or stages of growth (stage 1: 45 kg; stage 2: 100 kg and stage 3: 150 kg) as the difference between fecal digestibility values measured at the three stages and ileal digestibility values estimated with 45 kg BW ileo-rectal anastomized (IRA) pigs. Six diets were tested. Composition of diets allowed calculation (by the difference method) of ileal and hindgut digestion of corn starch, sucrose, rapeseed oil and a mixture of fibrous ingredients (so-called “fibre”). Fecal digestibility of energy and nutrients was improved when BW was increased with higher values in intact pigs at the three stages (except for ether extract) than in IRA pigs. As a consequence, the contribution of hindgut to energy supply amounted to 15, 17 and 18% at stages 1, 2 and 3, respectively. This contribution varied with diet characteristics and ranged from about 11% in high-starch or high-sugars diets to 30% in the high-fibre diet. A major fraction of dietary crude protein (90%) and ether extract (100%) was digested before the end of the ileum while cell-wall fractions were predominantly degraded in the hindgut (70% for NDF). Hindgut digestibility of energy and NDF entering the hindgut averaged 48% and increased (P

Digestible energy (DE), metabolizable energy (ME) and net energy for maintenance (NEm) values of a set of fourteen diets were measured in six adult sows fed at and below their maintenance energy level. The efficiency of ME for NEm was estimated from heat production (HP) measurements (indirect calorimetry) at these different feeding levels. HP was partitioned between HP due to physical activity, thermic effect of food (TEF) and fasting heat production (FHP). The amounts of DE digested in the small intestine or in the hindgut were measured. Equations for prediction of NEm from dietary characteristics were calculated. HP at maintenance level averaged 400 kJ/kg body-weight0.75, 16 and 19% of the total being due to physical activity and TEF respectively. The efficiency of ME for NEm averaged 77·4% with higher values for digestible diethyl ether extract (100%) and starch + sugar (82 %). The efficiencies of digestible crude protein (N × 6·25) and digestible residue averaged 69 and 56 % respectively. The energy absorbed from the small intestine was used more efficiently than the energy fermented in the hindgut (82 v. 59%). These values are comparable with those obtained in growing pigs. The NEm content of diets can be predicted accurately from equations including DE (or ME) values and some dietary chemical characteristics.