Experimental Evidence of Intrinsic Current Generation by Turbulence in Stationary Tokamak Plasmas.

High-ß_{θe} (a ratio of the electron thermal pressure to the poloidal magnetic pressure) steady-state long-pulse plasmas with steep central electron temperature gradient are achieved in the Experimental Advanced Superconducting Tokamak. An intrinsic current is observed to be modulated by turbulence driven by the electron temperature gradient. This turbulent current is generated in the countercurrent direction and can reach a maximum ratio of 25% of the bootstrap current. Gyrokinetic simulations and experimental observations indicate that the turbulence is the electron temperature gradient mode (ETG). The dominant mechanism for the turbulent current generation is due to the divergence of ETG-driven residual flux of current. Good agreement has been found between experiments and theory for the critical value of the electron temperature gradient triggering ETG and for the level of the turbulent current. The maximum values of turbulent current and electron temperature gradient lead to the destabilization of an m/n=1/1 kink mode, which by counteraction reduces the turbulence level (m and n are the poloidal and toroidal mode number, respectively). These observations suggest that the self-regulation system including turbulence, turbulent current, and kink mode is a contributing mechanism for sustaining the steady-state long-pulse high-ß_{θe} regime.

Dietary calcium levels regulate calcium transporter gene expression levels in the small intestine of broiler chickens.

1. This study investigated the effect of dietary calcium (Ca) levels on growth performance, bone development and Ca transporter gene expression levels in the small intestine of broiler chickens.2. On the day of hatch, 350, Ross 308 male broilers were randomly allotted to one of five treatments with five replicate pens each and 14 birds per pen. Dietary Ca levels in feed were 5.0, 7.0, 9.0, 11.0 and 13.0 g/kg, in which 9.0 g/kg was in the control diet. All diets contained 4.5 g/kg non-phytate phosphorus (NPP).3. The increase in dietary Ca levels from 5.0 to 13.0 g/kg did not affect the growth performance of 1- to 18-day-old broilers (P > 0.05).4. Increasing the Ca levels linearly increased the ash weight and the contents of ash, Ca and phosphorus (P) in the tibia of broilers at 18 days of age (P < 0.05). The contents of ash, Ca and P in broilers fed with 9.0 g/kg Ca were higher than those in birds fed with 5.0 g/kg Ca (P < 0.05).5. Increasing the Ca levels linearly decreased mRNA expression levels of the Ca-binding protein 28-kDa (CaBP-D28k), plasma membrane Ca-transporting ATPase 1b (PMCAlb), sodium (Na)/Ca exchanger 1 (NCX1), nuclear vitamin D receptor (nVDR) and membrane vitamin D receptor (mVDR) in the duodenum of broilers at 18 d of age (P < 0.05). Similar results were seen in the jejunum and ileum. Broilers fed 9.0-13.0 g/kg Ca in feed had lower mRNA expression levels of CaBP-D28k and PMCAlb in the small intestine than birds fed 5.0 g/kg Ca in feed (P < 0.05).6. The data indicated that low levels of dietary Ca stimulated its transporter gene transcription and promoted absorption, but high levels of Ca inhibited transporter gene expression and prevented excessive absorption in the small intestine of broiler chickens.

Evaluation of Relative Bioavailability of 25-Hydroxycholecalciferol to Cholecalciferol for Broiler Chickens.

This study was conducted to evaluate the relative bioavailability (RBV) of 25-hydroxycholecalciferol (25-OH-D3) to cholecalciferol (vitamin D3) in 1- to 21-d-old broiler chickens fed with calcium (Ca)- and phosphorus (P)-deficient diets. On the day of hatch, 450 female Ross 308 broiler chickens were assigned to nine treatments, with five replicates of ten birds each. The basal diet contained 0.50% Ca and 0.25% non-phytate phosphorus (NPP) and was not supplemented with vitamin D. Vitamin D3 was fed at 0, 2.5, 5.0, 10.0, and 20.0 µg/kg, and 25-OH-D3 was fed at 1.25, 2.5, 5.0, and 10.0 µg/kg. The RBV of 25-OH-D3 was determined using vitamin D3 as the standard source by the slope ratio method. Vitamin D3 and 25-OH-D3 intake was used as the independent variable for regression analysis. The linear relationships between the level of vitamin D3 or 25-OH-D3 and body weight gain (BWG) and the weight, length, ash weight, and the percentage of ash, Ca, and P in femur, tibia, and metatarsus of broiler chickens were observed. Using BWG as the criterion, the RBV value of 25-OH-D3 to vitamin D3 was 1.85. Using the mineralization of the femur, tibia, and metatarsus as criteria, the RBV of 25-OH-D3 to vitamin D3 ranged from 1.82 to 2.45, 1.86 to 2.52, and 1.65 to 2.05, respectively. These data indicate that 25-OH-D3 is approximately 2.03 times as active as vitamin D3 in promoting growth performance and bone mineralization in broiler chicken diets.

One Alpha-hydroxycholecalciferol Improves Growth Performance, Tibia Quality, and Meat Color of Broilers Fed Calcium- and Phosphorus-Deficient Diets.

An experiment was conducted to evaluate the effects of one alpha-hydroxycholecalciferol (1α-OH D3) on growth performance, tibia quality, and skin and meat color in broilers fed calcium (Ca)- and phosphorus (P)-deficient corn-soybean meal diets. A total of 288 male Ross broilers, at 21 days of age, were randomly assigned to three treatments with eight cages per treatment. Three levels of 1α-OH D3 (0, 5, and 10 µg/kg) were added to a basal diet (0.50% Ca, 0.13% non-phytate phosphorus (NPP), and 0.35% total phosphorus (tP)) without vitamin D3. As a result of this study, the addition of 1α-OH D3 increased body weight gain (p<0.001), feed intake (p = 0.007), feed efficiency (p<0.001), tibia weight (p = 0.002), length (p<0.001), breaking-strength (p = 0.012), ash (p<0.001), Ca (p<0.001), and P content (p = 0.004). Dietary 1α-OH D3 enhanced breast meat yellowness (p = 0.015) and the length and weight of the small intestine of the broilers. Moreover, 1α-OH D3 decreased serum Ca concentration (p = 0.074) and breast meat redness (p = 0.010). These results indicate that the 1α-OH D3 improves growth, tibia quality, and meat color in broilers fed Ca- and P-deficient corn-soybean meal diets.

1α-Hydroxycholecalciferol improves the growth performance and up-regulates the mRNA expression of vitamin D receptor in the small intestine and kidney of broiler chickens.

1α-Hydroxycholecalciferol (1α-OH-D3) is a vitamin D derivative. The objective of this study was to evaluate the effects of 1α-OH-D3 on the growth and the mRNA expression of vitamin D receptor (VDR) in the small intestine and kidney of chickens. A total of 240 males of one-day-old Ross 308 broilers was randomly assigned to 4 treatments with 5 replicates of 12 birds per replicate. Three levels of 1α-OH-D3 (1.25, 2.5, and 5 µg/kg) were added to a basal diet containing 0.50% calcium (Ca), 0.25% non-phytate phosphorus (NPP), and without supplemental cholecalciferol (vitamin D3). The control diet contained 1.00% Ca, 0.45% NPP, and 25 µg/kg cholecalciferol. Dietary 1α-OH-D3 levels linearly improved the average daily feed intake (ADFI), average daily gain (ADG), femur and tibia mineralization, and plasma Ca concentration, and retained Ca and total phosphorus (tP) amounts in broilers from 1 to 21 d of age (P < 0.05). In addition, 1α-OH-D3 also linearly up-regulated the mRNA expression levels of VDR in the duodenum as well as those of VDR and sodium-phosphate cotransporter NaPi-IIa and NaPi-IIc in the kidney of broilers (P < 0.05). However, 1α-OH-D3 did not affect the mRNA levels of 25-hydroxylase in the liver or NaPi-IIb in the duodenum (P > 0.05). No differences were observed in the ADFI, ADG, bone length, plasma mineral concentration, retained tP amount, or the mRNA levels of the above genes (except for VDR in the kidney) between the birds fed the diet with 5 µg/kg 1α-OH-D3 and the birds fed the control diet (P > 0.05). By contrast, the weight, ash weight, ash percentage, and Ca percentage of the bone, retained Ca amount, and the mRNA level of VDR in the kidney were lower in the birds fed the diet with 5 µg/kg 1α-OH-D3 than in the birds fed the control diet (P < 0.05). These data indicate that 1α-OH-D3 up-regulates the gene expression of VDR in the small intestine and kidney at the transcriptional level, thereby improving the growth performance and bone mineralization of broiler chickens from 1 to 21 d of age.

Age, phosphorus, and 25-hydroxycholecalciferol regulate mRNA expression of vitamin D receptor and sodium-phosphate cotransporter in the small intestine of broiler chickens.

Four experiments were conducted in this study. Experiment 1 was carried out to examine mRNA expressions of nuclear vitamin D receptor (nVDR), membrane vitamin D receptor (mVDR), and type IIb sodium-phosphate cotransporter (NaPi-IIb) in the small intestine of broiler chickens. Experiments 2, 3, and 4 were implemented to evaluate effects of age, non-phytate phosphorus (NPP), and 25-hydroxycholecalciferol (25-OH-D3) on mRNA expressions of nVDR, mVDR, and NaPi-IIb in the duodenum of chickens. Results showed that mRNA expression levels of nVDR and NaPi-IIb were highest in the duodenum of 21-day-old broilers, lower in the jejunum, and lowest in the ileum. By contrast, no differences in mRNA expression levels of mVDR were detected among the duodenum, jejunum, and ileum. Age quadratically affected mRNA expressions of nVDR, mVDR, and NaPi-IIb in the duodenum and 25-hydroxylase in the liver of 7- to 42-day-old broilers, with the highest levels observed at 21 d of age. By contrast, age linearly decreased mRNA expression level of 1α-hydroxylase in kidneys. Dietary NPP levels quadratically affected mRNA expression levels of nVDR and mVDR in the duodenum and 25-hydroxylase in the liver of 21-day-old broilers. The highest mRNA expression levels of nVDR and mVDR and lowest mRNA level of 25-hydroxylase were observed at 0.55% NPP. mRNA expression level of NaPi-IIb linearly declined when dietary NPP levels increased from 0.25 to 0.65%. Addition of 12.5 µg/kg of 25-OH-D3 increased mRNA expression level of 1α-hydroxylase in kidneys and those of nVDR, mVDR, and NaPi-IIb in the duodenum of broilers compared with birds fed the diet without 25-OH-D3. These data indicate that mRNA expressions of nVDR and NaPi-IIb are highest in the duodenum, and the greatest mRNA levels of nVDR, mVDR, and NaPi-IIb are observed at 21 d of age. Dietary NPP levels quadratically increase mRNA expressions of nVDR and mVDR but linearly decrease NaPi-IIb mRNA level. 25-OH-D3 up-regulates the above gene transcription.

Relative biological value of 1α-hydroxycholecalciferol to 25-hydroxycholecalciferol in broiler chicken diets.

This study was conducted to evaluate the relative biological value (RBV) of 1α-hydroxycholecalciferol (1α-OH-D3) to 25-hydroxycholecalciferol (25-OH-D3) in one- to 21-day-old broiler chickens fed calcium (Ca)- and phosphorus (P)-deficient diets. On the d of hatch, 450 male Ross 308 broiler chickens were weighed and randomly allotted to 9 treatments with 5 replicates of 10 birds per replicate. The basal diet contained 0.50% Ca and 0.25% non-phytate phosphorus (NPP) but was not supplemented with cholecalciferol (vitamin D3). The levels of Ca and NPP in basal diets were lower than those recommended by NRC (1994). 25-OH-D3 was fed at zero, 1.25, 2.5, 5.0, and 10.0 µg/kg, and 1α-OH-D3 was fed at 0.625, 1.25, 2.5, and 5.0 µg/kg. The RBV of 1α-OH-D3 to 25-OH-D3 based on vitamin D intake was determined by the slope ratio method. Results showed that 25-OH-D3 or 1α-OH-D3 improved the growth performance and decreased the mortality in one- to 21-day-old broilers. A linear relationship was observed between the level of 25-OH-D3 or 1α-OH-D3 and mineralization of the femur, tibia, or metatarsus. The RBV of 1α-OH-D3 to 25-OH-D3 were 234, 253, and 202% when the weight, ash weight, and Ca percentage of femur were used as criteria. The corresponding RBV of 1α-OH-D3 to 25-OH-D3 were 232 to 263% and 245 to 267%, respectively, when tibia and metatarsus mineralization were used as criteria. These data indicate that when directly feeding a hormonally active form of vitamin D as 1α-OH-D3 proportionally less is needed than when using the precursor (25-OH-D3) in diets deficient in Ca and P.