Bone Ash Weight Research Articles

Effect of Augmentation Cystoplasty on Bone Metabolism in Chronic Uremic Rats

We examined the impact of urinary diversion using several types of intestinal segments on the bone metabolism of growing rats with renal insufficiency. A total of 110, 8-week-old Sprague-Dawley rats underwent 2-stage subtotal nephrectomy by removal of 5/6 of the renal mass or sham operation. Except for a uremic control group all uremic rats underwent enterocystoplasty using stomach, ileum or colon. An additional group with colic augmentation received the bisphosphonate ibandronate. Bone mineral density of the tibia and lumbar spine, serum analysis and urinary excretion of the bone resorption marker deoxypyridinoline were determined monthly for 12 weeks. At study termination bone ash weight, bone mineral analysis and serum osteotropic hormone levels were determined. All groups undergoing subtotal nephrectomy had a decreased endogenous creatinine clearance of approximately 30%. The lowest gains in tibial and lumbar spine bone mineral density were observed in animals undergoing ileocystoplasty. Femoral calcium content was significantly decreased in uremic ileocystoplasty rats compared with uremic controls. These changes were not induced by alterations in serum pH, nor were they associated with accelerated bone resorption as assessed by deoxypyridinoline. Ibandronate prevented changes related to bone resorption and increased bone mass. Our results suggest that cystoplasty using ileum segments can aggravate renal bone disease in growing rats with mild uremia. Since the acid-base state was unchanged, other properties of the interposed ileum segment must be responsible for the negative effect on bone metabolism.

Preventive and therapeutic effects of acupuncture on bone mass in osteopenic ovariectomized rats.

This study was designed to (1) test the preventive and therapeutic effects of acupuncture on osteopenia in ovariectomized (OVX) rats, and (2) assess whether treatment of different acupuncture points causes different effects on tibiae, femora or lumbar spines. Thirty-five female Sprague-Dawley rats were divided into four groups: Sham (sham-operated, non-acupuncture); Model (OVX, non-acupuncture); Acp-A [OVX, bilateral needling of points Tsu-San-Li (ST-36) and San-Yin- Chiao (SP-6)]; and Acp-B (OVX, bilateral needling of P'i-Shu (Bl-20) and Shen Shu (Bl-23)). Operations were performed at 8 weeks of age, 1 week later the study was started and continued for 16 weeks. Ovariectomy resulted in decreased bone mineral density (BMD) compared to the sham group over time, and Acp-A tended to have higher BMD than the other OVX groups, especially for tibiae. In addition, the bone ash weight of the Acp groups tended to be heavier than the model group. Deoxypyridinoline, the urinary marker of bone resorption, also appeared to be decreased in both acupuncture groups. Similarly, microarchitecture and bone morphometry of lumbar vertebrae and tibiae, such as bone volume, trabecular thickness, trabecular number, mineralizing surface, bone formation rate, mineral apposition rate, number of nodes and number of node-terminus struts, also showed the same improvement in the acupuncture groups as compared to the model control group. Our findings showed that acupuncture may prevent the development of osteopenia in rats induced by ovariectomy. Needling of Tsu-San-Li (ST-36) and San-Yin- Chiao (SP-6) seems more effective than needling of P'i-Shu (Bl-20) and Shen Shu (Bl-23) in bone anabolic regulation.

A Efficacy of Ginseng radix on the Preservation of Spinal Bone Mineral Density and Bone Inorganic Substance of Oophorectomized Rats

This study was undertaken to investigate the effects of the Ginseng radix in osteoporosis of the oophorectomized rats. In this experiment, the rats were oophorectomized and administered the water extracts of the Ginseng radix. The spinal bone mineral density, calcium, phosphorus and ash weight of the bones were measured. The spinal bone mineral density was significantly increased in the ovariectomized (OVX)-Ginseng radix group at 8 weeks as compared to the OVX-saline group. Furthermore, the calcium and phosphorus contents of the femoral and fibula-tibia were significantly increased in the OVX-Ginseng radix group as compared to the OVX-saline group. The ash weights of the femoral and fibula-tibial bones were increases in the OVX-Ginseng Radix group, although it was not statistically significant. On reviewing these experiments, it appears that the Ginseng radix possess efficacy for the prevention of osteoporosis. Further study would be of value to confirm the efficacy of the Ginseng radix for the treatment and/or prevention of osteoporosis in humans.

Effects of dietary vitamin k levels on bone quality in broilers

This study was conducted to evaluate the effects of dietary vitamin K (menadione) on bone quality in cage-raised broilers. Three hundred and sixty male broilers were randomly allotted to one of six treatments, with six replicate pens per treatment and 10 chicks per pen. Broilers were fed one of six diets including a control diet or the control diet plus graded levels of vitamin K (0.5 mg/kg, 2 mg/kg, 8 mg/kg, 32 mg/kg and 128 mg/kg). Water and feed were provided ad libitum during the 7-week experimental period. Results indicated that vitamin K supplementation of broilers diets significantly effected bone quality and feed efficiency. The treatment containing vitamin K at 8 mg/kg improved growth performance (during weeks 6 - 7) and bone quality (during weeks 0 - 3). In our study, hydroxyapatite binding capacity of serum osteocalcin (during weeks 0 - 3), bone breaking strength, bone flexibility, bone ash weight increased linearly (P < 0.05) and bone mineral density, bone mineral content increased quadratically (P < 0.05) with increasing supplementation of vitamin K. In conclusion, to gain optimum bone quality and broiler performance, our studies suggest that the concentration of vitamin K in broilers diets should be 8 mg/kg, 2 mg/kg, and 2 mg/kg, for the starter, grower and finisher phases, respectively. Furthermore, it was shown that the starter period is an important phase for improving bone quality. In addition, this study validated the mechanism of vitamin K effects on bone quality. Vitamin K boosts the carboxylation of osteocalcin and decreases the concentration of serum undercarboxylated osteocalcin enhancing hydroxyapatite binding capacity of serum osteocalcin and improving bone quality.

Chemical and biomechanical characterization of hyperhomocysteinemic bone disease in an animal model.

BackgroundClassical homocystinuria is an autosomal recessive disorder caused by cystathionine β-synthase (CBS) deficiency and characterized by distinctive alterations of bone growth and skeletal development. Skeletal changes include a reduction in bone density, making it a potentially attractive model for the study of idiopathic osteoporosis.MethodsTo investigate this aspect of hyperhomocysteinemia, we supplemented developing chicks (n = 8) with 0.6% dl-homocysteine (hCySH) for the first 8 weeks of life in comparison to controls (n = 10), and studied biochemical, biomechanical and morphologic effects of this nutritional intervention.ResultshCySH-fed animals grew faster and had longer tibiae at the end of the study. Plasma levels of hCySH, methionine, cystathionine, and inorganic sulfate were higher, but calcium, phosphate, and other indices of osteoblast metabolism were not different. Radiographs of the lower limbs showed generalized osteopenia and accelerated epiphyseal ossification with distinct metaphyseal and suprametaphyseal lucencies similar to those found in human homocystinurics. Although biomechanical testing of the tibiae, including maximal load to failure and bone stiffness, indicated stronger bone, strength was proportional to the increased length and cortical thickness in the hCySH-supplemented group. Bone ash weights and IR-spectroscopy of cortical bone showed no difference in mineral content, but there were higher Ca2+/PO43- and lower Ca2+/CO32- molar ratios than in controls. Mineral crystallization was unchanged.ConclusionIn this chick model, hyperhomocysteinemia causes greater radial and longitudinal bone growth, despite normal indices of bone formation. Although there is also evidence for an abnormal matrix and altered bone composition, our finding of normal biomechanical bone strength, once corrected for altered morphometry, suggests that any increase in the risk of long bone fracture in human hyperhomocysteinemic disease is small. We also conclude that the hCySH-supplemented chick is a promising model for study of the connective tissue abnormalities associated with homocystinuria and an important alternative model to the CBS knock-out mouse.

Architecture Is One of the Determinants of Bone Strength

In our recent publication in JBMR, we assessed the effects of risedronate on trabecular architecture and compressive strength of lumbar vertebrae from ovariectomized (OVX) minipigs. Regression analysis showed that trabecular bone volume (BV/TV) explained 76% of the variability of compressive strength. Adding architectural parameters to BV/TV in a three-parameter multiple linear regression model increased the R2 value to 91%. We concluded that risedronate improves the three-dimensional trabecular architecture in the vertebra of OVX minipigs in a way that contributes to an increase in bone strength.1 In their letter to the editor, Drs Kiebzak and Miller commented that our data lacked critical information, namely, ash weight or mineral content. Our decision not to include bone mineral content (BMC) or ash weight was based on data from a previous study on minipig vertebral cores in which there was a strong correlation between BV/TV and BMC (R2 = 0.82).2 For completeness, however, we now report dual-energy X-ray absorptiometry (DXA) data that we collected from the minipig vertebral cores before microcomputed tomography measurements. After 18 months of treatment, risedronate significantly increased bone mineral density (BMD) compared with OVX controls (0.303 ± 0.040 vs. 0.248 ± 0.037 g/cm2). Trabecular BV/TV (measured by microcomputed tomography) and BMD (measured by DXA) correlated strongly (R2 = 0.96). In a simple linear regression model, BMD correlated strongly (R2 = 0.80) with strength. Adding the architectural parameters TSVI and Tb.N to BMD in a three-parameter multiple linear regression model increased R2 to 0.91. The conclusion, therefore, is that although BV/TV and BMD correlate strongly with compressive strength, neither explains all the variance in bone strength. Although the contribution of trabecular architecture to bone strength, as indicated by change in R2, was less than 15% in these minipigs, trabecular bone volume was high (∼25–33%). Architecture is likely to contribute more to bone strength and fracture risk in low bone mass conditions, and this is supported by data from several studies. Key architectural parameters have an exponential relationship with BV/TV.3 Furthermore, there were larger changes in architectural parameters when BV/TV was less than 11%, a value that has been suggested as threshold for spontaneous vertebral fracture.3-5 For trabecular bone in human biopsy specimens from different skeletal sites, BV/TV explained only 37–67% of the variance in elastic constants, especially at low bone volume.6 The prediction of the mechanical properties was significantly improved when architectural indices were included with bone volume.6 These data show that the relative contribution of architecture to strength increases as the bone mass decreases. It was not our intention to downplay the importance of BMD. Low BMD is clearly associated with a high risk of fragility fracture. However, there is now strong clinical evidence that an increase in BMD does not fully explain the fracture benefits of antiresorptive agents.7-9 It is appropriate, therefore, that we revisit the paradigm that BMD alone is an adequate surrogate for bone strength. We agree with Drs Kiebzak and Miller that the effectiveness of antiresorptive therapies for osteoporosis may be related to increase in BMD as well as to changes in one or several other factors that contribute to better bone quality.10 Our focus on the role of architecture does not preclude the importance of other components such as decreased bone turnover and osteocyte viability. Continued investigation into the effects of treatments on bone quality will improve our understanding of the pathophysiology and treatment of bone diseases.

Prevention of bone loss in calcium deficient ovariectonized rats by OST-6, a herbal preparation

OST-6, a herbomineral preparation, was studied for its inhibitory effects on the progress of bone loss induced by ovariectomy (OVX) and concurrent calcium deficiency in rats. Calcium deficient ovariectomized rats were administered with OST-6 at 250 mg/kg b. w. twice a day orally for 16 weeks. Compared with sham operated animals, OVX animals showed an increase in serum ALP, urinary excretion of calcium and phosphorus, which were significantly prevented in OST-6 administered rats. Evaluation of cortical bone morphometric indices by CT-Scanning technique showed an increased medullary width and cross-sectional medullary area (MA), decreased periosteal area (PA), combined cortical thickness (CCT), cortical area/periosteal area (CA/PA) and maximal metaphyseal radial density (MMRD) in OVX animals when compared with sham operated. OST-6 treatment significantly prevented these bone resorption variables. Scanning Electron Microscopy (SEM) study revealed porous and erosive appearance of femur bone at the epiphyseal region and decreased calcium to phosphorus ratio (Ca:P) in the OVX rats when compared with sham operated rats. The treatment with OST-6 prevented the epiphyseal bone resorption and maintained Ca:P ratio. The results of ash analysis indicated a reduced bone mineral content (calcium and phosphorus) and ash weight and percent ash in OVX animals when compared with sham operated animals. All results are statistically significant at P<0.05. These finding suggest the usefulness of OST-6 in the prevention of bone loss in a natural way through utilization of herbal resources.

Low-phytic acid barley improves calcium and phosphorus utilization and growth performance in growing pigs1

Thirty-five crossbred barrows averaging 13.5 kg starting BW were used in a 35-d experiment to compare the availability of P and the nutritional value of two near-isogenic progeny of the barley cultivar 'Harrington'. Low-phytic acid barley (LPB, 0.35% total P, 0.14% phytic acid P) was homozygous for the low-phytic acid 1-1 allele, and the normal barley (NB, 0.35% total P, 0.24% phytic acid P) was homozygous for the normal allele of that gene. Pigs were fed individually twice daily in metabolism pens. Barley was the only source of phytate in semipurified diets, 1 to 3. Diet 1 contained 75% NB, 0.14% estimated available P (aP), and 0.50% Ca. Diet 2 contained 75% LPB, 0.22% aP, and 0.50% Ca. No inorganic P (iP) was added to Diets 1 and 2 in order to measure the animal response to the different concentrations of aP in these cultivars. Diet 3 was NB Diet 1 supplemented with iP to equal the concentration of aP in LPB Diet 2. Practical barley-soybean meal (SBM)-type diets, NB Diet 4 and LPB Diet 5, were formulated to meet all minimum nutrient requirements, and contained 0.30% aP and 0.65% Ca. For the semipurified diets, pigs fed LPB Diet 2 had higher (P < or = 0.05) bone ash weight, bone breaking strength, P absorption and retention, and Ca absorption and retention compared with pigs fed NB Diet 1, with a trend (P = 0.10) for pigs fed LPB Diet 2 to have a higher ADG and gain:feed ratio than pigs fed NB Diet 1. However, pigs fed LPB Diet 2 or NB Diet 3 were not different (P > or = 0.3) in growth performance, fresh bone weight, fat-free dry bone weight, bone ash, bone breaking strength, or N utilization. This indicates that LPB and NB were equal in nutritional value after supplementation of NB with iP to equal the estimated aP in LPB. For the practical barley-SBM diets, there were no differences (P > or = 0.4) between pigs fed NB Diet 4 or LPB Diet 5 for growth performance, fresh bone weight, bone breaking strength, the percentages of P and Ca utilization, or N, DE, and ME utilization. The use of LPB in pig diets reduced P excretion in swine waste by 55% and 16% in our semipurified and practical diets, respectively, compared with NB. Using our in vitro procedure designed to mimic the digestive system of the pig, the availability of P for pigs was estimated at 52% for LPB and 32% for NB.

Effects of Thermal Injury on Skeletal Metabolism in Two Strains of Mice

Long-term growth retardation occurs in children and osteopenias occur among children and adults who have been burned or suffer other injuries that result in a systemic inflammatory response. The purpose of this study was to define some of the growth, and to determine cancellous and cortical bone changes that occur following thermal injury in several contrasting strains of mice. Male C3H/HeN and Balb/c mice were given about a 20% total body thermal injury and 10 days later skeletal tissues were collected. The bone ash weights of the burned animals from both strains were less than their sham controls. In both strains, cancellous bone volumes were less in the burned animals than in their respective sham or baseline control groups. The loss of bone was particularly evident in the secondary spongiosa regions and also included a decrease in trabecular thickness and connectivity and an increase in trabecular separation. Longitudinal (endochondral) growth was suppressed in the burn animals. In the burned animals, indices of cancellous bone formation were substantially reduced whereas those in cortical bone were essentially nonexistent. The numbers of osteoclasts were increased in cancellous bone, and endocortical eroded surface was increased in the burn animals. These data show that there are rapid and profound changes in skeletal growth and metabolism in an experimental model of thermal injury. In general, a greater relative response was observed in the Balb/c vs. the C3H/HeN strain. Thermal injury resulted in a rapid and dramatic suppression of bone formation and endochondral growth with increased bone resorption in both cancellous and cortical bone.

Phosphorus requirement of finishing feedlot calves.

Dietary P supplied to feedlot cattle is important because an inadequate supply will compromise performance, whereas excess P may harm the environment. However, P requirements of feedlot cattle are not well documented. Therefore, 45 steer calves (265.2+/-16.6 kg) were individually fed to determine the P required for gain and bone integrity over a 204-d finishing period. The basal diet consisted of 33.5% high-moisture corn, 30% brewers grits, 20% corn bran, 7.5% cottonseed hulls, 3% tallow, and 6% supplement. Treatments consisted of 0.16 (no supplemental inorganic P), 0.22, 0.28, 0.34, and 0.40% P (DM basis). Supplemental P was provided by monosodium phosphate top-dressed to the daily feed allotment. Blood was sampled every 56 d to assess P status. At slaughter, phalanx and metacarpal bones were collected from the front leg to determine bone ash and assess P resorption from bone. Dry matter intake and ADG did not change linearly (P > 0.86) or quadratically (P > 0.28) due to P treatment. Feed efficiency was not influenced (P > 0.30) by P treatment and averaged 0.169. Plasma inorganic P averaged across d 56 to 204 responded quadratically, with calves fed 0.16% P having the lowest concentration of plasma inorganic P. However, plasma inorganic P concentration (5.7 mg/dL) for steers fed 0.16% P is generally considered adequate. Total bone ash weight was not influenced by dietary P for phalanx (P = 0.19) or metacarpal bones (P = 0.37). Total P intake ranged from 14.2 to 35.5 g/d. The NRC (1996) recommendation for these calves was 18.7 g/d, assuming 68% absorption. Based on performance results, P requirements for finishing calves is < 0.16% of diet DM or 14.2 g/d. Based on these observations, we suggest that typical grain-based feedlot cattle diets do not require supplementation of inorganic mineral P to meet P requirements.

Structural skeletal impairment induced by immunosuppressive therapy in rats: cyclosporine A vs tacrolimus.

The exact role of immunosuppressive drugs in the development of osteoporosis and pathologic fractures frequently reported in patients following organ transplantation is still not known. In two experiments, the effects of immunosuppressive drugs were studied on growing rats allocated randomly into five groups of eight rats each which received either FK506 (1.5 mg/kg or 3 mg/kg) or cyclosporine A (15 mg/kg or 30 mg/kg) for 28 days by daily oral gavage. In experiment I ( n=40), bone mineral content (BMC) of the femur by dual energy X-ray absorptiometry (DXA), and bone ash weight were measured. In experiment II ( n=40), stereologic measurements of decalcified tibiae were carried out. The BMC and ash weight values of the whole femur were significantly lower both in the low- and high-dose FK506 groups as well as in the high-dose CsA group. Decalcified sections showed lower volume density of trabecular bone of the tibial metaphysis in both CsA-treated groups and in the high-dose FK506 group. Furthermore, the volume density of the hypertrophic zone volume of the growth plate was higher in high-dose CsA-treated rats. Our data demonstrate that both CsA and FK506 have adverse effects on bone and that high doses of CsA or FK506 alter both cortical and trabecular bone with subsequent osteopenia. In addition, CsA-treated groups showed histological changes in some aspect resembling rickets/osteomalacia.

Structural skeletal impairment induced by immunosuppressive therapy in rats: cyclosporine A vs tacrolimus

Abstract The exact role of immunosuppressive drugs in the development of osteoporosis and pathologic fractures frequently reported in patients following organ transplantation is still not known. In two experiments, the effects of immunosuppressive drugs were studied on growing rats allocated randomly into five groups of eight rats each which received either FK506 (1.5 mg/kg or 3 mg/kg) or cyclosporine A (15 mg/kg or 30 mg/kg) for 28 days by daily oral gavage. In experiment I (n=40), bone mineral content (BMC) of the femur by dual energy X-ray absorptiometry (DXA), and bone ash weight were measured. In experiment II (n=40), stereologic measurements of decalcified tibiae were carried out. The BMC and ash weight values of the whole femur were significantly lower both in the low- and high-dose FK506 groups as well as in the high-dose CsA group. Decalcified sections showed lower volume density of trabecular bone of the tibial metaphysis in both CsA-treated groups and in the high-dose FK506 group. Furthermore, the volume density of the hypertrophic zone volume of the growth plate was higher in high-dose CsA-treated rats. Our data demonstrate that both CsA and FK506 have adverse effects on bone and that high doses of CsA or FK506 alter both cortical and trabecular bone with subsequent osteopenia. In addition, CsA-treated groups showed histological changes in some aspect resembling rickets osteomalacia.

Low-phytic acid barley improves calcium and phosphorus utilization and growth performance in growing pigs

Thirty-five crossbred barrows averaging 13.5 kg starting BW were used in a 35-d experiment to compare the availability of P and the nutritional value of two near-isogenic progeny of the barley cultivar 'Harrington'. Low-phytic acid barley (LPB, 0.35% total P, 0.14% phytic acid P) was homozygous for the low-phytic acid 1-1 allele, and the normal barley (NB, 0.35% total P, 0.24% phytic acid P) was homozygous for the normal allele of that gene. Pigs were fed individually twice daily in metabolism pens. Barley was the only source of phytate in semipurified diets, 1 to 3. Diet 1 contained 75% NB, 0.14% estimated available P (aP), and 0.50% Ca. Diet 2 contained 75% LPB, 0.22% aP, and 0.50% Ca. No inorganic P (iP) was added to Diets 1 and 2 in order to measure the animal response to the different concentrations of aP in these cultivars. Diet 3 was NB Diet 1 supplemented with iP to equal the concentration of aP in LPB Diet 2. Practical barley-soybean meal (SBM)-type diets, NB Diet 4 and LPB Diet 5, were formulated to meet all minimum nutrient requirements, and contained 0.30% aP and 0.65% Ca. For the semipurified diets, pigs fed LPB Diet 2 had higher (P < or = 0.05) bone ash weight, bone breaking strength, P absorption and retention, and Ca absorption and retention compared with pigs fed NB Diet 1, with a trend (P = 0.10) for pigs fed LPB Diet 2 to have a higher ADG and gain:feed ratio than pigs fed NB Diet 1. However, pigs fed LPB Diet 2 or NB Diet 3 were not different (P > or = 0.3) in growth performance, fresh bone weight, fat-free dry bone weight, bone ash, bone breaking strength, or N utilization. This indicates that LPB and NB were equal in nutritional value after supplementation of NB with iP to equal the estimated aP in LPB. For the practical barley-SBM diets, there were no differences (P > or = 0.4) between pigs fed NB Diet 4 or LPB Diet 5 for growth performance, fresh bone weight, bone breaking strength, the percentages of P and Ca utilization, or N, DE, and ME utilization. The use of LPB in pig diets reduced P excretion in swine waste by 55% and 16% in our semipurified and practical diets, respectively, compared with NB. Using our in vitro procedure designed to mimic the digestive system of the pig, the availability of P for pigs was estimated at 52% for LPB and 32% for NB.

Accuracy and precision of bone mineral density and bone mineral content in excised rat humeri using fan beam dual-energy X-ray absorptiometry

The aim of this study was the evaluation of fan beam dual-energy X-ray absorptiometry (DXA) for measuring bone mineral density (BMD) and bone mineral content (BMC) of isolated rat humeri. Defleshed rat humeri from male Lewis rats were examined with a Hologic QDR 4500 A (Hologic, Inc., Bedford, MA) high-resolution densitometer both in water and 0.9% saline solution. The small animal scan protocol with the regional high-resolution mode was used. BMC measured by DXA was compared with bone dry weight, ash weight, and bone calcium content. Furthermore, DXA BMD and BMC precision were determined. We also evaluated the effect of salinity of the water bath in which the bones were measured. Correlations (r2) of BMC, as determined by DXA with dry weight, ash weight, and bone calcium content, were 0.978, 0.988, and 0.890, respectively. DXA overestimated ash weight by 5%–9%. Precision errors for BMC (BMD) were 0.90% (0.76%) without and 1.3 (0.86) with repositioning. Changes in the salinity of the water bath had a significant influence on the DXA results: At the 0.9% physiological level, BMC (−4.4%) and area (−4.1%), but not BMD, values were significantly lower (p < 0.005) compared with measurements in tap water. Fan beam DXA is a highly accurate and precise technique for measuring BMC and BMD in excised small animal bones. A physiological saline concentration in the water bath had a significant impact on BMC and area, but not on BMD, and should therefore be strictly controlled to avoid an underestimation of BMC.

The effects of phytase on growth performance, carcass characteristics, and bone mineralization of late-finishing pigs fed maize–soyabean meal diets containing no supplemental phosphorus, zinc, copper and manganese

Late-finishing pigs ( n=408) with an average initial weight of 84 kg were used to evaluate the effects of supplementing microbial phytase to maize–soyabean meal diets in which sources of supplemental phosphorus (P), zinc (Zn), copper (Cu), and manganese (Mn) were removed. The four dietary treatments employed were: (1) positive-control which included a standard trace-mineral premix and inorganic P supplementation (1.6 g/kg available P, 4.6 g/kg Ca); (2) negative-control in which a trace-mineral premix without Zn, Cu, and Mn was fed, and no inorganic P was added (0.6 g/kg available P, 4.6 g/kg Ca); and the negative-control diet supplemented with either (3) 300; or (4) 500 U/kg microbial phytase. With the exception of available P, Zn, Mn and Cu, diets were formulated to meet or exceed National Research Council (NRC, 1998) nutrient recommendations for late-finishing pigs. Each supplementation regimen was fed to 102 pigs (6 pens of 17 pigs comprising triplicate replicates of both castrates and gilts) from 84 to 123 kg body weight. Removing inorganic P and selected trace minerals, or the addition of either 300 or 500 U/kg phytase to the negative-control diet did not affect ( P>0.10) weight gain, feed intake, or feed efficiency. Moreover, carcass characteristics were not affected ( P>0.10) by any of the supplementation strategies employed in this experiment. Metacarpal III and IV bone ash weight, however, was reduced ( P<0.05) in pigs fed the negative-control diet compared to the fully-supplemented positive-control diet and the diets containing added phytase. These data indicate that supplemental levels of inorganic P, Zn, Cu, and Mn can be reduced or eliminated without deleteriously affecting growth performance and carcass characteristics of late-finishing pigs.

Bone composition and strength of female rats subjected to different rates of weight reduction

Seventy-two rats (7 months old) were assigned into three dietary groups. The control group was fed ad lib AIN-76 diet, the R60 group a diet providing 60%, and the R40 group a diet providing 40% of the energy consumed by the control group. During the initial 4 weeks before switching to the R40 diet, the R40 group was fed the same as the control. At week 8, 8 rats each from R60 and R40 groups were given energy supplement plus the assigned diets for 4 weeks to regain their lost body weight before killed at week 12 (R60R and R40R groups). Eight rats from the control group were killed at the beginning. Eight rats each from the control, R60 and R40 groups were killed at week 8 and 12. Body weight of R60 group decreased within 8 weeks and that of R40 group did within 4 weeks both by 24% of their initial body weight, indicating the weight reduction rate for the R40 group was twice that of the R60 group. The R60 group had lower bone density, breaking strength, and bone Ca content (all at P<0.05) than the R40 group at week 8 and 12. Bone density, breaking strength, ash weight, and Ca content became lower from week 8 to week 12 for R60 and R40 groups. At week 12, fat-free bone weight, ash weight, and Ca content were higher for the control than for the other groups (P < 0.05), but they were not different between R60 and R60R or between R40 and R40R. In conclusion, body weight reduction at a slower rate resulted in more bone loss than a similar extent of weight reduction at a faster rate. Regardless of the weight reduction rate, bone density, breaking strength, ash weight, and Ca content could not recover along with body weight regain.

Metallothionein-null mice are more susceptible than wild-type mice to chronic CdCl(2)-induced bone injury.

Cadmium (Cd) is an environmental pollutant and is toxic to a number of organs. Chronic exposure to Cd causes loss of bone mass and increased incidence of bone fractures, as seen in Itai-itai patients and laboratory animals. Metallothionein (MT), a low-molecular weight, cysteine-rich, metal-binding protein, has been shown to play an important role in the detoxication of Cd. Thus, this study was designed to test the hypothesis that MT protects against Cd-induced bone injury. Wild-type and MT-I/II knockout (MT-null) mice were given repeated sc injections of CdCl(2) over a wide range of doses for 10 weeks, and Cd-induced bone injury was examined. Cd produced dose- and time-dependent increases in bone Cd content. However, the concentration of Cd in bone was much lower than that found in the liver and kidney (11 vs 400 and 120 microg/g, respectively) of the same mice. There was no difference in bone Cd content between wild-type and MT-null mice. Repeated Cd injections produced a dose-dependent loss of bone mass (up to 25%), as shown by analysis of the femur, tibia, and lumbar vertebrae. The loss of bone mass was more marked in MT-null mice than in wild-type mice, as shown by dry bone weight, defatted bone weight, bone ash weight, and total calcium content. X-ray photography showed decreasing bone density along the entire bone length with increasing dose and time of Cd exposure. The decrease in bone density was more marked in MT-null mice than in wild-type mice at the same dose and time points. Histopathology showed dilatation of haversian canals with increased osteoid seams, rounded osteocytes with expanded pericellular space, and expansion of hyperplastic bone marrow into metaphyseal cortical bone. Again, these lesions were more marked in MT-null mice. In conclusion, this study demonstrates that deficiency in MT renders animals more susceptible to Cd-induced bone mass loss and bone injury, and thus indicates that MT plays a protective role in Cd-induced toxicity in bone, as it does in other tissues.

Dietary Xylitol Protects Against Weakening of Bone Biomechanical Properties in Ovariectomized Rats

The effects of dietary xylitol (xyl) on bone biomechanical properties in ovariectomized rats (ovx) were studied. Forty-two 3-mo-old female Wistar rats were divided into three groups of 14. Rats in two groups were ovariectomized, while those in the control group underwent a sham operation. All rats received a basal diet, and half of the ovx were given an additional 10 g/100 g dietary xyl supplementation. Three months later the rats were killed and their tibias, femurs and humeri were prepared. The tibias were used for analyses of bone density and trabecular bone volume (BV/TV) and for the three-point bending test. The femurs were used for the torsion test and for the loading test of the femoral neck. The humeri were used for analyses of bone ash weight and bone concentrations of calcium and phosphorus. Dietary xyl gave a significant protection against ovariectomy-caused decline of tibial stress in the three-point bending test, of femoral shear stress in the torsion test, and of stress of the femoral neck, without affecting bone elasticity values. Xyl restricted the ovariectomy-caused reduction in bone density, in bone ash weight and in concentrations of bone calcium and phosphorus. Furthermore, trabecular bone loss in ovx was significantly suppressed by dietary xyl. These results indicate that a 10% dietary supplementation of xyl in ovx has a protective effect against the weakening of bone biomechanical properties. This is related to greater BV/TV and maintained bone mineral content.

A High Sucrose Diet Decreases the Mechanical Strength of Bones in Growing Rats

High sucrose diets alter mineral metabolism in humans and animals. We examined the effect of a high sucrose diet on bone growth, composition and mechanical strength in growing rats. Weanling Wistar rats received a high sucrose (43 g/100 g) diet (9 males, 11 females). In the control diet (8 males, 8 females), sucrose was replaced with potato starch, providing an equal energy value. At the onset of the experiment, bones were marked by tetracycline. After 5 wk, the tibias and femurs were weighed, and maximum breaking strengths were determined. Tibias were cut at the tibia-fibular junction; the widths of the bone at the start of the experiment, the periosteal bone formation during the experiment, the widths of the medullary cavity and the final bone width were determined from tetracycline lines. Bone ash weight, Ca and P contents were determined. The breaking strengths of both bones were significantly lower in the sucrose-fed groups of both sexes. In females, the weight of both bones and the final width of the tibias were significantly lower in the sucrose-fed group. The Ca concentration in both bones and the P concentration in tibias were significantly lower in the sucrose-fed group. It was concluded that the metabolic interference induced by sucrose was the reason for the differences. The alterations were more pronounced in females, but independent of body weight.

Lowering the dietary calcium to total phosphorus ratio increases phosphorus utilization in low-phosphorus corn-soybean meal diets supplemented with microbial phytase for growing-finishing pigs.

Crossbred growing-finishing pigs (n = 120) were used to investigate the effect of three dietary Ca:total P (tP) ratios (1.5:1, 1.3:1, or 1.0:1) on P utilization in low-P corn-soybean meal diets supplemented with microbial phytase at 500 phytase units/kg. The basal grower (23 to 54 kg BW) diet contained .39% tP including .07% added inorganic P (iP), and the basal finisher (54 to 123 kg BW) diet contained .32% tP without added iP. An adequate-P positive control diet without phytase supplementation contained .60% Ca and .50% tP during the growing phase and .50% Ca and .40% tP during the finishing phase. Lowering the Ca:tP ratio linearly increased ADG during the growing phase (P < .03) and overall (P < .08), gain:feed ratio during the growing phase (P < .001), and P absorption during the finishing phase (P < .04). Lowering the Ca:tP ratio linearly increased BW at slaughter (P < .02), carcass weight (P < .04), bone breaking strength (P < .04), and bone ash weight (P < .06), whereas dressing percentage and backfat depth remained unchanged. In conclusion, pig performance and P utilization were increased by lowering the Ca:tP ratio from 1.5:1 to 1.0:1 in low-P corn-soybean meal diets supplemented with microbial phytase.