Signalment differences in bone mineral content and bone mineral density in canine appendicular bones. A cadaveric study.

The objective was to determine signalment-related differences in bone mineral content (BMC) and bone mineral density (BMD) in dogs. Unilateral appendicular bones were harvested from 62 canine cadavers. Mid-diaphyseal regions of interest (ROIs) were scanned using a Hologic DXA device Braincon, Vienna, Austria). BMC and BMD were calculated within this region. Middle-aged dogs (3-10 years) revealed the highest BMC and BMD levels. Mean BMC and BMD were higher in males compared to females. Furthermore, body-weight of the male dogs was significantly higher compared to the females (P < 0.0001). Body weight and bone length were significantly associated with BMC and BMD (P < or = 0.023) in all bones but the radius. These data suggest that BMC and BMD appear to be highest in male large-breed dogs with a body weight greater than 30 kg. These results may help determine risk factors in fracture development and healing.     

Effect of prepubertal ovariohysterectomy on bone mineral density and bone mineral content in puppies

In this study, dual energy X-ray absorptiometry (DXA) was performed on the calcaneus (CAL) and accessory carpal bone (ACB) of early-age neutered (n = 11) and sham-operated puppies (n = 10) to investigate changes in bone mineral density (BMD) and bone mineral content (BMC) over time. Prepubertal ovariohysterectomy and sham surgery were performed at 10 weeks, while BMD and BMC were measured at 12, 16, 20 and 24 weeks of age. BMD and BMC of CAL and ACB of ovariohysterectomised puppies were found to be higher. The differences between the groups were statistically unimportant; however, the fourth measurement of the ACB showed a significant (P < 0.05) difference. Sexually intact puppies weighed less than gonadectomised puppies in all measurements. Because of the positive correlations between body weight and bone mineral density, BMD and BMC of early-age neutered puppies were found to be higher. These results suggest that BMD and BMC are not affected by prepubertal ovariohysterectomy until six months of age in mixed-breed puppies.     

Comparative assessment of bone mineral measurements obtained by use of dual-energy x-ray absorptiometry, peripheral quantitative computed tomography, and chemical-physical analyses in femurs of juvenile and adult dogs

OBJECTIVE: To compare bone mineral measurements obtained by use of dual-energy x-ray absorptiometry (DEXA), peripheral quantitative computed tomography (pQCT), and chemical-physical analyses and determine effects of age and femur size on values obtained for the various techniques. SAMPLE POPULATION: Femurs obtained from 15 juvenile and 15 adult large-breed dogs. PROCEDURE: n each femur, 7 regions of interest were examined by use of DEXA to measure the bone mineral content (BMC) and bone mineral density (BMD), and 5 were examined by use of pQCT to measure BMD. Among these, 1 region was examined by both noninvasive methods and an invasive method. Volume of the femur was determined by water displacement. Volumetric bone density (VBD) was calculated. Calcium (Ca), phosphorus (P), total Ca, and total P contents were determined. RESULTS: DEXA- and pQCT-derived results revealed that all values increased with age in juvenile dogs. In adults, VBD and pQCT-derived BMD decreased significantly and DEXA-derived BMD increased with increasing femur length.The pQCT-derived BMD correlated well with VBD and Ca content, whereas DEXA-derived BMC was strongly correlated with Ca content. In juveniles, values correlated regardless of the technique used, whereas in adult dogs, DEXA-derived BMD did not correlate with pQCT-derived BMD, Ca concentration, or VBD unless data were adjusted on the basis of femur length. CONCLUSIONS AND CLINICAL RELEVANCE: DEXA-derived BMD adjusted for femur length yields approximately the same percentage variability in VBD as for pQCT-derived BMD. However, pQCT-derived BMD is still more sensitive for determining variability BMD in Ca concentration, compared with DEXA-derived BMD adjusted for femur length.     

Bone and lean tissue changes following cranial cruciate ligament transection and stifle stabilization

Following cranial cruciate ligament transection and extracapsular stabilization, dual-energy X-ray absorptiometry was used to analyze bone mineral content and lean tissue mass in the surgical and nonsurgical legs (n=14) at 0, 2, 4, and 8 weeks, and to evaluate bone mineral content and bone mineral density (BMD) of the proximal, mid-, and distal tibia of both the surgical and nonsurgical legs (n=15) at 0, 5, and 10 weeks. There was significant loss of bone mineral content and lean tissue in the surgical leg compared to the nonsurgical leg. Significant loss in bone mineral content and BMD was detected in the tibia of the surgical leg and was most pronounced in the metaphyseal region.     

Age-related changes of bone mineral density and microarchitecture in miniature pigs

Bone mineral density (BMD), distribution of its density and bone histomorphometric parameters were evaluated in lumbar vertebra of normally growing miniature pigs. The fourth lumbar vertebra (L4) of the G?ttingen miniature pig were used in this cross-sectional study in vitro. The BMD of the miniature pig was similar to that of humans in tendency of gender differences and some growth patterns during puberty. In these regards this animal appears useful as a model for human bone study. However, the trabecular and cortical BMDs of lumbar spine were extremely high value (399.43 +/- 26.36 mg/cm(3) in female trabeculae; 973.06 +/- 69.55 mg/cm(3) in female cortical bone; 419.04 +/- 34.84 mg/cm(3) in male trabeculae; 1038.81 +/- 125.72 mg/cm(3) in male cortical bone in pigs 30 months or more). Furthermore, histomorphometric analysis yielded values that were remarkably different from those found in humans. From these results, it was revealed that miniature pig had a higher bone mass and denser trabecular network than human, indicating that its bone is probably stronger. Therefore, care should be taken in choosing the miniature pig as a bone study model.     

Influence of a vegetarian diet versus a diet with fishmeal on bone in growing pigs

This study was conducted to examine if substantial bone loss occurs in growing pigs fed a vegetarian diet in comparison with a diet containing fishmeal. Twelve 6-week-old weaned pigs were assigned to two groups: group V [vegetarian diet; 0.61% phosphorus (P) in dry matter until 25 kg and 0.46% P until the end of the experiment] and group F (fishmeal diet; 0.61% P in dry matter until 25 kg and 0.46% P until the end of the experiment). Phytase was added to both diets. These two diets were fed to the two groups for a period of 6 weeks. Blood samples were collected weekly, faeces were collected three times a week. Concentrations of osteocalcin (OC) and carboxyterminal telopeptide of type I collagen (ICTP) were measured in serum, using a radioimmunoassay, and bone-specific alkaline phosphatase (bAP) was measured using an enzyme immunoassay. Bone mineral density (BMD) and content (BMC) were determined by peripheral quantitative computer tomography (pQCT) in the tibia and phalanx. In addition, 1,25-dihydroxyvitamin D (VitD) and parathyroid hormone (PTH) were measured in serum. The digestibility of P was significantly decreased in group V. Significant changes in bAP activities and OC concentrations occurred with time during the 6 weeks. ICTP concentrations were significantly higher in group V. Total BMC and BMD in the tibia and BMD in the phalanx significantly decreased in group V. The results show that a vegetarian diet induces a significant loss of bone and a higher bone formation in group V compared with group F, although phytase was added to both diets. The dietary requirements for P in pigs, especially in the context of feeding vegetarian diets and adding an appropriate amount of phytase, should be investigated further.     

Bone mineral density and bone mineral content of the bilateral first phalanges of the thoracic limbs in horses

The bone mineral density (BMD) and the bone mineral content (BMC) in the bone tissue of the bilateral first phalanges of horses' thoracic limbs were analysed. The research material consisted of isolated pastern bones derived from 22 horses. The research was conducted with the use of a Norland model Excell Plus densitometer (Fort Atkinson WI, USA), using affinited beam X-ray technology and an animal research programme (Research Scan, 3.9.6. version) at the following parameters: scanning resolution of 1.5 x 1.5 mm, scanning speed 60 mm/s. The differences between BMC and BMD values in bilateral first phalanges in the thoracic limbs in horses were found to be nonsignificant. It also appeared that there are statistically significant positive correlations between values of the left and right bone of both analysed variables.     

Bone development of suckling piglets after prenatal,neonatal or perinatal treatment with dexamethasone

In mammals, the release from growth‐inhibiting conditions results in catch‐up growth. To investigate animal evidence for whether prenatal dexamethasone (DEX) treatment leads to the development of growth restriction especially reduced mineralization of skeleton, and release from it leads to the phenomenon of catch‐up, piglets were prenatally exposed to DEX (3.0 mg/sow per day^?2) during the last 24 days of prenatal life and tested further in two different ways: discontinued at birth and continued administration of DEX (0.5 mg/kg day^?2) to piglets through 30 days of neonatal life. Using dual energy X‐ray absorptiometry methods, bone mineral density (BMD) and bone mineral content (BMC) were measured. The three‐point bending test was applied to determine the mechanical properties of the bones. Furthermore, geometric properties of the bones were assessed. Serum concentration of osteocalcin (OC) was determined. Histomorphological analysis of the ribs was also performed. The consequences of neonate DEX treatment and in utero DEX exposure were reflected in a dramatic decrease of BMD, BMC and blood serum OC concentration and geometric parameters of piglets’ bones. Prenatal action of DEX during the last 24 days of pregnancy resulted in continued neonatal modification of bone tissues, thus diminishing bone quality, and negatively influenced structural development and mechanical properties, finally increasing the risk of fractures of ribs and limb bones. Prenatal DEX treatment limited to the last 24 days of foetal life did not reduce the term birth weight and the growth of suckling piglets followed up to 30 days of neonatal life, and catch‐up in bone mineralization did not occur.     

In growing pigs, chlortetracycline induces a reversible green bone discoloration and a persistent increase of bone mineral density dependent of dosing regimen

We studied in growing pigs the effects of exposure to dietary chlortetracycline on bone mineral density (BMD) and bone color. Pigs were randomly allocated to a drug-free diet (n = 48) or a diet fortified with 800 ppm of chlortetracycline, starting either at 28- or 84-d of age, and for either a 28- or 56-d duration (n = 16 pigs/group). The lumbar vertebral discoloration and BMD of randomly chosen pigs were evaluated at 28-d intervals up to 168-d of age. The odds of bone discoloration increased with dosing duration and age at treatment onset, and decreased with the withdrawal time and age at treatment onset interaction (p ? 0.001). The measured trabecular BMD linearly increased with age and squared treatment duration (p ? 0.005). Therefore, TC-induced bone discoloration is reversible, and may be prevented with proper dosing regimen design. Moreover, TC induces a persistent increase on BMD that could be detected with quantitative computed tomography.     

Influence of phytase added to a vegetarian diet on bone metabolism in pregnant and lactating sows

The purpose of the study was to find out if the supplementation of phytase to a diet of gestating and lactating sows has any effects on performance and bone parameters of the animals. Forty primiparous gilts were assigned into four groups: group A with phytase [4.2 g total phosphorus (P)/kg (gestation) and 4.5 g total P/kg (lactation)], group B without phytase (with phytase supplementation in diet for rearing) and same P content as group A, group C without phytase and higher P contents [5.0 g total P/kg (gestation) and 5.5 g total P/kg (lactation)] and group D with the same diet as group B (no phytase during the rearing). A 6-phytase was used in this trial (750 FTU/kg diet). The four diets were fed during gestation and lactation. Faeces were collected to determine apparent digestibility of minerals. Blood samples were taken to analyse minerals and bone markers. After weaning the sows were slaughtered and the bones of one hind leg were prepared to measure bone mineral density (BMD) and bone mineral content (BMC) of the tibia. Bone ash and mineral content of the phalanx III were determined. Mean P concentrations in serum decreased during gestation and lactation. But there were no significant differences between the groups. Bone formation marker bone-specific alkaline phosphatase decreased at the beginning of lactation whereas bone resorption marker serum crosslaps increased. The BMD and BMC of the tibia were slightly higher in the groups fed higher concentrations of P and phytase. The ash and mineral contents of the phalanx were the highest for the group fed the highest concentration of P. The apparent digestibility of P increased during gestation mostly in group A (57%--> 69%). In conclusion, high P content and addition of phytase to the diet induced a slightly higher ash content of the bones. It is of high importance, that sows during gestation absorb enough P, to avoid lamenesses and sudden fractures. As not many studies with phytase have been performed during gestation and lactation in sows yet, we can recommend, that phytase as supplement can be used to keep P in the diet at a lower level without negative consequences for bone health.     

Influence of dietary phosphorus deficiency with or without addition of fumaric acid to a diet in pigs on bone parameters

The purpose of this study was to examine if substantial bone loss occurs in weaned pigs by feeding a phosphorus-deficient diet with or without fumaric acid. Eighteen weaned pigs were used. The animals were assigned to three groups: group C (control; 0.65% P on DM basis), group LP (low phosphorus; 0.37% P on DM basis) and group LPF (low phosphorus plus fumaric acid; 0.35% P on DM basis plus 2% fumaric acid). These three diets were fed to the groups for a period of four weeks after a two-week adaptation period. Blood samples were collected once a week. Carboxyterminal telopeptide of type I collagen (ICTP) in serum was used as a bone resorption marker. Osteocalcin (OC) and bone-specific alkaline phosphatase (bAP) were used as bone formation markers. Bone mineral density (BMD) and content (BMC) were determined by peripheral quantitative computer tomography. BAP activities significantly increased (24%) in group LPF, and at the last sampling day group LPF had significantly increased activities in comparison to group C. In contrast, ICTP concentrations significantly increased with time in group LP and LPF, and at the last sampling day group LPF had significantly increased activities in comparison to group C. BMD and BMC in femur and tibia significantly decreased in group LP and LPF. The results show that P-deficient diets induce a bone loss. Fumaric acid did not influence the degree of bone loss. With a better understanding of its effect on bone, dietary phosphorus requirements in pigs could be more precisely defined.     

Effect of human growth hormone-releasing factor on bone and mineral metabolism in growing pigs

Little information is available on the effects of growth hormone (GH) and growth hormone-releasing factor (GRF and GHRH) treatment on bone metabolism in pigs. Thus, tibial bending moments and ash contents were studied in 12, 6-wk-old pigs weighing 13 +/- .2 kg. Six pigs (GRF group) were injected s.c. twice daily with 75 micrograms GRF (hGRF [1-29] NH2)/kg BW for 52 d and six remained untreated (control group, C). Average daily gain was slightly (5%; P less than .10) increased in treated pigs. At slaughter, plasma measurements related to calcium homeostasis, such as concentrations of Ca, inorganic P, and vitamin D metabolites (25-OH and 1,25-(OH)2 vitamin D3), were not changed by GRF injection. At slaughter, plasma GH levels were 3.3 times greater in treated (11.3 +/- 3 ng/ml) than in untreated pigs (3.4 +/- .5 ng/ml, P less than .02), whereas those of insulin-like growth factor I were increased by approximately 38%. No difference was observed between the two groups at slaughter in tibial weight, density, bending moment, ash relative to bone volume (29 +/- 1 vs 30 +/- 2 g/100 cm3, GRF vs C), total ash content, or ash relative to dry matter in cortical or medullary bone. Our GRF treatment did not affect bone and mineral metabolism in young, growing pigs.     

Influence of a novel consensus bacterial 6-phytase variant on mineral digestibility and bone ash in young growing pigs fed diets with different concentrations of phytate-bound phosphorus

A 20-d experiment was conducted to test the hypothesis that phytase increases nutrient digestibility, bone ash, and growth performance of pigs fed diets containing 0.23%, 0.29%, or 0.35% phytate-bound P. Within each level of phytate, five diets were formulated to contain 0, 500, 1,000, 2,000, or 4,000 phytase units (FTU)/kg of a novel phytase (PhyG). Three reference diets were formulated by adding a commercial Buttiauxella phytase (PhyB) at 1,000 FTU/kg to diets containing 0.23%, 0.29%, or 0.35% phytate-bound P. A randomized complete block design with 144 individually housed pigs (12.70 ± 4.01 kg), 18 diets, and 8 replicate pigs per diet was used. Pigs were adapted to diets for 15 d followed by 4 d of fecal collection. Femurs were collected on the last day of the experiment. Results indicated that diets containing 0.35% phytate-bound P had reduced (P < 0.01) digestibility of Ca, P, Mg, and K compared with diets containing less phytate-bound P. Due to increased concentration of total P in diets with high phytate, apparent total tract digestible P and bone ash were increased by PhyG to a greater extent in diets with 0.29% or 0.35% phytate-bound P than in diets with 0.23% phytate-bound P (interaction, P < 0.05). At 1,000 FTU/kg, PhyG increased P digestibility and bone P more (P < 0.05) than PhyB. The PhyG increased (P < 0.01) pig growth performance, and pigs fed diets containing 0.35% or 0.29% phytate-bound P performed better (P < 0.01) than pigs fed the 0.23% phytate-bound P diets. In conclusion, the novel phytase (i.e., PhyG) is effective in increasing bone ash, mineral digestibility, and growth performance of pigs regardless of dietary phytate level.     

Effect of dietary inulin and phytase on mineral digestibility and tissue retention in weanling and growing Swine

The effect of dietary phytase and the prebiotic inulin on apparent mineral digestibility, bone mineralization, and tissue mineral contents was evaluated in weanling and growing pigs. In Exp. 1, inulin and phytase were incorporated in a 2 × 3 factorial arrangement of treatments with 8 replicate pens per treatment in a randomized complete block design. There were 2 levels of phytase [0 and 1000 phytase units (FTU)/kg] and 3 levels of chicory inulin (0, 3, and 6%). Weanling pigs (17 d of age; 5 or 4 pigs per pen) with an initial BW of 6.0 ± 0.6 kg were evaluated for 35 d postweaning. Macromineral digestibility was calculated using chromic oxide as an index in fecal samples collected during the final week of the experiment in replicates 1 through 4. On d 36, 1 pig per pen was killed and the heart, liver, kidney, and left tibia were excised and weighed. Inulin did not have any effect on growth performance measurements. Phytase increased (P < 0.05) BW on d 35 and ADG and ADFI during the 21-to-35-d and 0-to-35-d periods. Inulin did not result in increased tissue mineral concentrations on a per unit (mg/kg) or total tissue basis. Phytase increased (P < 0.05) the concentration of Zn in the liver, Mn and Zn in the heart, and Mg and Mn in the kidney. Phytase also increased (P < 0.05) total P, Mg, S, Mn, Se, and Zn in the liver as well as tibia ash. Phytase increased the digestibility of Ca (P < 0.01) and P (P < 0.05). Experiment 2 was conducted with growing pigs (initial BW, 41 ± 5 kg) to evaluate 2 levels of inulin (0 or 6%) and 2 levels of phytase (0 or 1000 FTU/kg) in a 2 × 2 factorial with 6 replicates in a randomized complete block design. Total urine and feces were collected for 10 d from each of 24 barrows after a 21-d acclimation period. Inulin inclusion resulted in reduced Ca digestibility (P < 0.05). Phytase increased (P < 0.05) the digestibility of both Ca and P. These results indicate that dietary inulin does not affect the overall mineral status or growth performance of pigs, whereas phytase increases the utilization of Ca and several microminerals, in addition to P, and also increases growth performance. Inulin and phytase do not appear to interact to affect pig growth or mineral status.     

Vertebral mineral density measured by dual-energy X-ray absorptiometry (DEXA) in a group of healthy Italian boxer dogs

We studied the feasibility of using dual-energy X-ray absorptiometry (DEXA) to obtain reference bone density values in relation to age, gender and body weight in growing and young adult Italian boxer dogs. The study was performed on eight animals (three males and five females) at 7, 12 and 18 months of age. Animals were carefully examined and blood samples were collected from each dog to detect any sign of metabolic and/or endocrine disease. Each subject underwent radiographs to evaluate growth of the spine and hip. One female was not considered in the statistical model because of the development of grade 4 spondylosis deformans during the study period. All animals were serially scanned using DEXA; the region of interest was the whole spine T12-L2, while the subregions of interest were the four vertebrae (T12-T13-L1-L2) within the scanned spine. Statistical analysis was performed separately for each region of interest. Age had the strongest relationship with bone density (P < 0.001). Gender effect on spinal mineral density was not significant while vertebral site effect was highly significant. Average bone mineral density (BMD) +/- SD for the whole spine trait was 0.862 +/- 0.108 g/cm2 while average BMD +/- SD for subregions of interest ranged from 0.836 +/- 0.141 g/cm2 for T12 to 0.928 +/- 0.119 g/cm2 for L2. Estimated reference BMD values at 7, 12 and 18 months of age for each vertebral site in males and females are provided.     

Leg weakness in pigs. I. Incidence and relationship to skeletal lesions, feed level, protein and mineral supply, exercise and exterior conformation

Out of 373 Landrace boars and gilts involved in feeding experiments, 18.2 % showed severe degree leg weakness and 30 % mild degree leg weakness at 100 kg live weight. Of the boars at pig A.I. stations 23.9 % were slaughtered because of leg weakness, 75 % of these being under 1½ years. The practical significance of leg weakness is greatest in young breeding stock. High feed level in slaughter pigs resulted in poorer locomotory ability than medium feed level. Exercise resulted in pigs showing better movements. Variations of minerals and protein within limits used in practical feeding did not have any influence on the incidence of leg weakness. There was no statistically significant relationship (P > 0.05) between joint lesions and locomotory ability in pigs at 100 kg live weight, although severe lesions seemed to lead to poorer mobility. The joint regions which seemed to be mainly involved in severe degree leg weakness in boars were the elbow and stifle joints (31.3 %), the lumbar intervertebral joints (28.1 %) and the hip region (15.6 %). There was a significant relationship between narrow lumbar region, broad hams, large relative width between the stifle joints, and poor locomotory ability in slaughter pigs.     

The influence of dietary crude protein intake on bone and mineral metabolism in sheep

Increased dietary protein consumption is thought to cause calciuresis, a negative calcium balance and increased bone loss that may result in skeletal deformities and fracture. To explore this hypothesis, 40 approximately 100-day-old meat-type Merino ram lambs were fed, for 6 months, diets with an increasing crude protein (CP) content (114, 142, 171 and 190 g/kg DM) but approximately on an iso-nutrient basis with regard to metabolisable energy, calcium and phosphorus. Increased protein consumption modestly (NS) enhanced calciuresis and resulted in significant (P < or = 0.01) limb skewness. This could not, however, be ascribed to osteopaenic bones, and compared with animals consuming lower protein rations, the bone mineral density (BMD) and vertebral trabecular bone volume of animals fed high protein diets were significantly increased: the BMD of thoracic vertebrae was positively related to the CP intake (r = 0.62; P < or = 0.001). In animals consuming higher protein diets, skeletal radiology and quantitative bone histology revealed no evidence of increased bone turnover as would be expected in animals that are in negative calcium balance. No relationship existed between limb skewness and the growth rate of lambs. However, the ratio of Ca:P in the forelimb (r = -0.98), vertebrae (r = -0.72) and rib (r = -0.42) was found to be inversely correlated with increased protein intake and resulted from an increase in the phosphorus content of bone, while the amount of bone calcium was unaffected. We conclude that qualitative micro-architectural abnormalities, and not mere bone loss, may underlie the skeletal deformities induced by increased protein consumption in sheep.     

Relationship between bone strength and dual-energy X-ray absorptiometry measurements in pigs

Computed tomography and a 3-point bending test were performed on the metacarpal bones of adult production pigs to test the hypothesis that bone strength is strongly correlated with areal bone mineral density (BMD) in this population. The aim of the study was to subject material from adult production pigs grouped by BMD to 3-point bending, to test this hypothesis and determine any correlations. In all, 168 individual computed tomography scans and mechanical tests were performed on the collected material. For evaluation purposes, the material was divided into the categories low, medium, and high BMD (<1, 1 to 1.4, and >1.4 g/cm(2), respectively). The results showed a difference in the maximum load, in the stress at maximum load, and stiffness among each BMD group (P < 0.001) and in elastic modulus between the low BMD group and the 2 other groups (P < 0.001). A correlation between both intrinsic and extrinsic measures of bone strength and BMD was thus demonstrated. The projected change in each of the variables reported, for a 0.1 g/cm(2) alteration in BMD (within the BMD range evaluated in this study), is as follows: maximum load, 708 N; stress at maximum load, 50 N/mm(2); stiffness, 391.6 N/mm; and elastic modulus, 108 N/mm(2) (P < 0.001). The results confirm the relationship between BMD and bone strength and indicate that BMD screening can be used in fracture risk assessments in production pigs.     

Impact of supplement withdrawal and wheat middling inclusion on bone metabolism, bone strength, and the incidence of bone fractures occurring at slaughter in pigs

The objective of this study was to determine if supplement withdrawal (omission of dietary vitamin and trace mineral premixes and 2/3 of inorganic P) 28-d preslaughter and the feeding of wheat middlings (dietary concentrations of 5, 15, or 30% from weaning to 16 kg, 16 to 28 kg, and 28 kg to slaughter, respectively) affect bone metabolism, bone strength, bone density, and the incidence of bone fractures at slaughter in pigs. Crossbred barrows (n = 64) were assigned to a 2 x 2 factorial arrangement of treatments (with or without supplement withdrawal, and with or without wheat middlings). Serum was collected on d 0, 14, and 27 of the preslaughter withdrawal period to determine changes in the concentrations of osteocalcin, an indicator of bone formation, and pyridinoline, an indicator of bone resorption. The serum osteocalcin and pyridinoline concentrations on d 14 and 27 were analyzed as change from the d-0 concentration. At slaughter, radiographs of the lumbar vertebrae and of the right and left femurs were taken to determine the incidence of bone fractures. Third metacarpal bones were analyzed for bone mineral density, peak load, ultimate shear stress, and percent ash. Supplement withdrawal increased (P < 0.05) serum osteocalcin and pyridinoline concentrations, indicating an increase in osteoblast activity and bone resorption. Supplement withdrawal decreased (P < 0.01) bone mineral density, peak load, ultimate shear stress, and percent ash of the metacarpal bones. Dietary wheat middling inclusion did not alter bone quality. Neither supplement withdrawal nor wheat middling inclusion affected the incidence of bone fractures at slaughter. The results of this study indicate that removing inorganic P, vitamin premix, and trace mineral premix for 28 d preslaughter increases bone turnover and decreases bone quality.