Influence of age and housing systems on properties of tibia and humerus of Lohmann White hens1: Bone properties of laying hens in commercial housing systems.

This study was aimed at analyzing bone properties of Lohmann White hens in different commercial housing systems at various points throughout production. Pullets reared in conventional cages (CC) were either continued in CC or moved to enriched colony cages (EN) at 19 weeks. Pullets reared in cage-free aviaries (AV) were moved to AV hen houses. Bone samples were collected from 60 hens at each of 18 and 72 wk and 30 hens at 26 and 56 wk from each housing system. Left tibiae and humeri were broken under uniform bending to analyze mechanical properties. Cortical geometry was analyzed using digital calipers at the fracture site. Contralateral tibiae and humeri were used for measurement of ash percentage. AV pullets' humeri had 41% greater cortical areas, and tibiae had 19% greater cortical areas than the CC pullets (P < 0.05). Average humeri diameter was greater in AV pullets than in CC pullets (P < 0.05), whereas the tibiae outer dimensions were similar. Aviary pullet bones had greater stiffness (31 and 7% greater for tibiae and humeri, respectively) and second moment of inertia (43 and 13% greater for tibiae and humeri, respectively) than CC pullets (P < 0.05). The differences between bones of AV and CC hens persisted throughout the laying cycle. Moving CC pullets to EN resulted in decreased endosteal resorption in humeri, evident by a 7.5% greater cortical area in the EN hens (P < 0.05). Whole-bone breaking strength did not change with age. Stiffness increased with age, while energy to failure decreased in both the tibiae and humeri. These results indicated that tibiae and humeri of laying hens become stiffer but lose toughness and become brittle with age. Furthermore, AV and EN systems can bring positive changes in mechanical and structural properties that are more pronounced in the humerus than the tibia.

Housing conditions alter properties of the tibia and humerus during the laying phase in Lohmann white Leghorn hens.

Osteoporosis in caged hens is one driving factor for the United States egg industry to explore options regarding alternative housing systems for laying hens. The aim of our research was to study the influence of housing systems on tibiae and humeri of 77-week-old Lohmann White hens. Pullets raised in an aviary system were either continued in aviary hen systems (AV) or conventional cages (AC) whereas pullets reared in conventional cages continued in conventional hen cages (CC) or enriched colony cages (EN) at 19 weeks. From each group, 120 hens were randomly euthanized and right and left tibae and humeri were excised for structural and mechanical analysis. Volumetric density of the cortical bone was measured using quantitative computed tomography (QCT). Aviary (AV) hens had greater cortical thickness and density but similar outer dimensions to AC hens (P < 0.05). Hens in EN system had humeri with similar cortical thickness and density but wider outer dimensions than the humeri of CC hens (P < 0.05). Cortical geometry of the tibiae was the same for the EN and CC hens, whereas EN hens had denser tibial cortex than CC hens (P < 0.05). Geometrical changes in the humeri suggest that hens in the AV system were better able to protect their structure from endosteal resorption during the laying phase. Humeri of AV and EN hens had increased second moment of area compared to the AC and CC hens; however, the changes were not observed in tibiae. Mechanical property differences were observed, with bones of AV hens having greater failure moment and stiffness than AC hens and the same difference was observed between the EN and CC hens, (P < 0.05). These findings indicate that movement limitation causes loss of bone mass and density whereas provision of moderate movement increases certain bone quality parameters during adulthood in laying hens.

Effect of rearing environment on bone growth of pullets.

Alternative housing systems for laying hens provide mechanical loading and help reduce bone loss. Moreover, achieving greater peak bone mass during pullet phase can be crucial to prevent fractures in the production period. The aim of this study was to determine the housing system effects on bone quality of pullets. Tibiae and humeri of White Leghorn pullets reared in conventional cages (CCs) and a cage-free aviary (AV) system were studied. At 16 wk, 120 birds at random from each housing system were euthanized. Right and left tibiae and humeri were collected and further analyzed. Cortical bone density and thickness were measured using computed tomography. Periosteal and endosteal dimensions were measured at the fracture site during mechanical testing. At 4, 8, 12, and 16 wk, serum concentrations of osteocalcin and hydroxylysyl pyridinoline were analyzed as markers of bone formation and resorption. Cortical bone density was higher (P<0.05) in humeri of AV pullets, and tibiae were denser (P<0.05) for AV pullets in the distal section of the bone compared to CC pullets. Ash content was higher (P<0.05) in AV humeri with no difference in tibiae ash content. Tibiae and humeri of AV pullets had a thicker cortex than the CC pullets (P<0.05). Additionally, the tibiae and humeri of AV pullets had greater (P<0.05) second moment of areas than the CC pullets. While some bone material properties between groups were different (P<0.05), the differences were so small (<7%) that they likely have no clinical significance. Serum osteocalcin concentrations were not different between the treatments, but hydroxylsyl pyridinoline concentrations were higher in CC pullets at 12 wk compared to the AV pullets and the effect reversed at 16 wk (P<0.05). These findings indicate that tibiae and humeri respond differently to load bearing activities during growth. The improved load bearing capability and stiffness in bones of AV pullets were related to increased cross-sectional geometry.

The impact of dietary long-chain polyunsaturated fatty acids on bone and cartilage in gilts and sows.

Dietary long-chain PFO including arachidonic acid (ARA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) are precursors for several inflammatory mediators. The objective of this study was to characterize the effects of dietary PFO supplementation on bone, cartilage, and synovial fluid in 2 ages of pigs. Sows and gilts were fed either control corn/soybean meal based diets or the control diet supplemented with PFO from Gromega (PFO; JBS United, Sheridan, IN). Sows were fed their diets for 24.5 mo and slaughtered at 43 mo while gilts were fed their diets from weaning until slaughter at 111 kg. Cartilage was harvested from both humeroulnar joints of 14 sows (7/treatment) and 16 gilts (8/treatment) within 30 h of slaughter for fatty acid analysis and explant cultures. Synovial fluid was collected from the carpal joints of each pig postmortem. The right fused radius/ulna was collected for computed tomography (CT) analysis. Cortical width and density were determined and trabecular density was measured at the distal radius. Cartilage explants were allocated to 24-well culture plates with 2 discs per well and cultured over 72 h at 37°C in serum-free Dulbecco's modified Eagle's medium: nutrient mixture F-12 (Ham) medium. Six wells/pig were treated with 10 ng/mL of recombinant porcine interleukin-1 (rpIL-1). At 24, 48, and 72 h of culture, media were removed and reserved for analysis of proteoglycans, nitric oxide (NO), and PGE2 concentrations. The CT scans of the radius/ulna from gilts revealed no differences for cortical width and bone density. Sows fed PFO had greater cortical width of the proximal ulna (P < 0.05) and decreased cortical width of the distal radius (P < 0.05). Sows fed PFO had increased DHA (P < 0.01) and a decrease in the omega-6 to omega-3 ratio (P < 0.05) in cartilage. Gilts fed PFO had increased DHA (P < 0.01), C22:1 (P < 0.01), and docosapentaenoic acid (P < 0.01) and a tendency for increased EPA (P = 0.093) concentrations in cartilage. Changes in dietary fatty acids in the gilts and sows had no effect on the variables tested in vitro. Although the PFO diet increased omega-3 incorporation into chondrocytes, the biological significance is unclear since concentrations of ARA were at least 9-fold higher than EPA or DHA. Therefore, if omega-3 fatty acids can mitigate inflammation in joints, the benefit would likely either be the result of systemic changes in inflammatory mediators or higher concentrations in the diet.

Bone characteristics and femoral strength in commercial toms: the effect of protein and energy restriction.

Selection for rapid growth in turkeys has resulted in skeletal problems such as femoral fractures. Slowing growth rate has improved bone structure, but the effect on mechanical properties of the bone is unclear. The current study's hypothesis was that slowing the growth of turkeys by reducing energy and CP in the diet would result in increased femur integrity. Commercial turkeys were fed 1 of 3 diets: control with 100% of NRC energy and CP levels, as well as a diet feeding 80 or 60% of NRC energy and CP levels. All other nutrients met or exceeded NRC requirements. Control birds were grown to 20 wk of age, whereas the 80 and 60% NRC birds were sampled when BW matched that of control birds at wk 4, 8, 12, 16, and 20. Both femurs were extracted, with one being measured and ashed and the other twisted to failure to evaluate mechanical properties. Total bone length, diameter, cortical thickness, and cortical density were measured. The total femur length was longer in the 60% NRC birds at 5 and 10 kg of BW compared with control (P < 0.05); this significance was lost by the time birds reached 16 kg of BW. At 5 and 10 kg of BW, ash content was higher in the control birds than in the 60% NRC birds (P < 0.05). At 16 kg of BW, the 60% NRC birds had the highest femur ash (P < 0.05). The mechanical testing parameters were failure torque, shear strength, and shear modulus of the bones. The 60% diet produced the highest failure torque (P < 0.05), at 16 kg of BW and onward. The shear strength was greater (P = 0.01) once the birds reached 5 kg of BW for the 60% diet than other diets. In conclusion, reducing the energy and protein in the diet to 60% of NRC recommendations, thus slowing growth, improved bone strength, as measured by failure torque, and bone quality, as measured by shear strength, without altering bone length or ash content by the time birds reached market weight.

The effect of dietary phosphorus on bone development in dairy heifers.

Phosphorus requirements, as percent of dietary dry matter for heifers (0.20-0.35%) and endogenous levels of P in feeds (0.20-0.35% of dry matter) are similar, suggesting that supplementation of P in heifer diets may be infrequently required. Because long-term studies are unavailable, 183 Holstein heifers and 182 Holstein x Jersey crossbred heifers were fed diets with (0.39%) and without (0.29%) supplemental P from 4 to 21 mo of age in a replicated pen design. Two subpopulations of heifers were selected mid-trial for intensive measurement of bone development and metabolism. Thirty-two heifers at 628 d (+/-10.0 d) of age, balanced by breed and diet, were evaluated for bone development. External frame measurements included hip height, length, heart girth, hip width, cannon bone circumference, pelvic length, pelvic height, and pelvic width. Tails of heifers were surgically amputated with the 13 and 14th coccygeal vertebrae retained. After tissue removal, the 13th coccygeal vertebrae were scanned using peripheral quantitative computed tomography with cortical, trabecular, and total bone densities determined. A second subpopulation (n = 64) of heifers (375 d +/- 33 d), balanced for breed and diet, were evaluated for serum pyridinoline and osteocalcin to assess systemic bone metabolism. Data were analyzed as a completely randomized design with breed, treatment, and their interaction in the model. External skeletal measurements revealed significant differences in hip height, hip width, heart girth, cannon bone circumference, and pelvic length between Holstein and crossbred heifers. Supplementing P had no effect on external frame measurements, bone density, or bone metabolism markers. Bone P content was lower (18.1 vs. 18.6%) in heifers fed no supplemental P. Data suggest P supplementation to heifers modestly increased bone P content but increased bone P was not reflected in frame growth, bone density, or bone metabolism.

Sodium zeolite a supplementation and its impact on the skeleton of dairy calves.

Twenty calves were placed on study at 3 days of age and were placed according to birth order into one of two groups: SS, which received 0.05% BW sodium zeolite A (SZA) added to their milk replacer, and CO, which received only milk replacer. Blood samples were taken on days 0, 30, and 60 for osteocalcin (OC) and deoxypyridinoline (DPD) analysis. On day 60, the calves were euthanized, and synovial fluid, articular cartilage, and both fused metacarpals were collected for bone quality analyses such as architecture and mechanical properties, mineral composition, and glycosaminoglycan concentration. There were no differences in OC concentrations because of treatment (p = 0.12), and CO calves had lower DPD concentrations than SS calves (p = 0.01), but the OC-to-DPD ratio was not different between treatments (p = 0.98). No differences in bone architecture or mechanical properties were detected. SZA supplementation increased cortical bone (p = 0.0002) and articular cartilage (p = 0.05) aluminum content. Glycosaminoglycan concentrations were not different in synovial fluid or cartilage. Supplementation of SZA appeared to alter the rate of bone turnover without altering bone strength. Aluminum concentrations in the bone and cartilage increased, which may be a concern, although the long-term consequences of such remain to be determined.

Tissue response to a supplement high in aluminum and silicon.

The objective was to determine the effects of sodium zeolite A (SZA) on mineral metabolism and tissue mineral composition in calves. Twenty calves were placed on study at 3 days of age and were placed into one of two groups: SS, which received 0.05% BW SZA added to their milk replacer, and CO, which received only milk replacer. Blood samples were taken on days 0, 30, and 60 for mineral analysis. Urine and feces were collected on day 30 for mineral metabolism, and on day 60, the calves were euthanized, and samples were taken from numerous organs for mineral analyses. Aluminum retention was increased in the SS calves (p = 0.001). Silicon concentrations were increased in the aorta, spleen, lung, muscle, and kidney of the SS calves, and aluminum was increased in all SS tissues (p < 0.05). Calcium concentrations were increased in aorta, liver, muscle, and tendon; phosphorus concentrations were increased in aorta, but decreased in plasma; magnesium concentrations were increased in aorta, heart, kidney, liver, and pancreas, but decreased in plasma; and iron concentrations were decreased in kidney and liver (p < 0.05). The accumulation of tissue aluminum and therefore potential adverse consequences may preclude any benefits of using SZA as a dietary supplement.

Differential anti-inflammatory and chondroprotective effects of simulated digests of indomethacin and an herbal composite (Mobility) in a cartilage explant model of articular inflammation.

Herbs are an increasingly popular treatment option for horses with cartilage inflammation, despite a relative paucity of research demonstrating efficacy. The research objective was to evaluate the differential anti-inflammatory and chondroprotective efficacy of a simulated digest of indomethacin and a commercially available herbal product in a cartilage model of osteoarthritis. Cartilage explant was integrated with simulated digestion of indomethacin and the herbal product in order to account, at least in part, for the actions of major digestive enzymes and pH. The resulting digests were ultrafiltrated (50 kDa), to account for absorption from the GI tract and movement into the cartilage matrix. We hypothesized that (i) a simulated digest of indomethacin would block interleukin 1 beta-(IL-1) dependent formation of prostaglandin E2 (PGE2) and nitric oxide (NO) without protecting cartilage against IL-1-induced glycosaminoglycan (GAG) release, and (ii) the herbal product would reduce PGE2 and NO in IL-1-stimulated explants, and inhibit release of GAG, in IL-1-stimulated explants. Results showed that indomethacin is an effective anti-inflammatory, evidenced by strong inhibition of IL-1-induced PGE2 and NO from cartilage explants. However, indomethacin provided no protection against IL-1-induced GAG release. Simulated digest of the herbal extract significantly inhibited IL-1-induced NO production and GAG release, while having a slight increase in PGE2. These data provide evidence for the anti-inflammatory effect of indomethacin on IL-1-stimulated cartilage explants, and the herbal product Mobility may be a useful adjunct in arthritis because of its chondroprotective properties in IL-1-stimulated cartilage.

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.

Evaluation of phytase concentration needed for growing-finishing commercial turkey toms.

1. Growth performance, serum bone markers, and bone strength and mineralisation were determined in tom turkeys grown from 9 to 17 weeks of age. 2. Dietary non-phytate phosphorus was formulated to be reduced by 1.0 g/kg in the low phosphorus diet compared to a control diet and phytase was added to provide 0, 150, 300, 450 or 600 units/kg activity to the low phosphorus diet. 3. From 9 to 12 weeks of age, body weight and gain:food were reduced by the low phosphorus diet without added phytase, compared to the adequate phosphorus diet. Increasing the concentration of phytase linearly increased these growth parameters. There were no significant growth responses at 17 weeks of age. 4. Serum osteocalcin was reduced by increasing dietary phosphorus at 12 weeks of age when growth was affected, but not at later ages. Serum pyridinoline was reduced by higher dietary phosphorus and decreased linearly with increasing phytase activity at 17 weeks of age. 5. Fracture force of the ulna and femur increased linearly with increasing phytase activity but bone strength was not affected when corrected for bone cross-sectional area. Bone strength of the ulna and ash concentration of the ulna and tibia were increased by higher dietary phosphorus. Humerus and ulna ash increased linearly with increasing phytase activity. 6. Water-soluble phosphorus content of the litter was increased by higher dietary phosphorus and addition of phytase to the low phosphorus diet. The increase in water-soluble phosphorus content of the litter when phytase was fed may indicate that phosphorus could be fed at a lower concentration than used in this trial, at least in the finisher diet when phytase is added to the food. 7. Bone fracture force, strength and ash were generally optimised when 450 units/kg phytase activity was added to the low phosphorus diet. However, growth performance was best in the grower I (9 to 12 weeks) phase when 600 units/kg phytase was added to the diet.

Gene expression profile of mechanically impacted bovine articular cartilage explants.

Traumatic injury to a joint can initiate cartilage degradation. Blunt trauma increases matrix damage and decreases proteoglycan synthesis in in vitro models. Few studies have investigated gene expression of articular cartilage (AC) following mechanical loading. Recent advances in microarray technology allow analysis of a number of genes, and may elucidate pathways of AC degradation. In the present study, we used a bovine cDNA microarray to determine how acute trauma of cartilage explants in the absence of underlying bone alters gene expression. Results indicate that at least 19 genes were differentially expressed at 3 h after trauma. Fourteen genes were up-regulated and five genes were down-regulated relative to control explants. The up-regulated genes included cytokine and chemokine receptors, enzymes, and molecules involved in signal transduction. Genes of adhesion molecules and apoptosis were down-regulated. The results of this study highlight the potential benefits of using a bovine cDNA microarray to study cartilage metabolism.

Periparturient responses of multiparous Holstein cows fed different dietary phosphorus concentrations prepartum.

Our objective was to compare the effects of different prepartum dietary phosphorus concentrations on periparturient metabolism and performance. Forty-two late pregnant multiparous Holstein cows were fed 0.21, 0.31, or 0.44% P (dry basis) for 4 wk before expected calving. After parturition, all cows were fed a common lactation diet (0.40% P). In the prepartum period, cows fed 0.21% P had lower blood serum P concentrations compared with cows fed 0.31 or 0.44% P. However, serum P concentrations of all cows were within the normal range (4 to 8 mg/dL) until the day of calving when average concentrations dropped below 4 mg/dL. From 3 to 14 d postpartum, serum P of cows fed 0.21% P was greater than that of cows fed 0.31 or 0.44% P. No cows presented with or were treated for clinical hypophosphatemia in the periparturient period. Total serum Ca was lower before calving through 2 d postpartum for cows fed 0.44% P compared with those fed 0.21 or 0.31%. Prepartum dietary P treatments did not alter blood osteocalcin, hydroxyproline, and deoxypyridinoline, indicators of bone metabolism, or concentrations of parathyroid hormone or 1,25-dihydroxyvitamin D3. Energy-corrected milk yield and milk composition (first 28 d of lactation) were not affected by prepartum dietary P concentrations. It is concluded that feeding 0.21% P (34 g of P/cow daily) prepartum is adequate for periparturient multiparous Holstein cows with high metabolic demands and genetic potential for milk production. No adverse effects on periparturient health, dry matter intake, or 28-d lactation performance resulted.

Glucosamine and chondroitin sulfate regulate gene expression and synthesis of nitric oxide and prostaglandin E(2) in articular cartilage explants.

OBJECTIVE: Glucosamine (GLN) and chondroitin sulfate (CS) are widely used to alleviate symptoms of osteoarthritis (OA). However, the mechanism(s) of action of these nutraceuticals remains unresolved. In the present study, we determined the effect of physiologically relevant concentrations of GLN and CS on gene expression and synthesis of nitric oxide (NO) and prostaglandin E(2) (PGE(2)) in cytokine-stimulated articular cartilage explants. METHODS: Using bovine articular cartilage explants in culture stimulated with IL-1, the effects of physiologically relevant concentrations of GLN and CS on gene expression of inducible nitric oxide synthase (iNOS), endothelial nitric oxide synthase (eNOS), cyclooxygenase-2 (COX-2) and microsomal prostaglandin E synthase-1 (mPGEs1) were assessed with quantitative real-time polymerase chain reaction (Q-RT-PCR). The production of NO and PGE(2) was also quantified. RESULTS: CS and the GLN and CS combination at concentrations attainable in the blood down-regulated IL-1 induced mRNA expression of iNOS at 24 and 48 h post-culture. Up-regulated iNOS expression at 24h by IL-1 was also suppressed by GLN. GLN and CS transiently repressed the cytokine-stimulated mPGEs1 transcript. Synthesis of NO was reduced with CS alone and the combination after 24h of culture. Repression of COX-2 transcripts by GLN and CS was accompanied by concomitant reduction in PGE(2). CONCLUSION: Our results indicate that physiologically relevant concentrations of GLN and CS can regulate gene expression and synthesis of NO and PGE(2), providing a plausible explanation for their purported anti-inflammatory properties.

High-intensity exercise of short duration alters bovine bone density and shape.

The ability of short-duration high-intensity exercise to stimulate bone formation in confinement was investigated using immature Holstein bull calves as a model. Eighteen bull calves, 8 wk of age, were assigned to one of three treatment groups: 1) group-housed (GR, which served as a control), 2) confined with no exercise (CF), or 3) confined with exercise (EX). The exercise protocol consisted of running 50 m on a concrete surface once daily, 5 d/wk. Confined calves remained stalled for the 42-d duration of the trial. Blood samples were taken to analyze concentrations of osteocalcin and deoxypyridinoline, markers of bone formation and resorption. At the completion of the trial, calves were humanely killed, and both forelegs were collected. The fused third and fourth metacarpal bone was scanned using computed tomography for determination of cross-sectional geometry and bone mineral density. Three-point bending tests to failure were performed on metacarpal bones. The exercise protocol resulted in the formation of a rounder bone in EX as well as in increased dorsal cortex thickness compared with those in the GR and CF. The exercised calves had a significantly smaller medullary cavity than CF and GR (P < 0.01) and a larger percentage of cortical bone area than CF (P < 0.01). Dorsal, palmar, and total bone mineral density was greater in EX than in CF (P < 0.05), and palmar and total bone mineral densities were greater (P < 0.05) in EX than in GR. There was a trend for the bones of EX to have a higher fracture force than CF (P < 0.10). Osteocalcin concentrations normalized from d 0 were higher in EX than CF (P < 0.05). Therefore, the exercise protocol altered bone shape and seemed to increase bone formation comparison with the stalled and group-housed calves.

The extent and distribution of cell death and matrix damage in impacted chondral explants varies with the presence of underlying bone.

Excessive mechanical loading can lead to matrix damage and chondrocyte death in articular cartilage. Previous studies on chondral and osteochondral explants have not clearly distinguished to what extent the degree and the distribution of cell death are dependent on the presence of an underlying layer of bone. The current study hypothesized that the presence of underlying bone would decrease the amount of matrix damage and cell death. Chondral and osteochondral explants were loaded to 30 MPa at a high rate of loading (approximately 600 MPa/s) or at a low rate of loading (30 MPa/s). After 24 hours in culture, matrix damage was assessed by the total length and average depth of surface fissures. The explants were also sectioned and stained for cell viability in the various layers of the cartilage. More matrix damage was documented in chondral than osteochondral explants for each rate of loading experiment. The total amount of cell death was also less in osteochondral explants than chondral explants. The presence of underlying bone significantly reduced the extent of cell death in all zones in low rate of loading tests. The percentage of cell death was also reduced in the intermediate zone and deep zones of the explant by the presence of the underlying bone for a high rate of loading. This study indicated that the presence of underlying bone significantly limited the degree of matrix damage and cell death, and also affected the distribution of dead cells through the explant thickness. These data may have relevance to the applicability of experimental data from chondral explants to the in situ condition.

Inhibition of articular cartilage degradation by glucosamine-HCl and chondroitin sulphate.

Glucosamine and chondroitin sulphate in many animal and human trials has improved joint health. In vitro studies are beginning to clarify their mode of action. The objective of this research was to: 1) determine at what concentrations glucosamine-HCl (GLN) and/or chondroitin sulphate (CS) would inhibit the cytokine-induced catabolic response in equine articular cartilage explants and 2) to determine if a combination of the 2 was more effective at inhibiting the catabolic response than the individual compounds. Articular cartilage was obtained from carpal joints of horses (age 1-4 years). Cartilage discs (3.5 mm) were biopsied and cultured. Explants were incubated with lipopolysaccharide (LPS) in the presence of varying concentrations of GLN, CS, or both. Control treatments included explants with no LPS and LPS without GLN or CS. Media were analysed for nitric oxide (NO), prostaglandin E2 (PGE2) and keratan sulphate. Cartilage was extracted for analysis of metalloproteinases (MMP). Four experiments were conducted. In all experiments, GLN at concentrations as low as 1 mg/ml decreased NO production relative to LPS stimulated cartilage without GLN over the 4 day period. In general, CS at either 0.25 or 0.5 mg/ml did not inhibit NO production. The addition of CS to GLN containing media did not further inhibit NO production. GLN at concentrations as low as 0.5 mg/ml decreased PGE2 production, whereas CS did not effect on PGE2. The combination of GLN/CS decreased MMP-9 gelatinolytic activity but had no effect on MMP-2 activity. The combination in 2 experiments tended to decrease MMP-13 protein concentrations and decreased keratan sulphate levels in media. Overall, the combination of GLN (1 mg/ml) and CS (0.25 mg/ml) inhibited the synthesis of several mediators of cartilage degradation. These results further support the effort to understand the role of GLN and CS in preserving articular cartilage in athletic horses.

Effect of glucosamine on interleukin-1-conditioned articular cartilage.

Glucosamine inhibits recombinant human interleukin-1 stimulated cartilage degradation in equine cartilage explants. Recently, recombinant equine interleukin-1 has been cloned and purified. Therefore, the objective of this study was to characterise the effects of glucosamine on indices of cartilage degradation in recombinant equine IL-1beta-stimulated equine articular cartilage explants. Cartilage discs were harvested from the weight-bearing region of the articular surface of the antebrachiocarpal and middle carpal joints of horses (age 2-8 years) and cultured under standard conditions. Explants were exposed to recombinant equine interleukin-1beta (reIL-1beta) on Days 1-4 in the presence or absence of glucosamine (0.25, 2.5 or 25 mg/ml), with appropriate controls. Nitric oxide, prostaglandin E2, sulphated proteoglycan, stromelysin and gelatinase/collagenase activity released into conditioned media and total tissue proteoglycan content were measured as indicators of cartilage catabolism. Glucosamine inhibited cartilage catabolic responses in a dose dependent manner that was statistically significant at a dose of 0.25 mg/ml for stromelysin activity and 2.5 mg/ml for collagenase/gelatinase activity. At 25 mg/ml glucosamine also prevented IL-1beta-induced increases in nitric oxide production, prostaglandin E2 and proteoglycan release to media. Glucosamine prevents equine articular cartilage degradation experimentally induced by reIL-1beta in vitro. These data provide further support for the use of glucosamine in treatment or prevention of cartilage loss in athletic horses.

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.