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.

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.

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.

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.

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.

The presence of lysylpyridinoline in the hypertrophic cartilage of newly hatched chicks.

The presence of lysylpyridinoline (LP) as a nonreducible cross-link in appreciable quantities has primarily been limited to the mineralized tissues, bone and dentin. However, the results reported here show that LP is not only present in the hypertrophic cartilage of the tibiotarsus isolated from newly hatched broiler chicks, but it is approx. 4-fold as concentrated as hydroxylysylpyridinoline (HP). Bone and articular cartilage surrounding the hypertrophic cartilage do not contain measurable quantities of LP. Purified LP has a fluorescent scan similar to purified HP and literature values, confirming that we indeed were measuring LP. Also, the cartilage lesion produced by immature chondrocytes from birds with tibial dyschondroplasia had LP but the HP:LP ratio was > 1. Thus, the low HP:LP ratio could be a marker for hypertrophic cartilage in avians.

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.

The extent of matrix damage and chondrocyte death in mechanically traumatized articular cartilage explants depends on rate of loading.

Mechanical loads can lead to matrix damage and chondrocyte death in articular cartilage. This damage has been implicated in the pathogenesis of secondary osteoarthritis. Studies on cartilage explants with the attachment of underlying bone at high rates of loading have documented cell death adjacent to surface lesions. On the other hand, studies involving explants removed from bone at low rates of loading suggest no clear spatial association between cell death and matrix damage. The current study hypothesized that the observed differences in the distribution of cell death in these studies are attributed to the rate of loading. Ninety bovine cartilage explants were cultured for two days. Sixty explants were loaded in unconfined compression to 40 MPa in either a fast rate of loading experiment (approximately 900 MPa/s) or a low rate of loading experiment (40 MPa/s). The remaining 30 explants served as a control population. All explants were cultured for four days after loading. Matrix damage was assessed by measuring the total length and average depth of surface lesions and the release of glycosaminoglycans to the culture media. Explants were sectioned and stained with calcein and ethidium bromide homodimer to document the number of live and dead cells. Greater matrix damage was documented in explants subjected to a high rate of loading, compared to explants exposed to a low rate of loading. The high rate of loading experiments resulted in cell death adjacent to fissures, whereas more dead cells were observed in the low rate of loading experiments and a more diffuse distribution of dead cells was observed away from the fissures. In conclusion, this study indicated that the rate of loading can significantly affect the degree of matrix damage, the distribution of dead cells, and the amount of cell death in unconfined compression experiments on explants of articular cartilage.

Non-reducible collagen cross-linking in cartilage from broiler chickens with tibial dyschondroplasia.

Recent work has shown that hydroxylysylpyridinoline (HP), a non-reducible cross-link that stabilizes the collagen fibril network, is significantly greater (over 10-fold) in dyschondroplastic cartilage than in normal growth-plate cartilage in the tibiotarsi of chickens with homocysteine-induced tibial dyschondroplasia (TD). In the present study, broiler chicks with a genetic disposition to TD, as well as normal broiler chicks on a copper-deficient diet alone or supplemented with copper and thiram, were raised for 3 to 4 weeks (Expts. 1 and 2). Their dyschondroplastic cartilage from the proximal tibiotarsus was collected and analyzed for HP as well as lysylpyridinoline (LP) cross-links. Normal growth plate cartilage was obtained from chicks on the copper-deficient diet supplemented with copper. In a third experiment, another set of broiler chicks was raised on a corn/soybean meal-based diet with or without homocysteine, and their articular and sternal cartilage were isolated for cross-link analysis. In the first two experiments, dyschondroplastic cartilage from all birds with induced TD had higher HP and LP concentrations than growth-plate cartilage from birds without TD, although the ratios of HP to LP varied. In the third experiment, the sternal and articular cartilage from birds with homocysteine-induced TD appeared normal, having similar HP concentrations in the same types of cartilage in birds without TD.

Effect of antibiotics on in vitro and in vivo avian cartilage degradation.

Antibiotics are used in the livestock industry not only to treat disease but also to promote growth and increase feed efficiency in less than ideal sanitary conditions. However, certain antibiotic families utilized in the poultry industry have recently been found to adversely affect bone formation and cartilage metabolism in dogs, rats, and humans. Therefore, the first objective of this study was to determine if certain antibiotics used in the poultry industry would inhibit in vitro cartilage degradation. The second objective was to determine if the antibiotics found to inhibit in vitro cartilage degradation also induced tibial dyschondroplasia in growing broilers. Ten antibiotics were studied by an avian explant culture system that is designed to completely degrade tibiae over 16 days. Lincomycin, tylosin tartrate, gentamicin, erythromycin, and neomycin sulfate did not inhibit degradation at any concentration tested. Doxycycline (200 microg/ml), oxytetracycline (200 microg/ml), enrofloxacin (200 and 400 microg/ml), ceftiofur (400 microg/ml), and salinomycin (10 microg/ml) prevented complete cartilage degradation for up to 30 days in culture. Thus, some of the antibiotics did inhibit cartilage degradation in developing bone. Day-old chicks were then administered the five antibiotics at 25%, 100%, or 400% above their recommended dose levels and raised until 21 days of age. Thiram, a fungicide known to induce experimental tibial dyschondroplasia (TD), was given at 20 ppm. Birds were then killed by cervical dislocation, and each proximal tibiotarsus was visually examined for TD lesions. The results showed that none of these antibiotics significantly induced TD in growing boilers at any concentration tested, whereas birds given 20 ppm thiram had a 92% incidence rate.

Tetracycline derivatives inhibit cartilage degradation in cultured embryonic chick tibiae.

Tetracyclines have been used extensively as antibiotics and growth promoters in the poultry industry. However, they can inhibit angiogenesis and matrix degradation, both of which are essential for normal growth plate cartilage development. The purpose of this research was to test the ability of several tetracyclines to inhibit cartilage degradation in cultured embryonic chick tibiae. Based on gross observations and biochemical quantitation of collagen release into the media, minocycline, doxycycline, oxytetracycline, and tetracycline inhibited cartilage degradation at 20, 40, 60, and 80 micrograms ml-1 respectively. Chlortetracycline did not inhibit cartilage degradation at concentrations tested. The ability of the tetracycline derivative to inhibit cartilage degradation was in general related to its hydrophobicity. Since a majority of the cartilage in the embryonic chick tibia will develop into the post hatched growth plate, it may be important to determine if any of the tetracyclines used as antibiotics could cause problems in in vivo growth plate cartilage development.

The regulation of growth plate cartilage turnover.

The advances made in the areas of genetics and nutrition during this century have resulted in improved growth rates for livestock. However, one drawback has been the increased prevalence of long bone growth problems, such as rickets, avian tibial dyschondroplasia, and osteochondrosis. Growth plate cartilage, which regulates long bone development, must maintain a tightly controlled balance between cartilage synthesis and degradation as well as chondrocyte proliferation and apoptosis. This paper will briefly review the various nutritional factors, cell signals, and proteins that help regulate growth plate chondrocytes. Some of the growth plate diseases will be discussed with an emphasis on how a breakdown in growth plate metabolism is related to the observed problems. The author's intention is that readers will gain an appreciation for the complexity of this relatively small tissue and for why a better understanding of its physiology will be important in the years to come for the prevention of skeletal problems related to long bone growth.

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.

Supplemental silicon increases plasma and milk silicon concentrations in horses.

The primary objective of this research was to determine the effect of supplemental dietary silicon (Si) on plasma and milk Si concentrations of lactating mares and the subsequent effect on plasma Si concentrations in nursing foals. Additionally, the role of Si on altering biochemical markers of bone turnover was investigated, because supplemental Si may be advantageous in enhancing bone health. Twelve Arabian mare/foal units were pair-matched by foaling date and randomly assigned to two groups, Si-supplemented (Supplemented) or control (Control). Blood and milk samples were taken on d 0, 15, 30, and 45, d 0 being the 1st d after parturition. Plasma and milk (or colostrum) Si concentrations were determined and serum was analyzed for osteocalcin, carboxy-terminal pyridinoline cross-linked telopeptide region of type I collagen, and pyridinoline and deoxypyridinoline crosslinks. All Supplemented mares had higher (P < 0.01) plasma Si concentrations than Control by d 30, and Supplemented mares' milk had higher (P < 0.01) Si concentrations on d 45 than Control mares' milk. By d 45, foals of Supplemented mares had higher (P < 0.01) plasma Si concentrations than foals of Control mares. Supplemental Si did not influence (P > 0.36) bone metabolism in foals; however, trends (P < 0.10) for altered bone metabolism were observed in postpartum mares. Results indicate that supplemental Si increases plasma and milk Si concentrations. Further research is required to determine whether Si has a role in altering serum biochemical markers of bone and collagen activity.

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.

Effect of longeing and glucosamine supplementation on serum markers of bone and joint metabolism in yearling quarter horses.

The effect of longeing and glucosamine supplementation on known biological markers of joint disease was studied in yearling quarter horses. Twenty-one yearling quarter horses were randomly assigned to one of 4 treatments: 1) longeing (longeing 20 min daily) supplement control (LN); 2) longeing/glucosamine (LG); 3) walking (mechanical walker for 120 min daily (WN)); and 4) walking/glucosamine (WG). Oral glucosamine was administered at 5.5 g b.i.d. weeks 1-4, 3.5 g b.i.d. during weeks 5-6, and 2.0 g b.i.d. during weeks 7-8. Serum was obtained weekly for 8 wk and analyzed for keratan sulfate and osteocalcin concentrations. Walked horses receiving glucosamine showed slight elevation in serum keratan sulfate compared to controls (P = 0.04). Glucosamine or longeing exercise had no significant effect (6 > or = 0.08) on serum osteocalcin concentrations. Under these conditions, longeing and/or glucosamine supplementation did not significantly alter serum concentrations of keratan sulfate or osteocalcin.

Recombinant equine interleukin-1beta induces putative mediators of articular cartilage degradation in equine chondrocytes.

Interleukin-1 is considered a central mediator of cartilage loss in osteoarthritis in several species, however an equine recombinant form of this cytokine is not readily available for in vitro use in equine osteoarthritis research. Equine recombinant interleukin-1beta was cloned and expressed and its effects on the expression and activity of selected chondrocytic proteins implicated in cartilage matrix degradation were characterized. Reverse transcriptase polymerase chain reaction methods were used to amplify the entire coding region of the equine IL-1beta mRNA, which was cloned into an expression vector, expressed in E. coli, and purified using a Ni2+ chromatographic method. The effects of the recombinant peptide on chondrocyte gene expression were determined by Northern blotting using RNA from equine chondrocyte cultures hybridized to probes for matrix metalloproteinases (MMP 1, MMP 3, MMP 13), tissue inhibitor of matrix metalloproteinases 1 (TIMP 1) and cyclooxygenase 2 (COX 2). Effects on selected mediators of cartilage degradation (nitrite concentrations and MMP activity) were determined using conditioned medium from reIL-1beta-treated equine cartilage explant cultures. A recombinant peptide of approximately 21 kd was obtained. Northern blotting analyses revealed a marked up-regulation of expression of all MMPs, TIMP 1, and COX 2 in mRNA from treated chondrocytes. Furthermore, cartilage explants exposed to reIL-1beta had augmented collagenase/gelatinase and stromelysin activities as well as increased concentration of nitrite in conditioned media. The development of a biologically active, species-specific IL-1beta provides a valuable tool in the study of osteoarthritis pathophysiology and its treatment in horses.