Mineral Stores Research Articles

56 Vitamin and Mineral Supplementation Throughout Gestation Affects Liver Trace Mineral Status of Dam and Neonatal Calves but not Calf Morphometric Characteristics

Abstract Objectives were to evaluate the effects of feeding a vitamin and mineral supplementation (VMSUP) to heifers throughout gestation on trace mineral status of the dam and calf, calving parameters, and calf characteristics. We hypothesized that VMSUP throughout gestation would enhance mineral status in the dam and offspring at birth and positively impact calf morphometric characteristics. Thirty-one Angus-based heifers (body weight [BW]=273.7 ± 1.10 kg) were estrous synchronized, bred with female sexed semen, then were randomly assigned to either a basal diet targeting gain of 0.45 kg/d (CON; n=14) or the basal diet plus a vitamin and mineral supplement (VTM; n=17; 113 g•heifer-1•d-1). Liver biopsies were obtained from dams at breeding, d 84 and 180 of gestation, and at calving from dams and calves. Trace mineral concentrations were determined via inductively coupled plasma mass spectrometry. Calving ease, calf vigor and body weight were recorded at birth, and body measurements were recorded at 24 h after birth. Data were analyzed using the GLM Procedure of SAS using repeated measures analysis when appropriate. In maternal liver, concentrations of selenium and copper were affected by a treatment × day interaction (P < 0.0001), being greater (P < 0.001) for VTM than CON at all post-breeding timepoints and decreasing (P ≤ 0.05) from d 84 to calving; while zinc, molybdenum, manganese, and cobalt were not (P ≥ 0.20) affected by treatment. In calves, concentrations of liver selenium, copper, zinc, and cobalt were greater for VTM than CON (P < 0.05). Gestation length, calving distribution, ease and vigor scores, calf BW and body measurements were not affected by treatment (P = 0.278). Therefore, VTM supplementation throughout gestation affected liver trace mineral reserves of dam and calf; but did not affect calf size or any of the calving parameters evaluated. These results suggest that as gestation progresses, maternal liver mineral stores decrease to provide for the gestating calf.

226 Evaluation of a Low-Moisture, Molasses-Based Block Containing Organic Trace Minerals and a Saccharomyces Cerevisiae Fermentation Culture in Newly Weaned Beef Steer Calves

Abstract The objective of this study was to evaluate growth performance responses and hepatic trace mineral status of newly weaned steer calves offered a molasses-based “stress” tub. Steers [n = 46; body weight (BW) = 240; SEM = 1.0 kg) were used in a randomized complete block design experiment. On d -1 all steers were stratified by initial BW and allotted to pens (n = 4 to 5 steers per pen; 5 pens/treatment).Treatments were: 1) No “stress” tub (Con) or 2) Ad libitum access to a “stress” tub (Stress Tub; Purina Animal Nutrition, St. Louis, MO) for the first 21-d (Tub). Steers were allotted to their study pens within 36-h of weaning and the “stress” tub was introduced approximately 24-h post arrival. Tub disappearance was monitored daily. Liver biopsies (n = 2 steers/pen) were collected on d 7, 21, and 42 for determination of Co, Cu, Mn, and Zn. From d 1 to 21 and d 1 to 42 steers from in the Tub treatment consumed greater (P ≤ 0.01) amounts of Co, Cu, Mn, and Zn. A treatment × day interaction for hepatic concentrations of Co (P = 0.09), Cu (P = 0.01), and Zn (P = 0.01) were noted. On d 7, steers from Tub had greater (P≤0.01) hepatic Co, Cu, and Zn . On d 21, steers from Tub had greater (P ≤ 0.01) hepatic Co and Cu. On d 42 steers from Tub had greater (P = 0.01) hepatic concentrations of Cu. During the initial 21-d of the experiment gain efficiency was enhanced (P = 0.03) by 25.0% in steers from Tub compared with Con. Cumulative ADG, DMI, dietary NE utilization, and G:F did not differ (P ≥ 0.14). It is concluded that stress tubs do not influence overall growth performance or NE value of the diet during a 42-d period. Stress tub consumption increased hepatic mineral stores during the initial 21-d and enhanced Cu status of calves throughout the 42-d receiving period.

Evaluation of a Low-Moisture, Molasses-Based Block Containing Organic Sources of Trace Minerals and a Saccharomyces cerevisiae Fermentation Culture during the Feedlot Receiving Phase on Growth Performance, Efficiency of Dietary Net Energy Utilization, and Liver Trace Mineral Status in Newly Weaned Steer Calves

The objective of this study was to evaluate the growth performance responses and liver trace mineral status of newly weaned steer calves offered a low-moisture, molasses-based block “stress tub” containing organic sources of trace minerals and a Saccharomyces cerevisiae fermentation culture during the first 21-d of a 42-d feedlot receiving phase. Newly weaned, single source Charolais x Angus steer calves (n = 46; body weight [BW] = 240; SEM = 1.0 kg) were used in a 42-d randomized complete block design feedlot receiving experiment. On d -1 all steers were individually weighed in the morning for allotment purposes, and steers were then stratified by initial BW and allotted to one of ten pens (n = 4 to 5 steers per pen; 5 pens per treatment) that were randomly assigned to 1 of 2 treatments: 1) no cooked molasses “stress” tub (Con) or 2) ad libitum access to a cooked molasses “stress” tub (Stress Tub; Purina Animal Nutrition, St. Louis, MO, USA) for the first 21-d (Tub). Steers were allotted to their study pens within 36 h of weaning, and the “stress” tub was introduced approximately 24 h post arrival. During the initial 14-d on feed, intake was managed by feed calls to accommodate adaptation to the receiving diet. Following the adaptation period, bunks were managed using a slick bunk management approach. Tub disappearance was monitored daily. Liver biopsies (n = 2 steers/pen) were collected on d 7, 21, and 42 for the determination of Co, Cu, Mn, and Zn. From d 0 to 21 and d 0 to 42, steers from the Tub treatment consumed greater (p ≤ 0.01) amounts of Co, Cu, Mn, and Zn compared with those in the Con treatment. A treatment × day interaction for hepatic concentrations of Co (p = 0.09), Cu (p = 0.01), and Zn (p = 0.01) were noted. On d 7, steers from Tub had greater (p ≤ 0.01) hepatic Co, Cu, and Zn concentrations compared with Con. On d 21, steers from Tub had greater (p ≤ 0.01) hepatic concentrations of Co and Cu; hepatic Zn was similar between treatments (p = 0.83). On study d 42 steers from Tub had greater (p = 0.01) hepatic Cu; however, hepatic concentrations for Co or Zn did not differ (p ≥ 0.34). During the initial 21 d of the experiment, gain efficiency was enhanced (p = 0.03) by 25.0% in steers from Tub compared with Con. Cumulative ADG, DMI, dietary NE utilization and G:F did not differ (p ≥ 0.14) between treatments. It is concluded that the use of stress tubs does not influence the overall growth performance or NE value of the diet during a 42-d receiving period. Stress tub consumption increased hepatic mineral stores during the initial 21-d period and enhanced the Cu status of calves throughout the 42-d period.

Short Communication: Effects of low antioxidant mineral concentrations in the growing diet on marbling deposition in feedlot cattle

ABSTRACT Objectives This experiment investigates the effect of antioxidant mineral supplementation during a 28-d growing period on marbling deposition of feedlot steers. Materials and Methods After a 28-d adaptation period to the feedlot, 167 SimAngus steers (272 ± 28.2 kg, 219 ± 15 d of age) were divided into 4 weight blocks, placed in 1 of 24 pens, and randomly assigned a dietary treatment. Dietary treatments were applied during a 28-d growing period: (1) no supplemental Cu, Mn, Zn, and Se; (2) Cu, Mn, Zn, and Se supplemented at the requirement of growing beef steers; and (3) Cu, Mn, Zn, and Se supplemented at twice the requirement. Plasma was collected after the growing phase to quantify nonesterified fatty acid and thiobarbituric acid reactive substance concentrations. Afterward, steers were offered a common finishing diet until being removed from the experiment for slaughter at a similar backfat thickness. Statistical analyses used a mixed model in SAS, considering the fixed effect of treatment and the random effect of block. Results and Discussion There were no treatment differences (P > 0.35) for measures of feedlot performance, carcass, and blood metabolite. With the exception of Cu, it is possible adequate mineral concentrations supplied by the basal diet caused a lack of treatment differences. Additionally, liver and body mineral stores may not have been depleted during the 28 d of the experimental intervention. Implications and Applications Future research is needed to further investigate the effects of dietary antioxidant mineral level on marbling deposition of feedlot steers.

Calcium and phosphorus metabolism in peripartal dogs.

Recommended allowances for calcium and phosphorus are mostly based on factorial calculations partly set at the level determined adequate for giant breeds (Nutrient requirements of dogs and cats. Washington, DC, USA: The National Academies Press. 2006). Information about appropriateness of supply with both minerals during the peripartal phase is limited. From other species is known that bone mineral stores are used in addition to oral intake of calcium and phosphorus in periods of higher needs such as gestation and lactation. The aim of this study was to determine parameters of calcium and phosphorus homeostasis in female dogs receiving the recommended amount of these minerals according to NRC (Nutrient requirements of dogs and cats. Washington, DC, USA: The National Academies Press. 2006) during the peripartal phase. In five Beagles and four Foxhound crossbreds, all primiparous with a litter size of 1-8 puppies, apparent digestibility of calcium and phosphorus as well as serum parameters of mineral metabolism (total and ionised calcium, phosphorus, parathyroid hormone, bone specific alkaline phosphatase, crosslaps) was determined in the period of 12-9days before and 4-9days after parturition. The apparent digestibility of calcium was relatively low and did not differ significantly between both peripartal phases, whereas the apparent digestibility of phosphorus increased during lactation. Serum concentrations of calcium (total as well as ionised), phosphorus and parathyroid hormone did not differ between gestation and lactation. The bone resorption marker serum crosslaps increased in lactating dogs but most individual values were within the reference range for adult female dogs at maintenance. On the other hand, the bone formation marker bone specific alkaline phosphatase decreased from prepartal to postpartal phase with values clearly above reference range in both phases. Based on the results especially of the bone markers, which stayed within the reference range during the peripartal phase without indicating predominant bone resorption, we hypothesise that the applied recommended daily allowances defined for peripartal dogs are appropriate.

Screening for Metabolic Bone Disease of prematurity

Metabolic bone disease (MBD) of prematurity remains a significant comorbid condition in preterm, low birth weight infants. As the majority of in utero calcium (Ca) and phosphorus (Phos) accretion occurs during the third trimester, many of these children have inadequate mineral stores and are at risk for deficiencies of Ca and Phos. While fortification of formula has allowed for increased mineral delivery to premature infants, intestinal immaturity prevents optimal absorption. This is compounded by immobilization, delayed establishment of enteral feeds, long term parenteral nutrition and medications that may alter mineral levels. Over time, biochemical changes occur and accompany MBD, with poor bone mineralization during this period increasing the risk for complications such as osteopenia, rickets and fractures. Screening is largely based on risk factors, but despite the 2013 AAP Consensus Statement, there remains significant variation in screening practices across institutions. A combination of laboratory and radiologic testing is often used to diagnose and manage MBD of prematurity, but there exists a lack of consensus on which screening tests and thresholds to use. This is in part related to a lack of normative data and clinical trials for preterm infants, and a result, a lack of evidence-based guidelines on the diagnosis and timing of potential treatment. Biochemical markers, such as serum Phos, alkaline phosphatase (ALP) and parathyroid hormone (PTH), have shown some benefit in the diagnosis of MBD in some studies, but have not always been reproducible. Radiographs may identify different degrees of skeletal changes, but these changes may not be detected until later in MBD development. Other modalities, such as DXA and ultrasound, have also been used, but these may be limited by lack of standards in preterm infants or lack of availability in some centers. Further research, more specifically clinical trials, are needed to determine which combination of tests can detect MBD at its earliest, in order to promote early treatment and prevent short- and long-term complications of MBD.

A Mini review on kidney stones

Kidney stones are mineral stores in the renal calyces and pelvis that are discovered free or joined to the renal papillae. They contain translucent and natural parts and are framed when the pee gets supersaturated concerning a mineral. Calcium oxalate is the primary constituent of most stones, a significant number of which structure on an establishment of calcium phosphate called Randall's plaques, which are available on the renal papillary surface. Stone arrangement is exceptionally predominant, with paces of up to 14.8% and expanding, and a repeat pace of up to half inside the initial 5 years of the underlying stone scene. Weight, diabetes, hypertension and metabolic disorder are viewed as danger factors for stone development, which, thusly, can prompt hypertension, interminable kidney malady and end-stage renal infection. The executives of suggestive kidney stones has advanced from open careful lithotomy to negligibly obtrusive endourological medicines prompting a decrease in understanding dismalness, improved without stone rates and better personal satisfaction. Avoidance of repeat requires social and wholesome mediations, just as pharmacological medicines that are explicit for the kind of stone

Elemental and isotopic perspectives on the impact of arbuscular mycorrhizal and ectomycorrhizal fungi on mineral weathering across imposed geologic gradients

Symbiotic mycorrhizal fungi are thought to play a role in weathering by targeting minerals that contain required plant nutrients, such as phosphorus (P), magnesium (Mg) and calcium (Ca). Field experiments coupled with geochemical analyses can provide insights into nutrient cycling in forest landscapes dominated by arbuscular-mycorrhizal (AM) and ectomycorrhizal (EcM) fungi. In-growth bags containing different rock types of varying nutrient content (granite, tonalite) were fabricated to create an in-situ geologic gradient for 100-day deployment in two forest stands dominated by different mycorrhizal symbioses in Hubbard Brook Experimental Forest in New Hampshire, USA. Mineral dissolution within the substrate bags under different biologic conditions was assessed via analysis of major elemental nutrients (Ca, Mg, and P) and isotope ratios of lead (Pb) and strontium (Sr) on leachates representing both the easily exchangeable and future available weatherable mineral stores. We hypothesized that the two types of mycorrhizal fungi would differ in their weathering ability and would show significant variations in tracers of mineral weathering from the same rock type in the two stand but only Ca concentrations in the exchangeable solution of the tonalite and the future weatherable stores solutions of both tonalite and granite varied significantly between the two fungal types. The other measured nutrient concentrations (Mg, P) and Pb and Sr isotopic compositions of the exchangeable and weathering solutions were not significantly different within lithology. Taken together, the results suggest that weathering fluxes in AM- and EcM-dominated forest stands may be more comparable than previously argued.

Digestive Efficiency Mediated by Serum Calcium Predicts Bone Mineral Density in the Common Marmoset (Callithrix jacchus)

Two health problems have plagued captive common marmoset (Callithrix jacchus) colonies for nearly as long as those colonies have existed: marmoset wasting syndrome and metabolic bone disease. While marmoset wasting syndrome is explicitly linked to nutrient malabsorption, we propose metabolic bone disease is also linked to nutrient malabsorption, although indirectly. If animals experience negative nutrient balance chronically, critical nutrients may be taken from mineral stores such as the skeleton, thus leaving those stores depleted. We indirectly tested this prediction through an initial investigation of digestive efficiency, as measured by apparent energy digestibility, and serum parameters known to play a part in metabolic bone mineral density of captive common marmoset monkeys. In our initial study on 12 clinically healthy animals, we found a wide range of digestive efficiencies, and subjects with lower digestive efficiency had lower serum vitamin D despite having higher food intakes. A second experiment on 23 subjects including several with suspected bone disease was undertaken to measure digestive and serum parameters, with the addition of a measure of bone mineral density by dual-energy X-ray absorptiometry (DEXA). Bone mineral density was positively associated with apparent digestibility of energy, vitamin D, and serum calcium. Further, digestive efficiency was found to predict bone mineral density when mediated by serum calcium. These data indicate that a poor ability to digest and absorb nutrients leads to calcium and vitamin D insufficiency. Vitamin D absorption may be particularly critical for indoor-housed animals, as opposed to animals in a more natural setting, because vitamin D that would otherwise be synthesized via exposure to sunlight must be absorbed from their diet. If malabsorption persists, metabolic bone disease is a possible consequence in common marmosets. These findings support our hypothesis that both wasting syndrome and metabolic bone disease in captive common marmosets are consequences of inefficient nutrient absorption.

A review of factors affecting antler composition and mechanics

Antlers constitute the only mammal model for limb regeneration. A number of factors affect antler regeneration. In this review, we examine such factors and the potential consequences for organ regeneration. As body mineral stores are depleted to grow antlers, physiological exhaustion is shown in the mineral composition, mechanical performance and, according to preliminary studies, porosity of the antler bone material. Nutrition plays an important role in antler characteristics. Thus, antler composition can be used as a diagnostic tool to assess mineral deficiencies in deer. Studies on ecological effects of exceptional weather in plants suggest that minor minerals, particularly Mn, may play disproportionately roles in mechanical performance of bone material. This suggests that Mn (and perhaps other minerals) is essential to incorporate Ca and P from resorbed skeleton material in antlers. Apart from implications for game management, some effects may have applications for medicine.

Fetal and neonatal bone health: update on bone growth and manifestations in health and disease

The neonatal period is classically described as the first 28 days of life, but owing to the fact that changes in skeletal tissue occur at a somewhat slower pace than those of other organ systems, events of the first few months are considered herein. Neonatal bone health is a problem of growing interest and concern because of the increasing recognition of its impact upon childhood, adolescent and even adult bone health. Osteoporosis in adulthood often has its roots in childhood and some forms may be prevented by proper attention to neonatal and childhood bone health. The premature infant likely suffers lifelong decreased bone mineral density as a result of its early birth and lack of adequate mineral stores that are typically present in full-term infants. Adequate embryogenesis, growth and development of the skeletal system are multifactorial and under the influence of a host of genes, growth factors and enzymes. The evaluation of skeletal dysplasias and their recognition are beyond the scope of this paper and will not be considered in this discussion. Here the focus will be on the adequacy of mineralization and metabolic aspects of the growth and development of the fetal and neonatal skeleton, the effect of birth, both preterm and term, maternal illness and health as well as infant diseases.

Sauropod dinosaur osteoderms from the Late Cretaceous of Madagascar

Osteoderms are bones embedded within the dermis, and are common to select members of most major tetrapod lineages. The largest known animals that bear osteoderms are members of Titanosauria, a diverse clade of sauropod dinosaurs. Here we report on two titanosaur osteoderms recovered from the Upper Cretaceous Maevarano Formation of Madagascar. Each osteoderm was discovered in association with a partial skeleton representing a distinct ontogenetic stage of the titanosaur Rapetosaurus krausei. Combined, these specimens provide novel insights into the arrangement and function of titanosaur osteoderms. Taphonomic data confirm that Rapetosaurus developed only limited numbers of osteoderms in its integument. The adult-sized osteoderm is the most massive integumentary skeletal element yet discovered, with an estimated volume of 9.63 litres. Uniquely, this specimen possesses an internal cavity equivalent to more than half its total volume. Large, hollow osteoderms may have functioned as mineral stores in fecund, rapidly growing titanosaurs inhabiting stressed environments.

A New Role for Heme, Facilitating Release of Iron from the Bacterioferritin Iron Biomineral

Bacterioferritin (BFR) from Escherichia coli is a member of the ferritin family of iron storage proteins and has the capacity to store very large amounts of iron as an Fe(3+) mineral inside its central cavity. The ability of organisms to tap into their cellular stores in times of iron deprivation requires that iron must be released from ferritin mineral stores. Currently, relatively little is known about the mechanisms by which this occurs, particularly in prokaryotic ferritins. Here we show that the bis-Met-coordinated heme groups of E. coli BFR, which are not found in other members of the ferritin family, play an important role in iron release from the BFR iron biomineral: kinetic iron release experiments revealed that the transfer of electrons into the internal cavity is the rate-limiting step of the release reaction and that the rate and extent of iron release were significantly increased in the presence of heme. Despite previous reports that a high affinity Fe(2+) chelator is required for iron release, we show that a large proportion of BFR core iron is released in the absence of such a chelator and further that chelators are not passive participants in iron release reactions. Finally, we show that the catalytic ferroxidase center, which is central to the mechanism of mineralization, is not involved in iron release; thus, core mineralization and release processes utilize distinct pathways.

Cortisol mobilizes mineral stores from vertebral skeleton in the European eel: an ancestral origin for glucocorticoid-induced osteoporosis?

Endogenous excess cortisol and glucocorticoid (GC) therapy are a major cause of secondary osteoporosis in humans. Intense bone resorption can also be observed in other vertebrates such as migratory teleost fish at the time of reproductive migration and during fasting when large amounts of calcium and phosphate are required. Using a primitive teleost, the European eel, as a model, we investigated whether cortisol could play an ancestral role in the induction of vertebral skeleton demineralization. Different histological and histomorphometric methods were performed on vertebral samples of control and cortisol-treated eels. We demonstrated that cortisol induced a significant bone demineralization of eel vertebrae, as shown by significant decreases of the mineral ratio measured by incineration, and the degree of mineralization measured by quantitative microradiography of vertebral sections. Histology and image analysis of ultrathin microradiographs showed the induction by cortisol of different mechanisms of bone resorption, including periosteocytic osteolysis and osteoclastic resorption. Specificity of cortisol action was investigated by comparison with the effects of sex steroids. Whereas, testosterone had no effect, estradiol induced vertebral skeleton demineralization, an effect related to the stimulated synthesis of vitellogenin (Vg), an oviparous specific phospho-calcio-lipoprotein. By contrast, the cortisol demineralization effect was not related to any stimulation of Vg. This study demonstrates GC-induced bone demineralization in an adult non-mammalian vertebrate, which undergoes natural bone resorption during its life cycle. Our data suggest that the stimulatory action of cortisol on bone loss may represent an ancestral and conserved endocrine regulation in vertebrates.

Elevated Fibroblast Growth Factor 23 in a Patient With Metastatic Prostate Cancer and Hypophosphatemia

Elevated Fibroblast Growth Factor 23 in a Patient With Metastatic Prostate Cancer and Hypophosphatemia

Thyroid hormone-induced demineralisation of the vertebral skeleton of the eel, Anguilla anguilla

The role of thyroid hormones (TH) in bone remodelling is controversial. Indeed, in humans, while they are necessary for normal growth and development, their overproduction can induce important mineral bone loss and osteoporosis. Intense bone resorption is a natural phenomenon also observed in some teleosts, during reproductive migration and fasting. Our work aimed at investigating the effects of chronic treatments with TH (thyroxin, T4 or triiodothyronine, T3) on bone resorption in a migratory fish, the European eel ( Anguilla anguilla), a representative species of an ancient group of teleosts (Elopomorphs). The incineration method showed that TH induced a significant mineral loss in eel vertebral skeleton. Histology and histophysical (qualitative and quantitative microradiographs) methods were then applied to vertebral sections to determine which types of resorption were induced by TH. Quantitative image analysis of microradiographs showed that TH significantly increased the porosity of the vertebrae, demonstrating the induction of a severe bone loss. Histology revealed the appearance of large osteoclastic lacunae, indicating a stimulation of osteoclastic resorption. Quantitative image analysis of ultrathin microradiographs showed a significant increase of the size of osteocytic lacunae, indicating a stimulation of periosteocytic osteolysis. Finally, quantitative microradiographs indicated a significant fall of mineralisation degree. TH treatments did not stimulate the production of the calcium-bonded lipo-phospho-protein vitellogenin, indicating that TH-induced bone demineralisation was not mediated by any indirect effect on vitellogenesis. Our study demonstrates that TH may participate in the mobilisation of bone mineral stores in the eel, by inducing different types of vertebral bone resorption, such as osteoclastic resorption and periosteocytic osteolysis. These data suggest that the stimulatory action of TH on bone resorption may be an ancient regulatory mechanism in vertebrates.

Differences in Bone Mineral Content and Density between Male and Female Budgerigars (Melopsittacus undulatus) during the Non-reproductive Season

It is known that female birds increase medullary mineral stores in long bones shortly before egg laying. Here, we present results from two groups of budgerigars, in both of which females had significantly higher bone mineral contents and densities, as measured by peripheral quantitative computed tomography of the tibiotarsus, during a reproductively dormant period. The results could indicate that female birds can accumulate mineral stores outside of the breeding season.

Effects of dietary zinc and iron supplementation on mineral excretion, body composition, and mineral status of nursery pigs1,2

Two experiments were conducted to evaluate the effects of dietary Zn and Fe supplementation on mineral excretion, body composition, and mineral status of nursery pigs. In Exp. 1 (n = 24; 6.5 kg; 16 to 20 d of age) and 2 (n = 24; 7.2 kg; 19 to 21 d of age), littermate crossbred barrows were weaned and allotted randomly by BW, within litter, to dietary treatments and housed individually in stainless steel pens. In Exp. 1, Phases 1 (d 0 to 7) and 2 (d 7 to 14) diets (as-fed basis) were: 1) NC (negative control, no added Zn source); 2) ZnO (NC + 2,000 mg/kg as Zn oxide); and 3) ZnM (NC + 2,000 mg/kg as Zn Met). In Exp. 2, diets for each phase (Phase 1 = d 0 to 7; Phase 2 = d 7 to 21; Phase 3 = d 21 to 35) were the basal diet supplemented with 0, 25, 50, 100, and 150 mg/kg Fe (as-fed basis) as ferrous sulfate. Orts, feces, and urine were collected daily in Exp. 1; whereas pigs had a 4-d adjustment period followed by a 3-d total collection period (Period 1 = d 5 to 7; Period 2 = d 12 to 14; Period 3 = d 26 to 28) during each phase in Exp. 2. Blood samples were obtained from pigs on d 0, 7, and 14 in Exp. 1 and d 0, 7, 21, and 35 in Exp. 2 to determine hemoglobin (Hb), hematocrit (Hct), and plasma Cu, (PCu), Fe (PFe), and Zn (PZn). Pigs in Exp. 1 were killed at d 14 (mean BW = 8.7 kg) to determine whole-body, liver, and kidney mineral concentrations. There were no differences in growth performance in Exp. 1 or 2. In Exp. 1, pigs fed ZnO or ZnM diets had greater (P < 0.001) dietary Zn intake during the 14-d study and greater fecal Zn excretion during Phase 2 compared with pigs fed the NC diet. Pigs fed 2,000 mg/kg, regardless of Zn source, had greater (P < 0.010) PZn on d 7 and 14 than pigs fed the NC diet. Whole-body Zn, liver Fe and Zn, and kidney Cu concentrations were greater (P < 0.010), whereas kidney Fe and Zn concentrations were less (P < 0.010) in pigs fed pharmacological Zn diets than pigs fed the NC diet. In Exp. 2, dietary Fe supplementation tended to increase (linear, P = 0.075) dietary DMI, resulting in a linear increase (P < 0.050) in dietary Fe, Cu, Mg, Mn, P, and Zn intake. Subsequently, a linear increase (P < 0.010) in fecal Fe and Zn excretion was observed. Increasing dietary Fe resulted in a linear increase in Hb, Hct, and PFe on d 21 (P < 0.050) and 35 (P < 0.010). Results suggest that dietary Zn or Fe additions increase mineral status of nursery pigs. Once tissue mineral stores are loaded, dietary minerals in excess of the body's requirement are excreted.

Mechanism of acid-induced bone resorption.

This review presents our current understanding of the way metabolic acidosis induces calcium efflux from bone, and in the process, buffers additional systemic hydrogen ions associated with acidosis. Acid-induced changes in bone mineral are consistent with a role for bone as a proton buffer. In response to metabolic acidosis in an in-vitro bone organ culture system, we observed a fall in mineral sodium, potassium, carbonate and phosphate, which each buffer protons and in vivo should increase systemic pH towards the physiologic normal. Initially, metabolic acidosis stimulates physicochemical mineral dissolution and subsequently cell-mediated bone resorption. Acidosis suppresses the activity of bone-resorbing cells, osteoblasts, decreasing gene expression of specific matrix proteins and alkaline phosphatase activity. There is concomitant acid stimulation of prostaglandin production by osteoblasts, which acting in a paracrine manner increases synthesis of the osteoblastic receptor activator of nuclear factor kappa B ligand (RANKL). The acid induction of RANKL then stimulates osteoclastic activity and recruitment of new osteoclasts to promote bone resorption and buffering of the proton load. Both the regulation of RANKL and acid-induced calcium efflux from bone are mediated by prostaglandins. Metabolic acidosis, which occurs during renal failure, renal insufficiency or renal tubular acidosis, results in decreased systemic pH and is associated with an increase in urine calcium excretion. The apparent protective function of bone to help maintain systemic pH, which has a clear survival advantage for mammals, will come partly at the expense of its mineral stores.

Use of stable isotopes and mathematical modelling to investigate human mineral metabolism

Individuals have varying needs for minerals that are dependent, amongst other things, on their lifestyle, age and genetic makeup. Knowledge of exact individual nutritional requirements should lead to better health, increased quality of life and reduced need for expensive medical care. Bioavailability, nutrient-gene interactions and whole-body metabolism all need to be investigated further if we are to progress towards the goal of defining optimal health and nutritional status. The discussion which follows will critically review the latest developments in the area of metabolism for several of the minerals that are essential for human health: Ca, Zn, Cu and Se. Stable-isotope tracers and mathematical modelling are some of the tools being used to facilitate the greater understanding in uptake, utilisation and excretion of these minerals. Stable isotopes, administered in physiological doses, present little or no risk to volunteers and allow metabolic studies to be carried out in vulnerable population groups such as children and pregnant women. Intrinsic labelling of foodstuffs ensures that the tracer and the native mineral will behave similarly once inside the body. Advances in computing power and software dedicated to solving nutritional problems have made it possible for investigators to use mathematical modelling in their experimental work. Mineral metabolism is ideally suited to a form of modelling known as compartmental analysis, which allows rates of mineral transferand sizes of mineral stores to be calculated accurately without the need for invasive sampling of body tissues.