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Calcium metabolism in insectivores may be perturbed by insufficient calcium or vitamin D3. Insects may be gut loaded to increase calcium content, and recent research shows that exposure to UVB radiation can increase the vitamin D3 content of some invertebrates. Typical gut loading protocols result in peak calcium content after 24–48 h, while existing evidence with UVB irradiation involves exposure periods of tens of days. We UVB-irradiated fasted black field crickets (Gryllus bimaculatus) while feeding them on high calcium diets for 48 h, then fasted them for a further 24 h, and measured the vitamin D3, calcium, and phosphorus content compared with non-irradiated controls. UVB irradiation had no effect on vitamin D3 (crickets had no detectable levels of vitamin D3 at any point), or on calcium accumulation rates, which approximated existing research. Crickets significantly increased their calcium:phosphorus ratio from 0.17 to approximately 0.4 over 24 h and this did not increase over a further 24 h of feeding. Removal of the food source resulted in loss of all accumulated calcium within 24 h. Our results have implications for managing food sources for captive insectivores and highlight the importance of good feeder preparation and rapid consumption to ensure optimal calcium delivery to predators.

Osteopenia is a sign of osteoporosis that usually occurs in adolescent aged 18-24 years. One of the efforts to manage osteopenia is by giving a high calcium diet. Meatballs substituted by tempeh gembus can be used as an alternative to local food-based snacks as source of calcium. To analyze the effect of the substitution of tempeh gembus on the protein content, calcium, digestibility of the protein, and the acceptability of meatballs. The study was conducted in two stages, there are preliminary study and main study, and using randomized single factor experimental, tempeh gembus levels (25%, 50%, 75%, 100%) and control (0% tempeh gembus). The analysis of the content of protein was conducted using Kjeldahl method, calcium contents using Uv-Vis spectrophotometer, and protein digestibility using in-vitro method. Data was analyzed with mann-whitney. Organoleptic tests were carried out by hedonic testing of 30 semi-trained panelists. Substitution of tempeh gembus had significant effect on the protein contents and protein digestibility, but not significant effect on the calcium contents. Formulation with 25% tempeh gembus substitution was found to be a best formulation of meatballs containing protein content of 8.03%, calcium contents of 351.19 mg / 100 g, and protein digestibility of 53.22%. Meatball with 25% tempeh gembus with 78 mg per serving is sufficient for nutrition label reference in general category, 13% energy; protein by 11%; calcium by 25%.

Objective: Emerging evidence established the role of dietary calcium in the modulation of obesity. Obesity is known to induce inflammatory and oxidative stress in adipocytes resulting in several metabolic complications. In the present study, we evaluated the role of low and high calcium diet on systemic inflammatory response and oxidative stress markers in both plasma and hepatic tissues in male rats. Methods: A total of 30 male rats were divided into three groups and fed with control, low calcium (0.25%), and high calcium (1.0%) diet for 3 months. All the diets were isocaloric in nature. At the end of the treatment, all rats were sacrificed, followed by collection of blood and hepatic tissue for inflammatory, oxidative, antioxidant, and histological study. Results: Rats fed with a low calcium diet showed a significant increase in the body weight gain, liver mass, plasma inflammatory markers C-reactive protein, interleukin-6, and tumor necrosis factor-alpha. Low calcium diet significantly increased the lipid peroxidation and protein carbonylation and decreased the superoxide dismutase and glutathione peroxidase activities in both plasma and liver. High calcium diet, on the other hand, showed the reversed effect. Conclusion: Low calcium in the diet, along with obesity, increases the systemic inflammatory response, which in turn increases oxidative stress both in blood and hepatic tissues. This might be associated with obesity-induced hepatic disorder. High calcium in diet attenuates this effect.

An important function of feeding large breed puppies is providing appropriate amounts of calcium and phosphorus, which is used in skeletal mineralization during growth. National Research Council stated calcium requirements are 0.8–1.2%, and phosphorus 1.0–1.6%. The objective of this study was to compare a high calcium diet (Ca: 5.7%; P: 2.9%) (Nature’s Logic Canine Beef Meal Feast; Nature’s Logic) (HC) to a normal control diet (Ca: 1.6%; P: 1%) (Purina Puppy Chow; Nestle Purina) (CON) in growing Labrador Retriever puppies. Thirty-two puppies (16 HC/16 CON) were used in two 10wk modified AAFCO large breed puppy growth trials. Body weights were measured weekly, feed intake daily, and digestibility, body composition, hematology, chemistry, and bone metabolism biomarkers were measured at 8wks, 13wks, and 18wks of age. All puppies passed all AAFCO large breed puppy growth requirements, including veterinary exams, body weight gain, and bloodwork parameters. Both groups had similar average weight gains from baseline to the end of the trial. No significant differences in bone mineral density were found between HC and CON groups at any timepoint. No significant differences were found between groups after baseline for parathyroid hormone, calcitonin, or tartrate resistant acid phosphatase bone metabolism biomarkers. Total tissue mass, fat mass, and lean mass were lower in the HC group compared to CON group (P < 0.05), likely due to lower caloric content and metabolizable energy in the HC diet than expected. Calcium digestibility was significantly higher in HC diet vs CON diet (P < 0.01). Based on this data, a high calcium diet had no negative impact on major physiological parameters in growing Labrador Retriever puppies.

Thirteen female Rhesus macaques were intramuscularly injected with Sr(NO3)2 diluted in sodium citrate solution. The biokinetic data from these animals were compared against the predictions of the NCRP 156 wound models combined with the ICRP systemic models. It was observed that the activities measured in plasma of these nonhuman primates (NHPs) were consistently lower than those predicted by the default human biokinetic models. The urinary excretion from the NHPs at times immediately after injection was much greater than that in humans. The fecal excretion rates were found to be in relatively better agreement with humans. Similarly, the activities retained in the skeleton of the NHPs were lower than those in humans. These differences were attributed to the higher calcium diet of the NHPs (0.03 to 0.12 g d kg body weight) compared to that of humans. These observations were consistent with the early animal and human studies that showed the effect of calcium on strontium metabolism, specifically urinary excretion. Strontium is preferentially filtered at a much higher rate in kidneys than calcium because it is less completely bound to protein than is calcium. These differences, along with large inter-animal variability, should be considered when estimating the behavior of strontium in humans from the metabolic data in animals or vice versa.

Although the implications of long-term high Ca intakes have been well documented in growing dogs, the health consequences of Ca excess in adult dogs remain to be established. To evaluate the impact of feeding a diet containing 7·1 g/4184 kJ (1000 kcal) Ca for 40 weeks on Ca balance and health parameters in adult dogs, eighteen neutered adult Labrador Retrievers, (nine males and nine females) aged 2·5–7·4 years were randomised to one of two customised diets for 40 weeks. The diets were manufactured according to similar nutritional specifications, with the exception of Ca and P levels. The diets provided 1·7 and 7·1 g/4184 kJ (1000 kcal) (200(SD26) and 881(SD145) mg/kg body weight0·75 per d, respectively) Ca, respectively, with a Ca:P ratio of 1·6. Clinical examinations, ultrasound scans, radiographs, health parameters, metabolic effects and mineral balance were recorded at baseline and at 8-week intervals throughout the study. Dogs in both groups were healthy throughout the trial without evidence of urinary, renal or orthopaedic disease. In addition, there were no clinically relevant changes in any of the measures made in either group (all P>0·05). The high-Ca diet resulted in a 3·3-fold increase in faecal Ca excretion (PP>0·05). Ca intakes of up to 7·1 g/4184 kJ (1000 kcal) are well tolerated over a period of 40 weeks, with no adverse effects that could be attributed to the diet or to a high mineral intake.

Background: Diet plays a key role in the pathogenesis of kidney stones. In particular, recent findings have advanced knowledge on the protective role of a high calcium diet. However, not much is known about the specific role played by milk intake in the pathogenesis of kidney stones compared with other dairy products, especially cheese.

The present study is the second step (concerning the normal-diet restoration) of the our previous one (concerning the calcium-free diet) to determine whether the normal-diet restoration, with/without concomitant PTH(1-34) administration, can influence amounts and deposition sites of the total bone mass. Histomorphometric evaluations and immunohistochemical analysis for Sclerostin expression were conducted on the vertebral bodies and femurs in rat model. The final goals are: i) to define timing and manners of bone mass changes when calcium is restored in the diet; ii) to analyze the different involvement of the two bony architectures having different metabolism (i.e. trabecular versus cortical bone); iii) to verify the eventual role of PTH(1-34) administration. Results evidenced the greater involvement of the trabecular bone with respect to the cortical one, in answering to different calcium diet content, and the effect of PTH mostly in the recovery of trabecular bony architecture. The main findings emerged from the present study are: i) the importance of the interplay between mineral homeostasis and skeletal homeostasis in modulating and guiding bone answers to dietary/metabolic alterations and ii) the evidence that the more involved bony architecture is the trabecular one, the most susceptible to the dynamical balance of the two homeostases.

The serum calcium levels of patients were assessed as they attended a district hospital in a rural population for a period of one month. A majority of the patients were between the age group of 38-77 years. 55 cases were studied. The ratio of males to females was 3:8. The results show an increase in abnormal serum calcium level with age. The abnormality in serum calcium was higher in females than in males. The demonstration of poor nutritional intake and lack of other calcium supplements was a predisposing factor to the abnormal calcium levels. It was concluded that the abnormal levels of calcium were as a result of lack of calcium diet.

In order to clarify the effects of a high-calcium (Ca) diet on bone formation in magnesium (Mg)-deficient rats, this study focused on the effects of a high-Ca diet on serum insulin-like growth factor-1 (IGF-1) levels. Male rats were randomized by weight into four groups, and fed one of four experimental diets containing two different Mg concentrations (0.05% (normal-Mg) or Mg-free (Mg-deficient)), and two different Ca concentrations (0.5% (normal-Ca) or 1.0% (high-Ca)) for 14 days. Serum concentrations of osteocalcin and IGF-1 were significantly lower in rats fed the Mg-deficient diet than in rats fed the normal-Mg diet. On the other hand, dietary Ca concentration had no significant influence on serum concentrations of osteocalcin and IGF-1. This study suggested that: 1) a high-Ca diet has no preventive effects on the decreased bone formation seen in Mg-deficient rats; and 2) a high-Ca diet does not enhance serum IGF-1 levels in Mg-deficient rats. Moreover, unchanged serum IGF-1 concentrations may contribute to the decreased bone formation seen in Mg-deficient rats receiving a high-Ca diet.

Submitted by Boris Flegr (boris@uerj.br) on 2021-01-06T20:54:11Z No. of bitstreams: 1 TESE_FINAL_PUBLICADA_Jessica_Lopes_nobre.pdf: 1744205 bytes, checksum: 37b25eb634ba1d2a2639627f2f57a89f (MD5) Made available in DSpace on 2021-01-06T20:54:11Z (GMT). No. of bitstreams: 1 TESE_FINAL_PUBLICADA_Jessica_Lopes_nobre.pdf: 1744205 bytes, checksum: 37b25eb634ba1d2a2639627f2f57a89f (MD5) Previous issue date: 2015-09-30 Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro Obesity is a worldwide epidemic and in Brazil more than 50% of people are overweight/obese. We show that a rich calcium diet has an anti-obesity effect in obese animals programmed by early weaning (EW), an effect mediated by vitamin D action, which appears to directly regulate adipogenesis. Thus, we decided to evaluate the effect of vitamin D on the metabolism of adipose tissue in vivo with EW animals and in vitro with 3T3L1 lineage. At birth, lactating rats were divided into: EW Group, dams were wrapped with a bandage to interrupt lactation in the last 3 days of lactation; C Group, dams whose pups had free access to breast milk during the lactation period (21 days). At 120 days-old, EW offspring were subdivided into: EW standard diet; EW, received calcium supplementation (EWCa, calcium carbonate 10g / kg chow). We also use 3T3L1 cell line to incubated with calcitriol (1,25 (OH) 2D) or leptin. Significance level was at p

Objective Recent evidence suggests that diets high in calcium and dairy products are associated with lower body weight, particularly lower body fat levels. The purpose of this study was to compare weight and body fat loss on a calorie-restricted, low-dairy (CR) vs. high-dairy (CR+D) diet. Research methods and procedures Fifty-four subjects (BMI 30 +/- 2.5 kg/m2, 45 +/- 6.6 years, 4 men) were randomly assigned to calorie-restricted (-500 kcal/d) low-dairy calcium (n = 29; approximately 1 serving dairy/d, 500 mg/d calcium) or high-dairy calcium (n = 25; 3 to 4 servings dairy/d, 1200 to 1400 mg/d calcium) diets for 12 months. Main outcome measures included change in weight (kilograms) and body fat (percentage). Results There were no significant differences between groups at baseline. At 12 months, weight and body fat loss were not significantly different. Subjects in the CR vs. CR+D conditions lost 9.6 +/- 6.5 vs. 10.8 +/- 5.9 kg (p = 0.56) and 9.0 +/- 3.8 vs. 10.1 +/- 3.6 kg body fat (p = 0.37). Discussion These findings suggest that a high-dairy calcium diet does not substantially improve weight loss beyond what can be achieved in a behavioral intervention.

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An experiment was conducted to evaluate the potential dietary interaction between 1,4-diaminobutane (putrescine) and calcium on eggshell quality and overall laying performance. One hundred ninety-two 30-wk-old White Leghorn hens were fed a corn-and soybean-meal-based diet supplemented with 0.00, 0.05, 0.10, or 0.15% putrescine and 2.5, 3.0, 3.5, or 4.0% calcium in a factorial design (12 birds per diet) for 4 wk. The percentage of egg production increased linearly (P < 0.05) with increasing levels of dietary calcium. Significant interactions (P < 0.05) were observed between dietary putrescine and calcium for eggshell thickness, eggshell deformation, percentage of eggshell, calcium intake, total calcium retention, total eggshell calcium, and percentage of eggshell calcium. Interactions were due to quadratic effects of putrescine or calcium on these parameters. Eggshell thickness and percent eggshell increased when hens were fed 3.5% calcium in combination with 0.1% putrescine; however, calcium intake and calcium retention were significantly lower (P < 0.05). Eggshell quality improved with increasing dietary levels of calcium due to increased calcium retention and calcium balance. Increasing levels of dietary putrescine did not have a negative effect on eggshell quality; however, calcium intake was lower at higher-supplemented levels of putrescine. It was observed that dietary calcium in excess of requirements resulted in increased egg production and eggshell quality. Eggshell quality improved when hens were fed 3.5% calcium diet in combination with 0.10% putrescine. It was concluded that small supplements of dietary putrescine may improve eggshell quality, depending on dietary calcium concentration.

The requirement of parathyroid tissue for bone mineral loss during lactation was investigated. Lactating rats parathyroidectomized (PTX) at day 2 of lactation and consuming a 2% calcium diet are hypercalcemic and hypophosphatemic at day 13 of lactation. The high-calcium diet supports normal growth of pups nursing PTX mothers. PTX lactating rats mobilize bone mineral to the same extent as euparathyroid lactating rats consuming the same diet. Non-lactating PTX rats lose no bone mineral over a similar time period, indicating lactation-specific bone mineral mobilization in the absence of parathyroid tissue. PTX rats were verified to have physiologically insignificant amounts of parathyroid tissue, as evidenced by severe hypocalcemia and/or death in each rat after a shift from a 2% calcium to a 0.02% calcium diet. These results conclusively demonstrate that lactation-associated bone mineral mobilization does not require parathyroid hormone or parathyroid tissue.

The growth and development of bone play an important role in orthodontics, where bone calcification can be used the estimate bone maturity for diagnosis and treatment planning. Nutritional status during pregnancy and infant period will influence the growth and development of bone. Calcium diet is an important factor determining optimal calcification during bone growth and development stages. The purpose of this study was to investigate the possibility to restore calcium and phosphorus in bone after pre- and postnatal calcium deficiency. Three groups of Rattusnorvegicus rats were used in the experiments. The first group was the control group with standard diet, the second was infant group with pre- and postnatal calcium deficiency, and the third group consisted of young rats at weaning age with pre- and postnatal calcium deficiency but supplemented with enough calcium in the diet. Bone calcification stages were analyzed 1) histologically by measuring epiphyseal width on right femur, 2) by measuring calcium and phosphorus concentration on left femur with spectrophotomethry, atomic absorbtion and UV spectroscopy. The data were analyzed by one way Anova and t testing. The results showed that there were significant differences in the epiphyseal width and in calcium and phophorus concentrations between all three groups (p

This experiment was conducted to study the microscopic structure of tail bones in ovariectomized and non-ovariectomy rats. Fourteen femaleSprague Dawley rats 7 weeks old were randomly divided into 2 groups. The rats in the control group were non-ovariectimized. The rats in groupII were ovariectomized. The samples were then fed with phosphate/calcium diet with ratio of 2 to 1. The rats was sacrificed after 12 weeks. Thetail bone were collected and processed for microscopic examination with trichrome staining. The results showed that structurally theosteoporosis occurred in tail bone of group K2. Its could be concluded that estrogen deficiency condition (ovariectomy) caused osteoporosis intail bones.____________________________________________________________________________________________________________________Key words: osteoporosis, ovariectomy, tail bone

Twenty-one aged Jersey cows were fed a high calcium diet prior to parturition to predispose them to parturient paresis. Eleven cows were implanted subcutaneously with pellets containing 24F-1,25-dihydroxyvitamin D 3 7 d before the expected date of parturition and thereafter at 7-d intervals until parturition. Ten cows were left untreated to serve as controls. Incidence of parturient paresis among control animals was 80% (8/10). Treatment reduced the incidence of parturient paresis to 9% (1/11). The mean observed plasma calcium concentration nadir of implanted cows was 6.61±.40 mg/dl, which was significantly greater than the plasma calcium nadir of 4.45±.39 mg/dl observed in the control cows. Two steers were implanted with and three nonpregnant, nonlactating cows received intramuscular injections of 24F-1,25 dihydroxyvitamin D 3 to contrast circulating plasma concentrations achieved by the two routes. Intramuscular injection and implantation resulted in plasma 24F-1,25 dihydroxyvitamin D 3 concentrations above 300 pg/ml for the first 48h after administration. From d 4 until d 11 after administration, plasma concentration was maintained between 164 and 89 pg/ml in the implanted steers. Plasma concentration was undetectable 7 d after an intramuscular injection. These data indicate that, with refinement, sustained release of 24F-1,25 dihydroxyvitamin D 3 can be successfully used to reduce the incidence of parturient paresis

High calcium diet down-regulates kidney angiotensin-converting enzyme in experimental renal failure. Background Calcium salts are used as phosphate binders in renal failure, while high calcium diet also improves vasorelaxation and enhances natriuresis. The influences of calcium intake on renal renin-angiotensin system (RAS) are largely unknown. Methods Four weeks after NTX, rats were put on 3.0% or 0.3% calcium diet for 8 weeks (12-week study). In additional experiments, 15 weeks after NTX, rats were put on similar diets for 12 weeks (27-week study). Appropriate blood, urine, and kidney samples were taken. Renal angiotensin-converting enzyme (ACE) and angiotensin II receptors (AT 1 , AT 2 ) were examined using autoradiography, ACE also using Western blotting, and connective tissue growth factor (CTGF) using immunohistochemistry. Results In the 12-week study, albuminuria increased 5-fold in NTX rats, but only 2-fold in calcium NTX rats on 3.0% calcium. In the 27-week study, high calcium intake decreased blood pressure, retarded progression of renal failure, reduced glomerulosclerosis, interstitial damage, and aortic calcifications, and improved survival from 50% to 92% in NTX rats. In both experiments plasma parathyroid hormone and phosphate were elevated after NTX, and suppressed by high calcium diet, while kidney ACE was down-regulated by 40% or more after increased calcium intake. In the 27-week study renal CTGF was decreased and cortical AT 1 receptor density reduced after high calcium diet. Conclusion High calcium diet down-regulated kidney ACE, reduced albuminuria and blood pressure, and favorably influenced kidney morphology in experimental renal failure. These findings suggest a link between calcium metabolism and kidney ACE expression, which may play a role in the progression of renal damage.

Bone mineral density and urine calcium excretion among subjects with and without nephrolithiasis. Background Bone mineral density (BMD) is reduced among patients with idiopathic hypercalciuria (IH) and nephrolithiasis. To disentangle effects of diet, stone formation, and physiology upon BMD, we studied vertebral and femoral neck BMD among relatives of hypercalciuric stone formers, and contrasted those with to those without stones. Methods Among 59 subjects from 11 families, vertebral and femoral neck BMD, diet calcium intake, urine excretions of calcium, sodium, ammonium, titratable acid, sulfate, urea nitrogen, and serum levels of calcitriol and markers of bone turnover were studied. Results Stone formers (SF) consumed less calcium than non-stone formers (NSF). Spine and femoral neck BMD z-scores varied inversely with urine calcium loss and urine ammonium excretion among SF but not NSF. No correlations of BMD z-score were found for bone markers, calcitriol, or any of the other measurements. Conclusion SF consumed less calcium, presumably to prevent more stones, and displayed a bone mineral responsiveness to calcium loss and ammonium excretion not present among NSF, who ate more calcium. Lowered calcium consumption in IH, perhaps in response to stone formation, alters bone responses in a direction that can predispose to mineral loss and eventual fracture.

This study was investigated the influence by ovariectomy (OVX) and calcium diet on bone properties in eighty-one female ICR strain mice with age of 5 weeks. The animals were randomly assigned to sham operation (SHAM), OVX, SHAM+low Ca intake (L.Ca) and OVX+L.Ca group. They were euthanized with lethal dose of pentobarbital sodium at day 50, 100 and 140 post-operatively. For determining the bone properties, both femur and tibial bones were excised from the hind limb, and removed off surrounding tissues. Thereafter, bone length, bone dry weight, and also mechanical strength and ash content of the bones were determined. The bone length on both femur and tibia was significantly longer in OVX group than in the other groups after 50 day of experiment, this situation was continued to the end of the experiment. Bone dry weight, mechanical strength, and ash content were significantly decreased by OVX and L.Ca over the time of the experiment, and those of OVX+L.Ca group were the lowest in all groups. OVX and L.Ca have a great potential for weakening the mechanical strength and have an additive effect when combined. OVX and L.Ca block the gain of bone mass.

To investigate the role of parathyroid hormone (PTH) in the development of hypertension, the long-term administration of human PTH (hPTH) was performed in 7-week-old male spontaneously hypertensive rats maintained on a standard calcium diet (1.1% calcium) or a high calcium diet (2.8% calcium). The hPTH was infused subcutaneously at 0.9 U/h over 2 weeks using a minipump. Two weeks after minipump implantation, rat PTH (rPTH) and 1,25-dihydroxy vitamin D (1,25-D) levels were measured and the pressor response to norepinephrine (NE) was examined. Calcium loading both attenuated the development of hypertension and reduced the pressor response to norepinephrine. Chronic hPTH administration accelerated the development of hypertension and increased the pressor response to norepinephrine in rats fed a high calcium diet, but did not affect either parameter in rats fed a standard calcium diet. The serum concentrations of rat PTH and 1,25-D were significantly lower in rats fed a high calcium diet than in those fed a standard calcium diet (rat PTH: 351 +/- 16 v 430 +/- 1 pmol/L; 1,25-D: 125 +/- 19 v 206 +/- 31 pg/mL). Chronic administration of hPTH increased the serum 1,25-D concentration in rats fed a high calcium diet (186 +/- 35 pg/mL), but did not affect that of rats fed a standard calcium diet (165 +/- 16 pg/mL). It is concluded that PTH prevented the antihypertensive effect of calcium loading in young SHR, perhaps by enhancing blood pressure reactivity through causing an increase of 1,25-D.

Two experiments were conducted in which 270 hens received a choice of diets offered in two plastic cups. The treatments consisted of hens fed diets containing 3.0% calcium (Ca) in both cups, 6.0% Ca vs. 0.7% Ca, or 3.0% Ca vs. 0.7% Ca. Young hens exhibited the ability to discriminate between high and low levels of Ca. They greatly increased their consumption of the 3.0% Ca over the 0.7% Ca diet. Old birds showed an immediate marked aversion to the 6.0% Ca diet. They did not increase their consumption of the 3.0% Ca over the 0.7% Ca diet as did young hens. Reversing the position of the diets after the young hens' initial adjustment resulted in a reversal of the hens' positional preference for the feed. The birds tended to eat more of the higher calcium diet in the early morning and late afternoon, the times of greatest Ca need or anticipated need. This indicated that the young hens regulated their calcium intake according to metabolic need. Young hens in the regulating groups maintained egg production and egg weight, but not specific gravity of eggs nor serum calcium, at levels comparable to controls.

This study examined physiological and bone morphological changes resulting from parathyroidectomy (PTX) in male rats. Two diets were provided: one contained 1.2% calcium, 1% phosphorus; the other 0.4-0.6% calcium, 0.6% phosphorus. However, at 51/2 months post-PTX all rats were transferred to a diet containing 0.3% calcium. The daily ration for each rat was 16 g. The parameters examined were: (1) Plasma calcium concentrations; (2) plasma and thyroidal calcitonin levels; and (3) histomorphometry of metaphyseal trabecular bone. When maintained on the lower calcium diet, fasted plasma calcium concentrations of PTX rats stabilized between 5 and 6 mg/dl. In contrast, in rats fed the higher calcium diet, these values gradually rose to between 7 and 8 mg/dl (5 months post-PTX). After transfer to the 0.3% calcium diet, plasma calcium values fell to >6 mg/dl. Thyroidal calcitonin content following PTX rose to values three times those of age-matched controls regardless of the daily calcium intake. The volume...

The ability of pullets to selectively consume calcium to meet the requirements of the rearing and early laying period was studied in White Leghorns. In the first of two experiments, 456 pullets were fed either an .89% calcium rearing diet (control) or a .35% calcium diet in combination with a separate source of 38% calcium chick-sized grit (calcium self-selection) from 35 to 126 days of age. Twenty-four pullets from each of these rearing treatments were selected for the second experiment at 112 days of age and were housed in individual laying cages. Rearing treatments were continued until 176 days of age with mash and grit consumption recorded daily for each pullet. From 177 to 225 days of age these pullets were fed a 3.50% calcium diet containing either ground limestone or oyster shell as a calcium source or a .35% calcium diet fed in combination with a separate source of oyster shell. Pullet calcium intake reflected the requirements for growth during the rearing period, calcium storage in the medullary bone 19 days prior to lay, and egg shell formation during the laying period; average calcium intake for these periods was 1.18, 2.08, and greater than 3.50%, respectively. Pullets also demonstrated the ability to compensate for rearing deficiencies by increased calcium consumption when fed oyster shell on an ad lib basis. Calcium consumption was found to be significantly higher on days when an oviposition occurred than when no eggs were laid. Mash consumption during the early laying period also reflected the reproductive status of the hen with the highest consumption on days when both oviposition and ovulation occurred, intermediate consumption when either oviposition or ovulation occurred, and lowest consumption when neither oviposition nor ovulation was detected.