Calcium Shortage Research Articles

Positive effect of peptide-calcium chelates from Grifola frondosa on a mouse model of senile osteoporosis.

Calcium supplementation has been shown to be efficacious in mitigating the progression of senile osteoporosis (SOP) and reducing the incidence of osteoporotic fractures resulting from prolonged calcium shortage. In this study, Grifola frondosa (GF) peptides-calcium chelate were synthesized through the interaction between peptide from GF and CaCl2. The chelation reaction was shown to involve the participation of the amino and carboxyl groups in the peptide, as revealed by scanning electron microscope, Fourier-transform infrared, and ultraviolet spectrophotometry. Furthermore, a mouse model of (SOP) induced by d-galactose was established (SCXK-2018-0004). Results demonstrated that low dosage of low-molecular weight GF peptides-calcium chelates (LLgps-Ca) could significantly improve serum index and pathological features of bone tissue and reduce bone injury. Further research suggested that LLgps-Ca could ameliorate SOP by modulating the disrupted metabolic pathway, which includes focal adhesion, extracellular matrix receptor interaction, and PI3K-Akt signaling pathway. Using Western blot, the differentially expressed proteins were further confirmed. Thus, calciumchelating peptides from GF could serve as functional calcium agents to alleviate SOP.

Formulation and Evaluation of herbal preparation containing multiherb for hypocalcaemia

Calcium is a necessary vitamin for human health. It helps the body create strong bones and teeth. It is required for the correct functioning of heart and other muscles. Calcium shortage, known as hypocalcemia, is a disorder in which a person's blood calcium levels are abnormally low. Women must begin to increase their calcium consumption earlier in life than males. As a woman approaches menopause, it is especially vital to meet her calcium requirements. Calcium homeostasis is important for supporting human life functions like skeleton maintenance, hormone secretion regulation, nerve impulse transmission and vascular activity. Herbs with a high calcium content may aid in maintenance of calcium levels in the body. Though various supplements are available to address calcium shortage, herbal formulations are recommended since they have fewer side effects and are less expensive. This research focuses on the use of herbal plants to treat hypocalcemia. This study aimed to produce and test herbal candies that contained these herbs and used as natural excipients. Drumstick (Moringa oleifera), shingada (Trapa natans), hadjod (Cissus quadrangularis) and finger millet (Eleusine coracana) are among the ingredients in the formulation that will help with hypocalcemia. Organoleptic and other screening test are used to evaluate formulation. Calcium content was determined by the EDTA method and Atomic absorption spectroscopy.

Calcium's Role in Child Growth and Development and It's Complications

Calcium (Ca) is an important mineral used to build and maintain the skeletal system. Calcium is the body's most vital mineral. Bone and teeth contain calcium, phosphorus, and the rest of the body's calcium. This mineral aids in the creation of bones and teeth, blood coagulation and muscle contraction as well as nerve transmission and cell metabolism.
 Calcium deficiency in children causes physical and mental growth problems, as well as the development of Rashitisme, a kind of osteoporosis. This disorder is characterised by deformed bones, big joints, and mobility issues. Calcium shortage in adults produces osteomalacia, which causes hollow and brittle bones due to a reduction in calcium density in the bones.
 Vitamin D deficiency causes bone mineralization difficulties and severe muscle cramping. Calcium is required for bone and tooth development, blood coagulation, muscle contraction, nerve transmission, and cell metabolism, say the researchers.
 This study concluded that calcium causes bone strength. Children's meals should include enough calcium to prevent osteoporosis in adults. A new scientific barrier has been published, as well as the importance of calcium's function in the body and the repercussions of its deficiency on children's growth and development.

Investigation of Calcium-Binding Capacity and Functional Properties of Acetes Japonicus Protein Hydrolysate

Calcium-binding capacity (CaBC), amino acid profile and functional properties of proteolysate derived from Acetes japonicus were evaluated in this research. Firstly, effect of hydrolysis parameters including enzyme type, enzyme to substrate (E:S) ratio and hydrolysis time on the CaBC of the proteolysate was examined using single factor test method. Then, amino acid component and technological features involving solubility, heat stability, foaming and emulsifying property, oil holding capacity (OHC) and water holding capacity (WHC) of the protein hydrolysate were assessed. The result showed that the proteolysate exhibited the greatest CaBC of 261.61 ± 3.89 mg Ca2+/g protein, 1.77 folds lower than that of casein phosphopeptide, under the hydrolysis condition encompassing Flavourzyme, pH 6.5, 50 C, E:S ratio of 60 U/g protein and hydrolysis time of 5 hours. Solvability and heat stability of the proteolysate achieved over 75 % and over 70 % in the pH range from 5 to 8 The foaming capacity (FC), foaming stability (FS), emulsifying activity index (EAI) and emulsifying stability index (ESI) reached the peaks of 46.33 ± 0.57 %, 40.22 ± 0.38 %, 15.92 ± 0.07 m2/g and 48.06 ± 1.59 min at pH 8. The OHC and WHC of the proteolysate accomplished 4.76 ± 0.41 ml oil/g proteolysate powder and 2.81 ± 0.08 ml water/g proteolysate powder. The proteolysate contained 8 out of 9 essential amino acids for human, comprising approximately 45 % of total amino acid content. On the whole, the proteolysate could be served for calcium enhancement which could protect human body from disorders caused by calcium shortage or as a functional protein preparation to improve food properties. The findings likewise increase the economic value for the small shrimp which is quite cheap in Vietnam.

Respiratory metabolism and calorie restriction relieve persistent endoplasmic reticulum stress induced by calcium shortage in yeast.

Calcium homeostasis is crucial to eukaryotic cell survival. By acting as an enzyme cofactor and a second messenger in several signal transduction pathways, the calcium ion controls many essential biological processes. Inside the endoplasmic reticulum (ER) calcium concentration is carefully regulated to safeguard the correct folding and processing of secretory proteins. By using the model organism Saccharomyces cerevisiae we show that calcium shortage leads to a slowdown of cell growth and metabolism. Accumulation of unfolded proteins within the calcium-depleted lumen of the endoplasmic reticulum (ER stress) triggers the unfolded protein response (UPR) and generates a state of oxidative stress that decreases cell viability. These effects are severe during growth on rapidly fermentable carbon sources and can be mitigated by decreasing the protein synthesis rate or by inducing cellular respiration. Calcium homeostasis, protein biosynthesis and the unfolded protein response are tightly intertwined and the consequences of facing calcium starvation are determined by whether cellular energy production is balanced with demands for anabolic functions. Our findings confirm that the connections linking disturbance of ER calcium equilibrium to ER stress and UPR signaling are evolutionary conserved and highlight the crucial role of metabolism in modulating the effects induced by calcium shortage.

저칼슘 식이로 유발한 성장 저하 흰쥐에 대한 칼슘, 비타민 D 및 난황 펩타이드의 투여가 장골 길이 성장에 미치는 영향

Objectives : Egg yolk is composed of various important chemical substances for human health. A calcium shortage causes the growth retardation on the body growth. In this study, we examined the therapeutic effects of calcium, vitamin D and egg yolk peptide (EYP) treatment on the retardation of the longitudinal bone growth induced by low-calcium diet in adolescent rats. Methods : Low calcium diets were administrated for 15 days. During the last five days, calcium and/or vitamin D and/or EYP were administrated. The body weights, longitudinal bone growth rates, the heights of growth plates, and bone morphogenetic protein (BMP)-2 and insulin-like growth factor (IGF)-1 expressions were measured using histochemical analysis. Results : Low calcium diets caused the significant reduction in body weight gains and the longitudinal bone growth. The heights of growth plates and the expressions of BMP-2 and IGF-1 showed the impairment of body growth as well. Calcium and/or vitamin D administration could not significantly increase the longitudinal bone growth. However, calcium, vitamin D, and EYP administration significantly increased the bone growth, the growth plate height, and BMP-2 and IGF-1 expressions. Conclusions : These results suggest that EYP enhances the longitudinal bone growth in the calcium and/or vitamin D deficiency and it could be a promising agent for the treatment of children suffering from malnutrition.

Effect of Shortage Mineral Elements (Nitrogen, Phosphorus, Potassium, Magnesium and Calcium) on Antioxidant Enzymes Activity (Peroxidase, Glotation Reductase, Ascorbate Peroxidase and Catalase) in Fenugreek (Trigonella foenum graecum)

When needing nutrient elements hold suitable degree for plants, they performed their physiological and biochemical processes properly and so there will be no need to use defensive mechanism. In doing so, its growth and function level increases. In this study, effect of shortage nutrient elements (Nitrogen, Phosphorus, Potassium, Magnesium and Calcium) on antioxidant enzymes activity such as Peroxidase, Glotation Reductase, Ascorbate Peroxidase and Catalase were studied. The observations indicate that Ascorbate Peroxidase, Peroxidase and Catalase activity in root and shoot was reduced in all the shortage level of mineral elements than blank level. But Peroxidase activity in phosphorous shortage was increased than blank level. In plants with Magnesium shortage, Glutation Reductase activity in root was decreased than blank. While in plants with Potassium, Calcium and Nitrogen, Glutation Reductase activity was increased. In relation with Glutation Reductase measurement in plants shoot with Nitrogen, Phosphorous and Magnesium shortage showed no significant changes, while in Calcium and Potassium shortage was decreased than blank level.

Shortage on (Magnesium and Calcium) Dry Weight, Fresh Weight, Root and Shoot Length, Leaf Relative Water Content (RWC), Chlorophyll Content and Malondialdehyde Activity in Fenugreek (Trigonella Foenum Graceum)

Fenugreek ( Trigonella Foenum Graceum ) is one of the medicinal plants that have been used as a folk medicine in Iran and many countries. In this study, effects of macronutrient element shortage (Nitrogen, Phosphorous, Potassium, Magnesium and Calcium) on dry and fresh weight, root and shoot length, Leaf Relative Water and chlorophyll content in Fenugreek plant was investigated. In relation to Magnesium shortage which caused, increase of root and shoot dry weight, root and shoot fresh weight, root and shoot length and leaf relative water content, it was observed that this increment was meaningful in 0/05 of statistical level. In Calcium shortage, root and shoot length, root and shoot dry weight and shoot fresh weight decreased, which in statistical level 0/05 showed meaningful difference than blank level, while in relation to leaf relative water content, there was no meaningful difference to the control level. In Potassium shortage, shoot length, root and shoot fresh weight and leaf relative water content meaningful increased, while root and shoot dry weight, observed decrement in statistical level of 0/05 which was meaningful than blank level. Investigating the effect of Phosphorous shortage, shoot length meaningfully increased than in blank level, while in root dry weight, shoot fresh weight and leaf relative water content, meaningful decrement was observed than in the blank level (P<0.05). In Nitrogen shortage, root length and fresh weight and leaf relative water content meaningfully increased than blank, while shoot fresh weight, root and shoot dry weight were meaningfully decreased in statistical levels of 0/05 than blank. Macronutrient elements shortage caused decrement of chlorophyll in Fenugreek leaves with Nitrogen, Potassium and Phosphorous recording shortage than the blank level. In plants with Calcium and magnesium shortage, increase of chlorophyll was observed. Macronutrient elements shortage caused meaningful decrease in chlorophyll b and total chlorophyll concentration in Fenugreek leaves (P<0.05). Also, macronutrient elements shortage caused decrease in Malondialdehyde activity in root and shoot of Fenugreek plant.

Testing the structural–function hypothesis of eggshell maculation in the Great Tit: an experimental approach

The function of eggshell pigmentation has long been the subject of much speculation. Most of the proposed hypotheses have been based on a signalling function. According to the recently proposed structural–function hypothesis, birds use the pigment protoporphyrin to strengthen the eggshell in response to dietary calcium (Ca) shortage. The aim of the study reported here was to test this hypothesis in a Ca-provisioning experiment involving Great Tit Parus major populations breeding in Ca-poor coniferous and Ca-rich deciduous Estonian forests, respectively, over a 2-year period. Ca-supplemented birds laid eggs with ‘darker’ pigmentation than birds in the unsupplemented (control) group, which is at odds with the structural–function hypothesis. Although eggs were smaller and had thinner shells in Ca-poor habitat, eggshell maculation did not differ between the habitats. Eggshells were more pigmented in the year when they were also thinner, but their thickness was not related to their maculation within each year. Although the results of our study neither prove nor disprove the structural–function hypothesis, they do suggest that the relationship between eggshell pigmentation and Ca availability cannot be explained simply by this hypothesis.

Bone and Cellular Immune System of Multiparous Sows are Insensitive to Ovariectomy and Nutritive Calcium Shortage

Research in osteoporosis, which is a complex systemic disease, demands suitable large animal models. In pigs, most research has been done in growing minipigs, which probably are not ideal models for postmenopausal osteoporosis. Therefore, our aim was to analyze the effects of ovariectomy (OVX) and nutritive calcium shortage on multiparous Large White sows. 32 animals were randomly assigned to 4 groups in a cross design with OVX vs. sham and physiological calcium supplementation (0.75% calcium) vs. dietary calcium shortage (0.3% calcium). The observation period was 10 months with blood sampling every 2 months for hematological, immunological, and biochemical bone marker measurements. At the termination of the experiment, animals were sacrificed. Samples of trabecular bone of distal radius, proximal tibia, and sixth lumbar vertebra were subjected to micro-computed tomography imaging and ashed afterwards. Dual X-ray absorptiometry scans of the proximal femora were performed with prepared bones being placed in a water bath for mimicking soft tissue. Analyses of bone marker and cytokine profile kinetics, distribution of leukocyte subpopulations, and morphometrical and densitometrical analyses showed no evidence of any impact of OVX or calcium shortage. In conclusion, the skeleton of adult sows of a conventional breed is seemingly protected from effects of OVX and calcium shortage.

Effects of calcium diet supplements on egg strength in conventional and furnished cages, and effects of 2 different nest floor materials

Several studies have demonstrated a greater incidence of cracked eggs in furnished than in conventional cages. Hens kept in furnished cages may have greater bone strength, so they may lay eggs with weaker shells because they may utilize more calcium for bone mineralization and less for shell formation. The effects of increased dietary calcium content were therefore studied in 3-hen conventional and 8-hen furnished cages. In addition, the effects of 2 different nest floor materials were studied in furnished cages. A total of 1,216 Lohmann Selected Leghorn hens were housed in either furnished or conventional cages and offered either the normal calcium supplementation used in commercial diets (37 to 40 g of calcium/kg) or increased calcium supplementation (44 to 50 g of calcium/kg) consisting of added limestone for 3 consecutive feeding phases of 20, 16, and 16 wk. Dietary calcium had similar effects in both cage systems. Greater limestone supplementation increased the laying rate (P < 0.05). Increased dietary limestone had no significant effects on egg quality, and no effects on tibia-breaking strength or specific gravity were observed. The laying rate was higher in conventional than in furnished cages (P < 0.05), but there was no significant difference between the cage types in terms of total egg mass produced. The cage type had no effect on tibia-breaking strength. However, the specific gravity and ash content of tibias were higher in hens kept in furnished than in conventional cages (P < 0.001). Based on this study, the weakening of eggshells in furnished cages is not caused by a possible calcium shortage resulting from high bone mineralization.

Hachimijiogan ( Ba-Wei-Di-Huang-Wan), a herbal medicine, improves unbalance of calcium metabolism in aged rats

Aim of the study Aged animals as well as elderly humans commonly exhibit calcium (Ca) shortage because of increased Ca excretion into urine and decreased intestinal Ca absorption, which induce elevation of serum PTH levels to maintain serum Ca levels between a normal physiological range. The most important organ that regulates this Ca homeostasis is the kidney. Hachimijiogan (HJG), a traditional herbal medicine in Japan and China, has been used for treating clinical diseases associated with kidney dysfunctions in elderly humans. However, the mechanisms of its pharmacological actions remain to be understood poorly. The present study was designed to examine whether HJG improves age-related unbalance of Ca metabolism at the systemic level using aged rats. Materials and methods HJG was administered to 21-month-old aged rats for 3 months, and several parameters associated with Ca metabolism in serum and urine were measured. Results Although HJG as well as aging itself did not affect serum Ca levels compared to young (11-week-old) rats, HJG improved increase in urinary Ca excretion and elevation of serum parathyroid hormone (PTH) levels in aged rats. However, HJG did not improve marked reduction of intestinal Ca absorption in aged rats. Conclusion HJG showed regulating action for age-related unbalance of Ca metabolism at the systemic level. This finding would provide useful information for treating age-related several disorders associated with Ca unbalance.

Eggshell pigmentation indicates pesticide contamination

Summary Persistent pesticide residues remain a significant environmental pollutant, reducing breeding success of predatory birds even where such pesticides have been banned for many years. The ability to detect such residues inexpensively without destructive sampling would be a valuable tool for ecotoxicological monitoring. We suggest that assaying eggshell colour might provide such a tool. Recent studies have revealed two mechanisms affecting eggshell pigmentation in, and believed to be specific to, passerine birds. In the great tit Parus major, reddish protoporphyrin speckles on their otherwise white eggs coincide precisely with thin shell and are related to calcium shortage. In the pied flycatcher Ficedula hypoleuca, the intensity of the eggshell's blue‐green ground‐colour (pigment biliverdin) is related to the female's health (immunocompetence) at laying. We studied the effect of the insecticide DDT (notorious for reducing eggshell thickness in raptors by blocking calcium availability to the shell gland) on the eggshell pigmentation of Eurasian sparrowhawks Accipiter nisus (Falconiformes), whose eggshells show both protoporphyrin spotting and a blue‐green biliverdin‐based ground colour. Eggshells showing protoporphyrin spots as an internalized pigment layer also showed a strong correlation between DDE levels (DDT metabolite) and shell thickness. The shells were also significantly thinner at these spots. Eggshell thickness was uncorrelated with DDE levels in eggs that lacked such spotting. The green‐ness of the ground colour, related to biliverdin pigment, also increased with DDE levels but, unlike the protoporphyrins, this increase was independent of eggshell thickness. We also noted that the colour of eggs collected before 1930 was consistent with the environmental absence of DDT. Synthesis and applications. DDT occurrence in predatory birds indicates ecosystem‐wide contamination. Correlation between eggshell colour and DDT concentration indicates that pigmentation might be used as a non‐destructive assay for DDT (which is still in widespread use, particularly for combating malaria) in eggs. Further studies should allow our findings to be applied to other raptor species. Our results corroborate the associations of protoporphyrin pigmentation with shell thinning and biliverdin with female immunocompetence described for passerines, but their occurrence in a falconiform implies that these effects evolved long before the appearance of the order Passeriformes.

Calcium availability affects bone growth in nestlings of free‐living great tits (Parus major), as detected by plasma alkaline phosphatase

AbstractRecent studies have revealed that calcium limitation of avian reproduction may be a widespread phenomenon, affecting both egg properties and chick development. The effect of calcium shortage on the final body size of fledglings is usually rather weak, possibly owing to compensatory growth. Achieving full skeletal size is not, however, a reliable indication of complete ossification and it is possible that chicks with similar tarsus lengths are in different stages of skeletal development. We hypothesized that measuring plasma activity of the bone alkaline phosphatase (ALP), a highly specific marker for bone calcification, may reveal subtle developmental differences in full‐grown fledglings, having experienced different levels of calcium availability during growth. In two seasons, a number of pairs of great tit Parus major were provided with calcium‐rich material during the nestling period, while others were not supplemented (controls). While no significant differences in size of fledglings were detected between groups, bone‐ALP activity at the pre‐fledging stage was lower in the calcium‐provided nestlings than in the control nestlings. This may indicate that supplemented chicks had completed the rapid phase of bone formation, but this process was delayed in controls. Measuring ALP as a marker of skeletal development expands our knowledge of how delayed skeletal development of chicks can result in protraction of the nestling period, thereby reducing the breeding success of adult birds.

Does supplementary calcium reduce the cost of reproduction in the Pied Flycatcher Ficedula hypoleuca?

Studies in acidified as well as in naturally base‐poor areas have recently revealed that availability of extra calcium‐rich food items is an important component of habitat quality affecting breeding performance in several bird species. However, these mostly short‐term studies have provided equivocal results concerning the exact consequences of calcium shortage on different species in different regions. We studied the effect of calcium availability on reproduction of the Pied Flycatcher Ficedula hypoleuca breeding in pine forests in Estonia, NE Europe, over a period of 4 years. Experimental pairs were provided with supplementary calcium‐rich material when breeding, while control pairs were left unsupplemented. Experimental females laid larger eggs and their nestlings had longer tarsi than those of controls. Moreover, the mass and condition of females tending larger than average clutches were increased by calcium‐supplementation. Our results provide the first experimental evidence that calcium availability may affect the overall cost of reproduction in free‐living passerines. We compared these results with similar data for the Great Tit Parus major, collected from the same area during the same study period. Great Tits responded to low calcium availability mainly by restrained reproductive behaviour and reduced breeding success, while Pied Flycatchers invested significantly more in current reproductive effort despite the increased cost of reproduction. Thus, the effects of calcium deficiency on birds seem to be species‐specific or population‐specific. This partly explains discrepancies between the results of earlier studies.

Calcium shortage as a constraint on reproduction in great tits Parus major: a field experiment

Several bird species breeding in acidified habitats face serious problems caused by lowered availability of calcium‐rich foods. Moreover, recent studies have revealed that calcium shortage causes phenotypic variation in certain reproductive parameters of passerines even in non‐acidified habitats. However, to date, no clear evidence has been found of the limiting effect of calcium deficiency on the reproductive output of birds breeding in such habitats. In this paper, we present experimental evidence from a long‐term study that calcium shortage may indeed limit reproductive output of passerines that breed in non‐acidified habitats. We carried out calcium‐supplementation experiments with great tits Parus major breeding in coniferous and deciduous woodlands in Estonia. Calcium‐supplemented birds laid more eggs, tended larger broods and raised more fledglings with longer tarsi compared with control birds. Calcium shortage constrained reproduction of tits not only in spring, but also in mid‐summer, during second breeding attempts. Moreover, no significant differences were detected between deciduous and coniferous habitats with respect to the effect of calcium supplements on reproductive success.

Genome-Wide analysis of yeast transcription upon calcium shortage

Several regulatory circuits related to important functions, like membrane excitation, immunoresponse, replication, control of the cell cycle and differentiation, among others, cause an increase in intracellular calcium level that finally has a consequence upon transcription of specific genes. The sequencing of the whole genome of eukaryotic cells enables genome-wide analysis of gene expression under many conditions not yet assessed by conventional methods. Using the array technology, the effect of calcium shortage in yeast cells was studied. Correspondence analysis of data showed that there is a response in transcription that is correlated to calcium shortage. The distribution of up-regulated-genes in functional categories suggests a regulatory connection between the cell-cycle progression and the energetic metabolic requirements for growth and division. In silico analysis of promoters reveals the frequent appearance of the Mlu I cell cycle box (MCB) cis element that binds the transcriptional regulatory factor Mcm1.

Calcium, snails, and birds: a case study

Abstract. Recent studies have shown that wild birds breeding in acidified areas have difficulties with obtaining sufficient calcium for their eggshells, and that the cause of it is the shortage of land snails. Many birds have to search for Ca-rich snail shells on a daily basis during egg production. Molluscs depend on litter calcium, which has decreased due to acidification of the environment. Calcium limitation may be a widespread phenomenon also in non-acidified, naturally Ca-poor areas. The problem is that while in the latter areas the time for development of specific adaptations may have been sufficient, then in acidified areas, on the contrary, calcium shortage is a recent phenomenon. Therefore, since the extent of calcium limitation in non-acidified areas is hard to derive from observational data, experimental approach is needed. We provide experimental evidence that specific calcium deficit does affect reproductive traits also in the birds breeding in naturally base-poor habitats. Our study was conducted in a heterogeneous woodland area in Estonia containing deciduous forest patches as well as base-poor pine forest with low snail abundance. Ca supplementation, using snail shell and chicken eggshell fragments, was carried out for pied flycatchers and great tits. Extra calcium affected positively several reproductive traits like egg volume and eggshell thickness, start of breeding, and fledglings&amp;amp;#146; parameters. The negative relationship between calcium availability and lay-date suggests that birds adjust their breeding tactics to conditions of Ca deficiency, for example, by postponing laying.

Timing of the Calcium Intake and Effect of Calcium Deficiency on Behaviour and Egg Laying in Captive Great Tits, Parus major

The calcium demand of egg-laying birds is much higher than in other vertebrates during reproduction. We showed elsewhere that a low level of calcium availability can greatly affect the eggshell quality and reproduction of free-living passerines. However, there are few data on calcium demand and calcium intake in relation to egg laying and behaviour and egg-laying performance under conditions of calcium shortage in nondomesticated birds. We examined these aspects in an experiment with captive great tits, Parus major, on a diet deficient in calcium, with or without snail shells as an additional calcium source. More than 90% of the calcium intake for egg production took place during the egg-laying period. Females ingested about 1.7 times as much calcium as they deposited in eggshells. Removing the snail shells after the first egg resulted in eggshell defects and interruptions of laying after 1-3 d. Females without snail shells doubled their searching effort and started to burrow in the soil and to eat sand, small stones, and their own eggs. Most calcium was consumed in the evening, probably to supplement the calcium available from the medullary bone with an additional calcium source in the gut during eggshell formation. The results demonstrated that eggshell formation requires accurate timing of the calcium intake and that obtaining sufficient calcium is time-consuming, even in calcium-rich environments. These factors pertaining to calcium intake greatly affect the ability of birds to collect sufficient calcium for eggshell formation in calcium-poor areas.