Eggshell Characteristics Research Articles

Eggshell Water Vapor Conductance and Shell Structural Characteristics of Broiler Breeder in Different Flock Ages

The aim of the study was to investigate eggshell traits; including eggshell water vapor conductance, eggshell thickness, pore density, egg weight loss as well as eggshell surface area and volume in 28 and 40 week-old broiler breeders. Furthermore, the phenotypic correlations among the eggshell characteristics were determined. The eggs were ranged from 54.41 g to 60.78 g and 54.71 g to 60.62 g in 28 and 40 wk-old age groups, respectively. All eggs were weighed and numbered before setting and were monitored individually until the end of the incubation. Mean eggshell water vapor conductance (G) value was 11.00±1.01 mg H2O day-1 torr-1 in 28 wk-old flock and 11.99±1.28 mg H2O day-1 torr-1 in 40 wk-old flock respectively (P<0.05). The mean value of shell thickness and pore density mean along with the two regions (broad end and equator) were higher and significant in 28 wk-old flock (P<0.01). Egg weight loss was not found to be significant. Surface area was higher in 40 wk-old flock while as volume was higher in 28 wk-old flocks (P<0.01). There was no correlation between eggshell thickness and pore density. Both eggshell thickness and pore density were having significant positive correlation along with three eggshell regions in each flock ages (P<0.01).

Extraordinary adsorption of acidic fuchsine and malachite green onto cheap nano-adsorbent derived from eggshell

Abstract Removal of dyestuffs such as Acidic Fuchsine (AF) and Malachite Green (MG) being present in many forms in industries is vital to protect water reservoirs from their catastrophic effects on the ecosystem. This study attempts to effectively eliminate these dyes using a low-cost and eco-friendly material. Eggshell, as a biocompatible by-product, was initially characterized, then some modifications were conducted, and its morphology and chemical structure were then examined through (Atomic force microscopy) AFM, (Fourier-Transform Infrared Spectroscopy) FTIR, (Energy-Dispersive X-ray Spectroscopy) EDS and (Brunauer–Emmett–Teller) BET analyses. They revealed that the modifications on raw material gave rise to a natural nano-adsorbent presenting porous medium appropriate for targeted adsorbate molecules with the average particle size and average pore diameter of 54 and ~ 2 nm, respectively. Functional groups on the adsorbent surface were also of importance to assist the adsorption of AF and MG. The effect of contact time, adsorbent dose, solution pH and initial concentration was evaluated. Pseudo-second order model accurately correlated the experimental kinetic data for both dyes. Moreover, the participation of intra-particle diffusion along with film diffusion in controlling the process was suggested. Langmuir isotherm model fitted very well to the equilibrium data for both dyes and maximum monolayer adsorption capacity of AF and MG was accordingly calculated to be 5000 and 3333.33mg·g-1 respectively. The inherent characteristics of eggshell make it a potential material to remove contaminants from wastewater in future applications.

Great spotted cuckoo eggshell microstructure characteristics can make eggs stronger

Obligate avian brood parasites lay stronger eggs than their hosts or non‐parasitic relatives because they are rounder and have a thicker eggshell. Additionally, some other characteristics of the brood parasitic eggshells related to their microstructure such as size and orientation of calcite crystal units could also contribute to generating even stronger shells. An eggshell microstructure formed by small randomly oriented calcite crystal units can increase the robustness of the eggshells of birds. Here, the eggshell microstructure of avian brood parasites as well as their hosts have been characterized in detail, using X‐ray diffraction analyses to estimate the size and degree of orientation of calcite crystal units making the eggshell. Specifically, the brood parasitic great spotted cuckoo Clamator glandarius and two hosts (jackdaws Corvus monedula and magpie Pica pica) and one non‐host species (the pigeon, Columba livia domestica) were considered. Calcite crystal of the eggshell of the brood parasitic species was smaller and more randomly oriented than those of the eggshells of non‐parasitic species, which suggest that eggshell microstructure would contribute to explain why parasitic eggs are more resistant to breakage than those of their hosts.

Effect of different levels of tryptophan on productive performance, egg quality, blood biochemistry, and caecal microbiota of hens housed in enriched colony cages under commercial stocking density

A study was conducted to determine the tryptophan (Trp) requirement of brown hens housed in enriched colony cages. A corn and wheat-based diets with 8 levels of standardized ileal digestible (SID) Trp (0.10, 0.13, 0.16, 0.19, 0.22, 0.25, 0.28, and 0.31% of the diet) were manufactured. The diet containing SID Trp 0.10% had no supplemental Trp and was treated as control. A total of 1,344 hens were randomly allocated to 8 treatments, each having 8 replicate cages with 21 hens per cage. Body weight gain (BWG), egg production (EP), feed conversion ratio (FCR), egg quality, blood biochemistry, caecal microbial profile, and concentration of indoles were determined over a period of 16 wk. The EP was linearly improved by supplementing diet with Trp and was highest in 0.25% SID-Trp group compared to control. Trp supplementation improved (P < 0.05) FCR, overall BWG, egg shell characteristics compared to control. The microbial shift in the caecum in response to Trp supplementation was significant in response to higher than current recommendations (0.22% of SID Trp) and indicated a microbial shift towards beneficial bacteria. Indole and skatole concentrations were only significantly different (P < 0.05) when hens in control group were compared with those containing highest levels of SID-Trp. This study demonstrates that when hens are at its peak production and are reared in enriched colony cages their Trp requirement is higher than current National Research Council (1994) recommendations and 0.22% of the SID-Trp in diet can be considered as an optimal level based on regression analysis.

Use of The Eggshells in Removing Heavy Metals from Waste Water - The Process Kinetics and Efficiency

Abstract Studies of the efficiency of Ni, Cu and Cd cations removal from water solutions were carried out, with the use of clay limestone, hen eggshells from eggs for consumption and hen eggshells after hatching, which main element is calcium carbonate. Hen eggshells are a waste product, which can be used as a substitute of clay limestone in removing heavy metals from wet flue gas desulphurisation installation. Mixed solutions of Ni, Cu and Cd were used in the research, with the composition similar to the waste water from wet flue gas desulphurisation installation: Ni (0.009-0.053 mmol/dm3), Cu (0.008-0.057 mmol/dm3) and Cd (0.003-0.008 mmol/dm3). The metals were determined by flame atomic absorption spectrophotometry (F-AAS). Kinetics of the process was analysed and equilibrium parameters were estimated, taking into consideration changes of the solutions pH during the process duration. It was demonstrated that the dominating mechanism of cations removal is their binding in hydroxides and carbonates. The studies demonstrated comparable characteristics of hen eggshells versus clay limestone, in the context of their application in removal of heavy metal cations from solutions.

Latitudinal variation in biophysical characteristics of avian eggshells to cope with differential effects of solar radiation.

Solar radiation is an important driver of animal coloration, not only because of the effects of coloration on body temperature but also because coloration may protect from the deleterious effects of UV radiation. Indeed, dark coloration may protect from UV, but may increase the risk of overheating. In addition, the effect of coloration on thermoregulation should change with egg size, as smaller eggs have higher surface‐volume ratios and greater convective coefficients than larger eggs, so that small eggs can dissipate heat quickly. We tested whether the reflectance of eggshells, egg spottiness, and egg size of the ground‐nesting Kentish plover Charadrius alexandrinus is affected by maximum ambient temperature and solar radiation at breeding sites. We measured reflectance, both in the UV and human visible spectrum, spottiness, and egg size in photographs from a museum collection of plover eggshells. Eggshells of lower reflectance (darker) were found at higher latitudes. However, in southern localities where solar radiation is very high, eggshells are also of dark coloration. Eggshell coloration had no significant relationship with ambient temperature. Spotiness was site‐specific. Small eggs tended to be light‐colored. Thermal constraints may drive the observed spatial variation in eggshell coloration, which may be lighter in lower latitudes to diminish the risk of overheating as a result of higher levels of solar radiation. However, in southern localities with very high levels of UV radiation, eggshells are of dark coloration likely to protect embryos from more intense UV radiation. Egg size exhibited variation in relation to coloration, likely through the effect of surface area‐to‐volume ratios on overheating and cooling rates of eggs. Therefore, differential effects of solar radiation on functions of coloration and size of eggshells may shape latitudinal variations in egg appearance in the Kentish plover.

Cracking the egg: the use of modern and fossil eggs for ecological, environmental and biological interpretation.

A myriad of extant and extinct vertebrates produce eggs. Eggs and eggshells provide a useful substrate for reconstructing environment, ecology and biology over a range of time scales from deep time to the present. In this review, methods for analysing and understanding records of diet, climate, environment and biology preserved in eggshells are presented. Topics covered include eggshell structure, assessing diagenesis, stable isotope geochemistry and morphological investigations of eggshell characteristics. This review emphasizes the use of eggshells in the modern and fossil record, as they allow for interpretation of characteristics of a wide variety of amniotes across geological history, uniquely informing environmental and ecological investigations.

Thermal Decomposition of Biomineralized Calcium Carbonate: Correlation between the Thermal Behavior and Structural Characteristics of Avian Eggshell

This study focused on the thermal decomposition of biomineralized CaCO3, using avian eggshell. Biomineralized CaCO3, which exhibits a specialized structure, is a possible source of CaO used across various applications, including CO2 capture. An understanding of the relation between the thermal decomposition kinetics in producing CaO and the original structure of biomineralized CaCO3 may contribute to the further effective use of biowastes. The thermal decomposition of avian eggshell occurs via two mass-loss processes: the primary thermal degradation of the outer shell membrane and the subsequent thermal decomposition of calcite in the shell matrix. Each mass-loss process is composed of multiple reaction steps. The partially overlapping reaction steps originate from the structural characteristics of the eggshell, in addition to the physicochemical properties of the reactant in each process. The overlapping features of the component reaction steps were revealed by a detailed kinetic analysis of mass-loss cu...

Eggshell characteristics and cuticle deposition in three laying hen genotypes housed in enriched cages and on litter

The objective of the present study was to compare the eggshell characteristics and cuticle deposition of Lohmann Brown, Hy-Line Silver Brown, and Isa Brown layers kept in two different housing systems. The three laying hen genotypes were housed in enriched cages (100 hens, 750 cm&lt;sup&gt;2&lt;/sup&gt;/hen, 10 hens/cage) and in littered pens (100 hens, 9 hens/m&lt;sup&gt;2&lt;/sup&gt;, 10 hens/pen). The experiment was carried out in weeks 40–56 of hens age. Non-significant interactions of genotype and housing system for eggshell quality parameters and cuticle deposition were detected in this study. Egg weight was significantly affected by genotype (P ≤ 0.001) and housing system (P ≤ 0.043). The heaviest eggs were laid by Lohmann Brown, while the lightest eggs were produced by Hy-Line Silver Brown. Eggshell strength was not affected by genotype and housing system, however, genotype had a significant effect on eggshell thickness (P ≤ 0.033). Isa Brown eggs had thicker eggshells compared to Lohmann Brown and Hy-Line Silver Brown. However, a non-significant effect of housing system on eggshell thickness was observed. Eggshell percentage was significantly affected by both genotype and housing system. Genotype of laying hens had a significant effect on cuticle deposition; significantly higher cuticle deposition was observed in Lohmann Brown eggs (P ≤ 0.001). It could be concluded that genotype had a significant effect on eggshell quality parameters and cuticle deposition. However, the housing system effect was less important in these characteristics.

Relationship between eggshell thickness and other eggshell measurements in eggs from litter and cages

The objective of the present study was to determine the relationship between eggshell thickness and other eggshell characteristics in eggs produced in litter housing system and enriched cages. Eggs were collected from 200 birds of ISA Brown genotype at 40–42 weeks of age. Half of the birds were housed in enriched cages (750 cm2/hen, 10 hens/cage) and the other half were housed in littered pens (9 hens/m2, 10 hens/pen). Eggs in each housing system were split into three categories varying in shell thickness: the first category (thin shells 0.28–0.30 mm), the second category (medium shells 0.33–0.36 mm) and the third category (thick shells 0.39–0.41 mm). Results indicated that eggshell parameters differ significantly according to eggshell thickness. Significant interaction of shell category and housing system were observed in eggshell strength. As expected, the eggshell strength was increased with eggshells becoming thicker. Moreover, eggs with the thickest shells from enriched cages had significantly stronger shells than those from litter system. Eggshell weight was significantly increased in the thick eggshell category being higher in enriched cages (7.23 g) than in litter system (5.14 g). The Pearson’s correlation coefficients showed a positive correlation between eggshell parameters and eggshell thickness in both housing systems. Moreover, the correlation between eggshell thickness and eggshell strength was higher on litter (0.64, p < 0.001) in comparison with enriched cages (0.48, p < 0.001). Results of the present study indicated that in thin shells, housing system plays an important role in determining the eggshell strength.

Changes of Eggshell Characteristics during Embryo Development in Western Capercaillie (Tetrao Urogallus)

The influence of a developing bird embryo on eggshell thinning is well known, however this phenomenon has been described mainly for poultry, and in wild birds is poorly understood. This study focussed on Capercaillie ( Tetrao urogallus), in which the effect of a developing embryo on the change of eggshell thickness has not been described. However, problems relating to a large number of dead embryos and eggs cracking during incubation are observed in captive breeding centres giving us the opportunity to test how the developing embryo affects the eggshell and thereby its properties, including eggshell strength and thickness. In total, 196 unhatched eggs, including 146 infertile and 50 eggs with embryos which died at various stages of development, were analysed in relation to eggshell shape, thickness and strength. Moreover, 102 posthatched eggshells were also examined. Although the strength of eggshell was affected by egg shape and shell thickness, contrary to expectations, the stage of embryonic development had no significant influence on eggshell strength. As has been demonstrated in other species, etching of eggshells by the developing embryo reduces shell thickness in Capercaillie but it has minimal effect on the strength of the eggshell. Egg viability is not compromised during the later stages of development by contact incubation with the female. The eggshell of infertile eggs or eggs containing early-dead embryos were 10% thicker than posthatched eggshells and eggs with late-dead embryos, confirming that eggshell thinning in Capercaillie is typical for precocial species.

Eggshell speckling in a passerine bird reveals chronic long-term decline in soil calcium

ABSTRACTCapsule: Long-term changes in eggshell speckling correlated temporally and spatially with declining soil calcium in an English Great Tit Parus major population.Aims: Eggshell speckling in the Great Tit correlates with eggshell thickness and calcium availability. We investigated whether eggshell speckling changed in a Great Tit population during a period when soil calcium declined, and estimated changes in eggshell thickness.Methods: Eggshell pigmentation of 2313 Great Tit clutches was recorded in 1988–2007 across a geological gradient in Wytham Woods, UK. Soil surveys conducted in 1974 and 1991 were repeated in 2008. Temporal and spatial changes in eggshell speckling and soil calcium were examined using generalized linear mixed models. We also estimated the change in eggshell thickness over this period.Results: Soil-calcium availability declined 1974–2008 especially in calcium-rich limestone areas. A systematic change in eggshell speckling, approximating to a 6.5% reduction in eggshell thickness, occurred between 1988 and 2007. The change was greatest in parts of Wytham that experienced the greatest decline in soil calcium. Hatching success was unaffected.Conclusion: Soil-calcium availability has declined in Wytham Woods, affecting Great Tit eggshell characteristics. This is the first evidence that declining soil calcium affects birds nesting in calcium-rich areas. Practical applications of these findings are considered.

Annual Variability and the Influence of Embryonic Development On Red-Shouldered Hawk (Buteo lineatus) Eggshell Characteristics

Abstract Red-shouldered Hawk (Buteo lineatus) eggs were examined to determine whether mass, eggshell thickness, and a thickness index corrected for egg shape and blowhole size changed as embryos developed. Four different stages of embryonic development (fresh, slight, large, and advanced) were described by the collector (C.F. Stone), or inferred from blowhole diameter measurements, for 286 Red-shouldered Hawk eggs collected in the late 1800s and early 1900s in central New York State. We examined changes in eggshell mass, thickness, and thickness index with linear mixed models with year of collection and clutch size specified as random variables. We also evaluated annual differences in eggshell characteristics with linear mixed models. There was an 8.8% decrease in eggshell mass between eggs with fresh and advanced embryos at the time of collection (F3,242 = 3.4, P = 0.02). Eggshell thickness tended to decrease by 7.5% between eggs with fresh and advanced embryos, but the difference was not significant (F3...

Collection of the thinnest: A unique eggshell assemblage from the Late Cretaceous vertebrate locality of Iharkút (Hungary)

As a result of several years of screen-washing activity, a remarkable assemblage of eggshell fragments has been recovered from the Late Cretaceous vertebrate locality of Iharkut, Hungary. Detailed investigation of the assemblage by multiple visualization techniques (scanning electron microscopy, polarizing light microscopy, X-ray micro-computed tomography), quantitative morphometric analyses, and micro X-ray fluorescence spectrometry revealed a diverse composition of five different eggshell morphotypes (MT I–MT V) and three subcategories within the second morphotype (MT II/a, b, c), with MT I being by far the most abundant (83%) in the assemblage. MT I, MT III, and MT V represent theropod dinosaurian eggshells, whereas MT II and MT IV show characteristics of crocodilian and squamate eggshells, respectively. Hence, despite their fragmentary nature, these eggshells represent the first clear evidence that various sauropsid taxa had nesting sites near the ancient fluvial system of Iharkut. Besides the implied...

Changes in pigment, spectral transmission and element content of pink chicken eggshells with different pigment intensity during incubation.

Objective. The objective of this study was to investigate changes in pigment, spectral transmission and element content of chicken eggshells with different intensities of pink pigment during the incubation period. We also investigated the effects of the region (small pole, equator and large pole) and pink pigment intensity of the chicken eggshell on the percent transmission of light passing through the chicken eggshells.Method. Eggs of comparable weight from a meat-type breeder (Meihuang) were used, and divided based on three levels of pink pigment (light, medium and dark) in the eggshells. During the incubation (0–21 d), the values of the eggshell pigment (ΔE, L∗, a∗, b∗) were measured. The percent transmission of light for different regions and intensities of eggshell pigmentation was measured by using the visible wavelength range of 380–780 nm.Result. Three measured indicators of eggshell color, ΔE, L∗ and a∗, did not change significantly during incubation. Compared with other regions and pigment intensities, eggshell at the small pole and with light pigmentation intensity showed the highest percent transmission of light. The transmission value varied significantly (P < 0.001) with incubation time. The element analysis of eggshells with different levels of pink pigment showed that the potassium content of the eggshells for all pigment levels decreased significantly during incubation.Conclusion. In summary, pigment intensity and the region of the eggshell influenced the percent transmission of light of eggshell. Differences in the spectral characteristics of different eggshells may influence the effects of photostimulation during the incubation of eggs. All of these results will be applicable for perfecting the design of light intensity for lighted incubation to improve productivity.

Effects of experimental calcium availability and anthropogenic metal pollution on eggshell characteristics and yolk carotenoid and vitamin levels in two passerine birds

The maternal investment into egg quality depends on the condition of the female, the quality of the mate, and the quality of the environment. In that sense, availability of nutrients and exposure to pollutants are essential parameters to consider. The main aim of this study is to assess the effects of calcium (Ca) availability and anthropogenic metal pollution on early-stage reproduction in two passerine species, great tits (Parus major) and pied flycatchers (Ficedula hypoleuca), inhabiting a Ca-poor and metal-polluted area in SW Finland. Both species were able to obtain sufficient Ca for eggshell formation, and metal pollution was below the level of having negative effects in the egg size and eggshell characteristics. However, metal polluted environment negatively affected yolk lutein and vitamin D3 levels in both species, probably because of a lower access to carotenoid-rich diet and higher metal interference with vitamin D3 metabolism. The higher levels of vitamin D3 in yolks in the unpolluted zone could also be due to upregulated D3 levels as a response to the lower natural Ca availability. Yolk carotenoids and vitamin D3 were positively associated with nestling growth and size, supporting their importance for the appropriate chick development. The interspecific differences in yolk nutrient concentrations possibly reflect the different growth rate of these species. Pied flycatchers are likely adapted to low Ca availability through an efficient vitamin D3 metabolism, but their Ca intake could be close to a deficient level.

Plant-derived additives in chicken diets as related to physical properties of eggshell

The aim of the study was to estimate the impact of the laying hen standard diet with the addition of plant-derived preparation on eggshell quality from selected Polish layer hybrids. The experimental layers were divided into three feeding groups (group I – standard diet, group II – standard diet + 5% dried herbs, group III – standard diet + 5% fresh forage). It was shown that the differences in the quality characteristics of eggshell: weight, density and colour were not statistically significant, whereas such differences (p ≤ 0.05) were confirmed in the case of the thickness. In fact the thinnest (324.15 µm) eggshell had laying hens from group I – fed standard diet without plant-derived additives. Difference in comparison to group II was 2.95 µm and in relation with group III – 1.97 µm. Moreover, it was demonstrated that the most durable thus undergoing smallest deformation (27.19 µm) were eggshells from laying hens fed standard diet with the addition of 5% dried herbs (group II). The difference was confirmed statistically (p ≤ 0.05) in relation with group I, that is control group fed only standard diet.

Classification of eggs in hatchery for production broiler

This work aimed to analyze the eggshell characteristics from 14 cores production of fertile eggs. They were monitored for three months totaling 478,680 eggs that arrived at the hatchery, through a classification known as Egg Quality Assessment. The eggs were classified as dirty, face, thin skin and crooked. To grade eggs a table was used with a lamp which allowed a better view of them. After the classified eggs that had defects were discarded. After the evaluations, we determined that most centers have not reached the ideal indices, established by the company. However, eggs classified in receipt of hatchery clenched a higher percentage compared to dirty, crooked and deformed.

Effects of different vaccine combinations against Mycoplasma gallisepticum on the internal egg and eggshell characteristics of commercial layer chickens , ,

Live F-strain Mycoplasma gallisepticum (FMG) vaccines are presently being used to help control field-strain MG outbreaks. However, they may exert some adverse effects on egg production. Live strains of MG of lesser virulence as well as killed vaccines have little or no effect on egg production, but afford lower levels of protection. This has led to research investigating their use in combination with a subsequent overlay vaccination of FMG given later in the production cycle. In the present study, 2 trials were conducted to investigate the effects of prelay vaccinations of live and killed MG vaccines or their combination, in conjunction with an FMG vaccine overlay after peak production, on the egg characteristics of commercial layers. The following vaccination treatments were administered at 10 wk of age (woa): 1) unvaccinated (Control), 2) MG–Bacterin (MGBac) vaccine, 3) ts-11 strain MG (ts11MG) vaccine, and 4) MGBac and ts11MG combination (MGBac + ts11MG). At 45 woa, half of the birds were overlaid with an FMG vaccine. In each trial, internal egg and eggshell parameters including egg weight (EW), Haugh unit score (HU), eggshell breaking strength (EBS), percentage yolk weight (PYW), percentage albumen weight (PAW), percentage eggshell weight (PSW), eggshell weight per unit surface area (SWUSA), percentage yolk moisture (PYM), and percent total lipids (PYL) were determined at various time periods between 21 and 52 woa. At 28 woa, SWUSA was lower in the ts11MG and MGBac + ts11MG groups compared to the Control group. Conversely, at 43 woa, SWUSA was higher in the ts11MG than in the MGBac group. Between 23 and 43 woa, PYL was higher in the MGBac and ts11MG groups in comparison to the Control group. In conclusion, vaccination with MGBac alone or in combination with ts11MG at 10 woa with or without an FMG vaccine overlay at 45 woa does not adversely affect the internal egg or eggshell quality of commercial layers throughout lay.

The effect of different dietary vitamin and mineral levels on certain production parameters, including egg shell characteristics of breeding ostriches

Earlier studies on breeding birds indicated no effect of dietary energy-content on feed intake. This observation is contradictory to results for other animals and/or poultry where feed intake decreases with an increase in dietary energy level. Literature revealed that a lack of certain nutrients may cause animals to consume more feed than necessary to satisfy their nutrient requirements for these limiting nutrients. In this study eight diet groups were evaluated. A standard commercial diet plus one of the following supplements: (i) Standard diet without a vitamin and mineral premix pack (control diet), (ii) with a normal premix pack, (iii) with normal vitamin and 2 x trace elements (M x 2), (iv) with normal trace elements and 2 x vitamins, (v) with a normal premix pack and limestone added as calcium source; (vi) with a normal premix pack and monocalcium phosphate added as phosphorus source, (vii) with a normal premix pack and soybean oilcake added as crude protein source, (viii) with a normal premix pack and linseed added as a fatty acid source. Significant differences were recorded in the quantity of feed ingested by birds between the diet with surplus minerals (M x 2) (Group 3) (2.3 ± 0.3 kg/bird/day), the diet with no vitamins and minerals added (Group 1) (2.7 ± 0.3 kg/bird/day) and the diet with added fatty acids in the form of linseed (Group 5) (2.9 ± 0.5 kg/bird/day). This indicates the possibility that ostriches may adjust feed intake to satisfy their mineral requirements. No statistically significant relationship was found between the thickness and strength of the shell. Significant differences in shell strength (mean value of 154.7, 109.9, 140.4, 142.7, 153.0, 143.4, 138.4 and 151.1 N/cm2, respectively) were found between all treatments, but no specific pattern could be identified. Results further revealed no effect of dietary treatment on egg production, dead-in-shell eggs (DIS), infertile eggs or chick production. Further experiments that include certain dietary treatments during the five months rest period are currently being done to quantify the effect of the addition of minerals and vitamins during this period on the production of breeding ostriches.Keywords: Eggshell strength; feed intake, minerals, vitamins