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Significance of the problem of term paper about eggs

Critical points on egg production: It is important to consider that the problem of broken eggs is not due to a single factor but a combination of factors. Shell defects, irregularities in shell shape, texture and surface are commonly observed during a regular egg laying cycle and the causes are varied.

The incidence of downgraded eggs still represents an important source of economic loss for the egg industry due to products damage and need for further processing. It is possible to obtain significant reduction in the number of eggs lost due to the inferior quality of the shell attempting to an adequate nutrition, disease control, good management practices, and use of genetic lines with higher quality eggshell traits.

Defective shell, egg industry, eggshell quality, laying hens, shell integrity. Defeitos de casca, cadeia de ovos comerciais, qualidade da casca, poedeiras comerciais, integridade da casca. Hen's health and age, diet quality and safety and also, housing environment are intrinsic aspects that define the quality of laid eggs. After oviposition, the different stages relating to the egg manipulation, and collecting systems become important particularly the steps associated with collecting, grading and packing processes and transportation.

Most of the practices applied during egg processing occur to correct potential hazards that may threat the sanitary conditions, like the cleaning and disinfection strategies targeting the eggshells. As pointed out by Hincke et al. Such eggs are considered to be hazardous because their contents are exposed to bacterial pathogens and they may be used in products not thoroughly cooked.

However, the incidence of downgraded eggs still represents an important source of economic loss for the egg industry due to products loss and need for further processing. In addition, shell formation over one laying year is biologically a stressful event and the age-related changes in shell thickness and shell ultra-structure are reflected in deteriorating physical parameters such as breaking strength Solomon, 2010.

A decline in eggshell quality is detected as hens approach the end of a laying period, Mazzuco; Hester, 2005. In this way, the condition of the eggshell at the oviposition time can influence the incidence of shell breakage. Significance of the problem of term paper about eggs review covers the egg quality issues, particularly on the eggshell formation and mineralization, focusing on properties and conditions that influence the incidence of damage in the shells and the importance of shell integrity for consumers' safety and producer's revenue.

In the context of a farm, shell strength is necessary to prevent damage from handling and to preserve eggs during transport from farm to market Altuntas; Sekeroglu, 2008.

As pointed out by Washburn 1982the occurrence of shell breakage can be categorized into a number of stages and the opportunities for breakage could occur before lay, at the point of lay, during collection, processing and shipping. The breeder industry also incur greater economic losses due to reduced chicken embryo livability and hatchability because the successful development of chicken embryos is dependent upon a robust eggshell for mechanical resistance, protection from infection, prevention of water loss, and as a primary source of calcium for the embryonic skeleton Yang et al.

Eggs can be regarded as naturally packaged food. The eggshell serves to contain the egg contents, but it is also the first barrier against bacterial penetration and must be free from defects in order to optimize the safety of the contents for human consumption, Mabe et al. When examining the quality of packaging, one primarily considers the strength of the eggshell, Hamilton, 1982. Eggs with a broken shell are of inferior quality and can be a food safety hazard. For producers, cracked and broken eggshells are also regarded as major source of economic loss Kemps et al.

Once foodborne illness caused by Salmonella spp is known to be strongly associated with shell eggs and egg containing products Howard et al. It is among the most rapid mineralization processes known, with a precise temporal and spatial control of its sequential formation Nys et al.

Albumen or egg white, in addition to its nutritional function, also serves to buffering the yolk against mechanical injury, acting as bactericide and establishing a template for the deposition of the shell membranes Solomon, 1997. The ovum remains in the magnum approximately 2-3 hours and then moves along to the isthmus where significance of the problem of term paper about eggs paired shell membranes are formed during 1 to 2 hours, Solomon, 1997.

The shell gland tubular and pouch portions is the place where the calcification of the eggs occurs. Calcification within the shell gland is associated with stimuli initiated by ovulation or by neuroendocrine factors that control and coordinate both, ovulation and calcium secretion Johnson, 2000. During the early phase of shell formation a firm bond should be established between the shell membranes and the first crystals to seed from the supersaturated solution of calcium carbonate in which the egg is bathed Solomon, 2010.

Most interesting, eggshell formation is spatially and temporally controlled: The first layers covering the egg white are the fibrillar shell membranes and on its outer part are discrete aggregations of organic material, called mammillary bodies Panheleux et al.

These are the sites where the organic matrix of the shell shell matrix is attached and where the initiation of calcium carbonate crystal takes place. As pointed out by the previous authors, the hard shell proper, the palisade, is organized upon this shell matrix most external layer, referred to as cuticle. The protein components of biomineralized structures matrix proteins influence the properties of the final structure of calcium phosphate hydroxyl-apatite or calcium carbonate calcite by modulating nucleation and growth Hincke et al.

The uterine fluid contains high levels significance of the problem of term paper about eggs ionized calcium and bicarbonate such that calcite calcium carbonate is present 50-60 times its solubility product Nys et al. This supersaturated solution also contains a rich variety of proteins that are mainly the precursors of the matrix proteins that become incorporated into the eggshell and which fluid composition vary according to the stage of shell formation Hincke et al.

As indicated by Panheleux et al. This is because unfortunately, there are multiple factors affecting eggshell quality like genetics of the hen, nutrition and management of feed intake, disease and environment challenge and also equipment insult. The irregularities in shell shape, texture and surface are commonly observed during a regular egg laying cycle.

The causes are varied: As indicated by Solomon 1997if stress is experienced before the egg reaches the shell gland, the entire process of shell formation is affected and thin-or-soft shelled eggs are commonly observed. If the shell breaks in the shell gland during the process of mineralization, shell defects as corrugated eggs and body-checked eggs will occur.

A body-checked egg can be defined as one that has broken in the pouch region during the process of mineralization but that is partially repaired by additional calcification.

Besides genetic factors, any condition that causes disturbance to the birds 10-14 hours before the egg is laid, is likely to increase the incidence of these types of shell defect Coutts; Wilson, 2007. From a poultry welfare perspective, eggshell abnormalities associated with stress-induced oviposition delays can provide a convenient non-invasive means of assessing stress in flocks of hens as pointed out by Hughes, Gilbert and Brown 1986.

Anomalous eggshells and degree of abnormality can be used as indicators of environmental stress suffered by the flock of hens Reynard; Savory, 1999. The previous authors showed that the duration of environmental stress and associated oviposition delay affect the number of abnormal eggshells and degree of abnormality, and hence downgrading of table eggs and possible impairment of embryonic development in the case of fertile eggs hatching operations.

Stress and diseases have the potential to influence the deposition of eggshell pigmentation during egg formation Mertens et al.

Infectious bronchitis, is an example and has been implicated in the production of "watery white", a condition observed when chemical changes in the nature of secretions from the magnum affects the shell structure of eggs Solomon, 1997causing the shell membranes to become arranged in a distorted manner due to the absence of an adequate template for the regular shell mineralization as occur in body-checked or corrugated shells.

A New Spin on Eggs

When analyzing the egg breakage in the different chains, Mertens et al. The conventional and furnished cage systems showed a relatively high percentage of breakage after lay, 6. The aviary and free-range system had a similar total breakage 1. Grading and packing seems to be the second critical point in the logistic chain after laying and collecting Table 2.

The higher breakage percentages in the collecting and packing operation indicate a possible higher risk at those points in the logistic chain. In the first case, the collecting belts in chain 1 generated an extremely high percentage 36. Breakage due to transportation ranged from 0. In extreme cases of egg retention, the shell gland pouch can find itself accommodating two full-sized eggs and as the second egg comes into contact with the first and at this point, the pattern of mineralization is disrupted directing the first egg to acquire a characteristic white band and the second to be flattened on its contiguous surface Solomon, 1997.

Another common surface defect observed in the eggshell is the coated shell, when additional calcium deposits or extracuticular coverings are observed and possibly reflects the timing and magnitude of the stress or disturbance experienced by the flock Solomon, 1997.

Previously, a high incidence of breakage, about 3. As indicated by significance of the problem of term paper about eggs authors, a number of variables contributes to shell damage at significance of the problem of term paper about eggs point of lay like the age of the hens, the design of the cage system, number of hens, number of hens housed per cage, among others. Trace elements may also directly affect eggshell structure through a modifying effect on calcite crystal growth mechanisms and may influence eggshell quality either by their catalytic properties as key enzymes involved in the process of membrane and eggshell membrane and eggshell formation or by interacting directly with the calcite crystals in the forming eggshell, Mabe et al.

The organic matter of eggshell contains proteins as major constituents with small amounts of carbohydrates and lipids. As pointed out by Mann et al. Also, the organic matter of eggshells contains two glycosaminoglycans including hyaluronic acid and chondroitin sulfate-dermatan sulfate copolymer Nakano et al.

Sialic acid is another carbohydrate found in eggshell membranes Nakano; Ikawa; Ozimek, 2003. Also, the eggshell membranes contain relatively small but significant amounts of uronic acid. A total of 528 proteins have now been identified in the decalcified eggshell organic matrix, including all of the previously characterized eggshell-specific proteins ovocleidins and ovocalyxins and proteins known to be induced by the passage of the egg from isthmus to eggshell gland, such as osteopontin and glypican-4 Mann et al.

The structural constituent of the eggshell also has a genetic component. Average expression profiles of juvenile and sexually mature shell glands were compared using chicken cDNA microarray and resulted in the identification of 266 differentially regulated genes Dunn et al. The differentially expressed genes included several that showed involvement in shell gland function, like transport and shell matrix proteins and some unpredicted differentially expressed genes identified in the shell gland.

These genes are involved in shell formation, the production of antimicrobial peptides and the maintenance of a fully developed shell gland under the influence of ovarian steroids. These include those encoding osteoprotegerin, prostatic acid phosphatase ACPP and prostate stem cell antigen PSCAurea transporter, bactericidal permeability-increasing protein-like2 BPIL2 and other potential anti-microbials. Two proteins, calbindin and osteopontin OPN are known to be involved in calcium metabolism of the eggshell gland.

Samples taken from the sharp pole corresponding part of the eggshell gland that generates eggs with cracks at the sharp pole exhibited almost no OPN gene expression, whereas calbindin expression was similar to that of the eggshell gland of layers with normal eggshells Arazi et al. In other words, although the levels of calbindin gene expression were similar at both locations irrespective of the location of the cracks, OPN expression was almost completely absent at the location corresponding to the cracks, in contrast to its level at the opposite direction.

The importance of a single microelement for adequate eggshell formation and composition was pointed out by diverse authors: Leach and Gross 1983 observed that hens fed manganese Mn -deficient diets produced eggs with thinner shells, translucent areas and abnormalities in eggshell structure. In agreement, Yang et al. Copper Cu deficiency in hens results in atypical eggshell formation characterized by abnormal distribution of the shell membrane fibers due to alterations in lysine-derived-crosslinks, which results in egg shape deformation and altered mechanical properties Baumgartner et al.

Another trace element, Zinc Zn is a component of the carbonic anhydrase enzyme, which is crucial for supplying the carbonate ions during eggshell formation and inhibition of this enzyme results in lowered bicarbonate ion secretion and consequently greatly reduces eggshell weight Nys et al.

Improved breaking strength and fracture toughness resistance to fracture were observed by Mabe et al. The effect was observed regardless of the source of trace elements. A study conducted by the previous authors suggests that addition of organic or inorganic sources of combined Zn, Mn and Cu does not significantly influence the amount of eggshell material deposited during eggshell formation but can enhance some mechanical properties like, improved breaking strength and fracture toughness resistance to fracture and regardless the source of trace elements.

Additionally, the size and orientation of calcium carbonate crystals influence the structure and strength of the eggshells of chickens Dunn et al. Additionally, Sun et al. A fine-tuning on mineral balance should be carefully taken into account once an excess or a deficiency in the diet will compromise bird's performance. As indicated by Trindade Neto et al.

As indicated by Clunies, Parks and Leeson 1992the skeleton is the only major alternate source of calcium available to the hen during shell formation though, previously, Buss and Guyer 1984 showed that the skeletal metabolism was not a limiting factor in determining whether a hen produces a "thick" or "thin" eggshell. The previous authors conducted a study to make comparative measurements of bone parameters in lines of hens genetically divergent producing thick and thin eggshells.

Results showed that the skeleton's contribution of calcium for the eggshell is the same for both lines and bone metabolism was not a cause of thick or thin significance of the problem of term paper about eggs production. An interesting study was carried out by Clunies, Parks and Leeson 1992 to investigate Calcium and Phosphorus metabolism of hens laying thick or thinshelled eggs on shell forming days and days on which shell formation does not occur.

Differences in shell weight and shell Ca content were due primarily to differences observed in the efficiency of Ca retention: The scale of shell damage varies from farm to farm and several strategies should be practice to alleviate the problem. The genetic lines to be housed should be those that have a higher quality of shell, and carefully consider nutritional strategies to obtain more resistant shells. Effect of egg shape index on mechanical properties of chicken eggs.

Journal of Food Engineering, 85 4: