Discussion on the Color Properties of Brown-shelled Eggs

Analysis on the color and luster of brown-shelled eggs

The epithelial tissue cells of the eggshell gland mucosa of the hen’s uterus will undergo a series of physiological changes during the laying process, and secrete two types of particles of different sizes. The large particles form the organic matrix protein collagen and mucopolysaccharide, and the small particles are the pigment particles containing protoporphyrin. These two kinds of granules continue to increase until the cuticle is fully formed, and the pigment is secreted and deposited on the cuticle by the eggshell gland 3-5 hours before egg laying.

Protoporphyrin is synthesized from glycine and succinyl-CoA, and δ-amino-γ-levulinic acid (ALA) synthetase is the rate-limiting enzyme. Polin[4] found that in vitro the homogenized brown-shell hen liver tissue and uterine shell gland tissue were incubated with δ-amino γ-ketovaleric acid (δ-ALA) at 41°C for 24 hours, Porphyrin can be synthesized, and the synthesis amount of the uterine shell gland is twice that of the liver, while other tissue blocks can only synthesize trace amounts of porphyrin in vitro.

Uterine tissue blocks mainly synthesized uroporphyrin in vitro, among which uroporphyrin accounted for 91.4%, coproporphyrin accounted for 0.5%, and protoporphyrin accounted for 9.7%. However, those extracted from the intact uterus and eggshells are mainly protoporphyrins, of which 97.1% are protoporphyrins and 2.9% are coproporphyrins. Baird et al. [5] found that when the eggshell was formed, the shell gland cells were filled with mitochondria and their pH value changed.

At the same time, the content of porphyrin in the isthmus and shell gland of the oviduct was three times higher when eggs passed through. The change of pH value of the oviduct shell gland fluid during egg shell formation is an important factor affecting the process of pigment secretion. Eggshell pigment is in a dissolved state at low pH, and when the secretion of eggshell pigment ends, the pH begins to rise again. At this stage, local abnormal pH changes will cause uneven pigment distribution on the eggshell surface.

3 Good eggshell color traits are a sign of chicken health, and disease and stress can cause eggshell color traits to deteriorate

Brown-shelled eggs have a bright, bright, and even shell color that is a sign of the health of the flock. Therefore, any factors that affect the health of the flock, such as disease, stress, etc., will lead to deterioration of eggshell color traits. During the feeding process, once the color of brown-shelled eggs becomes lighter and whiter, uneven pigmentation, dull color, etc., it usually indicates that the chickens are in the early stage of disease and stress response or in the late stage of recovery.

When viruses, bacteria or other toxic and harmful substances enter the body of laying hens, it will cause edema and inflammation of the oviduct mucosa, even bleeding ulcers, dysfunction or loss of uterine shell gland pigment secreting cells, resulting in blocked pigmentation, eggshell whitening, spots, Sand skin, thin shell, what’s more, the egg white becomes thinner, the egg weight decreases, and the egg production rate decreases. There are three main factors that affect the color of eggshells by damaging the health of chicken flocks:

3.1 Disease factors

Many infectious diseases, such as Newcastle disease, influenza, infectious bronchitis, egg drop syndrome, etc., toxic diseases, such as mycotoxin poisoning, heavy metal poisoning, etc., can cause the eggshell color of brown-shell hens to change shallow. After the above-mentioned diseases occur in chickens, oviduct edema, congestion, and hemorrhage will occur, and in severe cases, the mucosal epithelial cells will die and fall off, and the eggshell gland synthesis and pigment secretion functions will be partially or completely lost[6].

In addition to causing clinical symptoms such as eggshell fading, lightening, and whitening, it is often accompanied by a sharp drop in egg production rate, thinning eggshells, an increase in shellless eggs, and deformed eggs. Electron microscope observation of the pathological sections of ovaries and fallopian tubes revealed that the secretory granules of the shell gland secretory cells were cavitated, the mitochondria were edematous and dissolved, and the cilia of the epithelial cells were greatly reduced, and some even disappeared completely.

Nutritional deficiency diseases, such as vitamin deficiency and trace element deficiency, can also cause poor eggshell coloring. Vitamins are involved in the metabolism of nutrients in the body. For brown-shell hen breeds, vitamins that have a greater impact on eggshell color include vitamin A, vitamin E, vitamin K3, vitamin B6, vitamin B12, folic acid, niacin, and so on.

Where:

Vitamin A deficiency can cause the fallopian tube mucosal epithelium to be replaced by stratified squamous keratinized epithelium, leading to its dysfunction.

Vitamin E is beneficial to the smooth surface of the eggshell and the uniform distribution of eggshell pigments during the laying period.

Vitamin K3 participates in the synthesis of various proteins, especially hemoglobin, and the metabolites of hemoglobin can be used as raw materials for the synthesis of eggshell pigments.

Vitamin B6 deficiency can lead to fallopian tube atrophy and affect the synthesis of hemoglobin and immunoglobulin.

Vitamin B12 can affect the development and maturation of red blood cells and the synthesis of pigment protoporphyrin, thereby affecting the color of eggshells.

Folic acid is an important cofactor for the normal development of the immune system and the maturation of blood cells.

Niacin is easily deficient in corn-soybean meal-based diets.

Vitamin C is an important biological antioxidant, which can maintainIt can maintain the integrity of body tissue cells, enhance disease resistance and anti-stress functions, and play an important role in the utilization of calcium and the synthesis of protein and collagen during eggshell calcification. These physiological effects can indirectly affect the color of eggshells.

Iron is the most abundant trace element in eggshell, and it is also an important cofactor of hemoglobin, cytochrome and other enzymes in poultry, which affects the secretion of eggshell pigment.

Zinc is a factor involved in carbonic anhydrase and protein synthase. It has an important influence on the formation of collagen and eggshell calcification. The high concentration of carbonic anhydrase in eggshell glands can illustrate this point. Zinc deficiency can also easily lead to developmental disorders of fallopian tubes, affecting eggshell quality and eggshell color.

Manganese is the main trace element affecting the quality of eggshells. Manganese deficiency will hinder the formation of mucopolysaccharides (the matrix of eggshell calcification), thus affecting the quality of eggshells, making them thin and whitish. Manganese is also a cofactor for aminoacyl coaminase and succinate dehydrogenase in poultry. According to the mechanism of eggshell pigment synthesis, it is more certain that it is an important factor affecting the color of eggshell.

3.2 Stress factors

Stress has a great impact on eggshell pigmentation. Many foreign experts even suggest that the reduction of eggshell pigmentation be used as the basis for whether laying hens are stressed. The high temperature in summer makes it difficult for the chicken body to dissipate heat. In order to accelerate excretion and heat dissipation, a large amount of water is consumed, and the feed intake is reduced, resulting in insufficient nutrient intake and the color of the eggshell becomes lighter. Cold stress will also affect metabolism and cause the color of the eggshell to change. Pale whitening [7].

Administrative stress such as group transfer, vaccination, shock, etc. can cause the contraction of the fallopian tubes, resulting in damage to the eggshell gland mucosa or retention of eggs, causing excessive calcium deposition to form powder-shell eggs, and it may also be due to stress The release of hormones such as adrenaline causes disorders in the secretion of eggshell pigments in chickens.

3.3 Drug factors

Antibiotics, sulfonamides, and some anticoccidials such as nicarbazine, etc., can damage the oviduct mucosa even in small doses, destroy the shell gland pigment secreting cells, and cause abnormal eggshell color.

4 There is no direct relationship between eggshell color and egg quality and diet formula

In fact, the color of the eggshell is not directly related to the quality of the egg. That is to say, the ruddy and bright color of an egg with uniform nutritional value is not necessarily higher than that of an egg with poor color. Because the quality of eggs depends on the nutritional chemical composition of egg yolk and egg white, both of which are closely related to the composition and formula of the diet.

Diet formulation also does not directly affect eggshell color. So far, there is no feed formula that can make white-shell hens or green-shell hens produce brown-shell eggs. There are often some misunderstandings in the feeding practice of the effect of dietary formula on the eggshell color of brown-shelled eggs.

The pigments contained in commercial feed, such as lutein, riboflavin and β-carotene, can only affect the color of the egg yolk, but cannot be deposited into the eggshell.

Therefore, the depth of eggshell color has no direct relationship with chicken feed materials, especially the use of pigment-containing raw materials or coloring agents has no obvious effect on improving the eggshell color of brown-shell eggs. In the practice of breeding, if the eggshell color becomes worse, it cannot be simply judged as a feed quality problem, but a comprehensive analysis and investigation of many diseases and stress factors that affect the health of the flock, especially the reproductive system, should be made before making a conclusion.

5 Common additives for improving eggshell color

Although there are many experimental research reports at home and abroad that show that pigments such as Spatholobus, tangerine peel, and chili powder can improve the color of brown-shelled eggs, there are many deviations in the interpretation of its regulation mechanism. The mechanism by which these substances improve the eggshell color of brown-shell eggs is not simply exogenous pigmentation, but by supplementing micronutrients (vitamins, trace elements, etc.), increasing feed intake and feed absorption utilization, promoting immunity, and accelerating blood circulation. , To improve the function of fallopian tube and shell gland.

5.1 Millet

Spathiphyllum is warm in nature, has the effect of nourishing blood and promoting qi, and can improve the body’s hematopoietic system, regulate immunity, anti-virus, anti-oxidation, and promote cell regeneration and other pharmacological effects. After ingestion by laying hens, it can increase the blood flow of the oviduct of the hen and promote the secretion of the cytochrome substances of the shell glands, thereby enhancing the coloring effect of the eggshell. In addition, Spatholobus can activate the secretion of endogenous pigment substances in brown-shell hens and improve the eggshell coloring effect of brown-shell eggs.

5.2 Chenpi

Orange peel is rich in volatile oil, flavonoids, tangerine, mitangerine, vitamin B1, etc. It can promote digestion, accelerate blood circulation, antibacterial and anti-inflammatory functions.

5.3 Chili

Chili powder enhances appetite, increases feed intake, and supplements vitamin C and other micronutrients.

5.4 Aminolevulinic acid

Adding aminolevulinic acid can effectively increase the blood oxygen content of livestock and poultry, activate cell functions, and accelerate intracellular redox reactions, thereby promoting vigorous metabolism and improving eggshell color[8].

To sum up, the eggshell color of brown-shelled eggs is determined by the genetics of the laying hen, and the eggshell pigment is synthesized and secreted by the shell gland epithelial cells. Disease and stress are the main factors affecting the eggshell color traits. Therefore, additive products for improving eggshell color should be used rationally, and the most fundamental problem is to treat diseases and eliminate stress factors.