Brown shell eggsAnalysis of egg shell color characteristics
The epithelial tissue cells of the hen’s uterine eggshell gland mucosa will undergo a series of physiological changes during egg laying, secreting two types of particles of different sizes. Large particles form organic matrix protein collagen and mucopolysaccharides, while small particles are pigment particles containing protoporphyrin. These two kinds of granules continue to increase until the cuticle is completely formed, and the pigment is secreted and deposited on the cuticle 3-5 hours before egg laying by the eggshell gland.
Protoporphyrin is synthesized from glycine and succinyl-CoA as raw materials, in which δ-amino-γ-levulinic acid (ALA) synthase is the rate-limiting enzyme. Polin[4] found that homogenized brown-shell laying hen liver tissue pieces and uterine shell gland tissue pieces were incubated with δ-aminoγ-levulinic acid (δ-ALA) at 41°C for 24 hours in vitro. Porphyrin can be synthesized, and the amount synthesized by 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 synthesize uroporphyrin types in vitro, of which uroporphyrin accounts for 91.4%, coproporphyrin accounts for 0.5%, and protoporphyrin accounts for 9.7%. However, the main types of protoporphyrin extracted from intact uterus and eggshells are 97.1% protoporphyrin and 2.9% coproporphyrin. Baird et al. [5] found that when the eggshell is formed, the shell gland cells are filled with mitochondria and their pH value changes.
At the same time, the porphyrin content in the isthmus of the fallopian tube and the shell gland when an egg passes through is three times that of when there is no egg. The change in pH value of fallopian tube shell gland fluid during eggshell formation is an important influencing factor in the pigment secretion process. Eggshell pigments are in a dissolved state when the pH value is low, and when secretion of eggshell pigments ends, the pH value begins to increase again. At this stage, abnormal local pH changes will cause uneven distribution of pigments on the eggshell surface.
3 Excellent eggshell color is a sign of chicken health. Disease and stress can cause eggshell color to deteriorate
Brown egg shells are bright, shiny and uniform in color, which is a sign of the health of the chickens. Therefore, any factors that affect the health of the chickens, such as disease, stress, etc., will cause the eggshell color properties to deteriorate. During the breeding process, once it is discovered that the color of brown-shell eggs has become lighter and whiter, the pigmentation is uneven, and the color is dull, it often indicates that the chickens are in the early stage of disease and stress response or in the late recovery stage.
When viruses, bacteria or other toxic and harmful substances enter the body of laying hens, it will cause edema and inflammation of the fallopian tube mucosa, and even bleeding and ulcers. The function of the pigment-secreting cells of the uterine shell glands will be disordered or lost, resulting in blocked pigmentation, whitening of the eggshell, spots, Sand skin, thin shell, and even worse, the egg white becomes thinner, the egg weight is reduced, and the egg production rate is reduced. There are three main factors that affect the color of eggshells by damaging the health of chickens:
3.1 Disease factors
Many infectious diseases, such as Newcastle disease, influenza, infectious bronchitis, egg production decline syndrome, etc., and toxic diseases, such as mycotoxin poisoning, heavy metal poisoning, etc., can cause the color of the eggshells of brown laying hens to change. shallow. After the above-mentioned diseases occur in chickens, the fallopian tubes will appear edema, congestion, and hemorrhage. In severe cases, the mucosal epithelial cells will become necrotic and fall off, and the functions of the eggshell glands to synthesize and secrete pigments will be partially or completely lost [6].
In addition to causing clinical symptoms such as fading, lightening, and whitening of eggshells, it is often accompanied by a sharp decrease in egg production rate, thinning of eggshells, and an increase in shellless eggs and deformed eggs. Electron microscopic observation of pathological sections of ovaries and fallopian tubes revealed that the secretory granules of shell gland secretory cells were hollowed out, mitochondria were edematous and dissolved, and the cilia of epithelial cells were greatly reduced, and some even disappeared completely.
Nutritional deficiency diseases, such as vitamin deficiency, trace element deficiency, etc., can also cause the eggshell coloring effect to deteriorate. Vitamins are involved in the metabolic process of nutrients in the body. For brown-shell laying hens, the vitamins that have a greater impact on eggshell color include vitamin A, vitamin E, vitamin K3, vitamin B6, vitamin B12, folic acid, niacin, etc.
Among them:
Vitamin A deficiency can cause the fallopian tube mucosal epithelium to be replaced by stratified squamous keratinized epithelium, leading to its dysfunction.
Vitamin E during the laying period is beneficial to the smooth surface of the eggshell and the even distribution of eggshell pigments.
Vitamin K3 is involved 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 cause 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 protoporphyrins, 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 and soybean meal-based diets.
Vitamin C is an important biological antioxidantAntioxidants can maintain the integrity of tissue cells in the body, enhance disease resistance and anti-stress functions, and play an important role in the utilization of calcium and the synthesis of protein collagen during eggshell calcification. These physiological effects can indirectly cause damage to eggshells. The influence of color.
Iron is the most abundant trace element in eggshells. It is also an important cofactor for hemoglobin, cytochromes and other enzymes in poultry, affecting the secretion of eggshell pigments.
Zinc is a factor involved in carbonic anhydrase and protein synthase. It has an important impact on the formation of collagen and the calcification of eggshells. The high concentration of carbonic anhydrase in the eggshell gland can illustrate this. Zinc deficiency can also easily lead to fallopian tube development disorders, affecting eggshell quality and eggshell color.
Manganese is the main trace element that affects the quality of eggshells. Manganese deficiency will hinder the formation of mucopolysaccharides (the matrix for eggshell calcification), thereby affecting the quality of eggshells and making them thin and white. Manganese is also a cofactor for aminoacyl coaminase and succinate dehydrogenase in poultry. According to the mechanism of eggshell pigment synthesis, it can be determined that it is an important factor affecting the color of eggshells.
3.2 Stress factors
Stress has a great impact on eggshell pigmentation. Many foreign experts even suggest that reducing eggshell pigmentation should be used as a basis for whether egg-laying hens are suffering from stress. The continuous high temperature in summer makes it difficult for the chicken body to dissipate heat. In order to speed up excretion and dissipation, the chicken drinks a lot of water, and the feed intake is reduced, resulting in insufficient nutritional intake and the color of the eggshell becomes lighter. Cold stress can also affect metabolism and cause the color of the eggshell to change. Light whitening[7].
Management stress such as group transfer, vaccination, fright, etc. can cause the contraction of the fallopian tube, causing damage to the eggshell gland mucosa or egg retention, causing excessive calcium deposition to form a pink-shelled egg. It may also be caused by stress. The release of hormones such as epinephrine causes eggshell pigment secretion disorders in chickens.
3.3 Drug factors
Antibiotics, sulfonamides and some anti-coccidial drugs such as nicarbazine, even in small doses, can cause damage to the fallopian tube mucosa, destroy the pigment-secreting cells of the shell gland, and cause abnormal eggshell color.
4 Eggshell color characteristics are not directly related to egg quality and dietary formula
In fact, eggshell color has no direct relationship with egg quality. That is to say, eggs with a bright, ruddy color and uniform nutritional value do not necessarily have higher nutritional value than eggs 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 dietary composition and formula.
The diet formula will not directly affect the color of the eggshell. So far, there is no feed formula that can make white-shell or green-shell laying hens produce brown-shell eggs. There are often some misunderstandings in the feeding practice about the effect of dietary formula on the shell color of brown-shell eggs.
Pigments contained in commercial feed, such as lutein, riboflavin and β-carotene, can only affect the color of egg yolk, but cannot be deposited into the eggshell.
Therefore, the color of eggshells has no direct relationship with the feed materials of chickens. In particular, the use of pigment-containing materials or colorants has no significant effect on improving the color of brown-shell egg shells. If the color of eggshells deteriorates during breeding production, it cannot simply be judged as a feed quality problem. Instead, a comprehensive analysis and investigation of the many diseases and stress factors that affect the health of the chickens, especially the reproductive system, should be conducted before making a conclusion.
5 Common additives for improving eggshell color currently on the market
Although there are many experimental research reports at home and abroad showing that pigment-containing substances such as Millet Spatholobus, tangerine peel, and paprika can improve the color of brown egg shells, there are many deviations in the interpretation of their regulatory mechanisms. The mechanism by which such substances improve the shell color of brown-shell eggs is not simply exogenous pigmentation, but by supplementing trace nutrients (vitamins, trace elements, etc.), increasing feed intake and feed absorption and utilization, promoting immunity, and accelerating blood circulation. , which is achieved by improving the functions of fallopian tubes and shell glands.
5.1 Millettia
Chicken Spatholobus is warm in nature, has the effect of nourishing blood and promoting qi, and can improve the body’s hematopoietic system, regulate immunity, resist viruses, antioxidants, promote cell regeneration and other pharmacological effects. After ingestion by laying hens, it can increase the blood flow of the hen’s oviduct and promote the secretion of pigment substances in shell gland cells, thus enhancing the coloring effect of eggshells. In addition, Millet Spatholobus can activate the secretion of endogenous pigment substances in brown-shell laying hens and improve the coloring effect of brown-shell eggs.
5.2 Chenpi
Tangerine peel is rich in volatile oil, flavonoids, mandarin, mitogenin, vitamin B1, etc. It can promote digestion, accelerate blood circulation, and has 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
The addition of aminolevulinic acid can effectively increase the blood oxygen content of livestock and poultry, activate cell functions, accelerate intracellular redox reactions, thereby promoting strong metabolism of the body and improving the color of eggshells [8].
To sum up, the shell color of brown-shell eggs is determined by the genetics of laying hens. Eggshell pigments are synthesized and secreted by shell gland epithelial cells. Disease and stress are the main factors affecting eggshell color traits. Therefore, additive products that improve eggshell color should be selected and used rationally. The most fundamental issue is to treat diseases and eliminate stress factors.
