УДК 636.52/.58:[637.4.04+591.111.05


T.I. Sereda, M.A. Derkho

The features of biological migration of macroelements in system blood—egg at the different time of reproductive period were studied in hens of the Loman White cross-country. It was established that the content of calcium, phosphates and magnesium in blood serum depends on period of oviposition. The content of calcium, phosphates and magnesium in hen egg practically did not depend on element concentrations in blood serum. The mineral composition of egg mass depends on demand for macroelements in process of development of embryo and their concentrations depend on only egg mass.

Keywords: macro cells, blood whey, egg, hens-layers.


Modern breeding programs include the creation in near future of poultry with increased resistance, as well as obtaining eggs and meat with desired medical and biological qualities (1). Understanding peculiarities of macroelements migration in the system blood-egg has both theoretical and practical interest because it allows to assess feeding conditions of poultry and mineral metabolism condition in the organism, which helps to control and improve nutritive quality of eggs.
Egg has a high biological value. All the nutrients contained in it are balanced both qualitatively and quantitatively (2, 3). Along with it, egg is a nutrient environment for the embryo, and the bird organism regulates its chemical composition even to the detriment of own health (4-6).
Contents of vitamins, proteins, fats and minerals in the egg depend on feeding conditions of birds during the laying period and the level of assimilation these compounds, which determines their content in the blood (7-11). Cells of the reproductive organs assimilate all necessary nutrients from the blood and use them for biosynthesis of egg components. In addition, chemical composition of eggs is affected by the poultry cross and time after laying.
Egg productivity of laying hens is connected with activity of egg formation and the organism supply with nutrients and bioactive substances. Macronutrients, especially calcium, are of particular importance. It is spent on physiological processes during the formation of eggs and egg shell (4, 9).
The purpose of this work was studying biological characteristics of macronutrients’ migration in the system blood-egg of laying hens the cross Lohmann white in different periods of reproductive cycle.
Technique. Experiments were carried out in the JSC "Chelyabinskaya poultry farm" (Oktyabr’skii village, Chelyabinsk province) in 2005-2008. The object of studies were lying hens the cross Lohmann white of the commercial even aged population. The birds were kept in main farm buildings with cell heating radiators and fed with the full-value mixed feeds prepared in feeding department of the farm. The content of calcium and phosphorus in the feed was normalized per 100 g of feed. In pre-laying period (18 weeks), the content of calcium in the diet was 2,50%, phosphorus – 0,60%, including the digestible phosphorus – 0,40%. In the first phase of feeding (early-productive period), the feed contained 3,50% calcium, 0,58% phosphorus and 0,35% available phosphorus; during the second (46th-57th weeks) and third phases (after the 57th week) - respectively, 3,75; 0,58; 0,55 and 3,84; 0,57 and 0,33%. The content of magnesium in feed was not normalized; it was provided by all components of the feed and limestone keeping 0,80-1,00% magnesium.
Experimental group of hens (n = 10) was formed according to the principle of approximate analogs. Biochemical analysis was performed on the blood sample and one egg laid on the 18th, 26th, 52nd and 80th weeks of oviposition during the first production cycle. Each analyzed egg had the weight linearly distributed relative the mean with normality parameter M±1s. Blood samples were taken in the morning in 3 hours after laying an egg, which time corresponds to location of the developing new egg in the protein-forming part of the oviduct.
Contents of macroelements were determined in a mixture of egg protein and yolk, as well as in blood serum using conventional colorimetric methods (12).
The correlation between contents of mineral elements in the egg and in the blood was assessed with the use of the metal bioaccumulation coefficient calculated under the formula: Caccum. = Ce/Cb, where Ce - metal content in the egg, Cb - metal content in the blood.
The obtained data were statistically processed using Microsoft Excel 2003.
Results. Calcium content in the blood serum of hens gradually decreased from 4,82±0,35 in pre-laying period to 2,73±0,06 mmol/l by the end of oviposition (P <0,001) (Table).

Contents of mineral elements in the blood serum and in egg of laying hens the cross Lohmann white depending on age (n = 10, Х±Sx, JSK “Chelyabinskaya poultry farm”,  2005-2008)


Age of the bird, weeks





Calcium content:





  in blood, mmol/l





   in egg, mmol/kg





Caccum. (Са)





Phosphorus content:





   in blood, mmol/l





   in egg, mmol/kg





Caccum. (P)





Magnesium content:





   in blood, mmol/l





   in egg, mmol/kg





Caccum. (Mg)





Са : Р:





   in blood





   in egg





Са : Mg:





   in blood





   in egg





Mg : Р:





   in blood





   in egg





Weight of an egg, g





Note. Caccum. (Ca) – bioaccumulation coefficient of calcium, Caccum. (P) – bioaccumulation coefficient of phosphorus, Caccum. (Mg) – bioaccumulation coefficient of magnesium. The calculation formula – see “Technique”.
* p < 0,05-0,001 compared to the 18th week of reproductive period.

Calcium is a strictly regulated electrolyte of the blood. The constancy of its concentration is maintained by coordinated action of hormones (parathyrin, calcitriol, calcitonin, somatotropin, catecholamines and corticosteroids) and a specific ratio between rates of calcium absorption and excretion. About 50% of serum calcium is associated with albumin and globulins (non-diffusing element). Another part of Ca2+ (metabolically active fraction) circulates in the ionized state or as a part of complexes with non-protein substrates  (diffusing element) (7).
The concentration of albumin in the blood serum of laying hens during the reproductive period varied from 18,57±0,80 to 19,63±0,11 g/l, so it can be assumed that the proportion of bound calcium was almost independent from laying activity. Consequently, changes in serum concentrations of Ca2+ in the process of laying was determined by a quantitative variability in unbound fraction of the element, which indicates the depletion of its reserves in the organism and uncompensated metabolic costs.
In turn, concentration of calcium in egg content gradually increased from 12,30±0,35 to 15,87±0,36 mmol/kg (p <0,001). The main cause of this trend was increasing egg weight. Calcium is assumed to be associated with albumin in egg white and with lipo-phosphoproteins in yolk (7). Probably, calcium provides embryogenesis during the first period of embryo development, and its concentration is determined by demand in this process.
The coefficient of calcium accumulation was 2,3 times higher in the end of oviposition than in pre-laying period. The authors see this fact as the result of decrease in share of the diffused calcium fraction in the blood of laying hens. To provide biosynthesis of eggs in the oviduct with necessary amount of macroelements, cells of reproductive organs should contact with lots of circulating blood, which increases time of egg formation and probably reduces bird’s productivity. The obtained data suggest the decrease in calcium assimilation from food and depletion of bone tissue calcium reserves by the end of oviposition, which initiates the increase in rate of biological migration of calcium in the system blood-egg.
Calcium metabolism in bird organism is associated with the metabolism of phosphorus. The interaction of these elements starts in digestive tract, where their ratio determines the level of absorption (9). In the blood, the ratio of calcium and phosphorus concentrations is almost the same as in the molecule of tertiary calcium phosphate. Along with it, contents of calcium and phosphorus in the blood and tissue fluids are controlled by the same homeostatic mechanisms.
Phosphate contents in the blood serum of the hens was minimal in pre-laying period (2,46 ± 0,11 mmol/l), then it slightly increased and varied from 2,83±0,07 to 3,14±0,09 mmol/l. Calcium and phosphates were present in the blood serum in reciprocal relations: increase in share of phosphates contributed to reduce in calcium content. The balance of electrolytes in pre-laying period was 1,96±0,40, and by the 80th week of oviposition in decreased to 0,90±0,10, or in 2,20 times (p <0,001). The content of PO43- in the egg depended on period of oviposition when it was laid. In pre-laying period, this parameter amounted to 47,26±0,32 mmol/kg; by the 80th week it increased in 1,21 times and reached 57,11±0,42 mmol/kg (p <0,001). However, the rate of biological migration of this electrolyte in the system blood-egg was almost constant during the reproductive period (18,03±0,51-19,21±0,40). Therefore, there is a positive balance of phosphates maintained during the oviposition of laying hens, which provides a relatively constant rate of the electrolyte extraction from the blood by cells of reproductive organs. It is possible that egg biosynthesis more actively involves organic forms of serum phosphates (lecithin, cephalin) which were not determined in this study.
The relationship between calcium and phosphorus in egg contents practically didn’t depend on the period of laying despite the increase in weight. In the authors’ opinion, the quantity of these macroelements is determined by demand in it during the embryogenesis, so it is regulated in eggs of hens even in commercial populations. Inorganic serum phosphate seem to be little used in biosynthesis of eggs, since there wasn’t found any correlations between phosphorus contents in the blood serum and in eggs.
Magnesium is an irreplaceable mineral element. Its content is not regulated in mixed feeds for laying hens because ingredients of these feeds contain enough magnesium. Magnesium content in the bird blood serum did not depend on time of the reproductive period and varied within 0,84-0,86 mmol/l. Relatively low serum concentrations of the element indicate that it is an intracellular component and its presence in the blood is a consequence of physiological cell regeneration of organs and tissues. Magnesium content in the egg didn’t depend on time of the laying period and varied from 5,66±0,62 to 6,22±0,48 mmol/kg. Probably, most of the magnesium is present in the egg in the form of magnesium-protein complexes. The rate of magnesium accumulation in the system blood-egg wasn’t any significantly dependent on time of the reproductive period. The authors believe that the revealed regularities of biological migration of magnesium in tissues of laying hens is determined by peculiarities of its relationship with calcium and phosphorus, as about 70% of the total magnesium is also found in bone tissue.
It was established that constant concentration of magnesium in the blood serum is maintained by reducing the proportion of calcium. The antagonism between Ca2+ and Mg2+ is the result of their competition for the carrier proteins and phosphate ions. At the same time, the ratio of Ca:P ratio gradually decreased during the reproductive period, Mg:P - remained almost unchanged. Consequently, magnesium displaced calcium in phosphate compounds of the blood serum. However, there wasn’t observed the antagonism between these elements of the egg. The ratios Ca:Mg and Mg:P were practically independent of time of laying period, which indicates that homeostasis of these macroelements in blood serum and the mechanism of their inclusion in egg contents are regulated differently.
Probably, serum concentration and balance of calcium and phosphates are to a greater extent determined by biological activity of parathyrin - the hormone of parathyroid glands secreted under control of magnesium content, so, the relationship of these electrolytes reflect the principle of "loopback".
The contents and proportion of macroelements in the egg are controlled by embryogenesis demands, so biosynthesis of eggs consumes necessary amounts of minerals equivalent to egg weight independent from the level of the organism supply with these elements and their serum concentrations.
Thus, calcium, phosphate and magnesium in the blood serum of laying hens the cross Lohman white depend on period of oviposition. The contents and the balance between these macroelements are determined by intensity of absorption, excretion and intracellular metabolism. Contents of calcium, phosphates and magnesium in a chicken egg are almost independent from serum concentrations of these elements. Consequently, mineral composition of the egg contents is determined by demands in macroelements during embryogenesis and it quantitatively depends on egg weight.


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Ural State Academy of Veterinary Medicine, Chelyabinsk province, Troitsk 457100, Russia,
e-mail: tvi_t@mail.ru

Received February 8, 2010