The decline in the reproductive potential of hens by the end of the first productive period is closely related to the biological process of ovarian aging. At the same time, the functioning of the reproductive system is de termined by the intensity and direction of metabolic processes in the body of females.

Objective: The aim of the presented work was to study the relationship between biochemical markers of metabolic status and the manifestation of age-related decline in egg production in domestic hens.

Materials and methods. We performed a comparative study of blood biochemical indicators in young laying hens with long egg clutches (YLC, n=17) and in middle-aged hens at different reproductive states: with long egg clutches (MLC, n=10), with anovulatory long clutches (MALC, n=9), with short clutches (MSC, n=15) and with short clutches after molting (MSC-M, n=9). Biochemical blood parameters were determined simultaneously in all samples using an automatic biochemical analyzer.

Results. The concentration of total protein in the blood plasma of young birds was 1.2 times lower (p<0.01 0.05) than that of older birds in the three groups (MLC, MSC and MSC-M). The blood content of lipid metabolism components in hens of different ages and reproductive status did not differ. In young birds, the activity of alanine aminotransferase in the blood was 1.5 times higher (p<0.05) than in hens after molting (MSC-M), and the de Ritis coefficient was 1.4 times lower (p<0.05) than in hens of the MLC group. At the same time, in aged individuals in the MLC and MSC-M groups, the levels of phosphorus and iron were 1.4 times higher (p<0.01-0.05) compared to those in individuals in the YLC (phosphorus) and MSC (iron) groups.

Conclusions. The findings indicate that in laying hens, the content of total protein in the blood increased with age, which did not depend on the presence of signs of reproductive aging. Furthermore, they point to com pensatory changes in mineral metabolism indicators and the aminotransferase activity in aged hens that main tain a high intensity of egg laying, as well as in birds that have resumed egg laying after molting.

Purpose: Morphological study of the spleen of white laboratory rats of the Wistar line when adding a mineral supplement based on chelate compounds to the feed. Materials and methods. The experiments were conducted on white male laboratory rats of the Wistar line weighing 200-250 g. “Chelavit C” was used as a mineral feed additive. After three months, the animals were euthanized using inhalation drugs combined with an overdose of anesthetic injection. Morphological analysis was performed on macro- and micropreparations of the spleen. For a general assessment of the histological organization of the spleen, hematoxylin and eosin staining was used. Iron accumulation in the spleen was assessed using Perls’ Prussian blue stain. Results. Differences in some of the main clinical and morphological parameters assessed on macroscopic specimens of the spleen of animals from the experimental and control groups were insignificant and were within the permissible physical and anatomical norm. Morphometric analysis of histological preparations of the spleen did not reveal differences between the groups; the indicators were within acceptable limits. Staining with Prussian blue according to Perls showed that the iron content in the spleen of animals in the experimental and control groups corresponds to normal values. Therefore, the used feed additive based on chelate compounds does not cause hemosiderosis, which can subsequently develop into hemochromatosis. Conclusion. A mineral feed supplement based on chelated compounds replenishes the loss of microelements without having a toxic effect on the spleen of rats. However, when administering this additive to animals, it is necessary to accurately calculate the dosage to avoid possible toxic effects.

Hypoxia, regardless of its origin, is in many cases the main factor in the formation of many pathological conditions and various diseases. The aim of the study is to study the disturbance of lipid and phospholipid metabolism in rats during modeling of hemic hypoxia.

Materials and methods. The studies were conducted on white outbred rats weighing 220-240 g. A model of hemic hypoxia was used. To determine lipoproteins, an electrophoretic method and standard techniques were used with standard sets of chemical reagents. The phospholipid spectrum was determined by thin-layer chromatography using silicone plates from Silufol.

Results. The results of the studies showed that in rats of group 1, the concentration of all phospholipid fractions during acute hemic hypoxia decreased by 5,4 % compared to the indices of intact animals, in rats of group 2 — by 6,5 %, in rats of group 3 — by 4,9 %, in rats of group 4 — by 3,1 %, and in rats of group 5 — by 5,6 % compared to the indices of intact rats. During hemic hypoxia, phospholipid metabolism disorders rapidly develop, characterized by a decrease in the proportion of total phospholipids, an increase in the concentration of LPH, a decrease in the level of the main phospholipid fractions PHH and an increase in PHEA, which indicates an increase in phospholipase activity in tissues.

Purpose: to study age-related changes in iron metabolism indices in Hanoverian mares.

Materials and methods. The study was conducted in the summer at a horse farm in the Tosnensky District of the Leningrad Region. For the study, 20 clinically healthy mares were selected, which were divided into 4 age groups of 5 horses each: the first group — 2—4 years old, the second — 5—10 years old, the third — 11—15 years old, the fourth — 16 years old and older. Blood was collected into vacutainer tubes for hematology with K3EDTA. The following parameters were determined in each sample: hemoglobin concentration (hemoglobin cyanide method using acetone cyanohydrin), serum iron content (determined using the ABRIS+ kit), total iron-binding capacity (TIBC, determined using the ABRIS+ kit), latent iron-binding capacity (LIBC, calculated value), transferrin content, transferrin saturation coefficient (TIC, calculated value), and erythrocyte concentration was counted using a counting chamber with a Goryaev grid. The reliability calculation was carried out using the Mann-Whitney criterion.

Results. When analyzing the obtained data, it was revealed that the average indicators, except for the transferrin saturation coefficient, are within the reference values. The transferrin saturation coefficient exceeds the permissible values by an average of 24,06 %. The highest values of this indicator are observed in animals aged 2—4 years (33,8 %). A reliable increase in the number of erythrocytes by 34,3 % was also established in the 2—4 years age group compared to the 5–10 years group (p<0,05). A significant increase in hemoglobin was noted in the group of horses aged 5-10 years by 16,4 % (p<0,05) compared to the group aged 2—4 years, which may be a consequence of the body reaching physiological maturity. The transferrin saturation coefficient was also significantly higher by 7,9 % in horses aged 2—4 years compared to the average for all ages (p<0,05). Horses in the 16-year-old and older age group have higher average serum iron, total serum iron-binding capacity, and latent serum iron-binding capacity than other groups of horses.

Purpose: a comprehensive assessment of the effect of chelated forms of trace elements on quantitative and qualitative characteristics of leukocytes in combination with growth processes. Materials and methods. The experimental part was carried out on male laboratory rats. 2 homogeneous groups of 5 individuals were formed: experimental and control. The feed additive “Helamax C” was introduced to the main diet of the experimental group. The experiment was conducted in 3 stages. At each stage, body weight measurements were carried out, as well as blood sampling with subsequent examination of leukocytes (counting the absolute and relative number of leukocytes, building leukograms, as well as analysis of leukocyte indices). Blood was taken from the caudal vein. Leukocytes were counted according to the generally accepted method using the Goryaev camera. Leukograms were calculated at each stage of the experiment, after which leukocyte indices were calculated.

Results. At the end of the experiment, there was an increase in the total number of leukocytes from 5,95±0,12 G/l to 7,47± 0,32 G/l in the blood of rats against the background of the use of a mineral supplement. A decrease in the absolute number of rod-shaped neutrophils from 0,19±0,08 G/l to 0,11±0,04 G/l, with a simultaneous increase in the level of segmented neutrophils to 1,39±0,18 G/l. In the rats of the experimental group, the absolute number of lymphocytes in the blood increased from 4.94±0,07 G/l to 5,64±0,26 G/l. There was an increase in the neutrophil lymphocyte ratio index from 0,06±0,03 to 0,26±0,02 in individuals of the experimental group, as well as a decrease in the nuclear shift index from 0,32±0,09 to 0,08±0,03. The body weight of the experimental rats increased from 368,40±20,27 g to 534,40±13,74 g.

Conclusion. The introduction of mineral supplements into the diet helps to improve the quantitative and qualitative indicators of leukocytes, stimulating and regulating their formation, differentiation, functioning and apoptosis. In addition, minerals have a positive effect on the immune system, increasing the body's natural resistance. Together with the activation and regulation of metabolic processes, this leads to stimulation of body growth and an increase in body weight.

Purpose: study of data from domestic and foreign authors on the morphofunctional features of the acrosome, methods for assessing the acrosomal reaction and comparison of fertility data. Fertility is the ability of a sexually mature organism to produce viable offspring.

Fertility can be determined by various criteria, but one of the key factors is the assessment of the integrity of the acrosome. The acrosome is a part of the sperm, located at the top of its head. There are two main functions of the acrosome: the isolation of proteolytic and hydrolytic enzymes for the sperm to pass through the transparent shell of the egg, and ensuring the fusion of the sperm with the membrane of the female germ cell. Golgi apparatus, cytoskeleton, Sertoli cells and various proteins are involved in the formation of the acrosome. The acrosomal reaction is the exocytosis of the contents of the acrosome, as a result of which the sperm penetrates through the egg shells. The integrity of the acrosome can be assessed by several methods: electron microscopy with differentiated staining of the acrosome using different techniques, functional tests, fluorescence microscopy, radioimmunoanalysis.

The response of the ovaries of cattle to polyovulatory stimulation is characterized by significant variability and may depend to some extent on the animal genotype. In Holstein cows with a weak superovulatory ovarian response, a decreased thyroid activity was detected on the day of insemination and one week after insemination. However, there is no information on the relationship between polymorphism of genes controlling the thyroid system and the ovarian response to polyovulatory stimulation in cattle.

Objective: To analyze the relationship between polymorphic variants of the deiodinase type 1 gene (DIO1) at position 13149 and the ovarian response to polyovulatory stimulation in Holstein cows.

Materials and methods. The experiments involved 37 Holstein cows of the first and second lactation, in which 2 to 9 cycles of polyovulation stimulation were studied. On the first day of insemination, the number of follicles with a diameter greater than 5 mm was recorded in each ovary using an ultrasound scanner. Seven days after insemination, the embryos were washed out and assessed, and the number of corpora lutea in both ovaries was determined. Analysis of single nucleotide polymorphism of the DIO1 gene at position 13149 was performed on DNA samples using real-time PCR.

Results. The frequency of occurrence of cows with the GG, CG and CC genotypes was 48,65 %, 43,24 % and 8,11 %, respectively. A tendency towards an increase in the occurrence frequency of individuals with a large number of corpora lutea (> 6,0) on the 7th day after insemination was found in animals with the GG genotype compared to the CG genotype (55,6 % versus 25,0 %, p<0,1). At the same time, among cows homozygous for the G allele, individuals with a higher number of degenerated embryos (> 1.0) per 1 washout were more common (33,3 % versus 0 % in cows with the CG genotype, p<0.05). Concurrently, the occurrence frequency of cows with a large number of high-quality morulae and blastocysts washed out during one session (> 4,0) was slightly higher in the group with the GG genotype than with the CG genotype (33,3 % versus 12,5 %).

Conclusions. The data obtained suggest that the response of the ovaries of Holstein cows to polyovulatory stimulation may partially depend on the polymorphism of the DIO1 gene at position 13149. Furthermore, they indicate that the effect of polymorphic gene variants on fertility traits in cattle should be considered in combination with the breed of animals.

The application of genomic selection in rainbow trout breeding is becoming more feasible with the advent of recent advances in molecular genetics. However, there are significant challenges in the field of aquaculture, as genomic and marker-assisted selection programmes for aquaculture are considerably behind those for terrestrial farm animals. Currently, there is an actual task to develop test systems for genotyping rainbow trout and for efficient enrichment of target populations with favourable polymorphisms. The objective of this study is to develop a test system based on the promising BMP-2 gene and to establish genomic associations between single nucleotide polymorphism (SNP) and the size-weight characteristics of fish.

Materials and methods. The material for the study was comprised of Rofor rainbow trout specimens (n=200), which were evaluated for the following size-weight parameters: fish weight, body length to the end of the caudal fin, length to the end of the scales, head length, height, and body thickness.

Results. The results of the study revealed that the overwhelming majority of fish (98 %) exhibited a heterozygous genotype (AG) while homozygous genotype AA was entirely absent from the sample. The analysis did not identify any notable correlations between size-weight parameters but a potential explanation for this could be the absence of the AA genotype within the population. Nevertheless, the test system was successfully developed and validated. The study of the influence of this polymorphism contributed to the knowledge of rainbow trout genetics. Further application of the developed test system in rainbow trout breeding programs is possible after conducting additional studies to identify economically useful genetic associations in larger samples of individuals.

The aim of the study was to obtain phenotypic characteristics of the resource population chickens characterizing the development of the musculoskeletal system and body build for the subsequent study of the structural variability of the chicken genome and the search for gene variants that determine the manifestation of meat productivity phenotypes, including the development of the musculoskeletal system. Materials and methods. The object of the study were chickens of the F0 generation of the Uzbek fighting breed (n = 65) and Cornish (n = 79); hybrids F1 (♂ Cornish x ♀ Uzbek fighting; n = 117) and F2 (♂F1 x ♀ F1; n = 133). At the age of one day, 2 and 4 weeks, the weight (g) of the chickens was determined. Exterior measurements were taken at the age of 4 weeks. The following indicators were estimated (cm): chest girth; metatarsus girth; keel length; metatarsus length. The body conformation indices were calculated. Results. The chickens of the original F0 breeds and F1, F2 hybrids differed significantly in live weight at the age of 2 and 4 weeks. The weight of the Uzbek Fighting breed gene pool chickens was 3,5–4,2 times lower than that of the Cornish breed; the F1 and F2 hybrids had intermediate indicators. In Cornish breed chickens (F0), the coefficient of variability in live weight at the age of 4 weeks was 13,8 %; in Uzbek Fighting breed chickens (F0) – 15,0 %; in F1 and F2 hybrids – 20,5 and 17,6 %, respectively. The maximum values of the massiveness, eirisomy and shortness indices were obtained on Cornish breed chickens, while Uzbek Fighting breed chickens had low indicators; F1 and F2 hybrids are intermediate. Heterosis was established for the relative length of the metatarsus in F1 and F2 hybrids compared to the original breeds. The data obtained proved the feasibility of using the Cornish and Uzbek fighting breeds to create a resource population for the purpose of conducting research to find gene variants that determine the manifestation of meat productivity phenotypes.

Purpose: to study the availability of genetic resources of the breed of Sychevka and their use for its conservation.

Materials and methods. The object of research is the daughters of sires the breed of Sychevka used in the breeding network of the Smolensk region over the past 30 years. The materials for the research were data on breeding and zootechnical accounting of animals in the IAS "SELEX – Dairy Cattle" and data from Yearbooks on breeding work in dairy cattle breeding in the farms of the Russian Federation for the period from 1990 to 2023. The methodology of this work is related to the study of zootechnical techniques aimed at improving dairy cattle using general scientific zootechnical and population-genetic analysis methods.

Results. It has been established that during the improvement of the breed of Sychevka, sires of Holstein and Simmental breeds were used in different time periods and with different intensity. The ratio of breeding bulls used in the region maintains a tendency to increase imported (Holstein and Simmental) and decrease domestic (breed of Sychevka) animals by 19,5 %. A comparative analysis of intra-linear selection options and selections at the cross of lines and related groups showed that the best results in milk yield in both cases were obtained with a combination of imported bulls, milk fat content at intra-linear — imported, at cross — domestic, milk protein content — domestic.

Conclusion. So, in order to restore the population of cattle the breed of Sychevka using the remaining reserve of breeding bulls, it is extremely necessary to create a gene pool farm in the Smolensk region and carry out breeding, both to improve the productive qualities of animals and to preserve the genetic component of the breed.

The purpose of the study is to monitor and analyze the breeding and productive qualities of Black-and-White cattle in the Russian Federation.

Materials and methods. The object of the study was digital data on the number, economically useful traits, breeding qualities of cattle and cows of Black-and-White, Holstein and other dairy breeds bred in the Russian Federation. The main method is monitoring and analysis of data in a comparative aspect with Holstein and other breeds of the Russian Federation.

Results. Analysis of the relative number of livestock by breed showed that among the 25 breeds assessed, the Black-and-White breed in this aspect takes second place (17,62%), and 4th in milk productivity. Animals of the 1st and 2nd lactation of this breed make up 62,4 % (n=161302), which indicates that this population is quite young. The average age of cows is 2,5 calvings, and the number of heifers transferred to the main herd is 32,8 % (n=84783). The milk flow rate, with the desired indicator (from 2,0 kg/min. and above) was detected in 56,8% (n=51652). An analysis of 526 farms for insemination of 258,543 cows and 114,745 heifers showed that only 88,8 % of them were inseminated (n=331,685), including 97,7 % artificially. 43,6 % of cows and 46,6 % of heifers were inseminated with improvement bulls. The average live weight of cattle at the first insemination was 386 kg. The average days open of the assessed livestock was 132 days. Extended days open (121 days or more) were detected only in 37,2 % of animals (n=82,536), which indicates good reproductive qualities of Black-and-White cows. The average dry period is 61 days, that is, it has an optimal value, but in 13 % of animals an extended dry period of more than 71 days was detected. The yield of live calves per 100 cows was 76 %. In total, during the reporting period, 4,686 heads of breeding cattle of the Black-and-White breed were sold, of which 4,616 heifers and 50 bulls were young animals.

Conclusion. The monitoring of the state of the breeding and productive qualities of Black and-White cattle in the Russian Federation showed that this population of dairy cattle is not only the second largest among all breeding dairy breeds, but also makes up almost half of the dairy cattle of the remaining 24 breeds, with the exception of Holstein. In terms of milk yield, Black and-White cows exceed the average for 23 breeds, except Holstein, by 300-500 kg of milk, but are inferior in quality indicators.

Purpose: Define physiological gestation length of hybrid sows large white x landrace PIC Russia’s genetic and find optimal model for farrowing synchronization.

Materials and methods. Studying was carrying out at platfrom of MPC "Romcor" Ltd. located at v. Nizhnyaya Sanarka, Troitskiy rayon, Chelyabinskaya oblast'. There are drugs for farrowing induction didn’t used at formed control group of 780 sows, thus farrowing was natural. Experiment on farrowing synchronization by cloprostenol – synthetic analog of prostaglandin F2α administered at dosage 175 mcg per sow was designed at thee phases. At first phase (506 sows) cloprostenol was administered for primigravida sows at 117 day of gestation, since second reproductive cycle at 116 day. At second phase (857 sows) for primigravida at 117 day, for second at 114 day of gestation  and over third cycle at 113 day. At third phase (803 sows)  primigravida sows at 117 day, for second cycle at 116 day and for over third at 115 day of gestation. Piglets’ mortality was calculated at each group.

Results. At control group gestation length was more than 115,7 days and piglets’ mortality was 18,9 %, there were oblique signs of overdue pregnancy at this group. At first phase of experiment gestation was 115,4 days and piglets’ mortality was 16,8 %. At second phase of experiment gestation was 114,8 days and piglets’ mortality was 20,5 %. At third phase of experiment gestation was 115,4 days and piglets’ mortality was 17,6 %. There are piglets’ mortality is depending from amount of born alive and also from gestation length uring the experiment have been confirmed. Usage of cloprostenol for farrowing synchronization is safe since 115 day of gestation.

Purpose: to study the composition and role of endobiont ciliates in the digestive tract of red deer living in Yakutia.

Materials and methods. The study was conducted on materials obtained from the forestomachs of animals delivered from the Amginsky ulus in December. In total, one animal was examined, from which two samples were taken. Microscopic examination of ciliates was carried out during the analysis of sample prints. Species affiliation, abundance and morphological parameters were determined.

Results. During the analysis, five species of endobiont ciliates were identified, including Entodinium fursa monolobum, Entodinium anteronucleatum, Epidinium ecaudatum and Eudiplodinium maggii, belonging to the genera Entodinium, Epidinium and Eudiplodinium. Of particular interest is the discovery of Entodinium anteronucleatum, specific to red deer, which makes it unique in the biodiversity of forestomach microorganisms. Comparative analysis showed the presence of common species of ciliates with cattle - Entodinium fursa, Epidinium ecaudatum, Eudiplodinium maggii, which may indicate the similarity of digestive processes in these animals, although in red deer they are more effective due to the limited food supply. Studies have confirmed the participation of endobiont microorganisms, especially microaerophilic organisms of the genera Entodinium and Eudiplodinium, in the processes of food processing, including coarse plant fiber. These processes play an important role in improving the quality and efficiency of digestion, as well as the availability of nutrients. Further study of endobiont microorganisms may have prospects for the development of new veterinary drugs aimed at regulating the composition and quantity of microflora and microfauna of the forestomachs not only in red deer, but also in other ruminants.