The purpose of the work is to evaluate the possibility of using the ND5/ND6 mtDNA site as a polymorphic marker for nelma differentiation using the example of two repair and brood herds of nelma "Kubenskaya" and "Obskaya" of the Forvat fish farm in the Leningrad region. 
Materials and Methods. Nelma haplotyping by PCR-RDF based on polymorphism of restriction sites of endonuclease enzymes and determination of the nucleotide sequence by Sanger sequencing of the ND5/ND6 mtDNA region. 
Results. The features of the ND5/ND6 nucleotide sequence presented in the work in representatives of the genus Stenodus had not previously been considered as an informative molecular genetic marker. It was found that the nelma from the repair and broodstock formed from the producers of Lake Kubensky demonstrates genetic differences from the repair and broodstock of the nelma from the Ob River. The analyzed mtDNA region can be used as a molecular genetic marker when carrying out nelma haplotyping at fish hatcheries in samples of a significant volume to control measures to restore geographically remote natural populations of nelma.

Objective: to develop a new model for differentiating between domestic pigs and wild boars based on autosomal SNP analysis, thereby improving the accuracy of species identification.
Materials and Methods: using the SRA-BLAST and GENIS bioinformatics algorithms, 1,639 genomes were analyzed: 91 wild boar (Sus scrofa scrofa) and 1,548 domestic pig (Sus scrofa domesticus). The differentiating potential of the studied polymorphisms was assessed, and a classification model for wild boar and domestic pig was calculated based on three SNPs (Sscrofa11.1 (GCF_000003025.6)): rs330419406 (Chr.5:55839440A>G), rs81293059 (Chr.8:52261272C>T), and rs326780270 (Chr.1:265347265A>G, NR6A1).
Conclusion. The model demonstrated high accuracy (99,84 %), specificity (100 %), and sensitivity (100 %). The model was successfully tested on a sample of 95 wild boars and 95 domestic pigs, with classification accuracy reaching 100 %. Testing on DNA from wild boar and domestic pigs confirmed the high discriminatory potential of the proposed polymorphisms. Of 190 samples, 100 % were correctly classified. Since the genetic similarity between wild boar and domestic pigs reaches 99 %, specialized methods and genetic markers are necessary for reliable differentiation of their samples, highlighting the particular importance of our developed model for precision scientific research.

Objective: to summarize and analyze the effects of phytobiotics on the physiological state of animals (mammals and poultry).
Materials and Methods. To achieve this objective, a scientific literature search was conducted using elibrary.ru, PubMed, Web of Science, and Scopus, with an emphasis on studies from the past five years focused primarily on growth-promoting properties.
Results. This review article provides a summary of the effects of phytobiotics on the physiological state of animals (mammals and poultry). The intensification of livestock farming is increasingly leading to the need for synthetic drugs produced by pharmaceutical companies. Antibiotics, including feed antibiotics, have a significant impact on the growth-promoting properties of the body. Their irrational use leads to microbial resistance to the active ingredients of drugs, meaning their subsequent use will no longer have a therapeutic effect. All these factors are leading scientists to search for alternative treatments that are equally effective as these medications. Phytobiotics could be such substances. Phytobiotics have a positive effect on the gastrointestinal tract and help stabilize the balance between normal flora, pathogenic, and opportunistic microorganisms. Equally important is research into phytobiotics as antioxidants. Further research should focus on optimizing dosages, studying synergism between various phytogenic compounds, and developing effective commercial formulations for widespread adoption in livestock and poultry farming.

Objective: to conduct a comparative analysis of the dynamics of exterior parameters in young crossbred foxes obtained by crossing snow fox males with silver fox females.
Materials and Methods. The study sample consisted of crossbred snow fox males with silver fox females bred at the Vyatka Animal Breeding Farm in the Kirov Region. Using the paired analog method, groups of male (n=50) and female (n=50) puppies were formed. The study was conducted from 2019 to 2024. Immature puppies aged 3, 4, 5, 6, and 7 months were used. Linear measurements were measured with a first-class precision measuring tape with a 0.2 cm division value in accordance with zootechnical regulations for fur farming.
Results. This article presents the results of a study examining the growth and development rates of males and females of crossbred types, using snow foxes as an example, during postnatal ontogenesis during the period of active growth: from the third to the seventh month. Changes in key linear measurements were studied: body weight, head length, cheekbone width, linear body length, chest circumference behind the shoulder blades, chest width and depth. Body conformation indices were calculated: broad-headedness, weight, compactness, and chest. The age periods of active growth and development of young male and female snow foxes under current housing and feeding conditions were determined. Using these parameters, the timing of the onset of sexual dimorphism in foxes of the original snow coloration was determined.

Objective: to determine the effects of different doses of an adsorbent on the state of interstitial metabolism in broilers when administered as part of complete feed.
Materials and Methods. Two hundred day-old Isa Hubbard F15 meat chickens were selected for the study. Four groups (50 birds each) were formed using the analog group principle. To ensure experimental integrity, NaNO3 (sodium nitrate) was added to the feed formulation used for the test birds at a rate of 40 g/t of feed to ensure subtoxic levels of these compounds. Three experimental groups were administered the adsorbent: Group 1—1 kg/t; Group 2—1,5 kg/t; and Group 3—2 kg/t. The adsorbent was not administered to the control group. During the experiment, the test birds were reared for 42 days, after which they were individually slaughtered. Blood samples were collected for biochemical and morphological parameters.
Results. The results demonstrate that, to optimize interstitial metabolism in broilers through more successful denitrification, it is advisable to add a feed adsorption agent at a dosage of 1,5 kg/t of feed to their feed with subtoxic nitrate levels. Thus, due to improved elimination of the studied toxins in blood samples, the birds in this group, compared to the control group, showed a 43,40 % decrease in methemoglobin concentration (P>0,95), while simultaneously increasing red blood cell count by 0,72×1012/L (P>0,95) and hemoglobin by 6,76 g/L (P>0,95). Protein, carbohydrate, and lipid metabolism also improved. There was a decrease in the mass fraction of nitrates by 2,26 times (P>0,95) and nitrites by 2,09 % times (P> 0,95).

Objective: to study the biochemical indices of the functional state of the liver during the dry and postpartum periods in Black-and-White cows s in relation to the dynamics of ovarian luteal activity resumption.
Materials and methods. The study included 69 cows in their second to fourth lactation periods, from which blood samples were taken 6, 4, and 2 weeks before calving and 1, 3, 7, and 13 weeks after calving. The functional state of the ovaries was assessed 7 and 13 weeks after calving using rectal and ultrasound examinations. The ovarian luteal activity was assessed based on the blood progesterone levels. The cows were divided into 4 groups: I – luteal activity was diagnosed by the 7th week postpartum (n=29); II – luteal activity was detected by the 13th week postpartum (n=16), III – luteal activity was not detected within 13 weeks after calving in the absence of signs of ovarian hypofunction (n=12), IV – the presence of signs of moderate or severe ovarian hypofunction (n=12).
Results. Throughout the observation period, albumin concentrations in the blood of cows in Group IV were 1,1— 1,2 times lower (p<0,001-0,05), and globulin concentrations were 1,2—1,3 times higher (p<0,01-0,05) than in Group I. Furthermore, compared with Group I, the albumin level was 1,1 times lower (p<0,01—0,05) in animals in Groups II and III from the 3rd to the 13th week of lactation, while the globulin level was 1,1—1,2 times higher (p<0,01—0,05) in individuals of Group II (6 weeks before calving) and Group III (1 week after calving). The concentration of bilirubin in the blood of cows was higher than in Group I, 4 weeks before calving — in animals of Group III (1,5 times, p<0,01) and 2 weeks before calving — in animals of Group IV (1,3 times, p<0,05). Aspartate aminotransferase activity was 1,2—1,3 times lower (p<0,01) in Group I than in Group II after 7 weeks of lactation and in Group III after 7 and 13 weeks. The activity of alanine aminotransferase in Group I was 1,2—1,3 times higher (p<0,05) than in Group III (6 weeks before calving) and in Groups II and IV (after 13 weeks of lactation). Triglyceride concentrations in Group I animals were 1,2—1,3 times higher (p<0,01—0,05) than in animals of the other three groups at different time periods from the 4th week before calving to the 7th week after calving.

Purpose: The aim of the study was to determine the efficiency of the freezing protocol for day-old chick ovaries depending on the composition of the cryoprotective medium.
Materials and Methods. Russian Snow White chickens (n=30) were used to obtain the ovaries of day-old chicks. Freezing was performed using a simple two-stage vitrification method, using DPBS-based cryoprotective media containing dimethyl sulfoxide, ethylene glycol, and sucrose as cryoprotectants in the control (medium A) and the addition of inositol (0.5 M) (medium B) in an experimental modification of the cryoprotective medium. The effectiveness was assessed after in vitro storage at -196°C for 30 days, based on the condition of primary follicles in histological samples.
Results. Data were obtained based on the results of evaluating histological samples for the integrity of oogonia in the cortex of thawed ovaries: when using cryoprotective medium A, the number of morphologically intact oogonia was 1,4 pcs. per field of view (magnification x400), which was 5,4 % of the indicator for native samples; when using medium B — 9,0 pcs. oogonia (34,5 % of native). 
Conclusion. The creation of a long-term cryobank for the storage of female gametes of the avian class (Aves) is a relevant strategic solution to the problem of preserving the genetic diversity of breeds and species. The efficiency of gonadal tissue freezing depends on the chosen donor age and the cryopreservation protocol, taking into account the composition of the cryoprotective media. The presented data prove the effectiveness of the protocol for freezing the ovaries of day-old chicks using a cryoprotective medium containing inositol (medium B) allows preserving a significant percentage of morphologically intact ovarian tissue structures and, directly, the oogonia in it.

Objective: evaluation of some factors of the phagocytic and lymphoid resistance systems in the blood of male laboratory rats.
Materials and methods. The experimental part was carried out on a group of 7 male Wistar laboratory rats. The experiment was conducted in three stages, corresponding to the two-, three-, and four-month ages of the males. At each stage, samples of venous blood were collected and analyzed for the absolute number of leukocytes and their populations. The analysis of T- and B-lymphocytes was performed using the method of cytochemical determination of non-specific esterase. Leukograms were obtained at each stage of the experiment, and leukocyte indices were calculated based on the data obtained.
Results. At the end of the experiment, the predominance of resistance factors of the lymphoid system was noted. Thus, the relative number of lymphocytes was in the range from 74,20±1,56 % to 75,40±1,86 %. The ratio of T- and B-lymphocytes throughout the experiment ranged from 54,80±1,39 % to 45,20±1,39 % to 57,40±1,36 % to 42,60±1,36 %. When assessing leukocyte indices, a low value of the neutrophil-lymphocyte ratio index (in the range of 0,28±0,03 to 0,29±0,03) and a high value of the Garkavi index (at least 4,18±0,48) were found. Conclusion. The leukogram of rats is characterized by a predominance of lymphocytes, which determines a higher activity of the factors of the lymphoid system of resistance. Nevertheless, it is assumed that rats can have a very rapid mobilization of neutrophils and monocytes from the bone marrow and marginal pool in response to infection, which provides a high efficiency of the phagocytic system, despite its low number in the circulating blood. It is important to note that T-lymphocytes are the predominant population of lymphocytes, while B-lymphocytes normally make up a smaller portion. The study of integral hematological indices allowed to establish the prevalence of humoral resistance over cellular, as well as a higher activity of the effector link of immunity.

Purpose: to determine whether transvaginal ultrasound-guided ovum pick-up (OPU) procedures influence the concentrations of stress-associated hormones in the serum of Holstein heifer oocyte donors, and to assess whether the intensity and duration of donor use affect these hormonal indicators.
Materials and Methods. The study was conducted at the L. K. Ernst Federal Research Center for Animal Husbandry (FGBNU FIC VIZh) on Holstein heifers (n = 10) with synchronized estrous cycles. Four days after the onset of estrus, transvaginal ultrasound-guided follicular aspiration was performed. Five animals (regimen 1w) underwent OPU once per week at 7-day intervals, while another five animals (regimen 2w) were subjected to OPU twice per week at 3—4-day intervals. The total number of procedures was 10 for regimen 1w and 20 for regimen 2w, each divided into two equal-duration periods. Blood samples were collected the day after estrus onset and on each OPU day. Serum concentrations of cortisol, adrenaline, and noradrenaline were determined using enzyme- linked immunosorbent assay (ELISA).
Results. Following the first OPU session, serum concentrations of stress-related hormones in donors increased significantly. Cortisol levels rose from 15,8 [4,8; 36,2] ng/mL before OPU to 26,8 [15,5; 49,0] ng/mL after the first aspiration (p = 0,0195); adrenaline increased from 60,3 [44,8; 108,1] to 105,0 [69,2; 132,6] pg/mL (p = 0,0488); noradrenaline from 51,0 [43,7; 53,9] to 70,7 [54,8; 82,5] pg/mL (p = 0,0137), respectively. No significant differences in hormone concentrations were observed between regimens 1w and 2w when compared within identical periods (p>0,05). Cortisol levels remained comparable across the studied time points (p>0,05). In both regimens, adrenaline and noradrenaline concentrations were higher during OPU sessions than outside OPU periods. In the twice-weekly regimen (2w), the concentrations of the analyzed hormones in the second period (OPU11—20) were significantly higher than in the first (OPU1—10) (p<0,05), whereas no such differences were detected under the once-weekly regimen (1w) (p>0,05). These findings are preliminary, as comprehensive evaluation of the technology’s efficiency requires consideration of reproductive outcomes in light of the obtained data.

Purpose: to study and summarize data from domestic and foreign authors on the mechanisms of follicular waves in female cattle, the cyclical nature of their manifestation, and the influence of various factors on them.
The maturation of follicles within the reproductive cycle in female cattle occurs in waves. Using ultrasound diagnostics and blood sampling for estradiol levels, it was found that in the sexual cycle of cattle, from one to four follicular waves are formed during the estrous cycle. Follicular waves consist of groups of growing follicles with a diameter of ≥ 4 mm, from which the dominant follicle is selected, while the remaining follicles undergo atresia. If the dominant follicle reaches its maximum size (>10 mm) during the wave, ovulation occurs – the cycle becomes two–wave, if it does not reach, then another wave begins, if the follicle reaches its maximum size during it, the cycle becomes three-wave. The frequency of occurrence of follicular waves affects the duration of the sexual cycle – three-wave cycles are longer than two-wave cycles. The use of knowledge about follicular waves is of particular importance for practical purposes, since in the future it will improve the reproduction rates of cattle by improving approaches to selecting the optimal scheme for synchronizing sexual hunting of animals, reducing the cost of insemination and increasing its effectiveness.

Purpose: to study the influence of gender on the assessment of spatial learning and short-term memory formation in white laboratory rats of the Wistar line.
Materials and methods. 2 groups of Wistar rats weighing 180-250 g were selected for the experiment. In the course of the study, the protocol of the neurobehavioral test "eight-octave radial maze" was used to assess long-term/working and spatial memory. It consisted of 3 stages, lasting 16 (1st stage) and 11 minutes (2nd and 3rd stages). The obtained data from stages 2 and 3 were analyzed, and the overall memory score was calculated using the formula.
Results. According to the results of the experiment, it was revealed that after the 3rd stage of testing, the average score of short-term memory increased in all groups of rats, and the group of males showed better results in the average score of short-term and spatial memory than the group of females. The sexual trait has an impact on the formation of short-term and spatial memory, which may be associated with better development of the hippocampus in females, as well as faster habituation to changed environmental conditions, compared with males. Despite the addictive phase, animals from both groups showed signs of stress, which differed depending on the gender of the group. The group of females distinguished themselves by a large number of studied moves in one session, while making more mistakes than the group of males. The first group (males) spent most of the time during the second and third stages in a stupor in the central part of the maze, making no attempts to explore more than 1 branch of the maze.