Semen quality is the main parameter for evaluating sires. Sperm freezing is considered the main method for preserving animals with certain reproductive capabilities. The aim of the study was to investigate the quantitative and qualitative parameters of native and frozen-thawed semen in sires depending on the selection direction. The study was conducted at the base of JSC "GCV" in the Moscow Region, Podolsk, on 3 groups of bulls in the amount of 12 heads: Simmental bulls of the dairy direction (n=4) and meat direction (n=4) and Montbéliarde bulls of the dairy direction (n=4). A total of 477 samples were analyzed, including 173 samples from meat Simmentals (the number of samples in a group varied from 41 to 46); 160 samplings of dairy Simmentals (the number of samplings in a group varied from 32 to 46) and 144 samplings of Montbéliarde (the number of samplings in a group varied from 29 to 47). It was found that the defective ejaculates of native semen in beef bulls averaged 22.7%, the number of fertile spermatozoa 32.6%, while the percentage of defective ejaculates in dairy sires of the Simmental breed averaged 12%, the percentage of fertile spermatozoa at the level of 44.6%. Similar indicators were obtained in Montbéliarde bulls and amounted to 8.2% and 53.6%, respectively. Semen losses per bull were greatest in beef Simmentals (9,808 doses). In Montbéliardes, this figure was 3,795 doses. At a reliable level, the dose of frozen semen per 1 ejaculate in Simmental bulls of dairy orientation was 236 doses and in beef orientation - 201 doses (at P < 0.05). Individual characteristics were also established in bulls in all groups.

Research has been conducted to study nonspecific resistance in breeding bulls depending on the breed, age within the breed and the body’s protein supply after a long winter period of operation. It was established that the general background for nonspecific resistance in animals in terms of the percentage of lysis was at the level of 32.4 ± 0.8; by the amount of lysozyme 0.29 ± 0.01 μg/ml; by specific units of protein activity 0.81±0.06 mg; bactericidal activity of blood serum 25.6±0.86%. The relationship between nonspecific resistance in breeding bulls depending on the breed has been determined. The condition of bulls in terms of total protein supply was at a relatively similar level within the reference values. In terms of the percentage of lysis, relatively low values were recorded in animals of the Jersey (24.6%), the highest in the Kostromsky and Brown Swiss — 40.3% and 40.5%, respectively. The Jersey breed also has the lowest level of specific activity units. A relatively high level of bactericidal activity of blood serum was noted in the Ayrshire (34.2%), while in other breeds bactericidal activity of blood serum was at the level of 23.7–26.4%. Significant differences were noted between the Holstein Black and motley color and Kostromsky in the amount of lysozyme in the blood serum, in specific units of activity (р ≤ 0.05), with the Jersey breed in specific units of activity (р ≤ 0.01), and with the Ayrshire breed in specific activity units (р ≤ 0.05) and bactericidal activity of blood serum (р ≤ 0.01). Between the Holstein Red red-and-white color and Jersey and Ayrshire animals, the reliability for a number of indicators was р ≤ 0.05; between the the Kostromsky, Jersey, Ayrshire and Simmental animals for total protein, the amount of lysozyme and for specific units of activity р ≤ 0.01.

The purpose of the research was to study the breeding and genetic characteristics of Kholmogory breed sires depending on their part of Holstein breed blood in diff erent regions of the Russian Federation. An analysis of data was carried out on 13 sires owned by JSC “Head Reproduction Center” (Moscow region), JSC Head Bull Stud “Elita” (Republic of Tatarstan) and OJSC “Arkhangelsk Bull Stud” (Arkhangelsk region). The milk productivity of female ancestors was studied, as well as the milk productivity of daughters of Holstein sires of diff erent part of Holstein breed blood. It was established that the highest live weight at the age of 36 and 48 months was characterized by the sires of the JSC Head Bull Stud “Elita”. In this breeding enterprise the sires also had the highest blood level of Holstein breed (81,20 %) compared to the sires of other Bull Studs. The best indicators of milk yield per lactation were in the dams of sires at OJSC “Arkhangelsk Bull Stud” – 11 669,2 kg of milk per lactation, which were signifi cantly higher then in dams of sires from other Bull Studs. In second place were the dams of the sires of the JSC “Head Reproduction Center”, where the blood of the sires of the improving breed was the lowest at 20,25 %, at the same time they had more fat in milk (4,16 %) compared to dams of sires from other Bull Studs. The best result in milk productivity was obtained from daughters of sires of Kholmogory breed in the Republic of Tatarstan, which was in average 6845,2±468,05 (p < 0,05) kg of milk per lactation. This was signifi cantly more by 2087,2 kg of milk than from the daughters of the sires of JSC “Head Reproduction Center” and by 2795,0 kg of milk than from the daughters of the sires of OJSC “Arkhangelsk Bull Stud”.

Неспецифическая резистентность организма является важным критерием селекции в животноводстве. Работа выполнена на быках-производителях голштинской породы (n=42) в возрасте от 2 до 10 лет разных линий (Р. Соверинг, n=23; В.Б. Айдиал, n=19) и происхождения на базе АО «ГЦВ» Московской области. В ходе исследований у животных определяли содержание общего белка, лизоцимную и бактерицидную активность в сыворотке крови (ЛАСК и БАСК). Анализ общей резистентности организма в зависимости от возраста быков позволил выявить высокодостоверную разницу по количеству лизоцима (Р≤0,001) и по проценту лизиса (Р≤0,01). По бактерицидной активности различие между группами было незначительным и варьировало в пределах 24,72—27,26%. Определена возможная взаимосвязь неспецифической резистентности у животных разных линий. Выяснено, что по всем изучаемым показателям разница была недостоверной. Однако по лизису у быков линии В.Б. Айдиал данные были больше на 8,6% (33,98%) по сравнению с этим показателем у особей линии Р. Соверинг, который находился на уровне 31,3%. Количество лизоцима в крови животных обеих групп было на одинаковом уровне: 0,29—0,30 мкг/мл. Показатель бактерицидной активности в сыворотке крови у быков линии Р. Соверинг был на 7,8% больше, чем у особей линии В.Б. Айдиал. Выявлена зависимость общей резистентности организма от возраста и между быками европейской и американской селекции. Nonspecific resistance of the organism is an important criterion for selection in animal husbandry. The work was carried out on Holstein breeding bulls (n=42) of different ages (2-10 years), of different breeding lines (R. Sovering, n=23, V.B. Aidial, n=19), origin (Russia, n=9, Europe, n=11 ((Nederland n=6, Germania n=3, Luxembourg n=2), America, n=16 (Canada), and colors (red-motley, n=3, black-motley, n=17) on the basis of Head Reproduction Center of the Moscow region. During the studies, the total protein content, lysozyme activity (the amount of lysozyme, specific units of activity) and bactericidal activity in the blood serum (LASK and BASK) were determined in animals. Analysis of the general resistance of animals depending on age revealed a highly significant difference in the studied groups in the amount of lysozyme (P≤0.001) and in the percentage of lysis (P≤0.01). In terms of bactericidal activity, the difference between the groups was insignificant and varied between 24.72% and 27.26%. The possible relationship of nonspecific resistance by line was determined (regardless of age). It was found that for all the studied indicators the difference was at an unreliable level. Thus, according to the percentage of lysis in bulls of the V.B. Ideal indicators were higher by 8.6% (33.98%) compared to the bulls of the R. Sovering line, where this indicator was at the level of 31.3%. The amount of lysozyme in both groups was at the same level and amounted to 0.29—0.30 μg/ml in the serum; BASK in animals of the R. Sovering line was 7.8% more than in the V.B. line Ideal. The dependence of the general resistance of the organism by age between bulls of European and American breeding has been revealed.

Humoral factors such as bactericidal and lysozyme activity are the most significant for the body's resistance. The purpose of the research was to study the nonspecific resistance of sires depending on age, place of adaptation before entering the Russian Federation, origin and breed. The work was carried out at JSC “Head Reproduction Center” (JSC “GCV”) on animals aged from 2 to 9 years in the amount of 34 heads. Such indicators as the percentage of lysis, the amount of lysozyme (mcg) in 1 ml of blood serum, specific units of activity (u.a.) calculated per 1 mg of protein and the bactericidal activity of blood serum as a percentage were studied. Lysozyme (LASK) and bactericidal activity (BASK) were studied using a Multiskan FC microbiological analyzer (Finland). Thus, it has been established that the general resistance of sires depends on age and has significant differences between animals of different age groups. At the age of 2-3 years there is no reliability. Significant differences between bulls according to the parameters we studied begin from 5 years of age at P <0.05 in the concentration of total protein and lysozyme and specific units. A. squirrel. Age range had no effect on BAS. More noticeable significant differences were recorded in animals (of contrasting age periods) in terms of general resistance and had significant differences at the level of P≤0.01 in the percentage of lysis, in the amount of lysozyme in the blood serum (P≤0.001), and specific units of activity (P≤0.001). It was found that sires coming from different regions of Europe (the Netherlands and Germany + Luxembourg) in the same age range do not have significant differences among themselves in the overall resistance of the parameters we studied (BASK and LASK) under the conditions of their operation in the Moscow region RF.

КОРТИЗОЛ КАК МАРКЕР ФИЗИОЛОГИЧЕСКОГО СТРЕССА У БЫКОВ-ПРОИЗВОДИТЕЛЕЙ (Bos taurus) А.И.АБИЛОВ 1 , А.А.ГУДИЛИНА 1 , Н.А.КОМБАРОВА 2  , В.В.ТУРБИНА 1 , Ю.А.КОРНЕЕНКО-ЖИЛЯЕВ 1 Эндокринный механизм стресса у животных до сих пор окончательно не выяснен.Социальный стресс из-за иерархии в стаде увеличивает выработку кортизола, катехоламинов, может влиять на половое поведение и фертильность, снижать продуктивность.Несмотря на огромное значение проблемы для племенных предприятий, занимающихся получением и криоконсервацией спермы сельскохозяйственных животных в коммерческих и научных целях, нет специальных исследований, посвященных связи качественных и количественных характеристик эякулята и оплодотворяющей способности сперматозоидов с уровнем постэякулятивного кортизола.В представленной работе мы впервые показали, что результативность искусственного осеменения прямо пропорциональна концентрации кортизола в сыворотке крови быков-производителей после эякуляции.У молодых быков-производителей доминировал стресс, связанный с взятием крови, у взрослых особей половое возбуждение подавляло стресс от этой ветеринарной манипуляции.Впервые выявлена зависимость оплодотворяющей способности сперматозоидов крупного рогатого скота от уровня кортизола в сыворотке крови у быков-производителей после эякуляции.Мы определили динамику концентрации кортизола в крови 11 быков-производителей голштинской породы иностранной селекции в возрасте 29-71 мес (холдинг АО «ГЦВ», дочернее племенное предприятие АО «Уралплемцентр», Свердловская обл., 2018-2021 годы) после эякуляции при периодичности получения семени согласно установленной технологии и оценили влияние кортизола на оплодотворяющую способность полученных сперматозоидов после их криоконсервации.Как у молодых, так и у взрослых животных выявлена достоверная положительная динамика уровня кортизола при ежесуточных ветеринарных манипуляциях по взятию крови в течение эксперимента.Средняя концентрация кортизола после эякуляции у молодых производителей (n = 6) в условиях стресса, вызванного этими регулярными манипуляциями, увеличивалась равномерно и в дни трех последовательных дуплетных взятий семени с 4-5-суточными интервалами составила 70,8; 91,1 и 144,7 нмоль/л.У взрослых быков (n = 5) старше 4 лет максимальный уровень кортизола (172,5 нмоль/л) зафиксирован после второго взятия семени, а к третьему отмечалось его незначительное снижение (на 5 %).С ростом концентрации кортизола после эякуляции увеличивается количество выделенных сперматозоидов.У молодых быков после трех последовательных дуплетных взятий семени с 4-5-суточными интервалами за одну эякуляцию получили соответственно 4,0; 5,5 и 6,2 млрд сперматозоидов, у производителей старше 4 лет -6,6; 7,3 и 7,5 млрд сперматозоидов.При оценке оплодотворяющей способности сперматозоидов крупного рогатого скота в зависимости от уровня кортизола в сыворотке крови после эякуляции лучшие результаты (59-60 %, р < 0,001) дали замороженные спермодозы из эякулятов, получение которых сопровождалось значительным выбросом кортизола в кровяное русло (концентрацией 162-216 нмоль/л).

A study was carried out to assess the quality of frozen-thawed semen using the sex separation method and the traditional method in a comparative aspect, and the authors believe that the work will be of some interest to specialists in zootechnical and biological fields, as well as to veterinary specialists. The work was carried out at the Federal Research Center for Animal Husbandry named after Academy Member L.K. Ernst and on the basis of LLC “Agrofirma Zarya”, Bogorodsky district, Nizhny Novgorod region in the period from 2017 to 2022. usng the semen of eight sires. To assess the quality of the semen, the index of nuclear DNA fragmentation (nDNA) in chromatin was determined, and the activity of spermatozoa was assessed visually and using the Biola AFS‑500 sperm analyser (ZAO Biola, Moscow). On the basis of the studies conducted, it was found that the morphology of the spermatozoa depends on the individual characteristics of the sires; the content of abnormal spermatozoa varies from 2 to 8% when collected by the traditional method and from 4.10 to 15% when collected by the sexing method. A significant difference between the sires is observed in the iDNA fragmentation index – this indicator varies from 2.66 to 8.62% and from 8.50 to 28.57%, respectively. The division of spermatozoa by sex has a direct effect on the quality indicators, leading to a decrease in their activity. This indicator is 11.2% higher in semen obtained by the traditional method than by the alternative technique. The number of abnormal cells in the semen divided by sex is 2.2% higher than in the semen collected by the traditional method, and the proportion of spermatozoa with fragmented iDNA is 7% higher. The velocity of spermatozoa in the studied doses of semen collected using the technique of sex separation was 96–113 μm/s immediately after thawing, and five hours after incubation at +38°C in a thermostat this indicator decreased to the level of 20–34 μm/s. The age of puberty of their calves obtained from the sexed semen from birth to fruitful insemination is 490 days, which is 16 days more than in group I, where heifers were obtained from the semen frozen in the traditional way (TS). The term of fruiting in heifers born from the use of the sexed semen (SS) was 273 days, while that of heifers born from the use of traditionally frozen semen (TS) was 275 days (2 days more). The age of heifers from birth to first calving in the SS group was 762 days and was 14.4 days more than in the TS group, which was 748 days.

The purpose of the research was to study in a comparative aspect the bioelemental status of sires of Kholmogorskaya breed under different natural and climatic conditions after a long winter period of using. The work was performed at the Federal Research Center for Animal Husbandry named after Academy Member L. K. Ernst, Russian State University of National Economy named after V. I. Vernadsky and on the basis of JSC “Head Center for Reproduction” (Moscow region) and JSC “Arkhangelsk Bull Stud” (Arkhangelsk region). In the experiment the sires of JSC “Arkhangelsk Bull Stud” (n = 6) and JSC “Head Center for Reproduction” (n = 5) were used. Biochemical parameters of blood were studied such as total protein, albumin, globulin, albumin-globulin ratio, total cholesterol, creatinine, urea, ALT, AST, total bilirubin, as well as macronutrients: calcium, phosphorus, calcium-phosphorus ratio, and trace elements: iron, magnesium, chlorides, copper, zinc, and alkaline phosphotase and glucose in a comparative aspect. A comparison of protein and lipid metabolism in breeding bulls, depending on the region, showed the following results. The diff erence between the sires of JSC “Head Center for Reproduction” and JSC “Arkhangelsk Bull Stud” in total protein was 8,75 g/l or 10,2 %, albumin by 27,5 %, total cholesterol by 42,2 %, creatinine by 11,5 %, urea by 58,8 %, ALT by 8,8 %, total bilirubin by more than 200 % in favor of the sires of JSC “Head Center for Reproduction”, the ratio between A/G by 32,6 %. However, signifi cant differences (p < 0,05) were found only in the content of urea and total bilirubin. It was concluded as a result of the research that the sires of JSC “Arkhangelsk Bull Stud” need to balance the ration in protein. and mineral content. In order to determine the needs of breeding bulls for essential elements, they should be monitored regularly, at least twice a year in blood serum taking into account the defi ciency or excess intake into the body according to the results of chemical analysis of water, soil and basic feeds, and compensated with targeted premixes.

Relevance . The periods of early postnatal ontogenesis are characterized by high plasticity, intensive metabolism and the need for nutrients and biologically active substances. Young animals weakened by diseases lag behind in growth and development, labor and feed costs for its cultivation increase. Maintaining and preventing the health of calves during growth and development is an important problem in modern animal husbandry. Methods . The work was carried out at the Federal Research Center for Animal Husbandry named after Academy Member L.K. Ernst in 2021–2022 and on the basis of «Agrofirma “Zarya”» LLC, Bogorodsky district, Nizhny Novgorod region. The experiments were carried out on heifers of different age groups (2 months — group I; 6 months — group II; 12 months — group III). In total, 36 female (calves), 12 heads in each group, were used in the experiment. Results . A significant difference was found between groups I and II in: total protein level, «albumin — globulin» ratio (A/G), cholesterol, iron, AST at the level of p < 0.05; globulin p < 0.01; bilirubin and creatinine p < 0.001. Between groups I and III, the reliability was established by phosphorus p < 0.05; between groups II and III — a highly reliable difference at the level of p < 0.001 in phosphorus, ALT and alkaline phosphatase, as well as the ratio «calcium — phosphorus» (Ca/P).

Relevance. The issue of studying metabolic processes is relevant not only for cows, but also for breeding bulls, due to the fact that it allows to identify various diseases in the early stages. The work is devoted to the study of the bioelemental state of breeding bulls after a long winter period of operation at an early stage of the spring season in the conditions of the Perm Territory Methods. The studies were carried out on 25 breeding bulls of the Holstein breed of black-and-white color, whose age varied from 2 to 10 years. The protein-lipid, mineral metabolism and enzymatic activity of the animal organism was studied. Results. It was revealed that only the content of bilirubin had an increased level in relation to the norm —at the level of 16%. It was established that among the animals there were individuals who had the highest individual indicators for some positions. In the group of animals with normal and elevated concentrations of bilirubin, a difference was found in the difference in alkaline phosphatase by 23.0%, the A/G ratio —by 11.0%, in total protein and globulin — by 4.5 and 8.3% respectively. Animal studies, taking into account the content of alkaline phosphatase in the blood serum of breeding bulls in the norm and above the standard values, showed that its concentration plays a significant role (at P < 0.001). In young bulls (30 months), this indicator was statistically significant and its values were higher than in animals of5 years and older. It is also worth noting that in adult bulls the level of total bilirubin was increased by 25%, difference in ratio of A/Gbetween groups of animals was 30.0%, total protein — 12.0%, globulin — 12.4% and albumin —15.4%. Based on the studies carried out, it can be said that it is necessary to conduct biochemical monitoring of the entire herd.

У всех млекопитающих сперматогенез находится под контролем пептидных и стероидных гормонов, в том числе тестостерона и эстрадиола. Тестостерон необходим для индукции сперматогенеза в пубертатном периоде, и нарушение ритма его секреции у быков-производителей может привести к торможению сперматогенеза. Цель исследования – изучить содержание тестостерона и эстрадиола в плазме семени и сыворотке крови у быков-производителей голштинской и симментальской пород в день взятия эякулятов и выявить характер вариации их уровня в зависимости от возраста и породы животных, а также изучить соотношение и связь с воспроизводительной способностью на уровне спермопродукции. Концентрация тестостерона увеличивается от 39,4 нМ в возрасте до 3-х лет до 97,4 нМ в возрасте 5 лет и старше; в то же время концентрации эстрадиола в сыворотке крови снижается. Cодержание тестостерона в плазме семени в два-три раза меньше, чем в сыворотке крови, а концентрация эстрадиола, наоборот, в 2-3 раза больше. Концентрация тестостерона в сыворотке крови у быков обеих пород в среднем составляла 42,6 нМ, а в плазме семени – 25,9 нМ (Р˂0,001), а концентрация эстрадиола – 0,36 нМ в сыворотке крови и 0,93 нМ в плазме семени. В диапазоне концентрации тестостерона в плазме семени в диапазоне 11-30 нМ отмечено наименьшее количество брака семени, которое через 5 ч после замораживания/оттаивания при инкубации +38 C⁰ составляло 18%, а при средней концентрации тестостерона 46,5 нМ данный показатель был на уровне 9,6%. Заключили, что определение уровня эндогенных гормонов в сыворотке крови и в плазме семени целесообразно проводить для прогноза качества спермопродукции и сохранности семени после замораживания и оттаивания. ABSTRACT. In all mammals, spermatogenesis is under the control of peptide and steroid hormones, including testosterone and estradiol. Testosterone is necessary for the induction of spermatogenesis in the pubertal period, and disruption of the rhythm of its secretion in sires can lead to inhibition of spermatogenesis. The aim of the study was to study the content of testosterone and estradiol in the seminal plasma and blood serum of Holstein and Simmental sires on the day of ejaculate collection and to identify the nature of the variation in their levels depending on the age and breed of animals, as well as to study the relationship and connection with reproductive ability on the level of sperm production. Testosterone concentration increases from 39.4 nM at the age of 3 years to 97.4 nM at the age of 5 years and older; at the same time, the concentration of estradiol in the blood serum decreases. The content of testosterone in semen plasma is two to three times less than in the blood serum, and the concentration of estradiol, on the contrary, is 2-3 times higher. The concentration of testosterone in blood serum in bulls of both breeds averaged 42.6 nM, in semen plasma 25.9 nM (P˂0.001), and the concentration of estradiol 0.36 nM in blood serum and 0.93 nM in semen plasma. In the range of testosterone concentrations in semen plasma in the range of 11-30 nM, the smallest amount of semen rejects was noted, which, upon incubation at +38 C⁰ 5 hours after freezing/thawing, was 18%, and with an average testosterone concentration of 46.5 nM, this indicator was at the level 9.6%. Concluded that it is advisable to determine the level of endogenous hormones in the blood serum and in semen plasma to predict the quality of sperm production and the semen safety after freezing and thawing.

This work is devoted to the general monitoring of mineral exchange in Holstein bullsproducers ( n = 50) of black-and-white color in the conditions of the Leningrad region. The mineral exchange of bulls was studied depending on the selection (American ( n = 7), Russian ( n = 11) and European (Netherlands) ( n = 32)) in the age range from 2 to 5.5 years. Such parameters as calcium, phosphorus, magnesium, iron, alkaline phosphatase, copper and zinc were studied using a biochemical analyzer Chem Well 2902 (Awareness Technology, USA) and an atomic absorption spectrometer “Kvant-2A”. It was found that the studied indicators for the content of minerals in blood serum are mainly at the level of reference values. There are significant differences in the bulls of Russian and European breeding ( P < 0.001). Above the reference values concentrations of phosphorus were noted in young bulls, magnesium in all age groups, which affected the ratio of changes in the ratio of calcium and phosphorus at a highly reliable level ( P < 0.001). There was also a shortage of copper in bulls of Russian and European origin (9.52 mmol/l and 8.35 mmol/l versus 9.81 mmol/l and 19.888 mmol/l in the norm). A relatively low level was observed in bulls of younger age (up to 24 months — of 6.33 mmol/l), and a zinc surplus in adult bulls over 37 months — of 59.2–62.4 mmol/l against 53.05 mmol/l the norm. We believe that it is necessary to constantly monitor the mineral metabolism of breeding bulls, not only taking into account their origin and age, but also their individual condition.

МЕТАБОЛИЧЕСКИЙ ПРОФИЛЬ И СПЕРМОПРОДУКЦИЯ У ГОЛШТИНСКИХ БЫКОВ-ПРОИЗВОДИТЕЛЕЙ ЗАРУБЕЖНОЙ СЕЛЕКЦИИ ПРИ СОДЕРЖАНИИ В РАЗНЫХКЛИМАТИЧЕСКИХ И ГЕОХИМИЧЕСКИХ УСЛОВИЯХ В РОССИИ И КАЗАХСТАНЕ А.И.АБИЛОВ 1 , Н.А.КОМБАРОВА 2  , Х.А.АМЕРХАНОВ 3 , С.А.ШЕМЕТЮК 2 , А.С.ШАМШИДИН 1 , С.В.МЫМРИН 4 , Е.А.ПЫЖОВА 5 , Н.В.БОГОЛЮБОВА 1 , А.А.ГУДИЛИНА 4 , С.Ф.АБИЛОВА 1 , П.Г

of interest for the practice of breeding the Holstein breed in countries with similar geo-climatic factors. We compared the influence of climatic and geochemical conditions of the Central Russia (the Head Center for the Reproduction of Farm Animals, Moscow Province), the Middle Urals (JSC Ural-plemcenter, Sverdlovsk Province), and the Northern Kazakhstan (RCPZh JSC Asyl-Tulik, Akmola region) on the adaptive status of the imported Holstein 3-9-year-old bull sires ( n = 122). Blood levels of bioelements Ca, P, Mg, Ca:P, Fe, chlorides, Se, Cu, and Zn were recorded. To assess protein-lipid metabolism parameters and blood enzyme activity, the total protein, albumin, globulins, urea, creatinine, total bilirubin, urea, triglycerides, cholesterol, alanine aminotransferase, aspartate aminotransferase and alkaline phosphatase were measured. The endogenous hormone levels (testosterone, estradiol, thyroxine, and cortisol) were measured. The volume of ejaculate, the concentration of spermatozoa in the ejaculate, and the number of spermatozoa in the ejaculate were assessed to evaluate sperm productivity. Climatic and geochemical characteristics of the regions were a temperate climate with sod-podzolic soils for the Moscow region, a sharply continental climate with bedrock rocks with sandy-clayey and sod-podzolic soils for the Middle Urals, and sever sharply continental climate with dark chestnut soil for the Northern Kazakhstan. The study revealed that the balance of macroelements was within the permissible limits and did not have significant differences between regions, i.e., 2.34-2.53 mmol/l Ca, 1.47-2.01 mmol/l P (Ca:P 1.20-1.65), and 0.79-0.98 mmol/l Mg. The iron supply in the Moscow region was within the normal range (23.82±6.18 μ mol /l), reached the upper limits in the Northern Kazakhstan (30.74±6.97

Relevance. The study will help to identify new perspectives in breeding; get new data about the biological processes occurring in the body of animals according to the endogenous hormones of breeding bulls. The hormonal-immunobiological relationship in the body of bulls and their adaptive ability in different climatic conditions is a very important issue today.Methods. The work was performed in a temperate continental climate with a long, snowy winter and warm summer in the conditions of the Udmurt Republic in the period from 2020 to 2021 on breeding bulls (n = 27) of modern breeding at the age of 15–69 months. The state of endogenous hormones testosterone, estradiol, thyroxine and cortisol after a long winter period was studied, depending on the age, breed and selection in the normal physiological functioning of breeding bulls. The average serum values of estradiol — 0.517 nmol/l, testosterone — 25.7 nmol/l, thyroxine — 74.7 nmol/l, cortisol — 420 nmol/l, and their cholesterol precursor at the level of 3.2 nmol/l were established in the blood of breeding bulls located in this region. It was found that, depending on age, there are differences in all the studied indicators, however, there is a reliability for thyroxine and cortisol. The concentration of cortisol by selection significantly differs in imported bulls of European selection from the Netherlands at the level of p > 0.05, which characterizes the presence of a certain stress adaptation factor in this group. In terms of variability, a significant difference between min and max indicators was noted for the concentration of testosterone, which varied between 2.4 nmol/l and 60 nmol/l, indicating the individuality of these hormones in breeding bulls in this region.Results. Based on the data obtained, the need to take these data into account when operating breeding bulls and analyzing sperm products, taking into account the concentration of these hormones, as well as the implementation of appropriate preventive measures, is revealed.