At breeding enterprises, the number of sires of Holstein breed homozygous for the genotype of the ЕАВ-locus is increasing, and there is a tendency for inbreeding coefficients to increase in populations of this breed. The dairy productivity of fi rst-calf heifers obtained from heterozygous and homozygous sires, as well as the change in indicators per generation with intra-line mating and line crosses were studied. It was found that in terms of the total yield of milk fat and protein for 305 days of lactation in the line Wes Back Ideal 1013415, the fi rst-calf heifers obtained from intra-line mating and line crossing exceeded the cows their mothers by 21,4 kg, and in the whole group of fi rst-calf heifers of homozygous sires this indicator was 51,0 kg higher against the average of fi rst-calf heifers of heterozygous sires. At the same time, for the cow-mothers of these groups, the corresponding diff erence was negative: –31,6 and –64,7 kg. Similar data were revealed for another main line Refl ection Sovereign 198998. When mating heterozygous sires according to the variants of line crosses, the milk yield was 227 kg higher (p < 0,05), but the mass fat fraction in milk decreased by 0,06 – 0,08 abs.% (p < 0,01). However, the levels of manifestation of traits among fi rst-calf heifers in comparison with cow-mothers with intra-line mating increased by groups of homozygous sires in milk yield by 32,5 %, mass fat fraction by 17,6 % and mass protein fraction by 25,0 %. The correlation coefficients «mother – daughter» for milk yield, mass fat fraction and mass protein fraction were relatively higher in the group of homozygous sires, whose heritability coeffi cient in one of the farms for milk yield was higher by 0,495, mass fat fraction by 0,305; mass protein fraction by –0,110, and in the other, respectively, by 0,026; 0,161; 0,121. The conclusion is made about a higher prepotency of heterozygous sires with improving mating.

По каталогам быков-производителей определена генеалогическая структура популяции голштинской породы, которая представлена в Российской Федерации преимущественно двумя линиями. Сократилось разнообразие видов подборов при выведении ремонтных бычков, поступающих по импорту. Для их воспроизводства в отечественных стадах имеются выдающиеся заводские семейства голштинской породы. Предложены оценка и выделение в группы «матерей быков» коров из «развивающихся» семейств племенных заводов с целью импортозамещения и передачи потомкам их лучших признаков. Приведены данные на коров и семейства, в которых на протяжении 9—10 поколений была поддержана реализация повышенного тренда за год относительно стада по удою на 194 кг молока. Такие же были итоги тандемной селекции на повышение показателей массовой доли жира и белка в молоке с годовым генетическим трендом, соответственно 0,007% и 0,025%, при однонаправленном векторе совершенствования типа экстерьера. Даны примеры выведения племенных быков в семействах племенного завода ООО «Ермоловское» по красно-пестрой породе, характеристика их роста и молочная продуктивность предков по родословным. Часть заводских семейств ориентирована на выведение быков определенной линии или родственной группы от лучших по оценкам по качеству потомства быков-производителей — Парадиза 1061, Глориуса 924349012, Скутера 105900749, Атласа 1052518082. Группа матерей быков красно-пестрой породы (n=48) имела средние удои по наивысшей лактации — 11344 кг молока, с МДЖ — 3,97% и МДБ — 3,16%. В 2017 году племзаводом ООО «Ермоловское» продано 49 быков с живой массой в 10 мес 357 кг, удой их матерей превышал более чем на 2,5σ показатели племенной части популяции области, на 0,10% — по МДЖ и на 0,03% — по МДБ. В условиях разведения по линиям их поддержание и поиск резервов генетической изменчивости при выведении племенных быков целесообразно проводить среди коров заводских семейств. The genealogical structure of the population of the Holstein breed, which is represented in the Russian Federation mainly by two lines, is determined according to the catalogs of breeding bulls. The variety of types of selections during the breeding of repair bulls arriving by import has decreased. For their reproduction in domestic herds there are outstanding factory families of the Holstein breed. The evaluation and allocation of cows from "developing" families of breeding plants into groups of "mothers of bulls" for the purpose of import substitution and transmission of their best traits to descendants are proposed. The data on cows and families in which for 9—10 generations the implementation of an increased trend for the year relative to the herd in milk yield per 194 kg of milk was supported are presented. The same were the results of tandem breeding to increase the mass fraction of fat and protein in milk with an annual genetic trend, respectively 0.007% and 0.025%, with a unidirectional vector of improving the type of exterior. Examples of breeding breeding bulls in breeding plant families are given LLC "Ermolovskoe" according to the red-mottled breed, characteristics of their growth and milk productivity of ancestors by pedigrees. Some of the factory families are focused on breeding bulls of a certain line or related group from the best in terms of the quality of the offspring of breeding bulls — Paradise 1061, Glorius 924349012, Scooter 105900749, Atlas 1052518082. The group of mothers of red-mottled bulls (n=48) had average milk yields for the highest lactation — 11344 kg of milk, with MJ — 3.97% and MDB — 3.16%. In 2017, the breeding plant LLC "Ermolovskoe" sold 49 bulls with a live weight of 357 kg in 10 months, the milk yield of their mothers exceeded by more than 2.5% the indicators of the breeding part of the population of the region, by 0.10% — for MJ and 0.03% — for MDB. In the conditions of breeding along the lines, their maintenance and search for reserves of genetic variability in breeding breeding bulls should be carried out among cows of factory families.

The use of inbred and homozygous sires reduces the share of variability in the biodiversity of the population when it occurs under uncontrolled management, which leads to a decrease in the heritability of the trait. Studying the features of the consequences of inbreeding of sires helps to make their evaluation on the quality of off spring more informative, because as a result of related mating, the genetic structure of the population changes. If a selection with the genotypes of an inbred sire, heterozygous for two aabb loci of body traits, is applied to a certain group of cows, then quantitative traits in the off spring will determine milk productivity. Positive variants should be considered omozygotes, in which dominance is manifested, and heterozygotes, i. e. approximately 70 % of off spring. The probability (frequency) of their appearance is high and one can count on a favorable combination of genes in off spring from inbred and homozygous sires, if the maternal population is heterozygous in terms of physique, which are associated with the level of manifestation of milk productivity. In the breeding herd of Holstein breed, the system of intra-linear selections and crosses of homo- and heterozygous sires revealed the disparity of milk yield increases, the mass fraction of fat and protein in milk in daughters relative to mothers. The superiority in the total yield of milk protein and fat for 305 days of the fi rst lactation of the group of daughters from intraline mating and homozygous sires over mothers was 82,6 (p < 0,01) and 112,9 kg (p < 0,01), respectively. The highest total rank according to the complex of breeding traits was assigned to the daughters of homozygous sires and then according to the increase in the indices of the genetic value of the traits of lactation, the group B was followed by the group derived at the crosses of the lines.