Comparative evaluation of the breeding value of Holstein bulls-producers

. Modern dairy cattle breeding efficiency is largely determined by the strategy of choosing a producer for herd reproduction, which determines the growth rate of herd productivity for the next 3 to 5 years. According to the results of 2022, there are 20 organisations in the Sverdlovsk region with milk production per feed cow of more than 9 thousand kg, including 10 farms with milk production of more than 10 thousand kg. The best farm in the region, APC "Kilachevsky", produced an average of 12829 kg of milk for each of 3000 cows. Two record-breaking cows were milked there, each of which yielded more than 21 tonnes of milk for a standard lactation. Thirty-four breeding bulls were included in the study. As a result of their evaluation, it was found that in bulls whose genomic breeding value for milk yield exceeded 1000 kg of milk 80.0% of producers were actual improvers for this trait, and in bulls with low genomic breeding value for milk yield (0-99 kg) only 25.0% of producers were actual improvers. Bulls with a negative breeding value for milk production in 66.6 percent of cases turned out to be actual improvers. In terms of protein content in milk, the dependence is similar, the higher the genomic value of the sire according to MDB, the more bulls actually have a positive effect on the protein-milk content of daughters (Tables 3,4). However, the number of sires that confirmed genomic breeding value for protein-milk yield is much less than for milk yield. For milk yield, 17 sires out of 34 (50.0%) received confirmation of breeding value, and for protein-milk yield only 11 (32.0%).


Introduction
The efficiency of modern dairy cattle breeding is largely determined by the strategy of choosing a producer for herd reproduction, which determines the growth rate of herd productivity for the next 3-5 years.The basis for selection of a producer is information about his breeding value, which is calculated by various methods, the most accurate of which is considered to be the traditional method of determining the breeding value of a producer by the quality of offspring.Along with this method of determining the breeding value of a sire, the method of genomic evaluation, based on the study of the genome of an individual, is now actively used.This method makes it possible to significantly increase the intensity of breeding by reducing the generation interval.However, genomic determination of breeding value of producers is carried out in foreign international cattle breeding centres and is based on phenotypic data obtained outside the Russian Federation [1][2][3][4].
In the world dairy cattle breeding at present, it is impossible to do without intensive mutual exchange of genetic material in order to minimise the negative impact of inbreeding and obtain maximum genetic progress, for which the semen production of bulls-producers from different world breeding centres is used.This practice also takes place in the Sverdlovsk region, where along with semen products of domestic production of Urapplemcentre JSC, foreign breeding bulls from various semen suppliers are intensively used.And, if the breeding value of domestic producers is determined by the traditional method on the quality of offspring in Russia, the breeding value of imported producers, as a rule, is determined by the genomic method, based on the study of the genome of the individual and its relationship with phenotypic traits in the conditions of foreign countries [5][6][7][8][9][10][11][12].In this connection, it is of great practical importance to study the degree of realisation of genomic breeding value of imported Holstein bulls in the conditions of the Sverdlovsk region.
In the article by V.S. Mymrin and M.Y.Sevostyanov "Influence of genetic trend and environmental factors on the breeding value of bulls-producers" published in the journal Agrarny Vestnik Urala) it was concluded that the results of evaluation of bulls-producers on the quality of offspring, carried out in other regions, do not always coincide with the results of actual use of producers in specific conditions of the Sverdlovsk region.At that time, the level and adequacy of feeding of cattle, especially new cows and cows of the first half of lactation were much worse than at present.The next important difference of dairy cattle breeding at the beginning of the century was the fact that the process of interbreed crossing of Ural black-and-spring cattle with Holstein cattle was still in progress, and the breeding population was a motley mixture of genotypes of different bloodlines on Holstein breed with not yet consolidated heredity.In 2008, the productivity of black-spring cattle in the Sverdlovsk region was 4119 kg of milk, and in breeding organisations -5897 kg.Over the past 14 years, the average milk yield in the region increased more than 2-fold to 8310 kg, and in breeding reproducers and breeding plants it reached 9453 kg of milk (Fig. 1).According to the results of 2022, there are 20 organisations in the Sverdlovsk Region with milk yield per feed cow of more than 9 thousand kg, including 10 farms with milk yields of more than 10 thousand kg.The best farm in the region -APC "Kilachevsky" produced an average of 12829 kg of milk for each of 3000 cows.Two record-breaking cows were milked there, each of which yielded more than 21 tonnes of milk for a standard lactation.This is the result of purposeful use of the genetic potential of the Holstein breed to improve the Ural black-and-brown cattle, significant improvement of the level and quality of feeding, active introduction of modern protocols of dairy cattle breeding into production.
The above-mentioned data testify to a significant formed and largely realised genetic potential of productivity of the bred cattle, which according to the data of breed inventory of 2021-2022 and researches of scientific workers of the Ural Research Institute of Agricultural Sciences -branch of the Federal State Biological Institute of the Urals Federal Academy of Sciences (Modorov M.V. et al., 2021) is currently purebred Holstein cattle.
Thus, modern cattle and conditions of dairy cattle breeding in the Sverdlovsk region have changed dramatically compared to 2008 and differ little from modern dairy cattle breeding in developed European countries.
As part of the development of breeding plans for breeding plants and reproducers in the Sverdlovsk region in 2021-2022, we compared the genomic evaluation of the breeding value of a Holstein bull breeder with its actual breeding value determined in a particular farm in the Sverdlovsk region by the quality of offspring.
The aim of this work was to conduct a comparative evaluation of bulls-producers by genomic evaluation with the evaluation by progeny quality in a particular farm.

Methods and Materials
The research involved 34 Holstein bulls used for herd reproduction in 2 breeding reproducers and 4 breeding plants of the Sverdlovsk region.Producers with data on the first completed lactation of at least 20 daughters were included in the processing.Data on breeding value of bulls-producers determined by genomic method were taken from breeding certificates provided by semen suppliers.The results of breeding value assessment by progeny quality were calculated by IAS Sellex programme and generated in Table 12 "Results of using bullsproducers".Breeding value was considered by three traits of the first lactation: milk yield for 305 days, fat and protein content in milk.According to the level of genomic breeding value, all producers were distributed into groups with different levels from negative to maximum breeding value.For example, by milk yield the producers were distributed into 5 groups: a group of producers with negative breeding value, breeding value 0-99 kg, 100-499 kg, 500-1000 kg and more than 1000 kg of milk.Similar distribution of producers was carried out by fat and protein content in milk.Coincidence of the results of genomic evaluation with the evaluation of progeny quality was considered as obtaining the same positive or equally negative evaluation result.

Results
Comparison of actual influence of Holstein sires on daughter milk yield calculated by IAS Selex programme with genomic breeding value shows that not all types have genomic evaluation of breeding value to some extent coincides with actual one (Table 1).Moreover, the number of sires whose genomic evaluation partially coincides with the actual one is in direct correlation with the level of genomic breeding value of the bull.The higher the genomic breeding value, the greater the number of sires has a positive influence on the milk yield of daughters.In bulls whose genomic breeding value for milk yield exceeded 1000 kg of milk 80.0% of sires were actual improvers for this trait, and in bulls with low genomic breeding value for milk yield (0-99 kg) only 25.0% of sires were actual improvers.Bulls with negative breeding value for milk yield in 66.6% of cases were actually improved (Table 2).The use in breeding herds with milk yields of more than 8-9 thousand kg of milk of quite a large number of bulls with low and negative breeding value for milk yield is a cause for concern.In this study, out of 34 producers, 10 (29.4%) belonged to this category.
In modern market conditions, there is a large number of semen suppliers offering a wide range of sires with different pedigree values, among which it is possible to choose a sire with a complex, including milk yield, which improves the quality of offspring.This fact testifies to insufficient demandingness of zootechnicians-breeders to the breeding value of sires assigned to the herd.
With regard to protein content in milk, the dependence is similar, the higher the genomic value of the sire according to MDB, the more bulls actually have a positive effect on proteinmilk content of daughters (Tables 3,4).However, the number of sires that confirmed genomic breeding value for protein-milk yield is much less than for milk yield.For milk yield, 17 sires out of 34 (50.0%) received confirmation of breeding value, and for protein-milk yield only 11 (32.0%).According to this trait 10 producers also had negative breeding value, the use of which is absolutely inexpedient in breeding herds.Comparison of genomic and actual breeding value of the studied bulls by fat content in milk of daughters does not fit into the revealed regularity in milk yield and protein-milk yield.Out of 34 bulls-producers 18 or 52,9% confirmed their genomic pedigree value by fat content in milk of daughters by the daughter-female method (Table 5).But at the same time the value of genomic pedigree value did not influence the number of bulls-producers who actually confirmed their pedigree value by this trait (Table 6).

Fig. 1 .
Fig. 1.Dynamics of milk productivity of cows in the Sverdlovsk region

Table 1 .
Breeding value of Holstein bulls by milk yield, kg

Table 2 .
Coincidence of the results of evaluation of breeding value determined by different methods depending on the value of genomic breeding value by milk yield

Table 3 .
Breeding value of Holstein bulls by protein content in milk, %

Table 4 .
Coincidence of results of breeding value assessment by different methods depending on the value of genomic breeding value by milk protein content

Table 5 .
Breeding value of Holstein bulls by milk fat content, %