Holstein is one of the most widespread dairy breeds in the world. In Russia, the most popular is black-motley breed, which has been improved over the past four decades through crossbreeding with the best world Holstein breed. The study aimed to investigate the productive traits of young replacement cows and cows of different years of birth of Holsteinized black-motley cattle of the Ural type. An increased intensity of rearing of young replacement animals was found to reduce the age of first fruitful insemination, to increase productivity, namely milk yield per lactation, and to reduce the length of the productive life of cows. Intensive rearing of young replacement animals has reduced the age of fruitful insemination by 5.7 months over seven years, particularly in the last 2 years, relative to the indicators observed in 2012. With age, the cow productivity changes insignificantly and remains at sufficiently high level. The study revealed that the genetic potential of the parents and intensive rearing of young replacement animals provide a steady increase in milk production of first-calf heifers. However, productivity of cows in subsequent lactations either remains stable or decreases. Productivity of cows increases in second (2013–2015) and third (2012) lactations and then starts to decline. With age, the length of the lactation service period reduces by 5.2–34.9 days, which is primarily due to synchronization of reproductive cycles with an economically viable waiting period implemented on commercial farms. Reproductive cycle synchronization has been implemented in the region since 2015, which immediately reduced the length of the cow service period.
The influence of genetic and paratypical factors on milk productivity has been studied for many years, but the influence of genotypes was considered as belonging to a genealogical line, which does not give correct results in terms of genetics, the influence of homo- and heterozygosity. The relevance of the work lies in the fact that for the first time a genome-wide study was carried out on the breeding stock of cattle in the Sverdlovsk region and the relationships between the influence of some genes and the paratype on milk productivity were established. In order to maximally reveal the influence of genotypes, farms with the same technological conditions, but giving a significant difference in milk productivity and quality, were selected. Analysis of complete genotypes by the method of principal components showed the genetic homogeneity of the sample, which forms a large general cluster, corresponding to the general trend of Holsteinization of black-and-white cattle. The influence of the environmental factor on productivity indicators turned out to be significant, with the exception of the proportion of protein in the third lactation, all of them were statistically significantly different P <0.01. Six genes were selected for this study: diacylglycerol-O-acyltransferase 1, leptin, growth hormone receptor gene, β-lactoglobulin, k-casein AB and CE. A high coefficient of homozygosity was revealed for two genes CSN_AB and CSN_CE (0.705 and 0.897, respectively), which may lead in the near future to purely linear animals in herds. Despite the fact that no significant difference in the influence of the genotype on productive qualities was revealed for most indicators, the actual difference in them for agricultural organizations
In the Sverdlovsk region, holstinized black-and-white cattle of the Ural type is bred, which is represented by large, highly productive animals with a high genetic potential for productivity. The purpose of the work is to study the productive qualities of Holsteinized black-and-white cattle with a high proportion of blood relationship in the Holstein breed, depending on the linear affiliation and their relationship. There are no differences in milk yield and milk quality indicators in cows of different lines. All cows were of dairy productivity, as evidenced by the high coefficient of milk production. There was a significant difference between groups of cows of different lines in terms of the lactation stability coefficient, which was higher in the group of cows of the Reflection Sovering line (P≤0.05). The figure clearly shows that the correlation between milk yield and milk quality indicators – FDM and PDM in milk is negative, that is, with an increase in milk yield, there is a decrease in FDM and PDM in milk. A positive correlation has been established between the phenotypic trait (live weight) and their productive qualities – milk yield and lactation stability coefficient, which makes it possible to recommend selection by live weight.
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