Based on the use of the best domestic and world gene pool of the Holstein breed, a domestic highly productive breed of cattle with a genetic potential of more than 10 000 kg of milk per lactation adapted to the climatic conditions of Siberia was created. When breeding it, different reproductive crosses were used. As a result, a competitive livestock breed with a population of 26 770 heads was obtained. The productivity of 10 129 cows at the time of breed testing averaged 7,461 kg of milk with a fat content of 3.78% and a protein content of 3.16%. In terms of milk yield and protein content in milk, they surpass Black-and-White cows by 1,460 kg and 0.05%, respectively. However, the animals of the original breed have a higher fat content of milk, by 0.14%. The live weight of cows of Sibiryachka breed is 36 kg (6%) more than that of Black-and-White cows. Young animals of the new breed are intensively growing and developing. At all ages, their live weight is higher than Black-and-White peers. The average daily increase from birth to one year for heifers of the new breed was 770 g, for Black-and-White peers – 700 g. For a growing period of up to 18 months, daily growth averaged 706 and 673 g, respectively. The live weight of heifers at 18 months is 424 kg, Black-and-White – 405 kg, which allows insemination of heifers of Sibiryachka breed 24 days earlier. The average yield of calves over 3 years in the new breed was 82.7%, in the original one it was 3.7% less. The period of use of the cows of the created breed is 3.47 calving, which is 8% more compared to the Black-and-White breed.
The research was conducted in the fi eld of dairy cattle breeding with the use of genetic markers (SNPs) in order to study their relationship with the period of economic use of cows and their productivity. The object of the study was 186 cows of Simmental breed from the farm situated in Novosibirsk region. To study cows’ productivity (milk yield, fat, protein, the number of lactations) the data of zootechnical records was used. Molecular genetic research and statistical processing of experimental results were carried out according to generally accepted methods. The paper presents the results of the herd assessment by polymorphism of CSN3, PRL, BLG, TNF-α-824 genes, whose genotype frequency corresponds to a particular breed. Gene balance is not disturbed (χ2 = 0.147– 2,306). Homo and heterozygosity are approximately in the same ratio, except for the homozygosity of the gene PRL (0,736). Genotypes of cows desirable for productive longevity were identifi ed: BLGBB, PRLAA, PRLAB, TNF-αGG, whose number in the third lactation was over 70% in relation to the fi rst. The highest productive longevity was observed in animals with genotypes BLGBB and PRLAA, where 9.0% and 8.3% of their number, respectively, had a fourth lactation. Genotype BLGAA can be referred to as a desirable genotype for milk productivity. The difference from carriers of genotype BLGBB was 624 kg (p < 0.01). In the gene TNF-α, a higher yield in the second lactation at 787.3 kg was observed in cows with genotype TNFAA, compared to genotype TNF-αGG (p < 0.01). The same animals were found to have an increased content of fat in milk by 0.07% and protein by 0.05% (p < 0.01).
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