No abstract

In 2002, a new Ural type of black-and-white breed was officially registered. Animals of this type have high productivity indicators, but at the same time there is a decrease in the productive longevity of the breeding stock. The conjugacy of milk yield for lactation is established, which allows for the first lactation to carry out selection fory milk yield. The relationship of milk yield for the first lactation weakens with the age of the animals and becomes negative for the fifth lactation. The conjugacy of such characteristics as milk yield per lactation and fat mass fraction in milk varies both by lactation and relative to milk yield per lactation. The conjugacy between milk yield and protein in milk for lactation was negative with fluctuations from low to medium-negative. For 5 lactation, there is a high positive relationship between milk yield for the first lactation and protein mass fraction in milk for 5 lactation. There are fluctuations in the correlation coefficients for fat mass fraction in milk for lactations, the conjugation of the trait with each other remains positive in the period from the first to the 4 lactation, excluding the correlation coefficient of this indicator between 1 and 5 lactation.

In the Sverdlovsk region, in herds of Holstein black-and-white cattle of the Ural type, up to 98% of cows are descended from bull producers of foreign selection. Assessment of the influence of a bull producer on the productive qualities of daughters is relevant and of practical importance, especially in conditions of increased blood in the Holstein breed. The daughters of the breeding bull Gavano had the highest indicators in terms of milk production, the daughters of the breeding bull Das were in second place. It should be noted that the milk yield for 305 days of lactation in all studied animals was within the range of 6583 (daughter of bull Cassio) - 8106 (daughter of bull Gavano) kg, which indicates a high potential for productivity in the cows of this herd. The superiority of the daughters of bull Gavano in milk yield ranged from 445 to 1523 kg or 5.5 - 18.8% and was reliable in favor of the former (P≤0.05 - P≤0.01). The highest rates for fat mass fraction in milk were found in the daughters of bull De-Su. 4,0 and 4,01% of fat was in milk of cows-daughters of the Sayan, Mers and Cassio bulls. In terms of protein mass fraction in milk, cows differed from bull De-Su for the worse. In the milk of cows-daughters of other bull producers the protein mass fraction was in the range of 3.13-3.17%. The yield of milk fat and milk protein was more influenced by milk yield in 305 days of lactation. Most of the nutrients were obtained from the milk of the cows-daughters of bull Gavano. The daughters of bull Sayan were in second place, only slightly inferior to them were the daughters of bulls Das and De-Su. Less nutrients were obtained with milk from the daughters of bull Cassio. All cows had a dairy production direction, as evidenced by a high milk yield ratio from 1186 to 1432 kg of milk per 100 kg of live weight of a cow. The farm uses daughter cows from Holstein bull producers with a high genetic potential for productivity.

Provision of the population with a sufficient amount of domestically produced food, including milk and dairy products, is directly related to advances in breeding of dairy cattle as the main supplier of raw materials for dairy processing enterprises. Along with increased requirements for the quality of milk – raw material in production of dairy products – the focus is placed on its technological properties, namely the possibility of its effective use for processing into certain products: fermented milk, cheese, butter, etc. It is known that milk is affected by many factors, including the season of the year, which impacts not only supply of raw materials to the dairy industry but also its quality. The study aimed to investigate the impact of the season of the year on raw milk intended for processing into various dairy products. The study revealed that sensory properties of milk met the requirements of the regulatory documents. The milk color changed depending on the season of the year. A more intense yellowish hue could be observed in summer and autumn milk, which is related to the carotene content in feed. The highest content of dry solids, milk solids-not-fat, fat and protein in milk was found in winter, while in summer these indicators were lowest. In spring, mechanical contamination of milk increased up to group 2. In general, the bulk of the milk was of the highest grade. The study of rennet coagulation of milk showed the superiority of milk produced in spring, as evidenced by a phase of coagulation of milk, which was shorter by 0’05“–2’35” (P <0.001). A clot formed faster in the presence of rennet in summer milk. Thermal stability of milk was high throughout the year.