Secretory activity of cattle mammary gland tissues during lactation and duration of the interlactation period

Changes in the secretory activity of mammary gland during the involution period are designed to create conditions for inexhaustible use of the mammary gland, ensure the normal course of structural and functional regression for the development for the next lactation. For animals in which the interlactation period lasted less than 45 days, the absorption of non-esterified fatty acids in the last week of the involution period was 2.8 times higher than in animals in which the interlactation period lasted at least 55 days, 1.48 times higher than the absorption of acetic acid, 1.24 times higher than βoxybutyric acid, 1.28 times higher than glucose, 2.82 times the total amount of phospholipids and triacylglycerols. For acetic acid, β-oxybutyric acid and glucose, not only higher absorption rates were observed, but also a tendency to increase the absorption level in the last weeks of lactation in animals with an interlactation period of less than 45 days, indicating metabolic changes in mammary gland tissue during the involution period. The duration of the dry period affects the secretory activity of breast tissue during lactation and the quality of milk produced during this period, which is expressed by lower fat content in the product while reducing the duration of the dry period to less than 45 days and reducing milk fat by 10.42% during the next calving. At the same time, the body weight of newborn calves in animals, whose interlactation period was less than 45 days by 19.3%, was lower than the animals of the control group, i.e. those who were in the interlactation period for at least 55 days, which indicates the negative impact of reducing the duration of the dry period on the body of animals.