Stress tolerance of black-motley breed cows in the Urals region

Abstract. In the Urals, one of the numerous breeds of cattle for the production of dairy products is common – black and motley. In recent years, there has been a tendency to decrease the level of livestock with an increase in their productivity indicators and a decrease in the duration of economic use. Scientific novelty. An assessment of the types of stress resistance of cows-daughters from among the first heifers, depending on the highest milk productivity of their mothers, was carried out, bulls-improvers were identified by the type of stress resistance of daughters. The purpose of the research was to study the stress resistance of cows of the black-and-white breed of the Urals. Research methods. The work was carried out in cattle herds of high-tech breeding enterprises of the Sverdlovsk region. 3315 daughters of 34 bulls-producers of various lines were evaluated to identify bulls-improvers on the stress resistance of offspring. The assessment was carried out in two stages: 1) breeding bulls were selected whose daughters did not reduce milk yield with seasonal changes in conditions of detention; 2) bulls whose resistance rank did not exceed the rehabilitation rank were identified by the method of overlapping breeding fields. At the same time, the reaction of the daughters of bulls to stress was assessed using the indices of reduction (Id) and recovery (Ir) of the value of milk yield per month. Results. It was found that the cows-daughters of the evaluated bulls-producers differed in the level of resistance to seasonal changes in housing conditions. Reliable bulls-improvers in terms of the level of stress resistance of offspring have been identified: Potter 128367894, Stardel 658867, Marcos 131801949 and Thaler 4091. The low type of stress resistance of cows-daughters was noted in the group of highly productive cows-mothers – 25 % of heads. In addition, the dependence of the level of stress resistance with the origin of cattle is also noted by other scientists, which confirms the need to carry out breeding work with dairy cattle with the inclusion of stress resistance of animals in the selection indicators.