A cow is, first and foremost, a ruminant animal. Its gastrointestinal tract is designed to digest a significant amount of structural fibers (fiber). Modern technological advances in genetics, breeding, feeding, retention and cows’ milking make it possible to obtain more than 10,000 kg of lactation milk from a cow, but this can be achieved only if a significant amount of concentrated fodder with high starch content has been included in the diet of these animals. These fodders are a source of energy for the cow, but the microorganisms of the rumen are also actively use it, forming a large amount of acid, which lowers the pH of the rumen and suppresses (sometimes even kills) the vital activity of the micro biota of the proventriculus. An important condition for the formation of lactic acid in the rumen is the presence of oxygen.

Addition to the cows’ diet of live yeast helps to reduce the amount of oxygen in the rumen, which, in turn, inhibits the development of lactic acid bacteria and the synthesis of lactic acid by them. On the other hand, anaerobic environment in the proventriculus actively develops cellulose- lytic microorganisms.

Many studies around the world have been devoted to the use of live yeast in feeding of cows. Most of them have been carried out at cows during the period of thermal stress. Part of the research covers only the period of early lactation. Almost all researchers note an increase in the milk productivity of cows; however, a relatively small number of publications are devoted to the problem of milk quality changes under the actions of these microorganisms.

The purpose of this study was to investigate changes in the chemical composition and milk qualitative indicators of cows, which received in the diet the probiotic preparations of live yeast of different manufacturers.

To study the effects of living yeast preparations in the diet on milk qualitative indicators and productivity of cows, they have conducted a scientific and economic experiment under the conditions of the educational and production center of the Bila Tserkva National Agrarian University. During the experiment, the chemical composition of milk, its density, acidity, bacterial insemination and the number of somatic cells have been investigated.

For conducting of the scientific and economic experiment under the conditions of the farm, 30 cows of Ukrainian black-and-white milk breed were selected, from which with the group method three groups were formed: one control group and two experimental ones. The cows of the control group did not consume probiotic preparations, animals of the 2nd experimental group were fed with LevuSell SC at a dose of 1 g/head/day, and the third experimental group – ActiSaf Sc-47 in the amount of 5 g/head/day. The experiment lasted 305 days.

The quality of milk has great importance, because it is a raw material for the further processing and production of a variety of dairy products, the main consumers of which are children. The current state of the livestock industry forces milk processing enterprises to transport milk over long distances (hundreds of kilometers). That is why the introduction of any feed additives in the diet of cows with a different purpose should not negatively affect the quality of milk.

The use of different preparations of live yeast in cows’ feeding has affected the chemical composition of their milk.

At almost unchanged indicators of the content of milk sugar and protein in the milk of cows of all groups, the increase in the content of crude fat in the milk of animals of the 2nd and 3rd experimental groups attracts attention. Obviously, such changes are the result of increasing of the digestibility of fiber (structural carbohydrates) in the rumen due to an increase in the micro biota population and normalization of digestion.

Increasing of the fat concentration in milk of cows of experimental groups resulted in a slight increase in the content of dry matter and milk density.

The acidity of milk is an indicator of freshness and its ability to be stored. According to this criterion, the animals of all groups were equal.

One of the largest problems in the dairy industry is the presence of a significant number of microorganisms in raw milk, which are delivered there due to a variety of violations during milking, storage, transportation of milk, etc. The feeding of live yeast to cows of experimental groups had to influence on the rate of bacterial colonization of milk, but even this slight change has taken place in the direction of improvement. Thus, milk of the cows of the 2nd experimental group according to the indicator of bacterial insemination decreased in comparison with the control analogues by 3.1 %. The advantage of the control animals over the cows of the 3rd experimental group was 4.0 % according to this criterion.

The largest changes in the diet with live yeast of dairy cows were measured by the content of somatic cells in milk. Thus, at cows of the 2nd experimental group, this indicator decreased by 28.9 % in comparison with the control animals. Almost identical, namely 28.7 %, the decrease in this rate was at animals of the 3rd experimental group. It is obvious that the normalization of digestion by the introduction of live yeast in the diet of cows, which in turn has led to the improvement of the health of the animal organism as a whole, and udder in particular. It is worth to note that the reduction of somatic cells number in milk of cows of experimental groups was statistically confirmed (P <0.001).

Consequently, feeding dairy cows with probiotic preparations that are the live yeast of Levucell SC and ActiSaf Sc-47 affects some of the qualitative parameters of milk, such as fat concentration, bacterial insemination and the content of somatic cells. According to these indicators, improvement was observed at cows of experimental groups relatively to control analogues.

Key words: a cow, live yeast, milk, Levucell SC, ActiSaf Sc-47, productivity.