One of the main conditions of valuable feeding of cows beside providing them with energy is supplying rations with sufficient level of protein and amino acids, that guarantees not only high productivity, but also saving fodders and reducing the cost of livestock production. Insufficient intake of protein, especially valuable in the first 2–3 weeks of lactation leads to mobilization of body protein. Since the mobilization of body proteins is limited, so the need for amino acids, which are not broken in the rumen increases. In this regard, in the first 100 days of lactation should raise adequate supply of amino acids from the sources of protein, insoluble in the rumen.

The source of insoluble protein fractions is by pass soybeans. But it is not set it’s effects on reproductive function of highly productive cows, live weight of calves at birth, it’s survival and optimal norms of feeding of highly productive cows during lactation. Therefore, setting efficiency by pass soybeans and it’s impact on milk production of cows during the first 100 days is one of the urgent problems of dairy farming in Ukraine.

The aim of our research was to determine the efficiency by pass soybeans in feeding of highly productive cows in the first 100 days of lactation.

Three groups of Ukrainian Black-and-White dairy cows of the first lactation were selected in the farm of Bila Tserkva Region, Kyiv District. In the preparation period during the first 30 days of lactation, experimental cows were fed the same rations and soybean meal was used for – 40 grams to one liter of milk. In the research period during 70 days of lactation, cows of the control group were fed the starter diet and continued to use soybean meal. Feeding rations of experimental groups differed from the 1-st control group that the 2-nd experimental group replaced soybean meal on extruded soy and the 3-rd experimental group – on by pass soybeans. Extruded soybeans and by pass were fed at the rate of 40 gr / l of milk.

If after the finishing of comparative period of experiment the difference in feeding cows was missing, during the main period of the experiment different amount of soluble fraction of raw protein differently affected the feeding of bulk feed.

Thus, from the given 5 kg of alfalfa hay cows consumed 4.2–4.9 kg, from 18 kg of corn silage – 15.8–17.7 kg, from 8 kg of silage clover – 7.2–7.7 kg. Cows were eating molasses and mixed fodder entirely. Consumption of dry matter of fodder per 100 kg of live weight of cows was 3.19 kg in the 1-st control group, 3.56 in the 2-nd experimental group and 3.66 kg – 3rd experimental group. Besides experimental cows responded better yields in advanced nursing, the rate of mixed fodder was 12 kg, and in the control group – 10 kg. Consume fodders provided the cows with raw protein on the level of 17.3–17.5 % from dry matter, soluble fraction of it’s on the level of 35.8% of raw protein in the 1-st control group, 37.2 % – in the 2-nd experimental group and 39.5 % – in the 3-rd experimental group.

Intake to the organism of experimental cows different levels of nutrients and soluble protein fractions provided dependency of average daily milk production on these indicators.

From the data in Table 2 it is shown that in the preparation period the cows of  control and experimental groups on daily milk yield did not significantly differ, but the last 70 days of the first 100 days of lactation average daily milk yields varied, depending on the soluble fraction of raw protein in the diet.

Cows of the 3-rd experimental group which were fed by pass soybeans, had the highest milk yield and exceeded cows of the control group on average daily milk yield of natural milk by 5.3 kg or 17.4 % (P <0,001). Cows of the 2-nd experimental group which were fed diets with extruded soy bean dominated cows of the control group by 1.8 kg or 5.9 %.

In the milk of experimental cows it was observed increase of fat content by 0.09–0.16 % due to better supply of diets with raw fat. Therefore, the advantage for the average daily milk yield of 4% milk was also significant compared to the control group and was in the 2-nd experimental group and 2.4 kg (P <0,001) or 8.5 % in the in the 3-d experimental group – 6, 3 kg (P <0,001), or 22.18 %.

In the milk of cows from experimental groups compared with control protein content increased (3.15–3.20 versus 3.12 % in the control).

According to the data from the cows of the control group during 70 days of the experiment 2.135 kg of milk of natural fat was received, and from the 2nd and 3rd experimental groups – 126 and 371 kg more respectively.

The main parameter that determines the efficiency of milk production is the costs of feed per 1 kg of milk. The studies show that milk production in cows by different content in diets soluble fraction of raw protein, the costs of feed per 1 kg of milk with increasing productivity decrease.

Thus, during the experiment, the lowest costs of feed for 1 kg milk of 4 % fat observed in the cows of the 3-rd experimental group fed diets with by pass soybeans that was 0.03 k. units less than in the control group.

The best indicators of milk production of cows and lower feed costs per unit of production were obtained in experimental cows receiving more soluble fraction of raw protein on the account of the use of by pass soybeans rate of 40 g / kg of milk.

Key words: highly productive cows, by pass soybeans, soybean meal, extruded soybean, raw protein, soluble protein fraction, average milk yield, protein, fat, feed costs.