Cobalt is necessary for plant and animal life. It regulates the protein, carbohydrate and mineral metabolism; plays an important role in redox processes; increases the body use of amino acids for protein synthesis. Cobalt is essential for hematopoiesis. Excess cobalt in practical terms is unlikely range between toxic and dozes element wide. The toxic dose of cobalt exceeds the rate of several hundred times.

Cows in the experimental and preparatory research periods were fed at the same rations. The difference in feeding consisted in the following: during the research period within 80 days, the cows of control group were fed on preparation period premix composed of zinc sulfate, copper, cobalt, sodium selenite, and research group cows were fed on mixed ligands complex of cobalt instead of cobalt sulfate feed additive. Animals ate feed with gusto and no changes in their behavior were noticed.

The first group of test animals served as a control group consuming the concentrated food containing cobalt sulfate in an amount of 8.9 grams per ton of food containing 1.85 grams of metal. The 2nd experimental group of cows was given the fodder in which mixed ligands complex of cobalt replaced cobalt sulfate, but the concentration of the metal remained at the level of the control group. The 3rd experimental group cows were fed in 75.0% cobalt form compared to the animals of the 2nd experimental group, the cows of the 4^th one – 50%, and 5^th one – 25%.

This diet provided all necessary nutrients, but supply of crude protein, starch and sugar was 98%, 94.8 and 85.2%, respectively. Despite the presence of experimental diets the cows were fed on premix, the rate of trace elements in the diet lacked: instead of 20.85 mg cobalt per 1 kg of food, it was 1.85 mg. Therefore, the need of the animals in this element we provide by giving inorganic feed additives to cobalt sulfate and organic – mixed ligands complex of cobalt.

 Changes in the productivity of highly productive cows by feeding them diets with different content mixed ligands complex of cobalt had been studied.

In the preparatory period within the first 20 days of lactation, the cows of the control and experimental groups hardly showed any difference in average daily milk yield. During the days of lactation the average daily milk production increased due to increasing the duration of lactation and improving the consumption of diets containing mixed ligands complex of cobalt. Thus, the highest average daily milk yield of natural fat cows had  the 3rd experimental group that consumed as part of a mixed ligands complex of cobalt in an amount of 75% of the concentration of metal that dominated counterparts in the control group on this measure, respectively, 4.4 kg (r≤0.01), or 9.7%. The cows of the 2nd, the 4th and the 5th research groups concerning average daily milk production of natural fat counterparts dominated control respectively, 2.1 kg, or 4.8%; 3.2 kg or 7.1% (r≤0,05); and 1.3 kg, or 2.9%. During the period of the experiment, the fat content of milk from the cows of the 3rd experimental group exceeded the fat content of milk from the cows in the control group and 0.03% in terms of milk 4% fat hope was 3649.7 kg, 10.8% (r≤0,01) higher milk yield of cows in the control group subjects. As regards the protein content in milk from the cows of the groups there was no significant difference observed.

Thus, feeding cows diets with highly concentrate in animal feed premix which contained organic additive mixed ligands complex of cobalt led to the increased production of cows of the 2nd-5th research groups during the first 100 days of lactation, respectively, 5.1%, 10.8 (r≤0,01), 7.8 (r≤0,05) and 3,0%.

The studies indicated that the level of milk production increased due to different content of organic-mineral supplements of the mixed ligands complex of cobalt, and the cost of food per 100 kg of milk decreased. It should be noted that the greatest advantage had been noted in the cows of the 3rd experimental group, because the diet contained 75% mixed ligands complex of cobalt.

Feed consumption per 1 kg of milk fat content of 4% was within 0,85-0,94 food units and 93,2-103,2 g of digestible protein. However, the lowest rate of 0.85 food units and 93.2 g of digestible protein in cows was in the 3rd experimental group, respectively, 9.6% and 9.7%, it was less than in the control group counterparts.

The best indicators of milk production of cows and the lower cost of feed per unit of output were obtained in high-yielding cows research groups at the expense of the balance diet for cobalt and mixed ligands complex of cobalt introduction of organic origin.

Key words: high producing cow, ration, premix, trace elements, sulfate, mixed ligands complex of cobalt, milk productivity, cost of feed.