Productivity, milk quality, viability of newborn calves and cows fertility depend on the full value of their feeding in the dry period, or period of lactation because maximum productivity in cows observed on the 40^th–80^th day after calving, and maximum feed intake – after 80–100 days.

Microelements such as Zinc, Iodine, Cobalt, Copper, Manganese, Selenium play a significant role in enhancing biological full feeding of cows. At the lack of microelements metabolism and protein synthesis in the body disturb, health condition becomes worse, reproductive ability and genetically programmed, defined breed features of high productive potential sharply reduce. These changes develop both in the mother’s and offspring’s body. Zinc deficiency in diets reduces fertility of females, and its lack can lead to infertility.

The purpose of the research is experimentally study the formulation of improved zonal premixes for highly productive Holstein cows Hungarian selection with different doses of mixed lygand complex of Zinc combined with sulphates of Copper, Manganese, Cobalt, Sodium Selenite in the dry period and the first 100 days of lactation and establish their impact on live weight of calves at birth and reproductive functions of cows.

The cows for the experiment were chosen on the 20^th–25^th day of dry period. All cows were pure bred, they had the similar productivity of females, average fattening and were clinically healthy, they were kept in the same conditions and they were brought in the farm as they were heifers. The cows were divided into five groups, one control group and four tested groups. The cows as in the second half of dry period and in the first 100 days of lactation were fed with few component mixed fodder in the compound of that we added 4 kg of oat and alfalfa hay, 10 kg of grain-bean hay, 25 kg of corn silage,
2 kg of molasses, 15.5 kg of concentrated mixed fodder, 0.19 kg of salt, 0.18 0f phosphate. These feeds had Zink, Copper, Cobalt Manganese and Selenium deficiency.  

Lack of Zinc in cows from the 1st control group were added to 100 % due to mixed lygand complex. Deficiency of Copper, Cobalt and Manganese were added to 100 % due to sulfuric acid salts. Selenium deficiency due to sodium selenite, at the rate of 0.3 mg Selenium per kg of dry matter. The difference in feeding cows of research groups was that the lack of Zinc was also added due to mixed lygand complex of Zinc, cows from the 2nd research group at 85 %, cows 3^rd, 4th and 5th research groups 70. 55 and 40 % respectively.

From the above data we can see that cows from the 1st control group received 788 mg of mixed lygand complex of Zinc to the diet and cows from the 2nd – 670 mg, 3rd – 552 mg, 4th – 433 mg and 5th – 315 mg. In the body of the cows in the control group received 156 mg of zinc, 2nd experimental group – 133 mg, 3rd – 109 mg, 4th – 89 mg and 5th – 62 mg due to mixed lygand complex.

During calving we watched at experimental cows. Calving were normal, without delay placenta, but some cows were assisted during calving. Of the 10 cows in 1-, 2- and 5 experimental groups 9 cows needn’t assistance during calving, that was 90 %, and in the 3rd and the 4th experimental groups all cows gave the birth without assistance. After calving such diseases as endometritis and mastitis in cows of the research groups were not observed.

Administrating lower levels of mixed lygand complex of Zink to mixed fodder to the tested cows during the whole period of pregnancy and first days of lactation is proved of the difference in the live weight of calves at birth. Average live weight of calves from the second tested group increased the calves from the control group on 9.0 %; the 3d on 8.9; the 4^th on 4.0 an the 5th on 0.6 %. At the result of the analysis it was noted that on one productive mating of each cow in the first control group it was necessary to conduct 2.3 mating, in the 2d – 2.2; the 3d –1.5, the 4^th – 1.9 and the 5^th – 2.1. The duration of service period of tested cows depended on the amount of mating. Thus in the cows from the first control group it was in average 89.2 days; in the 2d – 78.6; in the 3d – 75.4; in the 4th – 84.6 and in the 5th – 95.5 days that in the percent less compared with animals from the first control group except the 5th tested group on 11.88 in the 2d, 15.47 in the 3d and 5.16 in the 4th and in the 5th – more on 7.06.

Analysis of post calving state of tested cows proved that adding Cobalt on 70 and 55 % to the norm leads to the better calving and reproductive ability of cows.

Key words: highly productive cows, reproductive ability, premixes, microelements, helates, sulfate salts, trace elements of Copper, Cobalt, Manganese, mixed lygand complex of Zink.