DURATION OF PRODUCTIVE AND BREEDING USE AND REASONS FOR RETIREMENT OF BLACK-AND-WHITE COWS IN A HIG-PRODUCTIVE HERD WITH TIE-UP AND LOOSE HOUSING
The results of a comparative assessment of productive longevity and the reasons for retirement of Holsteinized black-and-white cows in a high-productive herd with tie- up (group 1) and loose (group 2) housing are presented. The cow housing method had a significant impact on the period of economic and breeding use of cows. Lifetime productivity of cows of the 1st group was 31038 kg of milk; the duration of productive and breeding use was 3.79 of lactation, life-78.7 months, milk yield per day of life-12 kg. These valuesin the 2nd group of cows were 23230 kg of milk; 3.16 of lactation; 65.4 months and 10.9 kg respectively. Themethod of keeping cows had a net effect on the qualitative characteristics of milk. The mass fraction of fat in milk in the 1st group of animals was 3.86%; protein-3.11%, and in the 2nd group of animals -3.70% and 3.13%, respectively. In loose housing most of the animals did not live to 4-7 lactations when they have a maximum productivity. The retirement of cows from the herd at the end of the first 3 lactations in the 1st group was 29.4%; in the 2<sup>dnd</sup> one - 36.4%. In subsequent lactations, the difference between the groups significantly increased. There were 52.7% of cows from the number of heifersin a herd with tie-up housing by the 4th lactation. This indicator in the 2nd group of cows was significantly lower and amounted to 36.7%. The main reasons for the retirement of cows from the herd, both in tie-up and loose housing were diseases of the reproductive organs, difficult labor and udder diseases. The tie-up housing to a greater extent satisfies the physiological needs of animals. However, this method of keeping cows is limited by possibilities of mechanization and automation of technological processes of milk production. In this regard, the loose housing has an advantage. Therefore in the construction of complexes with loose housing of cows it is advisable to provide a separate farm with tie-up housing of high-productive animals.