PRODUCTIVE LONGEVITY AND RETIREMENT OF COWS WITH DIFFERENT METHODS OF KEEPING UNDER INDUSTRIAL CONDITIONS
The scientific and economic experiment was conducted on the basis of the breeding factory of ZAO (closed joint-stock company) “Kalininskoe” in the Tver Region between 2015 and 2019. It specializes in breeding Black Pied breed. Two groups of Black Pied cows were formed, depending on the method of keeping and their age. The first group of cows was kept in loose housing system. Their milking was carried out at milking installation “Evroparallel”. The second group of cows was kept tied and milked at the milking installation “UNIKALA+”. The breeding stock was represented by 1100 high-bred holsteinized animals of their own breeding. For the last year it was 10660kg of milk yield per cow with mass fraction of fat 3.89%. The average duration of cows usage is 3-4 lactations. Longer use (4.1 lactation) is possible with tie-up housing, while with loose housing, the lactation is 1.4 less (P≤0.001). Lifetime milk yield with tie-up housing was 31.7 thousand kg of milk. With loose housing system, it was 17.9 thousand kg, which was 43.5% less (P≤0100). One-way analysis of variance showed that the duration of cow use was influenced by “servicing bull” - 23.8%, “selection variant” - 16.3%, “ancestral line” - 14.5% and “method of keeping” - 13.1%. Fathers' influence on the milk yield was 31.0%, the “selection variant” was 14.6 and the “method of keeping” was 11.7%. The mass fraction of milk fat and protein was influenced mainly by “servicing bull” - 22 .5%, “method of keeping” - 16.4%, and “selection variant” - 15.2%.