Dlugosc uzytkowania mlecznego krow - konsekwencje produkcyjne i ekonomiczne

The aim of research was to establish the relations between length of cows' performance and such production and economic indices as: milk yield (lactation and life-time yield) and costs of milk production, including depreciation costs of the heifer and its share in costs of production and in the market milk price. Production and economic results of dairy unit with the average herd size of 720 cows and milk yield of ca 7000 kg per cow and year were the basis for calculation. Significant effect of the length of performance on production efficiency was shown. Cost of milk production from cows performance of which lasted 1 lactation surpassed market value of milk by 44%. Subsequently, steady drop of production costs in relation to market value of milk was observed down to only 33% milk market value in cows performance of which lasted 8 lactations. The share of heifes depreciation cost was amounted 62 and 11% costs of milk production and 89 and 8% milk market value, when the performance lasted 1 and 8 lactations respectively. At the average length of cow performance in herd lasting 3.19 years and when costs of production equalled to 91% milk market value, the losses generated by cows culled after 1st lactation were compensated with cows kept producing for the 2nd and 3rd lactation. Not till the performance of cows lasted over 3 lactations the economic relations begun to be positive - cost of milk production was lower than ist value.