LAUSR

The aim of the study was to evaluate the effect of age at first calving on functional traits – longevity and productive life in dairy cows. The survey included 1490 Holstein cows from 5 cattle farms in Bulgaria. The average milk yield per cow in the farms studied ranged from 6031.68 kg to 8660.37 kg. The average age at first calving was 29.68 months. The highest percentage of cows calved for the first time at age 28–30 months – 29.53%, generally 38.06% of cows calved for the first time at a very high age – over 31 months and only 7.58% calved aged up to 24 months. The average longevity for all culled cows was 6.05 years and the productive life – 3.63 years. 22% of all culled cows at these farms were culled before the end of their first lactation. The highest total longevity was in cows calved for the first time at high age – over 28 months. Cows calved for the first time, both at low age (up to 24 months) and at high age (over 37 months), had a shorter productive life of 4.0 and 3.9 years, respectively. Cows with the shortest productive life – one year and less – had and the highest average age at first calving of 30.21 months.