867 ACTA UNIVERSITATIS AGRICULTURAE ET SILVICULTURAE MENDELIANAE BRUNENSIS Volume 68 80 Number 5, 2020 RELATIONSHIP BETWEEN AGE AT FIRST CALVING AND LONGEVITY AND PRODUCTIVE LIFE IN HOLSTEIN COWS Vladislav Valchev 1 , Ivaylo Marinov 2 , Teodora Angelova 3 1 Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria 2 Department of Animal Husbandry – Ruminants and Dairy Farming, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria 3 Institute of Agriculture, Stara Zagora, 6000 Stara Zagora, Bulgaria Link to this article: https://doi.org/10.11118/actaun202068050867 Received: 12. 3. 2020, Accepted: 17. 6. 2020 To cite this article: VALCHEV VLADISLAV, MARINOV IVAYLO, ANGELOVA TEODORA. 2020. Relationship Between Age at First Calving and Longevity and Productive Life in Holstein Cows. Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis, 68(5): 867–874. Abstract The aim of the study was to evaluate the efect of age at frst 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 frst calving was 29.68 months. The highest percentage of cows calved for the frst time at age 28–30 months – 29.53%, generally 38.06% of cows calved for the frst 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 frst lactation. The highest total longevity was in cows calved for the frst time at high age – over 28 months. Cows calved for the frst 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 frst calving of 30.21 months. Keywords: dairy cows, functional traits, AFC, culling rate INTRODUCTION Heifer rearing has an important role in dairy cattle farming. It requires large fnancial costs, which are usually the second largest after feed costs, and with no return until the animals enter the main herd. Cooke et al. (2013) indicate that an earlier age at frst calving (AFC) may reduce rearing costs because of the reduced feed, labor and investment costs. The efect of the AFC on longevity is not studied well. A number of studies have shown that age and body weight at calving can have a signifcant efect on both subsequent milk production (Pirlo et al., 2000) and productive life duration (Ettema and Santos, 2004; Evans et al., 2006), although the results are not always one-way. These diferences can be due to variations in genetics and management between diferent studies and countries. Also, the information on infuence of AFC on the survival rate is insufcient, although this trait is becoming increasingly important for the dairy industry (Shook, 2006). Farmers need such information to make informed management decisions about the heifer growth rate and strategies for their farming (Cooke et al., 2013). According to Do et al. (2013) AFC of dairy cows is an indicator that must be properly managed in order to achieve the highest economic return and longer productive live. Basic approach to reducing the inputs at the beginning can be the reduction of the unproductive period of the heifers, which can be accomplished by