EFFECTS OF HEAT STRESS AND PRODUCTIVE LEVEL ON THE MAIN REPRODUCTION INDICES AND INCIDENCE OF DYSTOCIA IN BROWN BREED COWS

R.I. Neamţ, L.T. Cziszter, Daniela E. Ilie, Silvia Erina, St. Acatincăi

Abstract
    The study was carried out on 98 Brown dairy cows from Research and Development Station for Bovine Arad. The following traits were analysed: the voluntary waiting period (from calving to first A.I.), interval between calving and new pregnancy, the number of artificial inseminations (A.I.), incidence of dystocia and dystocia scoring, according to the season and productive level. Thus, in the winter, the voluntary waiting period was 77.45 and 96.32 days to the new gestation, requiring a number of 1.71 AIs per pregnancy. In spring, the voluntary waiting period was 75.26 and 97.64 days for a new gestation, with 2.03 AIs per pregnancy. In the summer, time to first service was 88.16 days, requiring 113.18 days for the new gestation and using 2.16 AIs per pregnancy. Autumn, favoured reduced time to first service 82.66 days, while 104.44 days were required for installation of a new gestation, requiring only 2.11 A.I.s. According to the productive level, cows with a production level between 5000-6000 kg milk, needs 56.67 and 81.44 days, cows between 6000-7000 kg milk needs 81.16 and 103.27 days and those over 7000 kg milk needs 100.75 and 122.97 days for voluntary waiting period and interval needed for installation of a new gestation, respectively. Number of A.I.s needed for a new pregnancy according to the productive level, was 1.71 A.I.s in winter season, 2.03 A.I.s in spring, 2.16 A.I.s for the summer and 2.11 A.I.s for the autumn months. The incidence of total dystocia was 21.42% from total number of calving. The most severe dystocia was recorded in summer, at the 5000-6000 kg milk interval.

Key words: dairy cows, heat stress, reproduction indices, incidence of dystocia