Journal of Life Sciences 11 (2017) 30-34 doi: 10.17265/1934-7391/2017.01.004 Comparison of Two Different Protocols for Induction of Parturition in Heifers with or without Estradiol Benzoate Najmeh Mehrvar 1 , Hossein Hamali 2 and Adel Saberivand 2 1. Graduated Student, Veterinary Faculty, University of Tabriz, Tabriz 5166616471, Iran 2. Department of Clinical Sciences, Veterinary Faculty, University of Tabriz, Tabriz 5166616471, Iran Abstract: Objectives of this study were to investigate the efficacy of dexamethasone in combination with estradiol benzoate in controlled induction of parturition in heifers, especially in the subjects of retained fetal membranes and dystocia caused by fetal oversize. A total number of 100 Holstein-Friesian heifers aged 24-25 months, mean weight 450 kg and body condition score of 3-4 from a dairy herd located in the suburb of Tabriz with similar nutrition and management systems were allocated at random into two groups. Group A (Control, n = 50) heifers, after passing the minimum 270 d of pregnancy were injected with 30 mg dexamethasone IM. Group B (Treatment, n = 50) heifers with the same period of pregnancy received 30 mg dexamethasone plus 20 mg estradiol benzoate IM on the same days of pregnancy. The overall durations of initial treatments to induction of parturition were (41.50 ± 2.65) h in group A and (37.50 ± 1.27) h in group B. In group A, more dystocia cases were observed than in group B. After parturition, group A showed a higher percentage of retention of fetal membranes as well as the calf mortality and dystocia compared to group B. The differences between two groups were statistically significant (P < 0.05). In conclusion, our results indicate that induction of parturition by estradiol benzoate and dexamethasone together will be more effective than dexamethasone alone because of the less retention of fetal membranes, easy calving and shorter time from induction to parturition. Key words: Dexamethasone, estradiol benzoate, heifer, parturition, retained fetal membranes. 1. Introduction Induction of parturition is an important program for timing of parturition in cattle [1]. This program has many benefits for timing of parturition in dairy cows [2]. Advantages of planned parturition over spontaneous delivery may include saving time for observing and attending the parturition and preventing complications such as dystocia [3]. The procedure can help owners and veterinarians to detect and treat dystocia, reducing prenatal calf mortality [4]. In dairy herds, parturition time may be induced 10-15 days earlier than natural time of parturition to prevent excessive udder edema and fetal over sizes. Long-acting corticosteroids used for induction of parturition have gained widespread acceptance with dairy producers in New Zealand and Australia for Corresponding author: Hossein Hamali, DVM, Ph.D., research fields: clinical sciences, theriogenology. seasonal purposes [5]. Therefore, induction of parturition is a very important tool for prevention of calf and cow mortality caused by dystocia. Several regimens have been used to induce parturition in dairy cattle, including intravaginal misoprostol [6], ergomethrin [7], dexamethasone or prostaglandins in combination with estradiol and oxytocin in cows [8], but significant reduction in the rate of retained fetal membranes has not been seen. Increases in fetal cortisol and estrogen production are the key events during the complex signal cascade leading to the initiation of parturition in cattle and the timely release of the placenta [9]. The purpose of this study was to evaluate the efficacy of dexamethasone in combination with estradiol benzoate in induction of parturition of heifers in Tabriz dairy herds, especially in the subjects of retained fetal membranes and dystocia caused by fetal oversize. D DAVID PUBLISHING