Evaluation of the synchronization efficiency of GnRH or estradiol benzoate (EB) in resynchronization protocols in holstein cows

• Grant number: 13/23648-6
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Effective date (Start): February 01, 2014
• Effective date (End): January 31, 2015
• Field of knowledge: Agronomical Sciences - Veterinary Medicine - Animal Reproduction
• Principal Investigator: Pietro Sampaio Baruselli
• Grantee: Guilherme de Souza Floriano Machado de Vasconcellos
• Host Institution: Faculdade de Medicina Veterinária e Zootecnia (FMVZ). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

The overall goal of this project is to evaluate the effect of the GnRH or estradiol benzoate (EB) administration at the beginning of the resynchronization protocol in Holstein cows without prior diagnosis. Thus, a total of 50 females will be divided into two groups: GnRH (n = 25) and EB (n = 25). After 25 days of the first fixed-TAI (D25) all the females will receive an intravaginal progesterone device (P4; Primer ®, Tecnopec). Also, at this moment the GnRH group will receive 25 mg of Lecirelin (GnRH; Gestran, Tecnopec), and the EB group will receive 2.0 mg of EB (ICN -BE ®, Tecnopec). On D32, all P4 implants will be removed and the females subjected to pregnancy diagnosis to continue (empty females) or not (pregnant) in the resynchronization protocol. All females with negative diagnosis of pregnancy in D32 will receive 0,150 mg of d-cloprostenol (PGF2, Prolise, Tecnopec) in this moment. After 24h (D33), both groups will receive 1.0 mg EB and fixed-TAI will be performed in D34. The ultrasonographic examinations will be done every 24 h between the D25 and D32 for evaluation of follicular dynamics and every 12 hours from D32 to D36 to analyze the ovulation time. The variables to be evaluated are: ovulation rate at the beginning of the protocol, rate and timing of emergence of a new follicular wave, the occurrence of oestrus, ovulatory follicle diameter, maximum diameter of the ovulatory follicle, rate and timing of ovulation and ovulation rate of the new follicles. Data will be analyzed by the GLIMMIX procedure of SAS®.