Ovulation induction and functionality of the corpus luteum in prepubertal Nellore heifers

Author(s)

Dayane Priscila Vrisman

• Document type: Master's Dissertation
• Press: Jaboticabal. 2017-05-23.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Ciências Agrárias e Veterinárias. Jaboticabal
• Defense date: 2017-04-18
• Advisor: Maria Emilia Franco Oliveira; Fábio Morato Monteiro; Pedro Paulo Maia Teixeira

Abstract

Due to the common occurrence of premature regression (PR) of the corpus luteum (CL) in heifers after the first ovulation (OV), the aims of this study were to: 1) monitor the luteal dynamics after OV induction in prepubertal Nellore heifers, and 2) determine differences related to the functionality of this structure. Fifty-seven females (BW 289.61±32.28 kg, BCS 5.66±0.65 and 17.47±0.81 months old) were divided into two treatment groups for OV induction. In the group GP4+GnRH, an intravaginal progesterone (P4) device of 3rd use was used for 10 days and, 48 hours after its removal 0.02 mg of buserelin acetate (GnRH) was applied, and in the GGnRH group only GnRH was used. Formed CLs were monitored via ultrasonography every two days until functional regression (decrease of the vascular signal of color Doppler and serum P4 concentrations below 1 ng/mL), being determined for each day the diameter, area, numerical values (NV) and heterogeneity of the pixels, and vascularization percentage (%). The systolic and diastolic peak velocity, resistance and pulsatility index (PI) of the ovarian artery were also determined for each day in addition to the serum P4 concentration. These characteristics were compared between treatments, CLs functions (normal duration or prematurely regressed), days of evaluations and their interactions, using the MIXED procedure of SAS program (p≤0.05). Three animals from each treatment did not respond to the OV inductor (6/57=11%), which determined an ovulation rate of 89%. In GP4+GnRH, a higher percentage of CLs with normal duration was observed (81%), while in the GGnRH the percentage of nonfunctional CLs was higher (52%; serum P4 concentration of less than 1 ng/mL in all evaluations). The CLs of normal duration presented greater area, % of vascularization and concentration of P4 when compared with other categories. Lower values for the diameter, area (31.89±11.46mm2), NV (84.05±2.90) and concentration of P4 were observed for the nonfunctional CLs and, those that regressed prematurely, presented intermediate values for the area and serum P4 concentration and did not differ in relation to the % of vascularization with the nonfunctional. The P4 was effective in the diagnosis of regressed prematurely and nonfunctional of CLs, presenting a positive correlation with the area (r=0.62; p<0.001) and, with the % of CL vascularization (r=0.38; p<0.001). The diameter of CL and PI were important in the early diagnosis of the nonfunctionality and PR, respectively. Greater relation of the area of the CL with the concentration of P4 was observed (R2=0.53). In conclusion, the first CL formed after OV induction in prepubertal heifers showed differences in functionality that can be differentiated by ultrasonography parameters diameter and area of CL, NV, % of vascularization and PI. (AU)

• FAPESP's process: 15/13079-0 - Evaluation of attributes sonographic (mode-B and doppler) of corpus luteum after puberty induction in Nellore heifers and its relation with functionality
• Grantee: Dayane Priscila Vrisman
• Support Opportunities: Scholarships in Brazil - Master