Caracterização do pico de LH após protocolo de curta e longa duração para IATF em ovelhas ciclando na contra estação reprodutiva

Abstract

The hypothesis tested in this study was that the time of permanence of progesterone implant (short vs. long) in FTAI protocol change the characteristics of the LH surge. Thus, the aim of this study was to determine the timing, duration and amplitude of the LH peak in sheep (Santa Inês x Texel) using short FTAI protocols (6 days) or long (12 days) in cyclic sheep out of the breeding season. We used 43 sheep (Texel-Te x Santa Inês-SI), sorted into two groups according to the time of progesterone release s vaginal device 1st use (Easy-Breed CIDR®, Pfizer, Brazil). In group 12 days (G-12, n = 19) in stage random of the estrous cycle received the insertion of CIDR (D0). On the day of implant removal (D12) was administered intramuscularly, 0.075 mg cloprostenol (Veteglan®, Hertape Calier, Brazil) and 300 IU equine chorionic gonadotropin (eCG, Novormon®, MSD Animal Health, Brazil). The group 6 (G-6, n= 24) received the same protocol of G-12, however the permanence of CIDR was 6 days. Approximately 50 hours after CIDR removal, both groups were inseminated at fixed time by artificial insemination by laparoscopy with frozen semen containing 200x106 sperm of a single player of Dorper. Approximately 40 days after the artificial insemination pregnancy diagnosis was performed using ultrasound device. Blood samples were taken every 4 hours from 10 animals per group, to measure LH and progesterone plasma concentrations by radioimmunoassay (RIA). From the 20 animals used for progesterone plasma concentration, the percentage of animals showing LH surge in G-6 was 70% (7/10) and the G-12 was 90% (9/10). The maximum amplitude of the LH peak did not differ between the G-6 and G-12 groups (P> 0.05) and the lengh of LH peak was 16,60±2,76 h in the G-6 and 16,40±2,40 h in G-12 (P>0,05). The interval between the implant removal and the LH surge was (P >0.05) in the G-6 27,42±2,76 h and 28,88±5,20 h in G-12. The overall pregnancy rate per group was not different (G-6 58,33% e G-12 52,63%). It was concluded that the permanence of progesterone (6 vs 12 days) did not alter the characteristics of the LH peak in sheep (St. Agnes x Texel) in the tropics, out of the breeding season.