Characteristics of the dynamics follicular in heifers Girolandas under two FTAI protocols

The Fixed-Time Artificial Insemination (FTAI) is an animal reproduction biotechnique which has been widely used in dairy and beef herds in Brazil. The use of this tool offers substantial advantages on reproductive management of dairy herd, allowing the improvement of reproductive performance of high production cows, which is currently low. However, the conception subsequent to FTAI protocols are variable due to several factors as differences among the ovulation induction hormones, hormonal concentration and doses and the dominant follicle diameter at the moment of Artificial Insemination (AI). Accordingly, the aim of this current study, was to evaluate the diameter of the largest follicle in heifers receiving two different FTAI protocols, with different methods of follicular wave synchronization. Heifers Girolando (3/4 to 7/8 Holstein-Zebu) were submitted to two FTAI protocols: Protocol I (PI) (n = 30): injection via intramuscular (IM) of 10.5μg GnRH and the placing of intravaginal device containing progesterone (P4) (D0-day zero); injection IM of 150μg prostaglandin F2alfa (PGF2a), removal of P4 device on the fifth day (D5); injection IM of PGF2α on the sixth day (D6) and AI and injection IM of 10.5μg GnRH on the eighth day of the protocol (D8). Protocol II (PII) (n = 30): injection IM of 2.0mg of estradiol benzoate (EB) and the placing of intravaginal device containing progesterone (P4) (D0); injection IM of 150μg of PGF2α on the seventh day (D7); removal of P4 device and injection IM of 1mg of estradiol cypionate (EC) on the ninth day (D9) and AI on the eleventh day of the protocol (D11). Transrectal ultrasonography was performed in the beginning of the protocols (D0), two days after the beginning (D2) and on AI day (D8 of Protocol I and D11 of Protocol II). Vaginal device used were Primer (Tecnopec, Sao Paulo, Brazil) and hormones GnRH (Gonaxal), EB (Bioestrogen), EC (Croni-cip), PGF2α (Croniben) of Biogenesis Bago SA (Garin, Buenos Aires, Argentina). Aiming to confirm the ovulation of the animals, it was also performed transrectal ultrasonography seven days after the AI in each protocol. The follicles diameters in different days of the protocols, were statistically evaluated (ANOVA), means were compared using Mann Whitney Test and ovulation rate analyzed using Chi-Square Test, considering P < 0.05. The follicles diameters at D0, D2 and AI day, expressed as means ± SEM, were: 13.1 ± 0.4mm and 12.8 ± 0.6mm, 8.1 ± 0.5mm and 12.0 ± 0.6mm, 12.6 ± 0.6mm and 10.6 ± 0.7mm, respectively for protocol I and II. Significant differences P < 0.05 were observed between the follicular diameters at D2 and AI day. The ovulation rates were 83.3% and 60.0% for PI and PII, respectively. The follicles diameters differences observed, occurred due to the distinct wave synchronization methods in each protocol.