Taxa de gestação de novilhas ressincronizadas aos 14 dias pós-iatf com Progesterona ou Benzoato de Estradiol

Abstract

The objective of this work was to compare the pregnancy rates of Bos taurus x Bos indicus heifers resynchronized 14 days after the first TAI with long-acting injectable progesterone (iP4) associated with the intravaginal P4 device to those resynchronized by the

association of estradiol benzoate (EB) and intravaginal P4 device. Six hundred and seventy- seven heifers (Braford and Brangus) submitted to a TAI cycle (D0) were used. On D14, the

animals received a P4 intravaginal device (1 g, Sincrogest, Ourofino Saúde Animal, Cravinhos, SP) and were randomly divided into two groups to receive: EB (1 mg I.M., Sincrodiol, Ourofino; n=339); or iP4 (75 mg I.M., Injectable Sincrogest, Ourofino; n=338). On D22, the P4 devices were removed and the pregnancy diagnosis (PD) performed by assessing morphological luteolysis through Doppler ultrasound examination. Heifers considered non-pregnant (NP) had the diameter of the dominant follicle (DF) measured and received 1 mg of estradiol cypionate (SincroCP, Ourofino), 250 μg of sodium cloprostenol (Sincrocio, Ourofino) and 200 IU eCG (SincroeCG, Ourofino), followed by the second TAI no D24. The statistical model was adjusted for each dependent variable by logistic regression analysis (PROC GLIMMIX, SAS version 9.2) considering the following independent variables: treatment, race, age, ranch, and interactions treatment x ranch, treatment x race, treatment x age. The diameter of the DF on D22 in the NP heifers did not differ (P>0.05) between the EB (9.77 ± 0.25) and iP4 (9.92 ± 0.22) groups. No difference was observed between the EB and iP4 groups for pregnancy rate on D22 (56.3%, 191/339 versus 60.1%, 203/338, respectively), and D40 post-TAI (49.6%, 168/339 versus 53.3%, 180/338, respectively). The rate of pregnancy losses from PD22 to PD40 was similar between the EB (12%, 23/191) and iP4 (11.3%, 23/203) groups. The resynchronization pregnancy rate of the iP4 group (31.85%, 43/135) was lower than that of the EB group (45.95%, 68/148). In conclusion, it is proposed that supplementation with 1 mg EB or 75 mg of iP4 in combination with the P4 device at 14 days after TAI is equally safe for the ongoing pregnancy. Additionally, whereas the resynchronization of the follicular wave by the association of EB and intravaginal P4 device reaches satisfactory pregnancy rates to the second TAI, complementary studies are necessary to investigate the apparent low pregnancy rates obtained by the association of iP4 and P4 device.