Efeito de dispositivos vaginais impregnados com alta ou baixa concentração de progesterona na taxa de prenhez de novilhas submetidas à inseminação artificial em tempo fixo

This study aimed to evaluate the use of low- or high-dose intravaginal progesterone (P4)-releasing devices on pregnancy rates of Zebu heifers submitted to fixed-timed artificial insemination (TAI). Pubertal Bos indicus Nellore heifers were injected at day 0 with 2 mg estradiol benzoate (EB) and assigned randomly to three groups. Anintravaginal device containing 1.9 or 0.75 g P4 was inserted in animals of groups 1 (n=80) and 2 (n=79), while group 3 (n=76) received no device. The intravaginal devices were removed on day 8 and one luteolytic dose (125 μg) of d-cloprostenol was administered. Half of the animals in each group additionally received 300 IU of eCG. Twenty-fourhours later, the heifers received a second injection of 1 mg EB and TAI was performed 54 hours after the injection of cloprostenol. Pregnancy was diagnosed 40 days after TAI by transrectal ultrasonography. Data were analyzed by logistic regression. Pregnancy rates were 27.5%, 30.4% and 28.9% in groups 1, 2 and 3, respectively (P>0.05). This resultwas not influenced by body score, farm, eCG, or presence of CL at the beginning of the treatments. In conclusion, the use of intravaginal devices containing either a high (1.9 g) or low (0.75 g) dose of P4 resulted in similar pregnancy rates after TAI in pubertal Nellore heifers.