Impacto do diâmetro do folículo dominante no momento da retirada do dispositivo intravaginal de progesterona em um programa de IATF

Abstract

The preovulatory follicle size at the time of artificial insemination has a significant impact on the pregnancy rate of beef cattle submitted to estrus synchronization programs. The objective of this study was to verify the effect of dominant follicle diameter on pregnancy rate in an FTAI protocol based on estradiol and progesterone. For the development of the study 227 heifers with two years old and 143 Braford suckling cows were used. Heifers and cows was placed an intravaginal progesterone device, new device was use for cows and pre-used for heifers, and estradiol benzoate (im) on Day 0. Prostaglandin, estradiol cipionate and eCG was injected (im) at the time of progesterone device removal on Day 8, FTAI was proceeded 48 hours after device removal on Day 10. In addition, heifers received (im) prostaglandin on Day 0. Ultrasonography was performed on days 0, 8, 10 and 40 to check the presence of CL, follicle size and pregnancy rates. The study was carried out in a private farm, located in the western border of Rio Grande do Sul, Brazil. The distribution of the follicular size on day 8 was didactic divided in seven groups (≤7, 7.1 to 8, 8.1 to 9, 9.1 to 10, 10.1 to 11, 11.1 to 12 and >12 mm of diameter). Around 25% of the cows and heifers were in the ≤7 mm group with 5.88 and 23.08% of pregnancy rate, smaller (P <0.05) than the other groups of follicles in cows. However, heifers of the group > 12 mm the pregnancy rates are similar to the group ≤7 mm and below (P <0.05) of the other groups of follicles sizes. Additionally, the scientific knowledge obtained in this study provides that ultrasound exam an alternative for individual decisions according to the dominant follicle size at the progesterone device withdrawal on FTAI protocols. Enhanced reproductive efficiency for promote the preovulatory follicle to respond to the luteinizing hormone and to ovulate close the time of artificial insemination.