Use of injectable progesterone and CIDR in early resynchronization of Nellore cows and heifers submitted to 3 FTAIs in 48 days

Abstract

The high Progesterone (P4) concentration in the resynchronization protocols can induce a synchronized follicular emergence by the reason that the gonadotrophic hormones releasing decrease. The main objective of this study is evaluate the follicular dynamic and the pregnancy rate in Nelore beef cows submitted to two early resynchronization 13 days after the first fixed timed artificial insemination (FTAI), using a P4 device associated or not with short-action injectable P4 (Afisterone, Ceva, Paulínia, SP). In the Experiment 1, heifers (n=30) e and lactating cows (n=30) on 30-60 days postpartum will be submitted to a ovulation synchronization protocol. On D-11, all the animals will receive a releasing P4 device (1,9g, CIDR, Zoetis, Campinas, SP) and 2 mg of estradiol benzoate (BE; Gonadiol, Zoetis). On D-4, all the animals will receive 12,5 mg dinoprost tromethamine (PGF2±; Lutalyse, Zoetis). On D-2 devices will be taken out and the animals will receive 0,6 (heifers) or 1 mg (cows) estradiol cypionate (ECP; ECP, Zoetis) + 12,5 mg dinoprost tromethamide (Lutalyse, Zoetis) + 200 (heifers) or 300 (cows) IU of equine chorionic gonadotrophin (eCG; Novormon, Zoetis). The D0 will be considered the estrus day. On D13 after estrus, the animals will be divided in two groups (CIDR and CIDR + 100 mg P4i). In the CIDR group, the animals (nH11/category) will receive a new CIDR while in the other group (nH11/category) they will receive a new CIDR + 100 mg P4i (Afisterone, Ceva, Paulínia, SP). The diameter of the ovarian follicles and corpus luteum area will be measured daily until D22, using a duplex B-mode and Color Doppler Ultrasound instrument (MyLab Delta, Esaote, Italy). On D22, devices will be taken out, and the animals diagnosed as not pregnant will receive the treatment like mentioned at the first synchronization (PGF2±, eCG and ECP). The ovulation will be checked by ultrasonography every 12 hours between 36 and 96 hours. In the experiment 2, the pregnancy rate will be evaluated in animals submitted at 3 FTAI in 48 days at the same experimental groups of the experiment 1. 450 heifers and 450 lactating cows will be synchronized and resynchronized as realized in experiment 1, however, on D22, the animals will be submitted at ultrasonography using color doppler to identify no-pregnant cows by the corpus luteum blood perfusion, as described by Pugliesi et al., (2014). On D22 no-pregnant females will receive PGF2±, eCG and ECP to induce ovulation as described in Experiment 1 and will be inseminated on D24. On D37, all the females that received the second FTAI will be resynchronized according to the experimental groups (CIDR + P4i or CIDR). The cows identified with pregnancy loss between D22 and D37 will be ressynchronized using CIDR + 2 mg BE. On D46, the cows with detected luteolysis will receive an treatment to induce their ovulations (PGF2±, eCG and ECP) and will be submitted to the third FTAI on D48. The definitive pregnancy diagnosis will be realized on D85, by the beat heart embryo visualization. It is expected that the P4i use result in a better synchronic follicular wave, allowing a better pregnancy rate on the second and third FTAI in cows, not in heifers. (AU)