Use of injectable progesterone at the beginning of the TAI protocol is not necessary in super-early resynchronization started 14 days after artificial insemination in Bos indicus beef heifers.

In a protocol for the resynchronization of ovulation starting 14 days (D14) after timed artificial insemination, the effects of short-action injectable progesterone (P4i) administration and the length of treatment with an intravaginal progesterone (P4) device on follicular dynamics, the conception rate (P/AI) and the percentage of false positives were evaluated in 1065 Nelore heifers previously timed-inseminated. On D14, P4 devices were inserted, and heifers allocated, based on a 2 × 2 factorial design, to receive (P4i) or not 50 mg of P4i (NoP4i), and to remove the P4 device after 6 (6Day) or 8 days (8Day). At the time of P4 device removal (D20 and D22), non-pregnancy diagnosis was performed using vascularization of the corpus luteum (VCL) evaluated.

Comparison of estradiol benzoate doses for resynchronization of ovulation at 14 days after timed-AI in suckled beef cows.

We aimed to compare the effects of use of 1 or 2 mg estradiol benzoate (EB) associated with an intravaginal progesterone (P4) device for resynchronization of ovulation 14 days after timed-AI (TAI) in suckled beef cows. Nelore cows were submitted to a TAI (D0) and on D14, received an intravaginal P4 device and were randomly assigned to EB-1 group [n = 516] or EB-2 group [n = 510], which that received 1 or 2 mg EB, respectively. Also, cows had the ovaries scanned by ultrasound to detect an active CL on D14.

Effects of eCG and FSH in timed artificial insemination treatment regimens on estrous expression and pregnancy rates in primiparous and multiparous Bos indicus cows.

Effects were evaluated in Bos indicus cows of eCG and FSH on follicular growth, estrous expression, and pregnancy per artificial insemination (P/AI) as a result of fixed-time artificial insemination (TAI). In Experiment 1, extent of timing-of-ovulation synchronization among cows was evaluated after imposing an estrogen/progesterone-based treatment regimen. At progesterone device removal (D8), cows were administered: eCG, or FSH or served as untreated Controls.

Pre-TAI protocol strategies to increase reproductive efficiency in beef and dairy cows.

Ovulation synchronization protocols are well established in beef and dairy cows. However, the protocol response rate is around 70-90%. In beef cows, factors such as inadequate nutrition and calf presence negatively impact the response of progesterone (P4)/estradiol-based ovulation synchronization protocols by interfering with GnRH release and consequently reducing LH pulsatility and final follicular development.

Exposure to progesterone previous to the protocol of ovulation synchronization increases the follicular diameter and the fertility of suckled Bos indicus cows.

The objective was to evaluate the effect of injectable progesterone previous to the timed artificial insemination (TAI) protocol on follicular growth, ovulation and pregnancy rate of suckled Bos indicus cows. In experiment 1, 10 days before the beginning to TAI protocol (D-10), 431 suckled-anestrus Nelore cows (249 multiparous and 182 primiparous), were allocated to one of three treatments groups (control, P4i and P4iGnRH). At this moment, cows in the P4i and P4iGnRH group received 150 mg of injectable progesterone intramuscularly (Sincrogest injetável, Ouro Fino, Brazil).