Influence of the Length of Progestagen Treatment and the Time of Oestradiol Benzoate Application on the Ovulatory Follicle Size and Ovulation Time in Anoestrous and Cyclic Beef Cows

Abstract

Previous research from our laboratory in beef cattle suggests that the pre-ovulatory follicle size, maturity and subsequent susceptibility to gonadotropin are influenced by the length of progestagen treatment in artificial insemination programme in beef cows. To test this hypothesis, two experiments were conducted. In experiment 1, 35 anoestrous beef cows received an intravaginal sponge containing 200 mg of medroxyprogesterone acetate. The treatment lasted for 7 (n = 12), 8 (n = 11) or 9 (n = 12) days. Half of the animals in each group were injected with 0.7 mg of oestradiol benzoate (EB) at device removal (0 h) and the other half 24 h later. In experiment 2, 38 cycling beef cows were treated with the same protocols as in experiment 1. Ultrasound examinations were performed to determine the follicular diameter at device removal (dominant follicle), interval to ovulation and ovulatory follicle diameter. The dominant follicle of anoestrous cows with progestagen for 7 days (8.4 ± 1.6 mm) resulted smaller (p < 0.05) than the cows treated for 8 (10.5 ± 1.6 mm) and 9 days (10.6 ± 1.2 mm). However, regardless of the length of the treatments, ovulation time after device removal was longer (p < 0.05) when EB was injected 24 h after withdrawal than at 0 h in anoestrous cows (EB0 = 52.7 ± 4.0 h; EB24 = 70.8 ± 6.2 h) and in cyclic cows (EB0 = 50.0 ± 21.0 h; EB24 = 73.0 ± 20.0 h). In anoestrous cows, the treatment with progestagen for 9 days and EB at 24 h increased the diameter of the ovarian follicle (p = 0.033) but did not affect the diameter of the ovulatory follicle in cyclic cows. In conclusion, increasing the length of progestagen treatment for 8 or 9 days compared to 7 days increased the diameter of the dominant follicle, in anoestrous and cyclic beef cows. Oestradiol benzoate administered at device removal resulted in a shorter interval from device removal to ovulation compared with EB injection 24 h after the end of a progestagen treatment.

Superovulation in cows synchronized with two different progesterone+oestradiol protocols

“…Estradiol usage in cattle is still legal in most countries around the world and it is being used extensively for oestrus synchronization programs (Butler et al 2012, Manes et al 2012 while its application is not allowed in food producing animals in the European Union.…”

Effect of estradiol cypionate and GnRH treatment on plasma estradiol‐17β concentrations, synchronization of ovulation and on pregnancy rates in suckled beef cows treated with FTAI‐based protocols

“…The dominant follicle (DF) of a wave was defined as that one that reached the largest diameter (Ginther, Kastelic, & Knopf, ). The time of ovulation was defined as the average time between the last observation of the dominant follicle and the time at which the dominant follicle disappeared (ovulation), which also determined the ovulatory follicle diameter (Manes, Aller, Callejas, Hozbor, & Alberio, ; Uslenghi et al., ). On day 22 (approximately 12 days after ovulation), another ultrasound evaluation was performed to confirm ovulation by the presence of a CL (Carvalho et al., ); the CL area was measured with the ultrasound equipment's caliper system.…”

Different times to perform timed artificial insemination when using a P4/E2/eCG-based protocol in buffalo

“…Other evidence has confirmed EB treatment efficiency for the induction of ovulation in buffalo. Studies have shown that EB treatment induces considerable release of LH (JACOMINI et al, 2014), has a low cost (BARROS et al, 2000;MANES et al, 2012) and maintains high circulating oestradiol concentrations, which likely creates a better uterine environment for embryonic development (BRIDGES et al, 2012).…”