Prostaglandin treatment at the onset of norgestomet and estradiol-based synchronization protocols did not alter the ovarian follicular dynamics or pregnancy per timed artificial insemination in cyclic Bos indicus heifers

Randomised controlled trial of the effect of concentration of progesterone before artificial insemination on fertility in ovulatory and anovulatory Bos indicus cattle

“…No significant association between AFC and final pregnancy rates was found when AFC was entered as either a continuous (P = 0.975) or categorical variable (71.9%, 23/32 vs 79.9%, 163/204 for females with AFCs ≤ 4 and > 4, respectively; P = 0.929). Mean (AE SD) AFC was 7.6 AE 3.2 (range, [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20].…”

“…Other studies have failed to detect differences in pregnancy rates when cattle with synchronised oestrous cycles have been exposed to higher P4 concentrations before ovulation. 11,18,19 When anoestrous dairy cows were administered a single IVD containing 1.56 g of P4 or a modified IVD containing 4.7 g of P4, plasma P4 concentrations increased during treatment but pregnancy rates were not significantly affected. 31 These studies support the view that pregnancy rates are not always improved with greater P4 concentrations before AI in ovulatory or anovulatory females.…”

“…11 Adequate secretion of LH to support follicular development during treatment in females with greater P4 concentrations might have occurred in some studies, resulting in adequate follicular maturity at the time of AI. 18 Administration of prostaglandin F2α before removing P4-releasing IVDs may have counteracted any potential negative influences of high P4 concentrations on follicular development in some studies, as this would induce lower the P4 concentration towards the end of treatment, which would stimulate an increase in the pulsatile release of LH, thus stimulating follicles to reach an adequate size before ovulation. 15 In studies that have used GnRH-based protocols, greater P4 concentrations before a timed AI could have improved pregnancy rates to AI, through indirect means such as reducing the number of animals entering oestrus and ovulating before a scheduled AI, improving the synchronisation of oestrus and reducing pregnancy loss rates after AI.…”

“…13 In B. indicus cattle that have had their oestrous cycles synchronised, lower P4 concentrations before a timed AI have had a variable effect on fertility, with an increase in pregnancy rates being reported in some studies [14][15][16][17] but not others. 11,18,19 Thus more investigation of the effects of P4 concentrations before AI is needed.…”

The puerperium in dairy cows: ovarian activity, uterine involution and follicular dynamics

“…According to Sá Filho et al (2014), knowledge of follicular dynamics allows for the efficient control of reproduction and other related procedures such the manipulation of the estrous cycle and the induction of postpartum estrus, and promotes the more effective use of reproductive biotechnologies. The ovaries function as units, and primarily influence follicular development through the endocrine pathways that involve ovarian and uterine endocrine secretions, as well as gonadotropins and their receptors.…”