Selection of the Dominant Follicle in Cattle1

The aim was to define the pattern and physiological concentrations of FSH and LH required for the selection of a single dominant follicle in mono-ovulatory species. A series of five experiments was carried out using gonadotrophin-releasing hormone agonist-induced hypogonadal heifers. Animals were infused with different patterns of either FSH and/or LH followed by an ovulatory dose of human chorionic gonadotrophin. Follicular response was monitored by ultrasound scanning and blood samples were collected to measure concentrations of FSH, LH, oestradiol and progesterone. The main findings were: (1) physiological concentrations of FSH given as a continuous infusion and for an adequate duration, in the presence of basal LH, with or without LH pulses, are capable of inducing a superovulatory response, (2) initial exposure to FSH followed by LH pulses alone stimulate the development of multiple preovulatory follicles, confirming that ovarian follicles are capable of transferring dependence on gonadotrophins from FSH to LH, (3) while LH pulses appear not to have a major effect on the pattern of preovulatory follicle development, adequate LH pulsatile support is required for full oestradiol synthesis and (4) the duration of initial exposure to FSH and the ability to transfer the dependence from FSH to LH are critical for the selection of a single dominant follicle. In conclusion, this experimental series confirms that the duration of initial exposure to FSH and the ability of the selected follicle to transfer its gonadotrophic dependence from FSH to LH are critical for the selection of a single dominant follicle in cattle.

Download Full-text

Role of Diameter Differences among Follicles in Selection of a Future Dominant Follicle in Mares1

Biology of Reproduction ◽

10.1095/biolreprod57.6.1320 ◽

1997 ◽

Vol 57 (6) ◽

pp. 1320-1327 ◽

Cited By ~ 105

Author(s):

E. L. Gastal ◽

M. O. Gastal ◽

D. R. Bergfelt ◽

O. J. Ginther

Keyword(s):

Dominant Follicle ◽

Selection Of

Download Full-text

129 Ovarian dynamics and gonadotropins during selection of the dominant follicle in postpartum lactating versus non-postpartum cycling mares

Reproduction Fertility and Development ◽

10.1071/rdv32n2ab129 ◽

2020 ◽

Vol 32 (2) ◽

pp. 191

Author(s):

M. Pastorello ◽

M. O. Gastal ◽

G. K. Piquini ◽

D. B. Godoi ◽

E. L. Gastal

Keyword(s):

Growth Rate ◽

Maximum Diameter ◽

Sequential Data ◽

Dominant Follicle ◽

Follicle Diameter ◽

The Mean ◽

Low Levels ◽

Follicle Selection ◽

Ovarian Dynamics ◽

Selection Of

The mare, compared to other livestock, has the shortest interval from partum to the first ovulation. In monovulatory species, the follicle deviation process in a wave is characterised by the continued growth of the dominant follicle (DF) and regression of the subordinate follicle. Although follicle diameter deviation, a key event of follicle selection, has been investigated during the oestrous and menstrual cycles, the occurrence of this phenomenon before the first postpartum ovulation seems to be unclear in all species. This study aimed to compare the follicular dynamics and gonadotropin profiles around the follicle diameter deviation day in postpartum lactating (PP Lactating; n=24) versus non-postpartum cycling (NPP Cycling; n=15) mares. On the day of parturition, every PP Lactating mare was paired with an NPP Cycling mare, and ovarian follicles (>4mm) were tracked daily by transrectal ultrasonography, and blood samples were collected. Data were analysed in the PP Lactating group according to the length of the partum-ovulation interval (POI; ≤22 and >22 days) and the postpartum interovulatory interval (PPIOI), and in the NPP Cycling group during two interovulatory intervals (1st and 2nd IOI). In addition, regardless of group, all four intervals were compared. We performed the FSH and LH assays using radioimmunoassay. Ovarian and hormonal parameters were analysed using ANOVA for sequential data. The day and diameter of the DF at the deviation (overall mean: 14.9±2.5 days; 21.7±0.4mm, respectively) were not different (P>0.05) between PP Lactating and NPP Cycling mares. However, when considering the length of POI, follicle deviation occurred 4.4±0.8 days earlier (P<0.001) in mares with POI ≤ 22 days than in mares with POI>22 days. No difference was found between PP Lactating and NPP Cycling mares within and between groups for the intervals from deviation to maximum diameter of the DF (10.4±0.4 days), for the intervals from deviation to ovulation (12.1±0.5 days), or for the growth rates of the DF from deviation to maximum diameter (2.6±0.1mm per day). The growth rate of the DF from deviation to ovulation (2.4±0.1mm per day) did not differ between PP Lactating and NNP Cycling mares; however, this growth rate was lower (P<0.03) in the POI, PPIOI, and 1st IOI compared with the 2nd IOI. The mean diameter of the DF around deviation (days −3 to 3; 22.5±0.3mm), and systemic FSH (days −4 to 4; 10.3±0.2ngmL−1) were not different between PP Lactating and NPP Cycling mares. Level of LH was lower (P<0.0001) around deviation (days −4 to 4) in the PP Lactating (0.7±0.0ngmL−1) versus the NPP Cycling mares (1.8±0.1ngmL−1). Results demonstrated that a partum effect occurs only on the day of deviation in mares during the foal heat (POI ≤ 22 days) and that low levels of LH during both intervals in PP Lactating mares were not detrimental to prevent ovulation.

Download Full-text

Decline in Serum Follicle-Stimulating Hormone Concentrations Alters Key Intrafollicular Growth Factors Involved in Selection of the Dominant Follicle in Heifers1

Biology of Reproduction ◽

10.1095/biolreprod57.6.1328 ◽

1997 ◽

Vol 57 (6) ◽

pp. 1328-1337 ◽

Cited By ~ 68

Author(s):

M. Mihm ◽

T.E.M. Good ◽

J.L.H. Ireland ◽

J. J. Ireland ◽

P. G. Knight ◽

...

Keyword(s):

Growth Factors ◽

Follicle Stimulating Hormone ◽

Dominant Follicle ◽

Selection Of ◽

Stimulating Hormone

Download Full-text

Necessity for LH in selection and continued growth of the bovine dominant follicle

Reproduction ◽

10.1530/rep-19-0342 ◽

2020 ◽

Vol 159 (5) ◽

pp. 559-569 ◽

Cited By ~ 2

Author(s):

Victor E Gomez-León ◽

O J Ginther ◽

Rafael R Domingues ◽

José D Guimarães ◽

Milo C Wiltbank

Keyword(s):

Chorionic Gonadotropin ◽

Acute Treatment ◽

Gnrh Antagonist ◽

Underlying Mechanism ◽

Dominant Follicle ◽

Follicle Growth ◽

Follicular Wave ◽

Treatment Data ◽

Follicle Selection ◽

Selection Of

Previous research demonstrated that acute treatment with GnRH antagonist, Acyline, allowed follicle growth until ~8.5 mm and no dominant follicle was selected. This study evaluated whether deficient LH was the underlying mechanism for Acyline effects by replacing LH action, using human chorionic gonadotropin (hCG), during Acyline treatment. Holstein heifers (n = 24) during first follicular wave were evaluated by ultrasound and randomized into one of three treatments: Control (saline treatments), Acyline (5 µg/kg Acyline), or Acyline+hCG (Acyline plus 50 IU of hCG at start then 100 IU every 12 h). Pulses of LH were present in Control heifers (9 Pulses/10 h) but not during Acyline treatment. Data were normalized to the transition to diameter deviation (day 0; F1 ~7.5 mm). Diameter deviation of the largest (F1) and the second largest (F2) follicle was not observed in Acyline-treated heifers, whereas control heifers had decreased growth of F2 at F1 ~7.5 mm, indicating deviation. Selection of a single dominant follicle was restored by providing LH activity in Acyline+hCG heifers, as evidenced by F1 and F2 deviation, continued growth of F1, and elevated circulating estradiol. Separation of F1 and F2 occurred 12 h (~7.0 mm) earlier in Acyline+hCG heifers than Controls. Circulating FSH was greater in Acyline than Controls, but lower in Acyline+hCG than Controls after day 1.5. In conclusion, dominant follicle selection and growth after follicle deviation is due to LH action as shown by inhibition of this process during ablation of GnRH-stimulated LH pulses with Acyline and restoration of it after replacement of LH action by hCG treatment.

Download Full-text