Follicular waves and hormonal profiles during the estrous cycle of carriers and non-carriers of the Trio allele, a major bovine gene for high ovulation and fecundity

Temporality of ovarian steroids and LH/FSH pulse profiles encompassing selection of the dominant follicle in heifers†

The tested hypotheses were (1) LH/FSH pulses and F2 diameter are diminished by P4 and, (2) E2 increases during the transition to deviation and alters LH/FSH pulses. On Day 5 (Day 0 = ovulation), heifers were randomized into an untreated group (HiP4, n = 11), and a prostaglandin analog treated group (NoP4, n = 10). On Day 6, a follicular wave was induced by follicle ablation. Ultrasound and blood collections were performed every 12 h from Days 7 to 11. Blood was collected every 15 min for 10 h on Day 9 (largest follicle expected to be ~7.5 mm). Estradiol was ~75% greater (0.36 ± 0.14 vs 0.63 ± 0.19 pg/mL) in heifers with F1 ≥ 7.2 mm than in heifers with F1 < 7.2 mm. The HiP4 had smaller second largest follicle (F2) diameter, lower estradiol (P = 0.06), LH pulse baseline and peak concentrations (P < 0.007), in addition to half the frequency of LH/FSH pulses (4.1 ± 0.3 vs 9.6 ± 0.7 in 10 h) than the NoP4. Within HiP4, heifers with F1 ≥ 7.2 mm had ~25% fewer (P = 0.03) LH pulses compared to heifers with F1 < 7.2 mm. In contrast, within the NoP4, heifers with F1 ≥ 7.2 mm had ~75% greater LH (P = 0.05) and FSH (P = 0.08) pulse amplitude. We propose that greater F2 diameter at deviation in low P4 is related to greater LH baseline and peak concentrations, and greater frequency of LH/FSH pulses. A greater increase in E2 after F1 reaches ~7.2 mm results in further stimulation of LH/FSH pulse amplitude. Elevated P4 not only diminished frequency of LH/FSH pulses but also converted an E2 increase into a negative feedback effect on LH/FSH pulse frequency leading to smaller F2 at deviation.

Practical application of an impractical bovine genotype: creating bilateral twin pregnancies in Trio allele carriers

Bovine twin birth is associated with detriments, including increased embryo/fetal losses, malpresentation, and dystocia. Incidence of these is lessened in bilateral compared with unilateral twin pregnancy. This study was undertaken to assess the use of follicular ablation by aspiration to create bilateral twin pregnancies in females with genetic potential for ~3.5 ovulations per cycle (Trio allele carriers). In experiment 1, carriers (n = 30) and noncarriers (n = 10) were synchronized for ovulation and timed artificial insemination (TAI). Follicles (>5 mm) in excess of one per ovary were aspirated ~16 h preceding TAI. Follicle count for females with follicles on only one ovary was reduced to two. Blood was sampled 2 wk post-TAI to assess progesterone (P4) concentrations; embryo count was determined by ultrasound 6 wk post-TAI. Circulating P4 concentration post-TAI was significantly (P < 0.001) associated with both genotype and subsequent pregnancy status (pregnant noncarriers: 7.06 ± 0.68 ng/mL; pregnant carriers: 5.54 ± 0.55 ng/mL; nonpregnant noncarriers: 5.22 ± 1.05 ng/mL; nonpregnant carriers: 3.13 ± 0.42 ng/mL). Experiment 2 was undertaken to offset the negative effects of follicular aspiration on subsequent P4 concentration observed in experiment 1. Carriers (n = 38) and noncarriers (n = 32) were submitted to TAI and follicle ablation as described for experiment 1. Additionally, accessory corpora lutea (CL) were induced in carriers by the administration of human chorionic gonadotropin (carriers) at day 6 post-TAI. Consequently, P4 concentration post-TAI was significantly (P < 0.05) associated with subsequent pregnancy status (pregnant: 8.48 ± 0.61 ng/mL; nonpregnant: 6.70 ± 0.63 ng/mL) but not with genotype (carrier: 8.01 ± 0.59 ng/mL; noncarrier: 7.17 ± 0.64 ng/mL). Embryo number was greater in carriers (exp. 1: 1.64 ± 0.81; exp 2: 1.45 ± 0.09) vs. noncarriers (1.00 ± 0.00, both experiments). Single, twin, and triplet pregnancies occurred in carriers in experiment 1, whereas multiples in experiment 2 were limited to twin pregnancies. Genotype effects on pregnancy rate were not significant (P > 0.10) in either experiment. Results suggest that follicular ablation to create bilateral twin pregnancies in Trio carriers is feasible but requires the induction of accessory CL to offset the negative effects of follicular aspiration on subsequent P4 concentration and associated fertility outcomes.

Selection of fewer dominant follicles in Trio carriers given GnRH antagonist and luteinizing hormone action replaced by nonpulsatile human chorionic gonadotropin†

Studying selection of multiple dominant follicles (DFs) in monovulatory species can advance our understanding of mechanisms regulating selection of single or multiple DFs. Carriers of the bovine high fecundity Trio allele select multiple DFs, whereas half-sib noncarriers select a single DF. This study compared follicle selection during endogenous gonadotropin pulses versus during ablation of pulses with Acyline (GnRH antagonist) and luteinizing hormone (LH) action replaced with nonpulsatile human chorionic gonadotropin (hCG) treatment in Trio carriers (n = 28) versus noncarriers (n = 32). On Day 1.5 (Day 0 = ovulation), heifers were randomized: (1) Control, untreated; (2) Acyline, two i.m. doses (Days 1.5 and D3) of 3 μg/kg; (3) hCG, single i.m. dose of 50 IU hCG on Day 1.5 followed by daily doses of 100 IU; and (4) Acyline + hCG. Treatments with nonpulsatile hCG were designed to replace LH action in heifers treated with Acyline. Acyline treatment resulted in cessation of follicle growth on Day 3 with smaller (P < 0.0001) maximum follicle diameter in Trio carriers (6.6 ± 0.2 mm) than noncarriers (8.7 ± 0.4 mm). Replacement of LH action (hCG) reestablished follicle diameter deviation and maximum diameter of DFs in both genotypes (8.9 ± 0.3 mm and 13.1 ± 0.5 mm; P < 0.0001). Circulating follicle stimulating hormone (FSH) was greater in Acyline-treated than in controls. Finally, Acyline + hCG decreased (P < 0.0001) the number of DFs from 2.7 ± 0.2 to 1.3 ± 0.2 in Trio carriers, with most heifers having only one DF. This demonstrates the necessity for LH in acquisition of dominance in Trio carriers (~6.5 mm) and noncarriers (~8.5 mm) and provides evidence for a role of GnRH-induced FSH/LH pulses in selection of multiple DFs in Trio carriers and possibly other physiologic situations with increased ovulation rate.

Ovarian and uterine arteries blood flow waveform response in the first two cycles following superstimulation in cows

To investigate the ovarian and uterine blood flow responses, hemodynamic, circulating ovarian hormones and nitric oxide (NO) after end of treatment by Folltropin. Holstein Friesian (12) cows previously synchronized with CIDR underwent Doppler ultrasound after administrating of FSH daily for 4 days in eight injections started on day 10 of the second ovulation (day -5). Oestradiol (E2), progesterone (P4) and nitric oxide (NOMs) were measured. During the follicular phase, follicle area and antrum area of the second cycle reached maximum value on the day of ovulation compared with that in the first cycle, while during the luteal phase, both showed a pattern of increase and decrease. The luteal area and total coloured area increased till day 10 in the first and second cycle. The first cycle ipsilateral ovarian artery (Ov.A) had higher pulsatility (PI) (p = .001), resistance (RI) (p = .001), peak velocity (PSV) (p = .009) and lower end-diastolic velocity (EDV) (p = .003) compared with the second cycle. The increased ipsilateral Ov.A PSV (p = .009) was accompanied by lower EDV. The first cycle ipsilateral middle uterine artery (MUA) had higher PI (p = .001) and RI (p = .001), with lower PSV (p = .001) and EDV (p = .001). It was concluded that blood flow of ovarian and middle uterine arteries changed after the end of superstimulation as the increased ipsilateral Ov. A and MUA PSVs accompanied by lower EDV and both Doppler indices that reflect the amount of ovarian and uterine blood flow waveform.

Hormonal mechanisms regulating follicular wave dynamics II: Progesterone decreases diameter at follicle selection regardless of whether circulating FSH or LH are decreased or elevated

Selection of a single dominant follicle is morphologically manifested by diameter deviation between the future dominant follicle (F1) and the future largest subordinate follicle (F2). Conventional deviation is defined as F2≥7 mm when F1 reaches ∼8.5 mm whereas, undersized deviation is if F2<7 mm when F1 reaches ∼8.5 mm. Greater frequency of undersized deviation has been temporally associated with greater circulating progesterone (P4) and greater FSH but reduced LH in observational studies. Experiment 1 was conducted to directly test if elevating P4 increased the likelihood of undersized deviation and altered circulating concentrations of LH and FSH. Experiment 2 was conducted to test if increasing LH action by treatment with exogenous porcine LH or human chorionic gonadotropin (hCG) in the presence of elevated P4, would stimulate growth of F2 and increase the likelihood of conventional deviation. Ovaries were evaluated by ultrasound and blood samples collected every 12 h after development of a new wave following follicle ablation on D6 (D0 = ovulation). Data were normalized to F1≥7.5 mm and compared using SAS software. In experiment 1 (n = 20), the CL was regressed by prostaglandin F2α treatment and heifers were randomized on D6 into control (no P4 treatment) or P4 treatment (75 mg every 12 h for 5.5 d) beginning when F1 reached ∼3 mm (P4-3 mm group) or ∼6 mm (P4-6 mm group). The P4 treatment significantly increased the frequency of undersized deviation from 0% (controls) to 54%, decreased LH by 44%, and increased FSH by 32%. In experiment 2 (n = 27) heifers were randomized on D6 into control (saline) or treatment with the LH analogs - pLH (1.25 mg porcine LH/12 h) or hCG (160 IU initially and subsequently 96 IU/24 h). Treatment with LH analogs significantly increased P4 (control, 4.6 ± 0.3 ng/mL; pLH, 6.6 ± 0.4 ng/mL; and hCG, 8.9 ± 0.4 ng/mL) and decreased FSH (control, 0.46 ± 0.03 ng/mL; combined-pLH/hCG, 0.34 ± 0.02 ng/mL). However, F1 and F2 diameter and frequency of conventional (37%) and undersized (48%) deviations were similar between the control and combined-pLH/hCG groups. In conclusion, elevated P4 was directly linked to undersized deviation but the P4 effect on decreasing F2 diameter occurred independently of the P4 effects on FSH and LH concentrations.

Dynamics of uterine and ovarian arteries flow velocity waveforms and their relation to follicular and luteal growth and blood flow vascularization during the estrous cycle in Friesian cows

Doppler ultrasonography enabled understanding of the reproductive system hemodynamics in cyclic and pregnant cattle. To confirm the hypothesis that the ipsilateral ovarian and uterine arterial blood flows to the ovulating ovary are higher than the contralateral one along days and phases (follicular, early luteal, mid-luteal, late luteal) of the estrous cycle, eight cyclic spontaneously ovulating cows were scanned with Doppler ultrasound each other day along three oestrous cycles to monitor the follicular dynamics, the vascularization of the ovulatory follicle (OF), the corpus luteum (CL) developmental dynamics, the ipsilateral and the contralateral ovarian and uterine arterial diameters and their blood flow. Results proved the hypothesis. Both days and phases of the estrus cycle influenced (P = 0.0001) the follicular dynamic, the luteal hemodynamics, the ovarian and uterine hemodynamic. The ovulatory wave and the mid-luteal non-ovulatory wave had expanding numbers and the diameters of small, medium and large follicles. Though area, antral area, vascularization area of the OF ascended from Day -4 to the day of ovulation (Day 0), but the percent of its vascularization area and that of granulose layer increased till Day -3. The CL diameter increase till Day 15, and its vascularization area increased till Day 13, but its% of vascularization area ascended (P = 0.0001) from Days 1-4 and declined from Days 9-13. Both RI and PI of the ipsilateral ovarian artery were lower than the contralateral one; but, both obtained high values during the follicular phase. A linear increase (P = 0.0001) of uterine horns vascularization area and both ovarian and uterine arteries diameters, PSV and EDV from follicular to late luteal phases accompanied a linear decrease of their PI and RI. In conclusion, the ovarian and uterine blood flows vary according to the estrous day, estrous phase, the ovulating ovary, ovulatory follicle growth and corpus luteum developmental stage.

Update on Multiple Ovulations in Dairy Cattle

This review updates the causal mechanisms and risk factors for multiple ovulations (MOV) in cattle. Clearly, MOV can lead to twin pregnancies, which negatively affects the health, production, and reproduction of cows. Therefore, a better understanding of the factors causing MOV may help to reduce twinning. Multiple ovulations occur after two or more follicles deviate and achieve codominance. The MOV rate is influenced by a complex network of hormones. For example, MOV is more common during periods of low progesterone (P4), that is, in anovulatory cattle or when luteolysis coincides with the selection of the future ovulatory follicle. There is also strong evidence for the luteinizing hormone (LH) being the primary factor leading to codominance, as high P4 concentrations suppress the transient LH surges and can reduce the ovulation rate in cattle or even inhibit deviation. Rates of MOV are increased in older and higher-producing dairy cows. Increased milk production and dry matter intake (DMI) increases hormone clearance, including P4; however, the association between milk yield and MOV has not been consistent. Additional risk factors for MOV include ovarian cysts, diet, season, and genetics.

Proteomic analysis of follicular fluid in carriers and non-carriers of the Trio allele for high ovulation rate in cattle

This study was conducted to characterise differences in follicular fluid proteins between carriers and non-carriers of a bovine allele for high ovulation rate. A total of four non-carrier and five carrier females were used in an initial study with four and six additional non-carriers and carriers respectively used in a validation study. Emergence of the follicular wave was synchronised and the ovaries containing the dominant follicle(s) were extracted by ovariectomy for follicular fluid collection. A hexapeptide ligand library was used to overcome the masking effect of high-abundance proteins and to increase detection of low-abundance proteins in tandem mass spectrometry. After correcting for multiple comparisons, only two proteins, glia-derived nexin precursor (SERPINE2) and inhibin β B chain precursor (INHBB), were significantly differentially expressed (false-discovery rate <0.05). In a replicate study of analogous design differential expression was confirmed (P < 0.05). Joint analysis of results from the two studies indicated that three additional proteins were consistently differentially expressed between genotypes. For three of these five, previous studies have indicated that expression is increased by transforming growth factor-β–bone morphogenetic protein signalling; their reduction in follicular fluid from carrier animals is consistent with the ~9-fold overexpression of SMAD family member 6 (SMAD6) in carriers that is inhibitory to this pathway.