Ultrasonographic image attributes of non-ovulatory follicles and follicles with different luteal outcomes in gonadotropin-releasing hormone (GnRH)-treated anestrous ewes

How ultrasound technologies have expanded and revolutionized research in reproduction in large animals

Gray-scale ultrasonic imaging (UI) was introduced in 1980 and initially was used to examine clinically the reproductive tract of mares. By 1983 in mares and 1984 in heifers/cows, UI had become a tool for basic research. In each species, transrectal gray-scale UI has been used extensively to characterize follicle dynamics and investigate the gonadotropic control and hormonal role of the follicles. However, the use of transrectal UI has also disclosed and characterized many other aspects of reproduction in each species, including (1) endometrial echotexture as a biological indicator of circulating estradiol concentrations, (2) relative location of the genital tubercle for fetal gender diagnosis by Days 50 to 60, and (3) timing of follicle evacuation during ovulation. Discoveries in mares include (1) embryo mobility wherein the spherical conceptus (6-16 mm) travels to all parts of the uterus on Days 11 to 15, (2) how one embryo of a twin set eliminates the other without self-inflicted damage, and (3) serration of the granulosum of the preovulatory follicle opposite to the future rupture site as an indicator of imminent ovulation. Studies with color-Doppler UI have shown that vascular perfusion of the endometrium follows the equine embryo back and forth between uterine horns and follows the expansion of the bovine allantochorion throughout each horn. In heifers, blood flow in the CL increases during the ascending portion of an individual pulse of PGF2α metabolite and then decreases. These examples highlight the power of UI in reproduction research. Without UI, it is likely that these and many other findings would still be unknown.

Reproductive Response of Ewes Fed with Taiwan Grass Hay (Pennisetum purpureum Schum.) Supplemented with Duckweed (Lemna sp. and Spirodela sp.)

The effect of duckweed (DW) supplementation was evaluated on dry matter intake (DMI), presence and duration of estrus, percentage of ewes repeating estrus and pregnancy rate, as well as the concentration of progesterone (P₄) in multiparous crossbred ewes from Pelibuey, Dorper, and Katahdin breeds, fed with Taiwan grass hay (TWH). Eighteen ewes with 39.7±4 kg mean body weight, kept in individual pens, were randomly assigned to one of the following treatments: T₁: TWH, T₂: TWH plus 200 g DW, T₃: TWH plus 300 g DW. The ewes were synchronized with 40 mg fluorogestone acetate (FGA) and 400 UI equine chorionic gonadotropin (eCG). Data were analyzed as a completely randomized design using the GLM procedure. DW supplementation had no effect on dry matter intake (p>0.05); however, a slight decrease of TWH intake was observed as DW supplementation increased. No differences (p>0.05) were found in the beginning of estrus, percentage of ewes presenting it, its duration, or pregnancy rate. There were no differences (p>0.05) on P₄ concentration among treatments, or treatmentxperiod interaction (p>0.05). However the period was significant (p<0.01), since the P₄ levels increased as time increased after the removal of the FGA device and eCG application.

Expression of genes for oestrogen and progesterone receptors in the cervix of anoestrous ewes treated with gonadotrophin releasing hormone with or without progesterone priming

The aim was to determine the oestrogens receptor alpha (ERα) mRNA and the binding capacity of oestrogens (ER) and progesterone receptor (PR) in the cervix of anoestrous ewes treated with gonadotrophin-releasing hormone (GnRH) with or without progesterone (P) priming, at the expected time of induced ovulation and early luteal phase. In Experiment 1, ewes were treated with P for 10 days (n=4), with nine micro-doses of GnRH followed by a GnRH bolus injection (n=4), or with P plus GnRH treatments (n=3), and tissues were harvested either without treatment (n=4), when P was removed, or 24h after the GnRH bolus injection. In Experiment 2, ewes were treated with the same GnRH or P plus GnRH treatments and tissues were harvested on Day 1 (n=12) or Day 5 (n=10) after the GnRH bolus injection. In the cranial cervix, the P treatment decreased and the GnRH treatment (after P treatment) increased the ERα mRNA, ER and PR concentrations (P<0.002). The ERα mRNA and ER concentrations were greater on Day 1, than on Day 5 in P plus GnRH treated ewes (P<0.0005). In the caudal cervix, lesser ERα mRNA, ER and PR concentrations than cranial cervix were found (P<0.0001). In conclusion, the ERα transcriptional activity and ER and PR binding capacity were strongly influenced by P and/or GnRH treatments in the cranial cervix, while the steroid receptors binding capacity remained unchanged in the caudal cervix of anoestrous ewes at the expected time of induced ovulation and early luteal phase.

The effects of a low therapeutic dose of βCG fragment-lytic peptide conjugates on ovarian function and gonadotropin secretion in ewes: a randomized controlled trial

The main objective of this experiment was to determine and compare the effects of two lytic peptide conjugates, Phor21-ßCG(ala) and ßCG(ala)-Phor21, at a low therapeutic dose (0.2 mg/kg body weight i.v.), on periovulatory ovarian and endocrine activity, and ensuing luteal function in an ovine experimental model. We hypothesized that the dense expression of LH/hCG receptors on the preovulatory follicle would present an appropriate target for the drugs and disrupt normal ovarian dynamics in sheep. Serum levels of reproductive hormones and ultrasonographic images were used for the assessment of periovulatory events following drug administration in 14 Rideau Arcott ewes; seven animals served as controls. Ovulations were synchronized with intravaginal progestogen-releasing sponges (medroxyprogesterone acetate, 60 mg) that were left in place for 12 days and a single i.m. injection of 750 IU of equine chorionic gonadotropin (eCG) given at sponge withdrawal. Both drugs were administered by i.v. injection 36 h post sponge removal/eCG injection, during the period of increasing LH responsiveness of potential ovulatory follicles and around the expected onset of the preovulatory surge of gonadotropins. No difference (p>0.05) was detected in the number of luteal structures per ewe in control versus treated animals during early luteogenesis. After drug administration, peak FSH concentrations were higher (p<0.05) in Phor21-ßCG(ala)-treated compared to control ewes and circulating estradiol concentrations were lower (p<0.05) in ßCG(ala)-Phor21-treated animals. Mean serum progesterone concentrations were lower (p<0.05) in ßCG(ala)-Phor21-treated than control ewes during the luteal phase post-treatment. There were no differences (p>0.05) in the percentage of ewes that lambed or lamb characteristics between the three groups at lambing 9 months post-treatment. In summary, neither Phor21-ßCG(ala) nor ßCG(ala)-Phor21 demonstrated adverse effects on the ovulatory process but the treatment with ßCG(ala)-Phor21 significantly depressed follicular and luteal steroidogenesis. With a lack of evidence for disruptive effects on endocrine function and fertility, these obsevations support the use of Phor21-ßGG(ala) as a cancer pharmaceutical.

Evaluation of the ultrasound image attributes of developing ovarian follicles in the four follicular waves of the interovulatory interval in ewes

Computer-assisted quantitative echotextural analysis was applied to ultrasound images of antral follicles in the follicular waves of an interovulatory interval in sheep. The ewe has three or four waves per cycle. Seven healthy, cyclic Western White Face ewes (Ovis aris) underwent daily, transrectal, ovarian ultrasonography for an interovulatory interval. Follicles in the third wave of the ovulatory interval had a longer static phase than that of those in Waves 1 and 2 (P<0.05). The numeric pixel value for the wall of anovulatory follicles emerging in the third wave of the cycle was significantly higher than that for Waves 1 and 2 at the time of emergence (156.7+/-8.09, 101.6+/-3.72, and 116.5+/-13.93, respectively), and it decreased as follicles in Wave 3 reached maximum follicular diameter (P<0.05). The numeric pixel value of the antrum in the ovulatory follicles decreased as follicular diameter increased to > or =5mm in diameter (P<0.05). The pixel heterogeneity of the follicular antrum in Wave 1 increased from the end of the growth phase to the end of the regression phase for follicles in that wave (P<0.05). The total area for the wall and antrum of the follicles studied were correlated with follicular diameter in all follicular waves (r=0.938, P<0.01 and r=0.941, P<0.01 for the wall and antrum, respectively). Changes in image attributes of the follicular wall and antrum indicate potential morphologic and functional differences among antral follicles emerging at different stages of the interovulatory interval in cyclic ewes.

Relationships of changes in ultrasonographic image attributes to ovulatory and steroidogenic capacity of large antral follicles in sheep

Ovarian steroidogenesis and antral follicular development in ewes, following the treatment with medroxyprogesterone acetate (MAP) and equine chorionic gonadotrophin (eCG), are affected by the reproductive season. The objective of this study was to compare the ultrasonographic attributes of large antral follicles between cyclic (December) and seasonally anovular (June-July) ewes, after a 12-day treatment with MAP-soaked intravaginal sponges, with or without the administration of 500IU of eCG at sponge removal, and to determine whether there is a correlation between the ultrasonographic attributes of the follicular wall and serum concentrations of oestradiol. Digital images of ovulatory follicles from cyclic ewes and eCG-treated anoestrous ewes (n=34 follicles), and of anovulatory follicles attaining > or =5mm in control anoestrous ewes (n=8 follicles), were analysed using the spot and line techniques designed to determine the echotextural characteristics of the follicular antrum (central and peripheral), follicular wall and perifollicular ovarian stroma. The mean diameter of ovulatory follicles was greater (P<0.001) in cyclic than anoestrous ewes, with or without the eCG treatment. The mean pixel heterogeneity (SD of numerical pixel values) of the follicular antrum (P<0.05), as well as mean pixel intensity and heterogeneity of the peripheral antrum, follicular wall proper and perifollicular ovarian stroma (P<0.05), were consistently greater in anoestrous than cyclic ewes at the time of sponge removal and 24h after the treatment with MAP sponges or MAP/eCG. Mean oestradiol concentrations were greater (P<0.05) in cyclic compared to anoestrous ewes in both MAP- and MAP/eCG-treated animals, from 1 to 2 days after sponge withdrawal. There was a moderate negative correlation (r(2)=0.12, P<0.05; Pearson's Product Moment and r(2)=0.23, P<0.05; ANCOVA) between mean pixel heterogeneity (standard deviation of mean pixel values) of the follicular wall proper (all follicles > or =5mm in diameter) and serum concentrations of oestradiol after sponge withdrawal. Our results indicate that large antral follicles from cyclic and seasonally anovular ewes exhibit distinctive ultrasonographic characteristics. The differences in follicular echotexture appear to be related mainly to seasonal variations in ovarian follicular morphology and oestradiol production.