Restoring ovulation in beef donor cows with ovarian cysts by progesterone-releasing intravaginal silastic devices

Effect of Double-Ovsynch and Presynch-Ovsynch on postpartum ovarian cysts and inactive ovary in high-yielding dairy cows

Introduction

Optimizing the management of dairy cattle reproduction can reduce postpartum ovarian disease in high-yielding dairy cows and thus enhance ranch economic benefit. The hypothesis of this study was that the Double-Ovsynch (DO) protocol in high-producing dairy cows would result in a lower incidence of follicular cysts but a higher incidence of luteal cysts compared to those undergoing the Presynch-Ovsynch (PS) protocol.

Methods

In this experiment, 384 cows (204 primiparous and 180 multiparous) were allocated to the DO group, which followed the protocol: GnRH-7d-PGF2α-3d-GnRH-7d-Ovsynch-56 h (GnRH-7d-PGF2α-56 h-GnRH-16hTAI), starting on 39 ± 3 days in milk (DIM). Additionally, 359 cows (176 primiparous and 183 multiparous) were assigned to the PS group, which followed the protocol: PGF2α-14d-PGF2α-12d-Ovsynch-56 h, starting on 31 ± 3 DIM. In DO, B-mode ultrasound examinations were conducted 1 day after the GnRH-7d-PGF2α-3d-GnRH protocol to diagnose the presence of ovarian diseases followed by reexamination after 7 days of suspected cases. In PS, B-mode ultrasound examinations were conducted 1 day after the PGF2α-14d-PGF2α protocol to diagnose the presence of ovarian diseases followed by reexamination after 7 days. For all cows confirmed to having ovarian diseases, a second B-mode ultrasound examination was conducted at the time of the second GnRH and timed artificial insemination (TAI). If the ovary showed a normal developing follicle in combination with normal ovulation, the ovarian disease was considered to be cured.

Results

The current study revealed no significant difference in the overall incidence and cure rate of postpartum ovarian diseases between DO and PS (incidence rate: 3.9% vs. 6.7%, cure rate: 50% vs. 41.7%, DO vs. PS). Also, there was no significant difference in the incidence and cure rate of luteal cysts between DO and PS (incidence rate: 2.9% vs. 2.2%, cure rate: 50.0% vs. 50.0%). The incidence of follicular cysts was significantly lower in the DO group than in the PS group (0.8% vs. 2.8%, DO vs. PS, p = 0.037), but there was no significant difference in the cure rates (66.7% vs. 50%). The occurrence of inactive ovary was lower in DO compared to PS (0.2% vs. 1.7%, p = 0.047). There was no significant difference in the pregnancy rate between the DO and PS groups (48.2% vs. 41.8%), although the DO group had a higher rate. What is different from our assumption is that PS did not effectively reduce the incidence of postpartum luteal cysts.

Changes in the ovary and the peripheral concentrations of sex hormones after the aspiration of follicular fluid from the spontaneous follicular cysts of dairy cows

The aim of the present study was to clarify the ovarian and hormonal dynamics after the aspiration of follicular fluid in cows with follicular cysts. Follicular fluid was aspirated from the follicular cysts and follicles that were fated to become cystic follicles and other coexisting normal follicles, respectively, in lactating cows (n = 3). After the aspiration procedure, new follicles developed and reached a diameter of 25 mm without ovulation within 13–19 days. The plasma concentrations of inhibin decreased and follicle-stimulating hormone increased rapidly after the aspiration procedure, and subsequently increased and decreased, respectively, as a new follicle grew. No luteal structures developed after the aspiration procedure, and the animals’ plasma progesterone levels remained low. The present study indicates that the cystic follicles are never luteinized by the aspiration of follicular fluid, and consequently, new follicular cysts are observed to repeatedly develop.

Efficacy of ovulation synchronization with timed artificial insemination in treatment of follicular cysts in dairy cows

The efficacy of five ovulation-synchronization protocols with FTAI in treatment of cows diagnosed with follicular cysts was investigated in a nonrandomized study in a single herd. Cows identified with follicular structures >25 mm on two subsequent ultrasonographic (USG) examinations 7-10 days apart (n = 552) were assigned to one of the five treatment regimens on the day of the second USG examination. Treatment regimens were Ovsynch (GnRH-7d-PGF2α-56 h-GnRH-16 h-FTAI), New-CIDR (as Ovsynch with a new CIDR insert being fitted between days 0 and 7), Reused-CIDR (as New-CIDR but the CIDR insert was previously used for 7 days in another cow), G-New CIDR (Pre-GnRH on day 0 with the New-CIDR regimen being initiated 7 days later), and RG-Ovsynch (Pre-GnRH on day 0 and then every 7 days until detection of a luteal structure upon USG examination; at that point the Ovsynch was initiated). A subset of cows was subjected to ovarian USG examination at the time of PGF_2α administration, at insemination, and 8-10 days post-insemination. Progesterone-releasing ability of new and reused CIDR inserts were evaluated in cows diagnosed with severe ovarian inactivity (n = 16). The data were analyzed using logistic regression with pregnancy per AI on days 30 (P/Al 30) and 70 (P/AI 70) post-insemination were included as outcome measures. Compared with Ovsynch, RG-Ovsynch improved the P/AI 30 (OR = 2.6, P = 0.03) and the P/AI 70 (OR = 2.5, P = 0.05). New-CIDR and G-New CIDR were associated with non-significant increase in P/AI 30 (OR = 2.1, P = 0.09 and OR = 2.3, P = 0.07, respectively) and P/AI 70 (OR = 2.01, P = 0.09 and OR = 2.2, P = 0.09, respectively). Reused-CIDR was not associated with improvement in P/AI (P = 0.93 and 0.79 for P/AI 30 and P/AI 70, respectively). RG-Ovsynch had a longer diagnosis-to-FTAI interval (median 24, IQR 17,31). The dominant ovarian structures and the presence of a cyst or a luteal structure at PGF_2α administration or at insemination were not associated with P/AI. The new and re-used CIDR inserts produced comparable concentrations of serum progesterone 3 h, 3 days and 7 days post CIDR insertion. In conclusion, the RG-Ovsynch improved the P/AI whereas the New-CIDR and the G-New CIDR regimens tended to increase the P/AI compared with Ovsynch. Marginal differences in P/AI between RG-Ovsynch, New-CIDR, and G-New-CIDR together with prolonged diagnosis-to-FTAI in RG-Ovsynch should be considered if to evaluate the economic value of these regimens.

Research of postpartum endometritis in Japanese Black cattle with cystic ovarian disease by vaginal mucus test and endometrial cytology

The relationship between endometritis and cystic ovarian disease (COD) is still unclear in Japanese Black cattle. Endometritis is classified into clinical endometritis (CE) and subclinical endometritis (SE). The objective of this study was to clarify the interaction between postpartum endometritis (CE and SE) and COD in Japanese Black cattle. Twenty-six suckled cows with COD (COD group) and 16 suckled cows with cyclical ovarian activity (CA group) were submitted for the experiment. Uterine conditions of cows were classified into three groups (normal, CE, and SE) with vaginal mucus test and endometrial cytology. The combined data of CE and SE were represented as data for total endometritis (EMT total). The prevalence of EMT total in the COD group (42.3 %, 11 / 26 ) was significantly higher than that of the CA group (12.5 %, 2 / 16 ). The mean percentage of polymorphonuclear neutrophils (PMN %) in the COD group was significantly higher than that of the CA group at 40-60 DPP (days postpartum). Compared to 61-295 DPP, the mean PMN % at 40-60 DPP was significantly higher in the COD group. The diameters of uterine horn and cervix did not differ among normal uterine condition, CE and SE in the COD group, and they did not differ between normal uterine condition and SE in the CA group. However, endometrial thickness during both 40-60 and 61-295 DPP were greater in the COD group than in the CA group. In conclusion, Japanese Black cattle with COD have a potential implication on endometritis at 40-60 DPP compared to the normal ovarian cycle. As a specific symptom was not observed by transrectal ultrasonography, endometrial cytology is effective for diagnosis of SE in Japanese Black cattle.

Progestin exposure before gonadotropin stimulation improves embryo development after in vitro fertilization in the domestic cat

This study investigated the influence of progestin priming and ovarian quiescence on response to exogenous gonadotropin stimulation in the cat. Because a subpopulation of cats routinely ovulated spontaneously, there also was the opportunity to examine the ovary's reaction to the added impact of endogenously secreted progestagen. Queens were given 1) equine chorionic gonadotropin (eCG) plus human chorionic gonadotropin (hCG) only (control; n = 9 cats), 2) GnRH antagonist (antide) injections followed by eCG and hCG (n = 9), and 3) a progestin implant (levonorgestrel) followed by eCG and hCG (n = 9). Laparoscopy was used to assess ovarian activity and aspirate follicular oocytes that were graded on the basis of morphology. In five cats per treatment, half of the high-quality oocytes were assessed for glucose, pyruvate, and lactate metabolism as well as nuclear maturation. Remaining oocytes were inseminated in vitro, cultured, and examined at 72 h after insemination for cleavage. In the remaining four cats per treatment, all oocytes were inseminated in vitro and assessed at 72, 120, and 168 h after insemination for embryo developmental stage. Cats pretreated with progestin had more follicles and produced more embryos per donor (including at the combined morula/blastocyst stage) than controls or females treated with GnRH antagonist (P < 0.05). There were no differences among groups (P > 0.05) in oocyte carbohydrate metabolism, nuclear maturation metrics, or fertilization success, although there was a tendency toward improvements in all three (P < 0.2) in progestin-treated females. Interestingly, cats that spontaneously ovulated within 60 days of treatment onset also produced more embryos per cat than induced-ovulation counterparts (P < 0.05). Results indicate that prior exposure to exogenous progestin (via implant) or endogenous progestagen (via spontaneous ovulation) improves ovarian responsiveness to gonadotropins in the cat through a mechanism that is independent of the induction of ovarian quiescence.

Comparison of aspiration and hormonal therapy for the treatment of ovarian cysts in cows

Despite the variety of hormonal treating regimes used, a proportion of cows with cystic ovarian disease (COD) fail to be cured. The hypothesis of this study was that cyst aspiration would improve the curing rate and/or accelerate the resumption of ovarian activity in affected cows. In four groups of cows the following treatments were administered: Group A (n = 18) only cyst aspiration, Group AGP (n = 19) cyst aspiration and a combination of GnRH and PGF 2alpha , Group GP (n = 25) only GnRH and PGF 2alpha , and Group C (n = 15) untreated control. Cysts were aspirated without ultrasonographic guidance, using a new device. All cows from Group AGP responded to treatment, while 5.5% from Group A and 16% from Group GP remained anoestrous (P < 0.05). These refractory cases were re-treated with the AGP protocol and exhibited oestrus within 12.4 +/- 1.1 days. The interval from PGF 2alpha injection to oestrus was significantly reduced in cows treated with cyst aspiration. Until day 80 post partum (pp), 11 of the 15 untreated cows (73.3%) retained the initial cyst and remained anoestrous. It is concluded that persisting cases of COD can be treated by combining aspiration with a hormonal regime. The technique presented here has no complication for the cow, is efficient, easy, safe for the operator, and requires low-cost equipment.

Comparison of the effect of estradiol benzoate plus progesterone and GnRH on the follicular wave emergence and subsequent follicular development in CIDR-treated, lactating dairy cows with follicular cysts

This study examined the effect of estradiol benzoate (EB) plus progesterone (P4) as compared with GnRH on follicular wave emergence and follicular development, and synchrony of ovulation and pregnancy rates following a second injection of GnRH in a controlled internal drug release (CIDR)-based timed AI (TAI) protocol in lactating dairy cows with follicular cysts. Lactating dairy cows diagnosed with follicular cysts received a CIDR device, with an injection of 2mg EB plus 50mg P4 (EB+P4 group) or with an injection of 100 microg GnRH (GnRH group) at the beginning of the experiment (day 0). Thereafter, all received PGF(2alpha) at the time of CIDR removal on day 7, GnRH on day 9, and TAI 16 h later. Follicular wave emergence occurred within 7 days in 12/15 EB plus P4-treated and 14/15 GnRH-treated cows (P>0.05). The interval to wave emergence was longer in the EB+P4 group (4.8+/-0.4 days) than in the GnRH group (2.0+/-0.2 days). The mean diameters of preovulatory follicles and the proportion of cows with preovulatory follicles greater than 12 mm on day 9 did not differ between groups (P>0.05). The proportion of cows with synchronized ovulations by 40 h after the GnRH injection on day 11 and pregnancy rates to TAI did not differ between the EB+P4 (13/15 and 36.7%) and the GnRH (14/15 and 53.3%) groups, respectively. Results suggest that a single treatment with EB plus P4 as compared with GnRH simultaneously with CIDR insertion in lactating dairy cows with follicular cysts will result in relatively asynchronous emergence of a new follicular wave, but subsequently similar sizes of preovulatory follicles and synchronous ovulation, resulting in similar pregnancy rates to TAI.

Comparison of synchronization of ovulation with timed insemination and exogenous progesterone as therapeutic strategies for ovarian cysts in lactating dairy cows

The objective of this study was to compare the effectiveness of the Ovsynch and controlled internal drug releasing (CIDR) protocols under commercial conditions for the treatment of cystic ovarian disease in dairy cattle. A total of 401 lactating dairy cows with ovarian cysts were alternatively allocated to two treatment groups on the day of diagnosis. Cows in the Ovsynch group were treated with GnRH on Day 0, PGF2alpha on Day 7, GnRH on Day 9, with timed insemination 16-20 h later. Cows in the CIDR group were treated with a CIDR insert on Day 0 for 7 days; on Day 7, the CIDR was removed, and cows were treated with PGF2alpha. All cows in the CIDR group were observed for estrus and cows exhibiting estrus within 7 days following removal of the CIDR and PGF2alpha administration were inseminated. The outcomes of interest for this experiment were the likelihood to be inseminated, return to cyclicity (determined by a CL on Day 21), conception and pregnancy rates. Data for these variables were analyzed using logistic regression. The percentage of cows inseminated in the Ovsynch and CIDR groups were 82 and 44%, respectively. Cows in the Ovsynch group were 5.8 times more likely to be inseminated than cows in the CIDR group. Cows with a low BCS were 0.48 times less likely to be inseminated than cows with a high BCS. The percentage of cows with a CL on Day 21 for the Ovsynch and CIDR groups was 83 and 79%, respectively (P > 0.05). Cows with a low BCS were 0.49 times less likely to have CL on Day 21 than cows with a high BCS. Conception and pregnancy rates for cows in the Ovsynch group were 18.3 and 14.4%, respectively. Conception and pregnancy rates for cows in the CIDR group were 23.1 and 9.5%, respectively. There was no significant differences between conception or pregnancy rates in cows in both groups. Primiparous cows were 2.6 times more likely to conceive than multiparous cows. In conclusion, the results of this study suggested that fertility was not different between cows with ovarian cysts treated with either the Ovsynch or the CIDR protocols in this dairy herd. In addition, primiparous cows had an increased likelihood for conception compared to multiparous cows, and cows with a low BCS were less likely to be inseminated or have a CL on Day 21, regardless of treatment.

Fetal programming: prenatal testosterone treatment leads to follicular persistence/luteal defects; partial restoration of ovarian function by cyclic progesterone treatment

Prenatal testosterone (T) excess during midgestation leads to estrous cycle defects and polycystic ovaries in sheep. We hypothesized that follicular persistence causes polycystic ovaries and that cyclic progesterone (P) treatment would overcome follicular persistence and restore cyclicity. Twice-weekly blood samples for P measurements were taken from control (C; n = 16) and prenatally T-treated (T60; n = 14; 100 mg T, im, twice weekly from d 30-90 of gestation) Suffolk sheep starting before the onset of puberty and continuing through the second breeding season. A subset of C and T60 sheep were treated cyclically with a modified controlled internal drug-releasing device for 13-14 d every 17 d during the first anestrus (CP, 7; TP, 6). Transrectal ovarian ultrasonography was performed for 8 d in the first and 21 d in the second breeding season. Prenatal T excess reduced the number, but increased the duration of progestogenic cycles, reduced the proportion of ewes with normal cycles, increased the proportion of ewes with subluteal cycles, decreased the proportion of ewes with ovulatory cycles, induced the occurrence of persistent follicles, and reduced the number of corpora lutea in those that cycled. Cyclic P treatment in anestrus, which produced one third the P concentration seen during luteal phase of cycle, did not reduce the number of persistent follicles, but increased the number of progestogenic cycles while reducing their duration. These findings suggested that follicular persistence might contribute to the polycystic ovarian morphology. Cyclic P treatment was able to only partially restore follicular dynamics, but this may be related to the low replacement concentrations of P achieved.

Formation of Follicular Cysts in Cattle and Therapeutic Effects of Controlled Internal Drug Release

Follicular cysts in cattle result from excessive growth of the dominant follicle without ovulation and still constitute a major reproductive disorder in this species. One key hormonal characteristic of cows with follicular cysts is the lack of an LH surge, although they have increased plasma estradiol concentrations. Another is a relatively high level of pulsatile secretion of LH that promotes continued growth of the dominant follicle. These LH characteristics seem to result from a functional abnormality in the feedback regulation of LH secretion by estradiol. Treatment with controlled internal drug release devices that increase circulating progesterone levels is effective in resolving follicular cystic conditions by 1) lowering pulsatile LH secretion and 2) restoring the ability of the hypothalamo-pituitary axis to generate an LH surge in response to an increase in circulating estradiol.

Effect of CIDR-based protocols for timed-AI on the conception rate and ovarian functions of Japanese Black beef cows in the early postpartum period

Our objectives were to compare: (1) conception rates (in early postpartum Japanese Black beef cows) to timed-artificial insemination (timed-AI) among Ovsynch and Ovsynch plus CIDR protocols, and a protocol that used estradiol benzoate (EB) in lieu of the first GnRH of the Ovsynch plus CIDR; and (2) the effects of these protocols on blood concentrations of ovarian steroids. Cows in the control group (Ovsynch; n=35) underwent a standard Ovsynch protocol (GnRH analogue on Day 0, PGF(2 alpha) analogue on Day 7 and GnRH analogue on Day 9), with timed-AI on Day 10, approximately 20 h after the second GnRH treatment. Cows in the Ovsynch+CIDR group (n=31) received a standard Ovsynch protocol plus a CIDR for 7 days (starting on Day 0). Cows in the third treatment group (EB+CIDR+GnRH; n=41) received 2mg of EB on Day 0 in lieu of the first GnRH treatment, followed by the same treatment as in the Ovsynch+CIDR protocol. The conception rate tended to be greater in the Ovsynch+CIDR group (67.7%, P<0.15) and was greater in the EB+CIDR+GnRH (73.2%, P<0.05) and CIDR-combined (both CIDR-treated groups were combined) groups (70.8%, P<0.05) than in the Ovsynch group (48.6%). Plasma progesterone concentrations were higher on Day 7 (P<0.01) and lower on Days 14, 17 and 21 (P<0.001) in the CIDR-combined group than in the Ovsynch group. Plasma estradiol-17beta concentrations were higher on Day 7 in the Ovsynch group of non-pregnant cows than in the CIDR-combined group of non-pregnant cows and in an all-combined group (all treatment groups combined) of pregnant cows (P<0.01). Furthermore, estradiol-17beta concentrations were lower on Day 9 in the Ovsynch and CIDR-combined groups of non-pregnant cows than in the all-combined group of pregnant cows (P<0.05). In conclusion, both protocols using CIDR improved conception rates following timed-AI in early postpartum suckled Japanese Black beef cows relative to the Ovsynch protocol. Treatment with a CIDR may prevent early maturation of follicles observed in non-pregnant cows treated with the Ovsynch protocol, by maintaining elevated blood progesterone concentrations until PGF(2 alpha) treatment.

GnRH treatment at CIDR insertion influences ovarian follicular dynamics in Japanese black cows

Ovarian follicular dynamics and estrous synchronization after Gonadotropin-releasing hormone (GnRH) treatment at Controlled Internal Drug Releasing device (CIDR) insertion were investigated in Japanese Black cows. CIDR was inserted for eight cows at 7 days after estrus. Cows were allocated to either Group A: 8-day CIDR insertion with GnRH treatment on d 0 (n=4, d 0=CIDR insertion) or Group B: 8-day CIDR insertion (n=4). Both groups were injected with prostaglandin F2alpha (PGF2alpha) on d 7. Ultrasonography and blood sampling were performed twice daily. Intensive sampling was performed every 15 min for 8 hr to determine the pulsatile release of LH on d -1, d 5 and d 10. Three of four cows showed intermediate ovulation within 2 days after GnRH treatment during CIDR insertion in Group A, whereas no ovulation was found in Group B. Three of four cows in Group A and all four cows in Group B ovulated after CIDR removal. Plasma progesterone concentrations from d 3 to d 7 in three intermediate ovulatory cows in Group A (8.4 +/- 1.6 ng/ml) was significantly higher than those in Group B (4.1 +/- 1.2 ng/ml; 4 cows) during CIDR insertion (P<0.01). Interval to estrus and ovulation after CIDR removal was observed at 60.0 +/- 12.0 hr and 76.0 +/- 6.9 hr in three cows in Group A, and 75.0 +/- 15.1 hr and 93.0 +/- 20.5 hr in Group B, respectively. There was a significant increase in LH pulse frequency on d 10 compared on d -1 or d 5 in both groups (P<0.05), in addition those on d 10 in Group A tended to be higher than in Group B. As a result, GnRH treatment at CIDR insertion at 7 days after estrus induced intermediate ovulation with formation of corpus luteum (CL) and rather synchronized emergence of ovulatory follicle during CIDR insertion. These induced CL increased plasma progesterone concentrations and contributed to precise synchronization.

Plasma concentrations of inhibin A in cattle with follicular cysts: relationships with turnover of follicular waves and plasma levels of gonadotropins and steroid hormones

We investigated the profiles of circulating levels of inhibin A and total inhibin in beef cows with follicular cysts in relation to the patterns of follicular development and circulating gonadotropins and steroid hormones. Turnover of follicular waves was monitored in five cows every 2 days for 70 days from 10 days after detection of estrus without ovulation. The mean interwave intervals were 19.6 +/- 1.0 days (n = 18 waves with cysts from the five cows). Circulating levels of inhibin A were approximately 170 pg/ml before emergence of follicular waves with cysts and increased (P < 0.05) concomitantly with follicle emergence. High concentrations of inhibin A (greater than 300 pg/ml) were noted for 7 days during the growth phase of cystic follicles, but inhibin A levels decreased gradually when development of the cysts reached a plateau. This profile of inhibin A was similar to those of total inhibin and estradiol, but was inversely related to the changes in plasma FSH concentrations. LH pulse frequency and mean concentrations of LH in cows with cysts were higher than those observed in the luteal phase of normal cyclic cows. These results indicate that the capacity to secrete inhibin, as well as estradiol, is maintained in cystic follicles, the growth of which is extended by LH secretion at levels greater than those seen in the normal luteal phase. Inhibin A plays an important role in the extension of interwave intervals by suppressing recruitment of a new cohort of follicles.

Tylosin does not affect GnRH-induced LH secretion in rams

The aim of this study was to investigate the effect of a therapeutic dose of Tylosin (Tylan 50) on gonadotropin releasing hormone (GnRH)-induced luteinizing hormone (LH) secretion in sheep. A total of 10 mature rams were divided into two groups by balancing body weights (bw) and body condition scores. Five of the rams received 10mg/kg Tylosin intramuscularly (i.m., Tylosin group), while the other five were given placebo (Control group), for 5 days. On Day 5, all the rams were injected intravenously (i.v.) with the GnRH agonist Ovarelin at 0.1 microg/kg bw. Blood samples were collected at -30, 0, 30, 60, 90, 120, 150, 180, 210, 240, and 270 min for measuring LH levels in the plasma. Three days after the cessation of Tylosin application (Day 8) the injection of GnRH was repeated at the same dose. Although LH secretion appeared to be lower on Day 8 compared to Day 5, there were no significant differences between the groups for the mean LH concentrations, total LH secretion, peak LH concentrations, timing of LH peak, duration of LH secretion, and LH secretions on Days 5 and 8. These results indicate the absence of a negative effect of a therapeutic dose of Tylosin on GnRH-induced LH secretion in rams.

An Update on Cystic Ovarian Degeneration in Cattle

Cystic ovarian degeneration (COD) is considered to be one of the most important causes of reproductive failure in cattle. There is a severe economic loss to dairy industry because COD increases days-open in the postpartum period and the culling rates. The disease process is a consequence of a mature follicle that fails to ovulate at the appointed time of ovulation in the oestrous cycle. This anovulatory follicular structure either regresses or persists as a follicular or luteal cyst depending upon its structural/functional characteristics. The cells lining the follicular cyst synthesize oestrogen that, in certain instances, forces the animal to exhibit clinical signs of nymphomania. Besides oestrogen production, as per recent findings, they are also capable of secreting varying amount of progesterone which may dictate their fate. The animals that carry a luteal cyst may tend to be in anoestrus as the higher amount of progesterone secreted by this luteinized structure may change the pattern of gonadotrophins' secretion. Present findings suggest that perturbation of the hypothalamo-hypophyseal-ovarian (HHO) axis, due to many exogenous and endogenous factors, as the cause for anovulation. For example, it has been suggested that lack of hypothalamic or hypophyseal response to the positive feedback effect of oestrogens that are secreted by the dominant follicle as one of the many causes. The non-physiological changes that occur in the receptor expression of the HHO axis for the hormones involved in maturation, deviation, dominance and ovulation of the follicle may be yet another cause. The changes that occur at the cellular and molecular level in the ovary (in response to the factors mentioned above) that contribute to anovulation remain to be documented. This approach would allow us to completely understand the disease process. Hitherto, hormonal preparations that release luteinizing hormone from the anterior pituitary or have luteinizing hormone-like action are used to treat follicular cysts. GnRH belongs to the former group and human chorionic gonadotrophin (hCG) hormone forms the latter group. Treatment with a luteolytic agent, prostaglandin F2alpha (PGF2alpha), is successful if a luteal cyst is diagnosed properly. Many agents may be developed in the future if the cellular and molecular pathways of the disease process are delineated. This article will review recent advances in our understanding of the pathogenesis of COD and suggest direction for future studies to completely understand the disease mechanism. This review will also discuss the existing method of treatments for cysts and methods proposed for treatment of cysts that tend to be refractory in nature.

A Direct Time-Resolved Fluoroimmunoassay (TR-FIA) for Measuring Plasma Estradiol-17.BETA. Concentrations in Cattle

A direct Time-Resolved Fluoroimmunoassay (TR-FIA) system for measuring estradiol-17beta (E(2)) in bovine plasma was developed and evaluated. A 100 microl sample of bovine plasma was used for a TR-FIA without prior extraction and purification. The dose-response curves of reference standards ranged from 0.0625 to 10 pg/well. The minimum detectable concentration of this assay system was 0.625 pg/ml, and 19 pg/ml of E(2) caused a 50% reduction of maximum binding. The intra- and inter-assay coefficients of variation were 10.2 and 17.4%, respectively. The plasma E(2) concentrations measured by direct TR-FIA correlated closely with those measured after extraction (r=0.939). The results in the present study indicate that the TR-FIA reagent for E(2), designed for human research can also be utilized, with some modification, for direct assaying in bovine plasma. This assay type seems to fulfill the requirements for safety, sensitivity, specificity, reproducibility and practical convenience.

Retrospective Analysis of the Efficacy of Controlled Internal Drug Release in Follicular Cysts in an Embryo Donor Beef Herd

We investigated the efficacy of a controlled internal drug release (CIDR) device in the reproductive management of an embryo donor beef herd. Superovulation of embryo donors was routinely induced by a combination of FSH and prostaglandin F(2)alpha analogue (PGF(2)alpha) at intervals of a few months, and after embryo recovery estrus of the donors was synchronized with PGF2(2)alpha. Between 1996 and 1998, approximately 20% of donors were diagnosed as having follicular cysts every year. Twenty-eight cases of follicular cysts recorded between 1997 and 1998 were treated with a CIDR device for 14 days to evaluate the efficacy of CIDR in resolving follicular cysts in donor herds. Initial recovery was defined as the occurrence of ovulation with estrous behavior and subsequent formation of a corpus luteum after removal of the CIDR. Initial recovery was recognized in all cases (n=28). Follicular cysts did not recur after repeated embryo recovery in 64% of the initially recovered donors, but in 36% of affected donors cysts recurred after the next embryo recovery. Subsequently, with a CIDR device instead of PGF(2)alpha, we synchronized estrus after embryo recovery in the same herd from 1999 to 2000, to investigate the ability of CIDR to prevent the initiation of follicular cysts. Of the donors used between 1999 and 2000, approximately 30% had a history of follicular cysts. Use of CIDR for estrous synchronization after embryo recovery lowered the incidence of follicular cysts to 3% in 1999 and 0% in 2000. Treatment with CIDR proved effective at resolving follicular cysts in the embryo donor beef herd and enabled re-use of donors affected with follicular cysts. CIDR is also likely to be efficacious in lowering the occurrence of follicular cysts in donor herds when it is used for estrous synchronization after embryo recovery.

Perturbation of estradiol-feedback control of luteinizing hormone secretion by immunoneutralization induces development of follicular cysts in cattle

We used immunoneutralization of endogenous estradiol to investigate deficiencies in the estradiol-feedback regulation of LH secretion as a primary cause of follicular cysts in cattle. Twenty-one cows in the prostaglandin (PG) F(2alpha)-induced follicular phase were assigned to receive either 100 ml of estradiol antiserum produced in a castrated male goat (n = 11, immunized group) or the same amount of castrated male goat serum (n = 10, control group). The time of injection of the sera was designated as 0 h and Day 0. Five cows in each group were assigned to subgroups in which we determined the effects of estradiol immunization on LH secretion and follicular growth during the periovulatory period. The remaining six estradiol-immunized cows were subjected to long-term analyses of follicular growth and hormonal profiles, including evaluation of pulsatile secretion of LH. The remaining five control cows were used to determine pulsatile secretion of LH on Day 0 (follicular phase) and Day 14 (midluteal phase). The control cows exhibited a preovulatory LH surge within 48 h after injection of the control serum, followed by ovulation of the dominant follicle that had developed during the PGF(2alpha)-induced follicular phase. In contrast, the LH surge was not detected after treatment with estradiol antiserum. None of the 11 estradiol-immunized cows had ovulation of the dominant follicle, which had emerged before estradiol immunization and enlarged to more than 20 mm in diameter by Day 10. Long-term observation of the six immunized cows revealed that five had multiple follicular waves, with maximum follicular sizes of 20-45 mm at 10- to 30-day intervals for more than 50 days. The sixth cow experienced twin ovulations of the initial persistent follicles on Day 18. The LH pulse frequency in the five immunized cows that showed the long-term turnover of cystic follicles ranged from 0.81 +/- 0.13 to 0.97 +/- 0.09 pulses/h during the experiment, significantly (P < 0.05) higher than that in the midluteal phase of the control cows (0.23 +/- 0.07). The mean LH concentration in the immunized cows was also generally higher than that in the luteal phase of the control cows. However, the LH pulse and mean concentration of LH after immunization were similar to those in the follicular phase of the control cows. Plasma concentrations of total inhibin increased (P < 0.01) concomitant with the emergence of cystic follicles and remained high during the growth of cystic follicles, whereas FSH concentrations were inversely correlated with total inhibin concentrations. In conclusion, neutralization of endogenous estradiol resulted in suppression of the preovulatory LH surge but a normal range of basal LH secretion, and this circumstance led to an anovulatory situation similar to that observed with naturally occurring follicular cysts. These findings provide evidence that lack of LH surge because of dysfunction in the positive-feedback regulation of LH secretion by estradiol can be the initial factor inducing formation of follicular cysts.

Alterations in peripheral concentrations of inhibin A in cattle studied using a time-resolved immunofluorometric assay: relationship with estradiol and follicle-stimulating hormone in various reproductive conditions

The aims of this study were to develop a sensitive and specific assay for bovine inhibin A using europium and to investigate the endocrine role of inhibin A in various reproductive conditions by characterizing the relationship between profiles of inhibin A, FSH, and estradiol and follicle growth during the postpartum period, during the intact estrous cycle, and in cows with follicular cysts. The time-resolved immunofluorometric assay (Tr-IFMA) for bovine inhibin A, using purified polyclonal antibodies to alpha and beta(A) subunits, was specific for bovine inhibin A and did not cross-react with bovine activin A, activin AB, activin B, pro-alphaC or human recombinant inhibin B. The detection limit of the IFMA was 3.3 pg/ml expressed in terms of bovine 32-kDa inhibin A. Dose-response curves of plasma samples obtained from intact and FSH-stimulated cows and cystic cows were parallel to the standard without any preassay processing of samples. Plasma inhibin A levels increased (P < 0.01) concomitant with emergence of nonovulatory or ovulatory follicular waves during the postpartum period. In cystic cows, plasma inhibin A was sustained at high levels for a longer period, associated with growth of persistent dominant follicles. The highest levels of inhibin A were noted during the growth phase of normal and persistent dominant follicles; however, inhibin A levels declined (P < 0.01) as these dominant follicles ceased to grow or ovulated. An inverse relationship between patterns of plasma inhibin A and FSH existed during each follicular wave in the three physiologic conditions. Increases in plasma inhibin A levels were associated with increases in plasma estradiol levels during most follicular waves; however, there was no increase in plasma estradiol level and no relationship between patterns of estradiol and FSH during follicular waves observed during the early postpartum period or midluteal phase of the estrous cycle. In conclusion, the Tr-IFMA does not require pretreatment of samples and can be used for precise measurement of bovine inhibin A without interference with free inhibin alpha subunits. Inhibin A, produced primarily during growth of the dominant follicle, functions as a negative feedback regulator for FSH secretion throughout the postpartum period and the estrous cycle, whereas estradiol appears to have a minor role in regulation of FSH compared with inhibin A, especially during the early postpartum period and midluteal phase of the estrous cycle. The results also indicate that a persistent dominant follicle sustains inhibin A production for a longer period than the dominant follicle emerging in the estrous cycle and establishes long-term dominance by suppressing emergence of a new follicular wave.