Timing of preovulatory LH surge and ovulation in superovulated sheep are affected by follicular status at start of the FSH treatment.

The aims of this study were to evaluate the chronology of periovulatory events (oestrus behaviour, LH surge and ovulation) in 16 superovulated Manchega sheep and to determine whether follicular status at start of the FSH supply might affect their occurrence. Mean timing for onset of oestrus behaviour was detected at 28.1 +/- 0.7 h after sponge withdrawal; the preovulatory LH surge and ovulation started at 37.2 +/- 0.7 h and 65.4 +/- 0.7 h after progestagen withdrawal, respectively. The intervals between oestrus, LH surge and ovulation were affected by a high individual variability, which might be the cause for reported decreased efficiency in embryo production. Current results also addressed the role of follicular status at start of the superovulatory treatment on the preovulatory LH surge and the ovulation. The interval LH surge-ovulation was increased in ewes with a growing dominant follicle at starting the FSH treatment (32.3 +/- 0.9 vs 28.6 +/- 0.5 h, p < 0.05). The developmental stage of the largest follicle at starting the superovulatory treatment also affected occurrence of LH surge and ovulation; follicles in growing phase advanced the occurrence of the LH surge and ovulation when compared to decreasing follicles (33.0 +/- 1.0 vs 43.5 +/- 1.1 h, p < 0.05, for LH peak and 60.7 +/- 1.1 vs 72.8 +/- 1.2 h, p < 0.05, for ovulation). Thus, only ewes with growing follicles ovulated prior to 55 h after sponge withdrawal; conversely, no sheep with decreasing follicles ovulated earlier than 67 h, when an 85.7% of the ewes bearing growing follicles has ovulated at 63 h.     

Preovulatory follicle development in goats following oestrous synchronization with progestagens or prostaglandins.

The study reports on differences in the dynamics of growth and functionality of preovulatory follicles in response to oestrous synchronization, either by the administration of two doses of prostaglandin or by an intravaginal progestagen sponge, in goats. The progestagen-treated group (n = 8) showed more follicles of preovulatory size (> or =5.5 mm) than the cloprostenol group (n = 8) during the follicular phase (4.5 +/- 0.6 vs 1.9 +/- 0.2, p < 0.01). The diameters of the largest follicles (LF1, LF2 and LF3) were also larger in the progestagen group (LF1, 7.8 +/- 0.3 vs 7.0 +/- 0.2 mm, p < 0.05; LF2, 6.7 +/- 0.2 vs 5.6 +/- 0.2 mm, p < 0.01; LF3, 5.5 +/- 0.3 vs 4.2 +/- 0.2 mm, p < 0.01). The study of the preovulatory follicles showed that 27.2% (3/11) of the follicles were in the static phase in the cloprostenol group, whilst 71.4% (10/14) were static in progestagen group (p < 0.05). Higher plasma oestradiol levels were recorded in the progestagen-treated goats during the 48 h prior to cloprostenol injection or progestagen withdrawal (4.2 +/- 0.4 vs 3.0 +/- 0.2 pg/ml, p < 0.05). In conclusion, goats with oestrus synchronized by progestagen showed a higher number of preovulatory-sized follicles, but a decreased oestradiol secretion when compared with does with oestrus synchronized by using prostaglandin analogues. These would support the development of alternative protocols for assisted reproduction.     

Development of One vs Multiple Ovulatory Follicles and Associated Systemic Hormone Concentrations in Mares

Ablation of follicles ≥  6 mm in diameter and treatment with PGF2α 10 days after ovulation were used to induce the development of ovulatory waves. Comparisons were made between induced waves with one (33 waves, 72%) and multiple (13 waves, 28%) ovulatory follicles. Diameter deviation was defined as the separation of follicles into dominant and subordinate categories. Multiple ovulatory follicles were preceded by more (p < 0.001) follicles ≥ 20 mm at the beginning of deviation, higher LH preceding deviation (approached significance, p < 0.08), lower (p < 0.05) concentrations of FSH on the day of deviation and thereafter, and higher (p < 0.0003) oestradiol by 2 days after deviation. During the peri-ovulatory period, systemic hormone concentrations for waves with multiple ovulations involved higher oestradiol before ovulation (approached significance, p < 0.07), lower FSH (p < 0.04) before and after ovulation, and both higher progesterone (p < 0.05) and lower LH (p < 0.05) beginning the day after ovulation. Results indicated that by the beginning of deviation there were more follicles ≥  20 mm and subsequently greater oestradiol production in waves that led to the development of multiple ovulatory follicles, and during the peri-ovulatory period differences between one and multiple ovulations were consistent with the negative effects of the ovarian hormones on the gonadotropins.     

牛和绵羊在超数排卵情况下排卵受阻的卵巢组织学和内分泌研究

乏情母牛50头、有周期活动母绵羊38头,超排处理引起发情后的4(羊)或7～8(牛)天摘取卵巢进行组织学研究。观察到排卵阻断的5种类型:(1)典型黄体但包含未排的卵母细胞,(2)由未破卵泡黄体化而形成的非典型黄体,(3)纤维性结缔组织团块,其中有散在性黄体细胞(仅见于牛),(4)具备葛拉夫氏泡典型结构的滞留卵泡,(5)颗粒膜已黄体化的滞留卵泡。50头牛中共有滞留卵泡(≥10mm)127个、正常黄体29个、非正常黄体20个。严寒和饥饿可能是卵泡囊肿普遍发生的主要原因。试验牛曾用18甲基炔诺酮药管处理9天。在植入和取出药管时各注射1次(共2次)PMSG的母牛,具有很高的(28/30)早期反应率(出现≥3个卵泡的母牛数/接受处理的母牛数),而仅在去管时1次注射PMSG者,反应微弱(4/20)。试验羊中,只有单一用FSH处理者,在发情当天血清E_2—17β浓度形成峰值(168.1pg/ml),而且正常黄体数亦略高(P<0.1)于用FSH加LH处理者。发情后4天血清P_4浓度则以后者为高(P<0.05)。绵羊滞留卵泡表现为孕酮优势,卵泡液中E_2—17β对P_4的浓度比为1∶46。     

Preovulatory changes in follicular prostaglandins and their role in ovulation in cattle.

Indomethacin (INDO, n = 5) or vehicle (CONTROL, n = 4) was injected into superovulated heifers at 48 and 60 h following a luteolytic cloprostenol injection (0 h). One heifer from each group was ovariectomized (OVX) at 48, 56, 64 and 72 h. The fifth heifer of the INDO group was OVX at 80 h. Blood samples were collected at 0 h, every 2 h between 37 and 47 h, and at the time of each OVX to monitor plasma progesterone (P4) and luteinizing hormone (LH) concentrations. Following each OVX, the number and size of follicles were recorded and the incidence of ovulation determined. Follicular fluid (FF) was aspirated from follicles greater than or equal to 8 mm to determine the concentration of prostaglandins E2 (PGE2) and F2 alpha (PGF2 alpha). The highest PG concentrations were measured in both groups at 24-25 h following the preovulatory LH surge and the PGF2 alpha concentration at this time was significantly greater (p less than 0.01) in the CONTROL group compared to the INDO group. By 35-36 h after the LH surge, 75% (25/34) of the CONTROL follicles had ovulated, whereas there were no ovulations (0/50) on either ovary of the INDO treated heifer. These preliminary results suggest that the preovulatory rise of PGs in FF, particularly PGF2 alpha, is essential for ovulation and that suppression of this rise with indomethacin will inhibit ovulation in heifers.     

Origin and characterisation of preovulatory follicles of hyperstimulated oestrous cycles in goats

The origin and evolution of preovulatory follicles (POF) in 9 hyperstimulated (polyovulatory) Serrana goats were characterised. After oestrus synchronisation and detection, transrectal ovarian ultrasonography was performed daily during two complete oestrous cycles. Blood samples were taken every 4 h during 24 h after oestrus detection for preovulatory LH peak and twice a week for plasma progesterone determinations. The interovulatory interval of 14 oestrous cycles with double ovulations was 21.1 +/- 0.3 days. The onset of ovulatory follicular wave occurred 4 days (-3.9 +/- 0.3 days, n = 14) prior to the ovulation day (day 0) with a POF size of 6.9 +/- 0.2 mm (n = 28). In goats with ovulations in both ovaries (78.6%), the emergence of the first POF occurred earlier (-4.1 +/- 0.3 days) than the second POF (-3.3 +/- 0.2 days, n = 11, P < 0.05). No differences in the total number of follicles > or = 2 mm were found between the day of POF emergence (4.3 +/- 0.4) and the day before ovulation (3.5 +/- 0.3, P > 0.05). These results showed the existence of a delay between the emergence of first and second POF and suggest a weak dominance effect in goats with double ovulations.     

Peri-oestrus hormone profiles and follicle growth in lactating sows with oestrus induced by intermittent suckling.

This study describes follicle dynamics, endocrine profiles in multiparous sows with lactational oestrus compared with conventionally weaned sows (C). Lactational oestrus was induced by Intermittent Suckling (IS) with separation of sows and piglets for either 12 consecutive hours per day (IS12, n = 14) or twice per day for 6 h per occasion (IS6, n = 13) from day 14 of lactation onwards. Control sows (n = 23) were weaned at day 21 of lactation. Pre-ovulatory follicles (> or =6 mm) were observed in 100% of IS12, 92% of IS6 and 26% of C sows before day 21 of lactation and in the remaining 74% C sows within 7 days after weaning. All sows with pre-ovulatory follicles showed oestrus, but not all sows showed ovulation. Four IS6 sows and one IS12 sow developed cystic follicles of which two IS6 sows partially ovulated. Follicle growth, ovulation rate and time of ovulation were similar. E(2) levels tended to be higher in IS sows (p = 0.06), the pre-ovulatory LH surge tended to be lower in IS12 (5.1 +/- 1.7 ng/ml) than in C sows (8.4 +/- 5.0 ng/ml; p = 0.08) and P(4) levels were lower in IS12 and IS6 than in C sows (at 75 h after ovulation: 8.8 +/- 2.4 ng/ml vs 7.0 +/- 1.4 ng/ml vs 17.1 +/- 4.4 ng/ml; p < 0.01). In conclusion, sows with lactational oestrus induced by IS are similar to weaned sows in the timing of oestrus, early follicle development and ovulation rates, but the pre-ovulatory LH surge and post-ovulatory P(4) increase are lower.     

Physiological mechanisms of ovarian follicular growth in pigs--a review

Follicular growth after antrum formation is determined by follicle-stimulating hormone (FSH). Only two ways are possible for recruited follicles, continuing development or atresia. In gilts, intensive ovarian follicular growth begins between 60 and 100 days of age, and fluctuations of the ovarian morphological status last about 20 days; however, at that time there are no really large follicles. Final follicular development is under luteinising hormone (LH) control; this is why the attainment of puberty is related to an increase in serum oestradiol to a level that causes a preovulatory surge of this gonadotropin. The pool of follicles at the beginning of the oestrous cycle is about 30-40, most of which are small (< 3 mm) and growing. Then, the pool of follicles increases to about 80 in the mid-luteal phase but about 50 of them are small and 30 are medium sized (3-6.9 mm). Some of these follicles are in the growing phase, but some are atretic. Between days 7 and 15 of the oestrous cycle the percentage of atretic follicles fluctuates between 12 and 73%. At that time there are no large (> 7 mm) follicles because of the suppressing effect of progesterone. The number of small follicles declines after luteolysis. From the pool of medium follicles, large follicles are selected under the influence of LH, but about 70% of the medium-sized follicles become atretic. Because of the long-lasting selection process there is a significant heterogeneity in the diameter of large follicles in oestrus. However, the number of follicles correlates with the number of corpora lutea after ovulation. Individual follicular development and the relationship between follicles are still poorly known. The use of ultrasonography may give a closer insight into these phenomena.     

Multiple Factors Affecting Superovulation in Poll Dorset in China

To expand the breeding flock of Poll Dorset sheep in China, multiple ovulation and embryo transfer breeding program was applied to the limited number of imported Australian Poll Dorset sheep. This study investigated the effects of FSH from three different manufacturers, parity (nulliparous vs multiparous), repeated superovulation, oestrus induction, corpus luteum regression and oestrus delay on Poll Dorset superovulation. The results showed that gonadotropin FSH from Canada Folltropin‐V (Ca‐FSH) was successfully used for superovulatory treatment with 160 mg–200 mg dosage per ewe and recovered 12.91 ± 7.80 embryos. Multiparous ewes for superovulation treatment were significantly better nulliparous ewes (p < 0.05). The successive superovalution treatment reduced significantly embryo collection but did not affect transferable embryo number. Ewes with natural oestrus resulted in significantly higher number of embryos (13.83 ± 4.64) and of transferable embryos (12.00 ± 5.76) than ewes with induced oestrus (7.00 ± 4.92; 4.22 ± 3.42) and unknown oestrus cycle (5.94 ± 3.38; 3.19 ± 2.56, p < 0.05). The delayed oestrus ewes at 24 h after superovulatory treatment produced significantly fewer embryos and transferable embryos (0.92 ± 1.51 vs 0.42 ± 0.90) than those with normal oestrus (p < 0.01). Furthermore, the more transferable embryos were recovered from ewes with normal corpus luteum than those with corpus luteum regression (5.88 ± 5.09 vs 3.59 ± 4.30 and 8.83 ± 5.75 vs. 6.66 ± 5.41, p < 0.01). These results suggest that in our farm practice, a comprehensive treatment method by using the Canadian FSH (Folltropin‐V), plus choosing multiparous and natural oestrus ewes with normal corpus luteum might obtain an optimum embryo collection and embryos transfer in sheep.     

Ultrasonographic studies on ovarian dynamics and associated estrus manifestations of jennies under controlled management, Ethiopia

A serial ultrasonographic study was conducted on nine jennies aged 5–15 years from January to April 2008 with the objective of studying ovarian follicular dynamics and estrus manifestations under controlled management. Ovarian follicular activity was determined from the number and size distribution of follicles, length of interovulatory interval (IOI), growth rate of preovulatory follicles, diameter of follicles at the onset of estrus, and incidence of ovulation. Estrus manifestations were characterized using length of estrus and estrous cycle. The mean (±SD) number of follicle detected per ovary was 5.45?±?2.3 (range, 1–16) with sizes ranging from 2.9 to 44 mm. The mean (±SD) size of follicle encountered at the onset of estrus was 25.9?±?3.7 mm (range, 20.9–34.4) while that of the preovulatory follicles at ?1 day before ovulation was 36.81?±?3.78 mm. The mean (±SD) IOI, estrus, and estrous cycle length were 25.4?±?3.6, 7.9?±?2.9, and 24.2?±?7.4 days, respectively. The mean (±SD) growth rate of the preovulatory follicle after the day of divergence was 1.9?±?0.3 mm/day. Serum progesterone profile followed the same patterns of ovarian dynamics with maximum values being detected during midluteal phase. Serum progesterone assay revealed blood progesterone profiles of <1.0 ng/ml during estrus and up to 11 ng/ml during midluteal phase with a pattern following follicular dynamics. Body condition of the study jennies steadily increased and was positively correlated (r?=?0.52, p?<?0.001) with the diameter of the preovulatory follicle. In conclusion, the ultrasonic evaluation has revealed that follicular dynamics of jennies were generally related with body condition which might have been influenced by the type of management.     

Changes in LH Pulsatility Profiles in Dairy Heifers During Exposure to Oestrous Urine and Vaginal Mucus

Difficulty in observing oestrus is a problem for many dairy farmers performing AI. Finding ways to synchronize oestrous cycles or strengthen display of oestrus without hormonal treatments would be of great interest because many consumers object to the use of exogenous hormones on healthy animals. Modification of reproductive cycles through chemical communication has been reported in several species including cattle. LH is an important regulator of the follicular phase and could possibly be subject to pheromonal influence. This study focuses on the effect of volatile compounds from oestrous substances on LH pulsatility preceding the preovulatory LH surge in cattle. Four heifers of the Swedish Red breed were kept individually in isolation. Exposure to water during the control cycle (CC), and bovine oestrous urine and vaginal mucus during the treated cycle (TC), started simultaneously with induction of oestrus. Blood sampling at 15‐min intervals started 37 h after administration of PGF_2α and continued for 8 h. Monitoring of reproductive hormones, visual oestrus detection and ultrasonographic examination of the ovaries continued until ovulation had occurred. The mean concentration of LH at pulse nadir was significantly higher during TC (2.04 ± 0.18 ng/ml) than during CC (1.79 ± 0.16 ng/ml), and peak amplitude was significantly higher during CC (Δ1.03 ± 0.09) than during TC (Δ0.87 ± 0.09). No other parameters differed significantly between the two cycles. We conclude that the difference in LH pulsatility pattern may be an effect of exposing heifers to oestrous vaginal mucus and/or urine and that the mechanism behind this needs further investigation.     

Temporal Relationships and Repeatability of Follicle Diameters and Hormone Concentrations within Individuals in Mares

Data were collected daily from 23 mares during two consecutive interovulatory intervals (IOIs). Several significant (p < 0.05) new observations on temporal relationships were made. The FSH increase that begins before ovulation temporarily plateaued on the day of discharge of follicular fluid into the peritoneal cavity in association with ovulation. During the declining portion of the pre-ovulatory oestradiol surge, an abrupt reduction in the rate of decrease occurred in synchrony with the peak of the LH surge and is consistent with a negative effect of LH on oestradiol. Repeatability within mares was based on the following positive and significant correlations between the two IOIs: (i) length of the interval between ovulations and between ovulation and the beginning of follicle deviation; (ii) diameter of the pre-ovulatory follicle on days -3 to -1; (iii) number of follicles in diameter classes of 2–5 mm (correlation for 22/23 days of the IOI), 5.1–10 mm (18/23 days), 10.1–15 mm (12/23 days) and 15.1–20 mm (12/23 days) and (iv) concentrations of FSH (18/23 days) and LH (22/23 days). The greatest repeatability for the follicle-diameter classes occurred in the 2–5 mm class, and thereafter the repeatability progressively decreased as the diameters for the classes increased. Results demonstrated measurable repeatability within mares for several end points between consecutive IOIs.     

Hormonal Response of Female Goats to Active Immunization against a Recombinant Human Inhibin α-subunit, and establishment of an Enzyme-linked Immunosorbent Assay for Caprine Follicle-stimulating Hormone

The effect of selective immunosuppression of endogenous inhibin in goats on FSH, LH, progesterone and estradiol-17β profiles was studied during the breeding and nonbreeding seasons. Eighteen adult female Boer goats were immunized against the recombinant human inhibin α-subunit (hINH-α). With the exception of estradiol, which was determined by radio-immunoassay (RIA), all plasma hormone concentrations were determined by ELISA. The ELISA for FSH presented in this paper was established in the authors' laboratory, based on an existing RIA. Mean basal concentrations of FSH were not affected by immunosuppression of endogenous inhibin, nor was there a difference in the amplitude of the pre-ovulatory FSH surge. Immunization against inhibin appears to eliminate the slight secondary rise of FSH occurring 12–20 h after the major surge associated with ovulation. The LH profiles of the immunized goats were characterized by lower basal concentrations both before and after the pre-ovulatory LH surge which itself was reduced by 50% in immunized does. By contrast, concentrations of circulating estradiol were significantly elevated after inhibin-immunization. Progesterone profiles were not affected. Extending immunization into the anoestrous season by a booster injection of hINH-α, implicating oestrus induction with a progestagen and eCG, produced no discernible differences in FSH and LH profiles in comparison with nonimmunized control goats. The findings suggest that in goats, paracrine factors may play a more significant role in controlling follicular activity than a feedback mechanism acting via the pituitary.     

Ovulatory Response and Embryo Yield in Jakhrana Goats Following Treatments with PMSG and FSH

Superovulatory response and embryo production efficacy were investigated in adult (age 2–4 years, average body weight: 27–43 kg) cycling Jakhrana goats (n = 15) under semi-arid environmental conditions of India by administering different superovulatory regimens. Goats were reared under semi-intensive system of management in established farm conditions. To synchronize oestrus, a luteolytic dose of carboprost tromethamine (Upjohn, UK) was administered intramuscularly to all does at the dose rate of 5μg per kg body weight in a double dose schedule with an interval of 11 days. For superovulation, 750 IU of PMSG (Folligon, Intervet, Boxmeer, Holland) per goat was administered intramuscularly 24 h before administering a second dose of luteolytic agent in five does (treatment 1). FSH (Sigma, St. Louis, MO, USA) 12.50 IU per goat was administered intramuscularly in a decreasing daily dose schedule (2.50, 2.50; 1.875, 1.875; 1.25, 1.25; 0.625, 0.625) at 12 h intervals over four days, initiated 48 h before administering second dose of carboprost tromethamine in 5 does (treatment 2). FSH (Super-Ov, Ausa Intern, USA) was administered at a uniform dose rate of 8.33 units per goat intramuscularly at 24 h intervals over three consecutive days (total dose was 25 units), initiated 48 h before administering a second dose of carboprost tromethamine in 5 does (treatment 3). To synchronize ovulation in responders, human chorionic gonadotrophin (hCG, Chorulon, Intervet) was injected intramuscularly at a dose rate of 500 IU in each goat on the day of oestrus appearance. Goats were laparotomized 72–82 h following the onset of synchronized oestrus and their genitalia were flushed using a standard collection procedure. Variability (p > 0.05) in superovulatory response (number of established corpora lutea) was observed: FSH (Sigma), 11.8± 2.9; FSH (Super-Ov), 11.6±4.5; PMSG (Intervet), 8.4±2.3. A similar pattern was reflected in mean embryo and transferable embryo recovery, respectively (p > 0.05): FSH (Sigma), 8.0±1.8, 5.2±1.7; FSH (Super-Ov), 6.6±2.4, 5.4±2.4; PMSG, 5.8±1.9, 3.8±2.2. In PMSG-treated does, comparatively more unfertilized ova or retarded embryos were recovered than in FSH-treated does. The superiority of FSH preparations over PMSG was reflected in terms of total and transferable embryo production (p > 0.05). On average, five transferable embryos (excellent and good quality) were recovered per doe treated with FSH of either source. The mean ova/embryo recovery was satisfactory (55–68%). Results indicated that Jakhrana goats can be superovulated for embryo production using FSH of either source to augment productivity.     

Relationship Among Follicular Growth, Oestrus, Time of Ovulation, Endogenous Estradiol 17β and Luteinizing Hormone in Bos Indicus Cows After a Synchronization Program

To determine the pattern of follicular growth during oestrus and the relationship with estradiol and luteinizing hormone in ovulating and non-ovulating cows, three groups of (n = 10), thirty cyclic, Bos indicus cows were synchronized with CIDR, consecutively at 9-day intervals. Twenty-four hours after implant withdrawal, all cows synchronized in the same group with other cows displaying estrous behaviour after implant withdrawal were subjected to an intensive period of ultrasonographic observations (every 6 h for 120 h). Blood samples were taken to evaluate LH surge and 17-beta estradiol. No differences were observed in follicular growth, ovulatory diameter and growth average in the three groups of synchronized cows. Cows ovulating (CO) had a better growth average in comparison with the group of cows not ovulating (CNO) (1.4 +/- 0.7 mm vs 0.7 +/- 0.5 mm, p < 0.06). The average time from estradiol release to LH surge was 39.3 +/- 24.6 h. Differences were also observed between CO and CNO with respect to both the first concentration (27.7 +/- 5.2 vs 58.6 +/- 31.9, p < 0.004) and last concentration (79.3 +/- 23.3 vs 99.2 +/- 27.3, p < 0.05) of estradiol above 5 pg/ml. The average time from overt signs of oestrus to LH release was 8.4 +/- 7.7 h. In the CNO, the increase in LH concentration was never above two SD from the basal average. In conclusion, there is a wide variability in follicular growth and ovulatory diameter between CO and CNO, which can affect the intervals of LH release, estradiol peak and ovulation. Yet, LH surge might be a good marker for timing ovulation in Zebu cows.     

Causes, characteristics and consequences of anovulatory follicles in superovulated sheep

Efficiency of superovulatory protocols is affected by the occurrence of reproductive abnormalities, such as the presence of anovulatory follicles. The objective of current study was to assess the incidence and possible causes of anovulatory follicles in superovulated sheep, in order to characterize the endocrine functionality of these follicles in terms of estradiol production and to evaluate their relationship with development of embryos from other follicles. The number and size of all follicles present in the ovaries of 12 sheep treated with a superovulatory FSH step-down treatment was assessed by ultrasonography. On Day 3 after subsequent estrus behaviour, the number of corpora lutea and anovulatory follicles were recorded and the fluid of anovulatory follicles >or=5mm in size was aspirated and assayed for estradiol. At once, embryos were recovered to evaluate their viability. In current study, anovulatory structures averaged 34.6% of the follicles developing to preovulatory sizes. The number of anovulatory follicles was determined by the existence of follicular dominance effects, since they increased with a higher difference in size between the largest and the second largest follicle at the beginning of the superovulatory treatment (P<0.05, r(2)=0.420). Most of the anovulatory follicles showed signs of functionality failures, indicated by a low mean estradiol concentration (9.9+/-1.1 ng/ml). However, a 22.4% of them were highly estrogenic (>200 ng/ml) and their permanence beyond the ovulation was related to a drop in the embryo viability rate (P<0.005), leading to decreased final superovulatory yields.     

Periovulatory endocrinology and oocyte maturation in unmated mature blue fox vixens (Alopex lagopus)

Nine of 10 mature blue fox vixens (Alopex lagopus) in spontaneous oestrus ovulated approximately 2 days after the preovulatory increase in luteinizing hormone (LH). Plasma concentrations of follicle-stimulating hormone and progesterone increased simultaneously with the LH peak, whereas oestradiol-17 beta peaked 1 day previously. In the tenth vixen, an LH peak was not observed, and neither visible follicles nor corpora lutea were found in the ovaries 6 days after peak vaginal electrical resistance. Eggs were ovulated as primary oocytes, but oocyte maturation was initiated within the day of ovulation (2 days after the LH peak). Within the next 2 days (3-4 days after the LH peak) the first polar body was extruded, and the cumulus mass was completely dissociated from the zona pellucida. The interval between the preovulatory LH peak and initiation of the final oocyte maturation is thus considerably longer in the blue fox than for example in the cow (48-72 h compared with 9-12 h). This suggests that the relationship between these two events is somewhat different in the blue fox.     

Effect of hCG Treatment on the Oestrous and Ovulation Responses to FSH in Prepubertal Gilts

To ensure sufficient numbers of pregnant females, particularly at hotter times of the year, hormonal induction of gilt oestrus may be necessary. However, the gilt oestrus and ovulation responses to gonadotrophin treatment have often proven unpredictable. The objective of this study was to examine possible reasons for this unpredictability. Prepubertal gilts (approximately 150 days of age, n = 63) were assigned to one of three treatments: injection of 300 IU hCG (n = 15); pre-treatment with 100 mg FSH in polyvinylpyrrolidinone administered as 2 × 50 mg injections 24 h apart, followed by 600 IU eCG at 24 h after the second FSH injection (n = 23); or FSH pre-treatment as above followed by 300 IU hCG at 24 h after the second FSH injection (n = 25). To facilitate oestrus detection, gilts were exposed to a mature boar for 15 min daily for 7 days. Blood samples were obtained on the day of eCG or hCG injection and again 10 days later and gilt ovulation responses determined based on elevated progesterone concentrations. The oestrus responses by 7 days were 6.7%, 17.5% and 64.0% for gilts treated with hCG, FSH + eCG and FSH + hCG, respectively (p < 0.001). The oestrous gilt receiving hCG alone and one oestrous FSH + hCG gilt did not ovulate, all other oestrous gilts ovulated. A further two anoestrous FSH + eCG-treated gilts ovulated. These data suggest that FSH pre-treatment facilitated the development of ovarian follicles to the point where they became responsive to hCG, but had little effect on the response to eCG.     

Comparison of oestrus synchronisation programmes in dairy cattle using oestradiol benzoate, short-acting progesterone and cloprostenol, or buserelin and cloprostenol

AIM: To evaluate the efficacy of a programme using oestradiol benzoate, progesterone and the prostaglandin-F2 (PG) analogue, cloprostenol, to synchronise oestrus and ovulation in dairy cows, compared with a programme using a gonadotropinreleasing hormone (GnRH) agonist, buserelin, and cloprostenol. METHODS: Twenty non-lactating dairy cows, at random stages of the oestrus cycle, were randomly assigned to 1 of 2 treatments. In Treatment 1 ( OPPG; n=10), cows were injected with 2 mg oestradiol benzoate intramuscularly (IM) plus 200 mg progesterone subcutaneously (SC) on Day 0, followed by 500 microg cloprostenol IM on Day 9 and 1 mg oestradiol benzoate on Day 10. In Treatment 2 (GPG; n=10), cows were injected with 10 microg buserelin IM on Day 0, 500 microg cloprostenol IM on Day 7 and 10 microg buserelin on Day 9. The ovaries of all cows were examined by ultrasonography, using an 8 MHz probe, from 5 days before the initial treatment until ovulation. Cows were observed for oestrus 3 times daily for 7 days after cloprostenol treatment. Blood samples were collected daily for determination of progesterone, and 6-hourly for 36 h after the second oestradiol or buserelin injection for the determination of follicle stimulating hormone (FSH) and luteinising hormone (LH) concentrations. RESULTS: The percentage of cows observed in oestrus was higher in the OPPG group than in the GPG group (100% vs 55.6%, p=0.018). Treatment with either short-acting progesterone plus oestradiol benzoate or buserelin was followed by atresia or ovulation of the dominant follicle. Emergence of a new follicular wave occurred earlier (p>0.001) in the GPG group (2.2+/-0.2 days) than in the OPPG group (3.6+/-0.2 days). There was no significant difference between treatment groups in the variation of time of follicular wave emergence or size of the largest follicles at either the time of initial treatment (10.8+/-1.4 mm vs 11.1+/-0.8 mm), cloprostenol treatment (13.8+/-0.7 mm vs 14.0+/-1.3 mm) or of ovulation (15.4+/-0.7 mm vs 17.6+/-1.1 mm; p=0.10). The LH surge occurred sooner after the second injection of buserelin (4.0+/-1.0 h) than after the second injection of oestradiol benzoate (22.8+/-1.2 h; p>0.001). The interval between the second injection of oestradiol benzoate or buserelin and ovulation did not differ significantly between treatment groups (1.7+/-0.3 days vs 1.6+/-0.2 days; p=0.69). CONCLUSIONS: The use of short-term progesterone treatment, combined with oestradiol benzoate for follicular wave synchronisation, and cloprostenol to cause lysis of residual luteal tissue, is a promising alternative to established methods of oestrus synchronisation in cows.