Search

In an effort to develop an effective, minimum-handling protocol for the conservation of wood bison, the present study was designed to determine the effects of ovarian synchronization and superstimulation on cumulus oocyte complex (COC) collection and in vitro embryo production in wood bison during the ovulatory (Exp. 1) and anovulatory seasons (Exp. 2). We tested the hypotheses that COC collection and in vitro embryo production are 1) greater after follicular wave synchronization than at random stages of the follicular wave, 2) repeatable within individuals, 3) greater after ovarian superstimulation with a single dose of eCG than without treatment, and 4) greater during the anovulatory season than the ovulatory season. In Exp. 1, ultrasound-guided COC collection was performed on Day -1 in wood bison to induce follicular wave emergence the following day (Day = 0). Immediately after the COC collection on Day -1, bison were given a single im dose of 2500 IU eCG or saline (n = 6 per group). Subsequent COC collections were on Days 4 and 9. A similar design was used in Exp. 2, with an additional treatment group given 5000 IU eCG (n = 8 per group). In Exp. 1, compared to the saline-treated group, a single dose of 2500 IU eCG resulted in a greater number of ≥8 mm follicles at the time of the Day 4 COC collection (P = 0.03), but not at the Day 9. In Exp. 2, treatment with 5000 IU eCG resulted in a greater number of ≥8 mm follicles than 2500 IU eCG or the saline treatment (37.5 ± 6.9, 17.5 ± 2.0, 16.9 ± 2.0; P = 0.01, respectively). Although the number of embryos produced/COC submitted to IVM was not different among groups (mean = 18.6%), treatment with 5000 IU eCG produced more than twice as many embryos per bison as unstimulated bison (0.8 vs 1.9). In summary, embryo production rates were higher from COC collected subsequent to follicular wave synchronization vs random stages of the wave, and ovarian superstimulation with eCG resulted in a dose-related increase in the number of ≥8 mm follicles, COC collected, and embryos produced. Repeated COC collections after successive wave synchronization resulted in similar follicular counts and embryo production rates within individuals, and the greatest number of follicles aspirated, COC collected, and embryos produced was in the anovulatory season. We conclude that the minimum-handling COC collection protocols in the present study are effective and provide realistic options for embryo production in wild bison.

This study was undertaken to determine the effect of inflammatory status on different patterns of postpartum luteal activity and reproductive performance of Holstein cows during early lactation. The cows (n = 75) averaged 3.4 ± 1.2 (mean ± SEM) in parity and 3.1 ± 0.2 (mean ± SEM) in body condition score at calving. Transrectal ultrasonography was performed twice weekly from day 10-60 postpartum to consider ovarian dynamics. Plasma concentrations of progesterone (P4) and estradiol (E2) were measured twice weekly and plasma levels of tumor necrosis factor alpha (TNF-α) and lipopolysacchride binding protein (LBP) were measured weekly (week 3-6 postpartum). Based on plasma P4 and E2 results, 34 (45.3%) cows had normal luteal activity (NLA), whereas 19 (25.3%), 12 (16.0%), 7 (9.3%) and 3 (4.0%) cows had prolonged luteal phase (PLP), delayed first ovulation (DO), anovulation (AO) and short luteal phase (SLP), respectively. Plasma TNF-α and LBP concentrations were affected by postpartum luteal activity (NLA, SLP and PLP), ovulatory status (DO and AO) and number of weeks postpartum (P .05). These concentrations were greater in cows with PLP (P .05) as compared to NLA cows, and in cows that had delayed ovulation or anovulation compared to ovulated cows (P .05). Cows with PLP had greater open days and lower conception rate as compared to NLA cows (P .05). Healthy cows had a larger CL and greater plasma estradiol and progesterone concentrations at first and second cycle postpartum compared to inflamed cows and followed it with greater fertility (P .05). In conclusion, inflammatory statuses were different in high-producing dairy cows showing PLP, AO and DO in comparison with the postpartum normal luteal activity (NLA) cows that influenced reproduction outcomes.

The effectiveness of different treatments with recombinant equine FSH to stimulate follicular growth, multiple ovulations and embryo production in seasonally anovulatory mares was evaluated. During mid-winter season (July–August in Argentina, South America) forty light breed donor mares, presenting follicles 35 mm). Ovulations were detected in 80% of mares in Groups 1 and 2, 50% of mares in Group 3 and in none of Group 4 (Control). Among ovulating mares, no differences in number of ovulations, number of embryos recovered, or pregnancy rates were observed among reFSH treatments. Of treated mares, 6, 7, and 5 produced embryos in Groups 1, 2, and 3, respectively. The average embryo recovery rate per ovulated mare was 88%. The average embryo recovery rate per ovulation was 43%. Overall, a 59% pregnancy rate was achieved. These results indicate that treatment with reFSH during deep anestrus results in follicular development, ovulation of fertile oocytes, and production of embryos that established viable pregnancies after transfer. Also, a single daily administration of reFSH was as effective as two daily administrations, which allows for a simplified administration regimen.

Resumption of ovulation after parturition is a coordinated process that involves recoupling of the GH/insulin-like growth factor 1 axis in the liver, increase in follicular development and steroidogenesis, and removal of negative feedback from estradiol in the hypothalamus. Infectious diseases and metabolic disorders associated with extensive negative energy balance during early lactation disrupt this pathway and delay first ovulation postpartum. Extended periods of anovulation postpartum exert long-lasting effects on fertility in dairy cows including the lack of spontaneous estrus, reduced pregnancy per artificial insemination (P/AI), and increased risk of pregnancy loss. Concentrations of progesterone in anovular cows subjected to synchronized programs for AI are insufficient to optimize follicular maturation, oocyte competence, and subsequent fertility to AI. Ovulation of first wave follicles, which develop under low concentrations of progesterone, reduces embryo quality in the first week after fertilization and P/AI in dairy cows. Although the specific mechanisms by which anovulation and low concentrations of progesterone impair oocyte quality have not been defined, studies with persistent follicles support the involvement of premature resumption of meiosis and degradation of maternal RNA. Suboptimal concentrations of progesterone before ovulation also increase the synthesis of PGF2α in response to oxytocin during the subsequent estrous cycle, which explains the greater incidence of short luteal phases after the first AI postpartum in anovular cows compared with estrous cyclic herd mates. It is suggested that increased spontaneous luteolysis early in the estrous cycle is one of the mechanisms that contributes to early embryonic losses in anovular cows. Anovulation also leads to major shifts in gene expression in elongated conceptuses during preimplantation stages of pregnancy. Transcripts involved with control of energy metabolism and DNA repair were downregulated, whereas genes linked to apoptosis and autophagy were upregulated in Day 15 conceptuses collected from anovular cows compared with estrous cyclic counterparts. Similar changes in conceptus transcriptome were not observed in estrous cyclic cows induced to ovulate follicles that grew under low and high concentrations of progesterone, indicating an effect of anovulation on embryonic development that is not mediated solely by progesterone concentrations before ovulation. Finally, risk factors for anovulation have direct effects on embryo development and uterine receptivity to pregnancy that complement those determined by insufficient concentrations of progesterone during follicular growth. One approach to minimize the impact of anovulation on fertility is supplementation with progesterone during recruitment, selection and final stages of development of the preovulatory follicle. It is suggested that a minimum of 2.0 ng/mL of progesterone is needed during growth of the preovulatory follicle to achieve P/AI similar to that of cows growing the preovulatory follicle during diestrus.

The role of oxidative stress in the control of female reproduction has not been fully elucidated in ruminants; however, it seems that antioxidants can make influence to the reproductive axis at different levels. Therefore, the aim of this study was to determine the relationship between antioxidant status and concentrations of trace minerals (chromium (Cr), copper (Cu), iron (Fe), and zinc (Zn)) with postpartum luteal activity and fertility in Holstein dairy cows. The cows (n = 100, a parity range of 2–5, and a body condition score (BCS) of 3.0 ± 0.25, mean ± SEM) were assigned to the experiment at second week post calving. Ovarian follicular dynamics were monitored twice a week (from 3rd to 6th weeks post calving) by transrectal ultrasonography (US). Blood samples were collected twice weekly from the 3rd to the 6th weeks post calving at timed artificial insemination (TAI), and days 32 and 50 post AI to determine superoxide dismutase (SOD), glutathione peroxidase (GPX), total antioxidant capacity (TAC), and trace mineral concentrations. There were associations between plasma concentrations of SOD, GPX, and TAC with postpartum luteal activity (PLA, P = 0.01) and ovulation (P = 0.03). Mean plasma SOD and GPX activities and TAC levels (U/mL) were greater in cows with normal luteal activity (NLA) than prolonged luteal phase (PLP) and anovulation (AO) cows, as well as in ovulated compared to AO cows (P = 0.03). Pregnant cows had greater levels of SOD, GPX, and TAC (U/mL) at TAI than non-pregnant cows (P = 0.01). Plasma Cu and Zn concentrations increased in pregnant compared to non-pregnant cows at TAI. In conclusion, antioxidant levels and Cu and Zn concentrations were associated with PLA and fertility.

The aims of the present study were to initially determine the pattern of serum adiponectin concentrations during a normal estrous cycle in high-producing postpartum dairy cows and then evaluate the relationship between the serum concentrations of adiponectin and insulin with the commencement of postpartum luteal activity and ovarian activities in clinically healthy high-producing Holstein dairy cows. During a normal estrous cycle of cows (n = 6), serum adiponectin concentrations gradually decreased (P0.05) after ovulation by Day-17 estrous cycle and then increased before the next ovulation. Cows with higher peak of milk yield had lower serum adiponectin concentrations by week 7 postpartum (P = 0.01). Serum adiponectin and insulin concentrations in cows with different postpartum luteal activity (based on the progesterone profile) were evaluated using the following class of cows: normal (≤45 days, n = 11) and delayed (45 days, n = 11) commencement of luteal activity (C-LA) and four different profiles of normal luteal activity (NLA, n = 5), prolonged luteal phase (n = 6), delayed first ovulation (n = 6), and anovulation (AOV, n = 5). Serum adiponectin concentrations decreased gradually by week 3 postpartum in NLA and then increased; whereas in AOV and delayed first ovulation, they were decreased after week 3 postpartum (P0.05). Moreover, serum adiponectin concentrations in NLA were more than AOV at weeks 5 and 7 postpartum (P = 0.05). The increase in the milk yield from weeks 1 to 7 postpartum in prolonged luteal phase (P = 0.05) and AOV (P = 0.04) cows was more than that of NLA cows. Insulin concentrations were almost maintained at a stable level in NLA cows (P0.05), whereas they increased in the other groups (P0.05). Moreover, adiponectin concentrations in cows with C-LA greater than 45 days decreased more than those with C-LA 45 days or less after week 3 postpartum (P = 0.002). Serum adiponectin concentrations at week 7 postpartum were lower in delayed C-LA (P = 0.01). Milk yield in cows with C-LA greater than 45 days increased more than cows with C-LA 45 days or less postpartum (P = 0.002). Insulin concentrations increased relatively in parallel from weeks 1 to 7 postpartum in cows either with C-LA greater than 45 or with C-LA 45 days or less. We showed for the first time the profile of serum adiponectin concentrations in a normal estrous cycle of dairy cows, and furthermore, it was found that high-producing dairy cows with higher postpartum serum adiponectin concentrations had NLA and earlier C-LA.

Cystic ovarian disease (COD) is an important cause of infertility in dairy cattle. The main signs of this infertility are ovulation failure and follicular persistence. The aim of this study was to examine the expression of the cytokines IL-1β IL-1RI, IL-1RII, IL-1RA and IL-4 in ovarian follicular structures at different times of persistence in a model of follicular persistence induced by prolonged administration of progesterone in dairy cows. Protein expression of IL-1β IL-1RI, IL-1RII, IL-1RA and IL-4 was evaluated by immunohistochemistry. Additionally, IL-1β and IL-4 concentrations in follicular fluid and serum were determined by ELISA. In granulosa cells, IL1-RII and IL-4 expression was higher in follicles with different persistence times than in the control dominant follicles. IL-1RA expression was higher in persistent follicles of the P15 group (15 days of follicular persistence) than in those of the control group. In theca cells, IL-1RII expression was higher in persistent follicles of the P0 group (expected time of ovulation) than in dominant follicles from the control group (p

Onset of the winter anovulatory period in mares is associated with a marked diminution in adenohypophyseal synthesis and release of LH. Native GnRH, unlike its synthetic agonists, stimulates the synthesis and secretion of LH in mares without pituitary refractoriness. Herein we tested the hypotheses that (1) the average Julian day of pregnancy can be accelerated by up to 2 months in winter anovulatory mares treated continuously with native GnRH beginning on February 1 and (2) mares will sustain luteal function and pregnancy after treatment withdrawal. Forty-two winter anovulatory mares were stratified by age, body condition score, and size of the largest follicle across two locations in a randomized design and assigned to one of three groups (n = 14 per group): (1) CONTROL: untreated, (2) GnRH-14: GnRH delivered subcutaneously in saline at a rate of 100 μg/h for 8 weeks (February 1-March 29) using four consecutive 14-day pumps (Alzet 2ML2), or (3) GnRH-28: GnRH delivered as in (2), but using two 28-day pumps (Alzet 2ML4). On development of a 35-mm follicle and expression of estrus, mares were bred the following day and treated with hCG. Pregnancies were confirmed using transrectal ultrasonography on Days 14, 24, 33, and 45, with blood samples collected to assess luteal function. Mares treated with GnRH (GnRH-14 and GnRH-28) did not differ reproductively in their responses and data were pooled for statistical comparisons. Mares treated with GnRH exhibited marked increases (P ≤ 0.04) in the frequency of development of a 35-mm follicle, submission rate for live cover and/or artificial insemination, ovulation, and pregnancy compared with control mares on treatment Day 56 (March 29). Interval to the first 35-mm follicle was 51.8 ± 4.9 and 19.3 ± 3.5 days (least square mean ± standard error of the mean) for control and GnRH-treated mares, respectively. Interval to pregnancy was 65.3 ± 6.7 and 28.6 ± 4.8 days (least square mean ± standard error of the mean) for control and GnRH-treated mares, respectively, excluding one GnRH-14 mare that failed to become pregnant over four cycles. By the end of the treatment period (March 29), only 21% of control mares were pregnant compared with 79% of GnRH-treated mares. Furthermore, mean serum concentrations of progesterone were similar to (GnRH-28; P = 0.26) or greater than (GnRH-14; P = 0.01) that of control mares from Day 0 to 46 postbreeding. Data illustrate that continuous administration of native GnRH is a highly efficient option for managing seasonal anovulation in mares and could be effectively used in the breeding industry if a user-friendly delivery option were available.

The objective was to evaluate the efficacy of three previously unreported ovarian superovulatory treatment protocols in wapiti. Protocols were initiated specifically at the time of ovarian follicular wave emergence, and intended to enable determination of the effects of frequency of treatment (i.e., animal handling) and LH supplementation on ovarian response. Thirteen parous wapiti hinds, 2 to 4 y of age, were used late in the anovulatory season (July). The ovaries were examined daily by transrectal ultrasonography. Hinds were given 5 mg estradiol 17-β im (day of treatment designated as Day 0) to induce a new wave of ovarian follicular development. On the expected day of wave emergence (Day 3), hinds were assigned randomly to three treatment groups and given: (1) 100 mg FSH im once a day for 4 days (N = 5); (2) 200 mg FSH sc on Day 3 and Day 5 (N = 4); or (3) 200 mg FSH plus 2.5 mg LH sc on Day 3 and Day 5 (N = 4). All hinds were given 10 mg LH im on Day 6 to induce ovulation. The mean (± SEM) number of ovulations per animal in the respective groups was 6.2 ± 2.0, 15.5 ± 5.9, and 14.8 ± 2.7. In conclusion, the technique of inducing follicular wave emergence to initiate superovulatory treatment at the time of wave emergence was effective in wapiti during the anovulatory season. The most efficient and effective method of ovarian superovulation in this study involved administration of estradiol 17-β on Day 0, followed by 200 mg FSH sc on Days 3 and 5, and induction of ovulation (10 mg of LH) on the evening of Day 6. Compared with conventional methods that require 14 days and handling the hinds six times, the protocol used herein reduced the treatment period to 8 days and the number of animal handlings to four.

The purpose of this study was to evaluate the reproductive status and clarify the reproductive physiology of captive Sichuan golden monkeys. The concentrations of urinary estradiol-3-glucuronide (E2G) and pregnanediol-glucuronide (PdG) or fecal estradiol-17β (E2) and PdG in two females, and fecal testosterone concentrations in a male, were measured continuously using enzyme immunoassays. On the basis of these hormone profiles, the follicular phase, luteal phase, and ovarian cycle were calculated to be 14.7 ± 4.8, 10.4 ± 2.8, and 25.1 ± 3.3 days, respectively. The first ovulation (puberty) in a female monkey was observed at 5.1 years old, and the first pregnancy was diagnosed at 6.4 years old. For the first 2 months of pregnancy (204 days), fecal E2 and PdG maintained constant high values and then increased until parturition. These profiles were similar to urinary E2G and PdG changes. During the last trimester of a twin pregnancy, fecal PdG was up to approximately three times higher compared with a single pregnancy. Therefore, fecal PdG levels in late pregnancy may be effective for the detection of a twin pregnancy. The first postpartum ovulation occurred 66 (fetal death and artificial rearing), 143 (fetal death), and 189 (natural suckling) days after parturition. The anovulation period of the natural suckling case was longer than the others. Conception and postpartum ovulation were detected between September and January. Fecal testosterone levels of the male were correlated with the fecal E2 level of the nonpregnancy period in exhibited together female. Our results reported that urinary (E2G and PdG) and fecal (E2 and PdG) hormone measurement is effective for monitoring the reproductive status, thereby expanding knowledge of the reproductive endocrinology of this endangered species.

A single treatment with PGF2α is assumed to have no luteolytic effect on cows with corpora lutea < 5 days old. The objective of this study was to determine the effect of a single high dose of PGF2α administered to dairy cattle on the morphology and function of the early CL. The study followed a crossover design with a treatment cycle in which 50 mg of dinoprost were administered 3.5 days postovulation and a control untreated cycle. Ultrasound examination and blood samples were performed during the two consecutive cycles. Corpus luteum (CL) diameter, progesterone concentration, and follicular dynamics characteristics were compared between control and treated cycles. Two of nine cows (22%) developed full luteolysis. The remaining seven cows (78%) had partial luteolysis with a decrease (P < 0.05) in progesterone concentration and CL diameter for two and 12 days post-treatment, respectively. The interovulatory interval of treated cycles (19.7 ± 2.4 days) was not different (P > 0.05) from that of controls (23.8 ± 0.9 days). The transient reduction in progesterone of cows with partial luteolysis had no effect on the proportion of cows with two or three follicular waves, follicle growth rate, or preovulatory diameter (P > 0.05). Two cows developed ovarian cystic degeneration during the PGF2α-induced cycle. In conclusion, the treatment of cows with a high dose of PGF2α 3.5 days postovulation induced some degree of luteolysis in all treated cows. This resulted in partial luteolysis in 78% of treated animals and in full luteolysis in the remaining 22%. © 2011 Elsevier Inc.

We tested the hypothesis that continuous subcutaneous treatment with low-dose GnRH, administered to mares from late September/early October through March, would prevent the development of seasonal anovulation. Quarter Horse mares (n = 20) were stratified by age and body condition score and assigned randomly to either a saline control (n = 9) or a GnRH (n = 11) treatment group. Gonadotropin-releasing hormone was delivered continuously via osmotic minipumps, with sham pumps placed in control mares. Initial pumps were inserted on Day 3 following ovulation or during the follicular phase if the next anticipated ovulation did not occur by 9 October. Delivery rate of GnRH was 2.5 μg/h (60 μg/day) for the first 60 days, followed by 5.0 μg/h (120 μg/day) thereafter. Pumps were replaced every 30 days. Eighty and 100% of all mares had become anovulatory by 1 November and 1 December, respectively, and remained anovulatory through the end of February. Neither serum concentrations of LH throughout the study nor total releasable pools of LH in March differed between groups. Although control mares that exhibited ovulatory cycles after study onset had greater (P < 0.05) mean concentrations of LH during the follicular phase and metestrus compared to GnRH-treated mares, neither size of ovulatory follicles nor interovulatory intervals differed between groups. Serum concentrations of FSH were not affected by treatment, but were lowest (P < 0.05) from November through January. Continuous infusion of low-dose GnRH, beginning soon after autumnal equinox and continuing until just after vernal equinox, failed to prevent the occurrence of or to hasten transition from seasonal anovulation.

Hypothalamic unresponsiveness to an estradiol surge appears to be an underlying cause of large follicle anovular condition (follicular cysts), but progesterone exposure for 7 days resolves this condition. In this study, dairy cows with induced (Experiment 1) or naturally occurring (Experiment 2) follicular cysts were treated for different times with progesterone. In Experiment 1, 16 of 26 cows (62%) were induced into anovulation by causing a GnRH/LH surge when no ovulatory follicle was on the ovary. Anovular cows (n = 16) were assigned to one of four treatment groups ( 0, 1, 3, or 7 days of progesterone treatment) using an intravaginal, progesterone-releasing implant (CIDR). All anovular cows had low circulating progesterone concentrations before controlled internal drug releasing (CIDR) and greater concentrations that reached steady state (1.3 +/- 0.1 ng/mL progesterone) by 3 h after CIDR insertion. Circulating progesterone decreased to basal concentrations by 4 h after CIDR removal. Cows were treated with 5mg estradiol benzoate (EB) 12 h after CIDR removal. None (n = 4) of the control cows (0 day) had an LH surge after EB. All of the 3 days (5/5) and 7 days (4/4) CIDR-treated cows had an LH surge following EB, but only one of the 1 day (1/3) CIDR-treated cows. Magnitude of the LH peak was similar in the 3 and 7 days cows. All cows treated for 7 days ovulated (4/4), whereas, ovulation occurred in only 3/5, 1/3, and 0/4 of the cows treated for 3, 1, and 0 day, respectively. The two cows in the 3 days group that did not ovulate had a normal LH surge, but these two cows had a smaller maximal follicle size than cows that ovulated. In Experiment 2, naturally anovular lactating dairy cows (24 of 248) were identified using weekly ultrasonography. All anovular cows grew follicles to >12 mm, with 54% (13 of 24) having follicles larger than ovular size (15-24 mm) and 33% (8 of 24) having follicles that would be considered cystic (>25 mm). Anovular cows were randomly assigned to CIDR treatment for 0, 1, or 3 days. All (7/7) of 3 days, 33% (3/9) of 1 day, and 25% (2/8) of control (0 day) cows ovulated by 1 week after CIDR removal. Thus, 3 days but not 1 day of progesterone exposure appears to be sufficient to reinitiate estradiol responsiveness of the hypothalamus.

This study aimed to confirm that the luteolysis in normal-cycling dairy heifers seen during short estrous cycles induced with cloprostenol (Clp) and GnRH administered 24h apart is caused by a premature release of prostaglandin F(2alpha) (PGF(2alpha)). A further aim was to study the PGF(2alpha) release pattern more closely to determine whether it resembles the spontaneous release occurring during normal regression of the corpus luteum (CL) or whether PGF(2alpha) is continuously secreted after the induced ovulations, leading to short estrous cycles. Twenty-four Ayrshire heifers were allotted to four equally sized groups. After estrus synchronization with 0.5mg of Clp, a new luteolysis was induced with 0.5mg of Clp on Day 6 (groups T-d6 and C-d6) or Day 7 (groups T-d7 and C-d7) after ovulation. Gonadorelin (0.1mg i.m.) was given to groups T-d6 and T-d7 to induce premature ovulation 24h later. Groups C-d6 and C-d7 served as controls. Ovaries were examined daily by transrectal ultrasonography, while blood samples (for progesterone and 15-ketodihydro-PGF(2alpha) analyses) were obtained via a jugular catheter every 3h, starting from the second Clp treatment and continuing for 9 days postovulation. Unresponsiveness to Clp or anovulation resulted in 4 C-d6 heifers being excluded. Four heifers in group T-d6 and three in group T-d7 had a short estrous cycle of 8-12 days, while all others had a cycle of normal length. Significant elevations in 15-ketodihydro-PGF(2alpha) concentrations with recurrent high peaks coincided with a decrease in progesterone concentration and were detected in all heifers that showed a short estrous cycle, but not in any heifers with normal estrous cycles in groups T and C. In conclusion, a premature release of PGF(2alpha), which closely resembles its release during spontaneous luteolysis, causes luteal regression in these short cycles.

Evaluation of follicular growth patterns by ultrasound combined with measurement of circulating reproductive hormones has allowed designation of three functionally critical follicular sizes during the final stages of follicular growth: emergence (-4 mm), deviation (-9 mm), and ovulation (variable from 10 to 20 mm). Classification of anovulatory conditions on the basis of these three critical points is logical and provides for rational diagnosis and treatment of the underlying physiological condition. In extreme undernutrition, there is growth of follicles to emergence but not to deviation; however, the underlying pathophysiology is not defined because of relatively few scientific investigations of this condition. Anovulatory conditions with growth of follicles to deviation but not to ovulatory size have been extensively studied. Undernutrition and/or suckling can cause this anovulatory condition. It is characterized by a greater negative feedback effect of estradiol on GnRH/LH pulses than found in normally cycling cows. Another anovulatory condition that is common in high producing lactaing dairy cows is characterized by growth of follicles to larger than ovulatory size, such as is observed in cows with follicular cysts. This condition is characterized by an insensitivity of the hypothalamus to the positive feedback effects of estradiol. Thus, these last two common anovulatory conditions appear to be primarily due to changes in the responsiveness of the hypothalamus to estradiol. Treatments that increase circulating progesterone concentrations can help in the treatment of these two conditions by potentially altering GnRH/LH pulses and allowing the final stages of follicular growth or resetting the hypothalamic responsiveness to the positive feedback effects of estradiol.

An experiment was performed to compare the effects of 3 short-term treatments with progesterone and estradiol benzoate (EB) on follicular growth, synchrony of estrus and pregnancy rate after fixed-time insemination in lactating postpartum beef cows. In Treatment 1 (n = 46), each cow received a progesterone-containing intravaginal insert for 7 d with injection of EB (2 mg, im) at the time of device insertion. In Treatment 2 (n = 46), the insert was used for only 5 d with injection of EB (2 mg, im) at the time of insertion. Cows in Treatment 3 (n = 47) received an insert for 5 d with no EB at the time of insertion. Each cow in the 3 groups received PGF 2 α (25 mg, im) at the time of insert removal, followed by EB (1 mg, im) 30 h later. The cows were then inseminated 28 to 30 h after treatment with EB (58 to 60 h after insert removal). Treatment with 2 mg EB terminated the growth of the largest ovarian follicle (>5 mm in diameter) at device insertion in 16716 and 14/15 cows in Treatments 1 and 2, respectively. Estrus was detected within an 8-h target period (48 to 56 h after insert removal) in 93, 87 and 81% of cows in Treatments 1, 2 and 3, respectively (P > 0.05). Pregnancy rates at 39 d post insemination were 60, 50 and 51% for Treatments 1, 2 and 3, respectively (P > 0.05). The pregnancy rates did not differ between cows that were anovulatory or those that had ovulated before the initiation of treatments (54%), or among cows that were 28 to 40, 41 to 60 or >60 days post partum at insemination (43, 59 and 54%, respectively). Treatment with progesterone inserts for 5 or 7 d, PGF 2 α at the time of insert removal and 1 mg EB 30 h later induced the high degree of synchrony of estrus and ovulation necessary for fixed-time insemination.

Bovine viral diarrhea virus (BVDV) has been associated with several reproductive problems in cattle, including poor fertility, early embryonic deaths, abortion and congenital anomalies. Little is known about the cause of poor fertility in cows acutely infected with BVDV. The purpose of this study was to identify changes in ovarian function following acute infection with noncytopathic BVDV. The ovaries of 5 BVDV sero-negative and virus-negative pubertal heifers were monitored daily for 4 consecutive estrous cycles. The position and diameter of all follicles (> 5 mm) and luteal structures were recorded. Daily plasma samples were collected to measure peripheral progesterone and estradiol levels. Each heifer was infected intranasally with noncytopathic BVDV following ovulation of the second estrous cycle. The maximum diameter and growth rate of dominant anovulatory and ovulatory follicles were significantly reduced following acute BVDV infection. Similarly, the number of subordinate follicles associated with both the anovulatory and ovulatory follicle was reduced following infection. There were no significant differences in other follicle or luteal dynamic parameters or in peripheral progesterone or estradiol levels. Ovarian follicular growth was different during the first 2 estrous cycles following acute infection with BVDV when compared with the 2 estrous cycles preceding infection. These differences may be important in explaining reduced fertility in herds with acute BVDV infection.

The ovaries of periparturient pony mares (n=9 to 16 parturitions per month for January to April) were scanned ultrasonically on the day of parturition, while those of postpartum and control mares (n=12) were examined at least twice weekly. Four mares had apparent lactational anovulation (incidence, 7%) that corrected spontaneously (1 mare) or within 14 d after the weaning of foals on August 10 (3 mares). All but 2 of the postpartum ovulations occurred after April 29; that is, parturition did not effectively stimulate ovulation in ponies foaling during the anovulatory season. Mean diameter of the largest follicle per month increased (P

The beginning of postluteolysis (progesterone

The development of hemorrhagic anovulatory follicles (HAF) involves luteinization and hemorrhage of the follicle. This is observed on ultrasound as an increase in the echogenicity of the granulosa layer and formation of echoic particles in the antrum. The inhibition of prostaglandin synthesis with flunixin meglumine (FM) during the periovulatory period induces ovulatory failure with development of luteinized unruptured follicles (LUF). These two types of anovulatory follicles appear to share similar ultrasound features but they have not been compared critically. The following endpoints: follicle diameter, follicular contents score, interval from hCG administration to beginning of follicular hemorrhage, interval from hemorrhage to organization of follicular contents, and cycle length were studied and compared in mares with HAF (n = 11) and LUF (n = 13). The objective of this study was to elucidate whether these two unruptured follicles have a consistent clinical pattern of development and therefore can be considered as part of the same anovulatory syndrome. None of the endpoints analyzed differed significantly between HAF and LUF. However, there was a greater individual variation in HAF as compared with LUF in regards to interval from hCG to hemorrhage, follicular diameter at the administration of hCG, and beginning of hemorrhage. In conclusion, HAF share a similar cascade of ultrasound characteristics with the experimentally induced LUF. This finding may provide new insights in elucidating the pathogenesis of HAF.

Reproductive efficiency is not optimal in high-producing dairy cows. Although many aspects of ovarian follicular growth in cows are similar to those observed in heifers, there are numerous specific differences in follicular development that may be linked with changes in reproductive physiology in high-producing lactating dairy cows. These include: 1) reduced circulating estradiol (E2) concentrations near estrus, 2) ovulation of follicles that are larger than the optimal size, 3) increased double ovulation and twinning, and 4) increased incidence of anovulation with a distinctive pattern of follicle growth in anovular dairy cows. The first three changes become more dramatic as milk production increases, although anovulation has not generally been associated with level of milk production. To overcome reproductive inefficiencies in dairy cows, reproductive management programs have been developed to synchronize ovulation and enable the use of timed AI in lactating dairy cows. Effective regulation of the CL, follicles, and hormonal environment during each part of the protocol is critical for optimizing these programs. This review discusses the distinct aspects of follicular development in lactating dairy cows and the methodologies that have been utilized in the past two decades in order to manage the dominant follicle during synchronization of ovulation and timed AI programs.

The objective was to determine differences in follicle and reproductive hormone characteristics in mares with ovulatory and flunixin meglumine (FM)-induced anovulatory cycles. Estrous mares were given 1500 IU hCG when the follicle was ≥ 32 mm (0 h). In Experiment 1, control mares (n = 7) were not treated further. The remaining mares (n = 11) were given 1.7 mg/kg FM i.v. twice daily, from 0 to 36 h after hCG treatment. Blood samples and ultrasonographic examinations were performed every 12 h. All control mares ovulated normally between 36 and 48 h. In contrast, eight of 11 FM mares did not ovulate, but developed luteinized unruptured follicles (LUFs). Three FM-treated mares did not develop conventional LUFs. Plasma progesterone concentrations were lower (P < 0.05) in LUF mares at 96, 120, and 216 h than in controls, whereas plasma LH concentrations were higher (P < 0.05) between 108 and 120 h in LUF mares than in controls. Plasma concentrations of PGFM and estradiol did not differ significantly between groups. In Experiment 2, the three mares that did not develop LUFs were treated, during the consecutive cycle, with the same dose of FM but with increased frequency at zero, 12, 24, 30, 36, and 48 h after hCG. One mare formed a LUF, whereas the other two did not. These two mares had lower LH concentrations than LUF or control mares in the two consecutive cycles. In conclusion, systemic treatment with FM blocked ovulation in 73% of treated mares. Mares with LUFs had lower progesterone and higher LH concentrations than control mares.

In this paper, the effect of clinical symptoms of uterine inflammation on progesterone profile characteristics was quantified in dairy cows. A continuous scale based on visual observation of vaginal discharge (the previously developed D-index) was used to describe the clinical symptoms. Progesterone profiles in milk were used to describe the ovarian cycles, and to determine the distinguishing features of these profiles, a multivariate statistical procedure (principal component analysis) was performed. Significant negative effects of the D-index were seen during the first and second postpartum ovarian cycles. The D-index had a significant effect on the shape of progesterone profiles and the length of the ovarian cycles but it only accounted for a small proportion of the variation in these ovarian cycle features. The D-index was not a significant risk factor for the length of postpartum anovulatory period in the present study. In this paper, the effect of clinical symptoms of uterine inflammation on progesterone profile characteristics was quantified in dairy cows. A continuous scale based on visual observation of vaginal discharge (the previously developed D-index) was used to describe the clinical symptoms. Progesterone profiles in milk were used to describe the ovarian cycles, and to determine the distinguishing features of these profiles, a multivariate statistical procedure (principal component analysis) was performed. Significant negative effects of the D-index were seen during the first and second postpartum ovarian cycles. The D-index had a significant effect on the shape of progesterone profiles and the length of the ovarian cycles but it only accounted for a small proportion of the variation in these ovarian cycle features. The D-index was not a significant risk factor for the length of postpartum anovulatory period in the present study.

To test the efficacy and clinical safety of a low and high dose of the GnRH antagonist, acyline, on estrous cycle interruption and anovulation in female dogs, 20 proestrous (3d) bitches were randomly assigned to one of the following pharmacological protocols (given sc): acyline 110 microg/kg (ACY-L; n=6); acyline 330 microg/kg (ACY-H; n=8); or placebo (PLACE, n=6). The animals were monitored (clinical and vaginal cytology examinations) daily for 60d. Blood samples for serum progesterone serum concentrations were collected 14d after treatment to determine if ovulation had occurred. Appearance of side effects and days to the onset of the first spontaneous estrous cycle after treatment were also recorded. In both ACY groups, but not the PLACE group, estrous cycles were interrupted after treatment (P0.05). The interval from treatment to estrus interruption in ACY-L and ACY-H groups was 3.0+/-0.6 and 3.2+/-0.2d, respectively (LSM+/-SEM; P0.05). In the PLACE bitches, physical, behavioral and cytological proestrus slowly progressed to estrus and diestrus. Ovulation was absent in all ACY, but not in PLACE bitches (P0.05). None of the females manifested side effects related to the treatments (P0.05). Spontaneous return to a normal estrous cycle during the study period occurred in all ACY (ACY-L 19.5+/-2.7d vs ACY-H 24.8+/-2.0d; P0.05), but in none of the PLACE bitches (P0.05). In conclusion, acyline efficiently, safely and reversibly interrupted an early phase of the estrous cycle in bitches by preventing ovulation.

Most equine infertility cases can be solved with a methodical, thorough physical and reproductive examination and appropriate diagnostic laboratory aids. Repeated examinations may be needed in some cases to identify subtle anatomical abnormalities or irregularities between hormonal and physiological relationships of the reproductive tract. For pregnancy to occur, hormonal signaling must be exquisitely synchronized with physical changes of the reproductive tract and deposition of fertile semen in the uterus. Asynchrony of these events, infection, inflammation, previous trauma to the reproductive tract or “stress” can interfere with conception or maintenance of pregnancy. Infertile mares are presented for three common problems: (1) accumulation of intra-uterine fluid during or immediately after estrus; (2) long standing infection and/or chronic inflammation; or (3) irregular or no estrous cycles. By defining the problem, diagnostics can be chosen to determine the cause. Treatment protocols should be designed around the diagnosis and antibiotics, ecbolics or steroids should not be used indiscriminately. In all cases of mare infertility, semen quality needs to be determined to be satisfactory as a subfertile stallion bred to a subfertile mare greatly decreases the likelihood of pregnancy.

The primary objective was to evaluate fertility of anovular dairy cows given GnRH 4 d after first postpartum timed AI (TAI). Secondary objectives were to determine ovulatory response to treatment, effect of treatment on serum progesterone (P(4)) concentrations, and the proportion with a short luteal phase. Lactating Holstein cows (n=1047) were submitted for first postpartum TAI using a Presynch+Ovsynch protocol. Anovular cows were identified from an initial 1047 lactating Holstein cows using transrectal ultrasonography, based on the absence of a CL at the first GnRH injection of a Presynch+Ovsynch protocol, and anovular cows were randomly assigned to receive either no further treatment (Control, n=85), or 100 microg of GnRH 4 d after TAI (GnRH treated; n=71). For GnRH treated cows, 51% responded by ovulating a follicle in response to GnRH treatment 4 d after TAI; however, pregnancies per AI (P/AI) did not differ between GnRH treated cows that ovulated (36%) compared to GnRH treated cows that did not ovulate (21%). There was a quadratic effect of P(4) at the PGF(2 alpha) injection of Ovsynch on P/AI, and cows with P(4)or=1 ng/mL at the PGF(2 alpha) injection of Ovsynch had greater P/AI (41%) than cows with P(4)1 ng/mL (12%); however, no treatment difference was detected. Overall, P/AI did not differ between control (30.1%) and GnRH treated (29.6%) treatments for synchronized cows. Although treatment of anovular cows with GnRH 4 d after TAI failed to improve fertility, variation among cows in serum P(4) at the PGF(2 alpha) injection of Ovsynch dramatically affected fertility of anovular dairy cows.

The study was conducted to identify the mechanisms of endotoxin/cortisol action in the suppression of preovulatory LH surges in heifers infused with Escherichia coli (E. coli ) endotoxin. The hypotheses tested were that 1) endotoxin stimulates the release of progesterone, possibly from the adrenal leading to the LH blockade; 2) cortisol released in response to endotoxin infusion blocks the synthesis of estradiol at the ovarian level, culminating in a failure of the LH surge. Eight Holstein heifers were given two injections of prostaglandin F(2alpha) (PG), 11 d apart, to synchronize estrus. Starting from 25 h after the second injection of PG (PG-2), the uterus of each heifer was infused either with 5 ml of pyrogen-free water (control, n = 3) or with E. coli endotoxin (5 mug/kg of body weight) in 5 ml of pyrogen-free water (treated, n = 5), once every 6 h for 10 treatments. Blood samples were obtained every 15 min for 1 h before infusion and again 2 h after each infusion, then hourly until 1 h before the next infusion. After the tenth infusion, blood was collected daily until estrus. Serum progesterone concentrations remained at baseline values (< 1 ng/ml) in control and treated heifers. The total amount of progesterone measured starting 24 to 84 h after PG-2 injection was not different between control and treated heifers (P 0.05). In the control heifers, serum estradiol concentrations remained basal (< 10 pg/ml) until 4 h before the LH surge. Serum estradiol concentrations increased to 20 +/- 5.6 pg/ml, 4 h before the LH surge in control heifers (LH surge occurred 60 to 66 h after the PG-2 injection). There were no changes in serum estradiol concentrations in treated heifers during the sampling period, and the concentrations remained < 10 pg/ml. The total amount of estradiol measured in control heifers was higher (P < 0.05) than in treated heifers. The results if this study suggest that increases in cortisol concentrations after the infusion of endotoxin might block the synthesis of estradiol at the ovarian level, resulting in the failure of a preovulatory LH surge to occur.

Preovulatory serum progesterone concentrations are used to estimate the day of LH peak (day 0), not only to accurately time insemination and predict parturition, but to identify abnormal or unusual estrous cycles due to ovarian dysfunction. Early identification of these disorders is of therapeutic and economic importance. This review discusses anovulation, slow preovulatory progesterone rise, "split heat", insufficient luteal phase, and persistent estrus in the bitch. Some of these were temporary dysfunctions; with appropriate breeding management, pregnancy can be achieved. However, in other cases, these were signs of severe, permanent ovarian dysfunction associated with infertility, with potentially lethal sequelae.

Three experiments were conducted during the operational breeding season to confirm that continuous, subcutaneous infusion of low-dose GnRH would not disrupt established estrous cycles (Experiment 1), and test the hypotheses that a similar treatment would stimulate secretion of LH and induce development of ovulatory follicles in persistently anovulatory mares (Experiments 2 and 3). Treatment with GnRH (5 microg/h) increased (P0.001) serum P4 during the luteal phase (7.7+/-0.5 versus 6.4+/-0.5 ng/mL), tended to increase serum LH (2.6+/-0.27 versus 1.9+/-0.25 ng/mL), and did not modify interovulatory intervals. In Experiment 2, GnRH treatment (2.5-5 microg/h) of persistently anovulatory mares increased (P0.001) serum LH compared to controls (0.5+/-0.08 versus 0.1+/-0.03 ng/mL), with all GnRH-treated and no Control mares ovulating. Mares exhibiting Delayed Recrudescence (n=29) or Lactational Anovulation (n=18), were assigned randomly in Experiment 3 to receive either (1) GnRH/GnRH (n=23); 2.5 microg GnRH/h for 14 d (Period I) and 5 microg/h during the subsequent 28 d (Periods II and III); or (2) Control/GnRH (n=24); no treatment during Period I (control period) and GnRH treatments as in 1 during Periods II and III. Percentage of mares ovulating and pregnant during Period I was greater (P0.05) for GnRH-treated than Control mares. Thereafter, cumulative ovulation frequency (85%), pregnancy (72%) and cycles/conception (1.3+/-0.2) were similar between groups; however, interval to conception was reduced (P0.01) by 10.3 d in GnRH/GnRH compared to Control/GnRH.

We tested the hypothesis that continuous subcutaneous treatment with low-dose GnRH, administered to mares from late September/early October through March, would prevent the development of seasonal anovulation. Quarter Horse mares (n=20) were stratified by age and body condition score and assigned randomly to either a saline control (n=9) or a GnRH (n=11) treatment group. Gonadotropin-releasing hormone was delivered continuously via osmotic minipumps, with sham pumps placed in control mares. Initial pumps were inserted on Day 3 following ovulation or during the follicular phase if the next anticipated ovulation did not occur by 9 October. Delivery rate of GnRH was 2.5 microg/h (60 microg/day) for the first 60 days, followed by 5.0 microg/h (120 microg/day) thereafter. Pumps were replaced every 30 days. Eighty and 100% of all mares had become anovulatory by 1 November and 1 December, respectively, and remained anovulatory through the end of February. Neither serum concentrations of LH throughout the study nor total releasable pools of LH in March differed between groups. Although control mares that exhibited ovulatory cycles after study onset had greater (P0.05) mean concentrations of LH during the follicular phase and metestrus compared to GnRH-treated mares, neither size of ovulatory follicles nor interovulatory intervals differed between groups. Serum concentrations of FSH were not affected by treatment, but were lowest (P0.05) from November through January. Continuous infusion of low-dose GnRH, beginning soon after autumnal equinox and continuing until just after vernal equinox, failed to prevent the occurrence of or to hasten transition from seasonal anovulation.

The objective of this study was to monitor ovarian function in postpartum primiparous and pluriparous Mediterranean Italian buffaloes (Bubalus bubalis) during months of increasing daylength. Ovarian ultrasound monitoring was carried out for a total of 60 days from calving in 10 primiparous and 10 pluriparous buffaloes. Progesterone was determined from calving until a week after first postpartum ovulation. The study was undertaken during months of increasing day length. Time required for complete postpartum uterine involution was 31 +/- 1.0 and 33 +/- 1.3 days in primiparous and pluriparous buffaloes respectively (P = 0.1). The first postpartum ovulation was recorded on 4 primiparous and 8 pluriparous buffaloes (P = 0.16). Time for first postpartum ovulation to occur was 25.5 +/- 6.9 and 15.5 +/- 1.3 days in primiparous and pluriparous buffaloes, respectively (P = 0.07). Overall, 8 of the 12 first postpartum ovulations (66.6%) occurred in the ovary contra-lateral to the one bearing the gravidic CL, one out of 4 in primiparous and 3 out of 8 in pluriparous buffaloes (P = 1.0). Following a first postpartum ovulation, 3 primiparous and 4 pluriparous buffaloes displayed a complete wave of follicular development leading to a new ovulation. Ovulation following parturition was not recorded in 6 primiparous and two pluriparous buffaloes for the 60 days of ultrasound monitoring. Growth rate (mm/d) and largest size (mm) of first postpartum ovulating follicle was 0.95 +/- 0.18 and 1.07 +/- 0.07 (P = 0.4), and 13.5 +/- 0.8 and 14.1 +/- 0.4 (P = 0.4) in primiparous and pluriparous buffaloes, respectively. Following calving, the total number of available antral follicles (or =2 mm) declined gradually towards the end of the study period. Follicles greater or equal to 3 mm in diameter on the contrary showed a prominent increase in the first 2 weeks from calving. The number of follicles greater or equal to 3 mm in diameter was significantly higher in the ovary contra-lateral to the one bearing the gravidic CL. A balance in the number of such follicles was reached toward the end of the first month. In conclusion, although some follicular activity was recorded in the ovaries of all buffaloes, true postpartum resumption of cyclicity in the months of increasing daylight hours was delayed in the majority of animals.

Ovulation failure and double ovulation rates were examined in 1917 inseminations performed in high-yielding dairy cows under standard commercial conditions. The ovulation rate was determined 11 days post-insemination by ultrasound detection of at least one corpus luteum in the ovaries. Analyzing the double ovulation and pregnancy rates, the study population consisted only of ovulated cows (n = 1792). Data were analyzed using logistic regression methods. A failure to ovulate was recorded in 125/1917 (6.5%) services: 82/663 (12.4%) during the warm and 43/1254 (3.4%) during the cool period. Based on the odds ratios, the risk of ovulation failure was 3.9 times higher for inseminations performed during the warm period. No significant effects of estrous synchronization, milk production and days in milk at AI, and service and lactation number on ovulation failure were found. Double ovulation was recorded in 277/1792 (15.5%) services: 146 (52.7%) unilateral double ovulations (42.5% left versus 57.5% right); 115 (41.5%) bilateral double ovulations; and 16 (5.8%) triple ovulations. Double ovulation was recorded in 72 (12.4%) and 205 (16.9%) AI during the warm and the cool period, respectively. The percentages of double ovulation for first, second and third or more lactations were 6.7, 16.6 and 25%, respectively. Double ovulation rates for early (less than 90 days), mid- (90-150 days) and late (more than 150 days) lactation periods were 13, 20.7 and 14.2%, respectively. Reaching estrus during the warm period decreased the likelihood of double ovulation by a factor of 0.86; the risk of double ovulation was lower in cows with higher milk production (a 1 kg increase in milk yield led to a 0.97-fold reduced risk of double ovulation); cows in their second and in their third or more lactations showed a likelihood of double ovulation (using the first lactation as reference) increased by factors of 3.4 and 5.6, respectively; and reaching estrus during the early and late lactation period was related to a decreased probability of double ovulation (using the mid-lactation period as reference) by factors of 0.56 and 0.84, respectively. No significant effects of synchronization and service number on the double ovulation rate were found. Pregnancy was recorded in 914/1792 (51%) services: rates of 53.5% (811/1515) were recorded for single ovulations; 37.2% (103/277) for double ovulations: 28.8% (42/146) for unilateral double ovulations; 45.2% (52/115) for bilateral double ovulations; and 56.3% (9/16) for triple ovulations. The likelihood of pregnancy diminished in cows: inseminated during the warm period (by a factor of 0.5); inseminated by one particular bull (by a factor of 0.33); with higher milk production (a 1 kg increase in milk yield decreased the probability of pregnancy by a factor of 0.98); or undergoing unilateral (by a factor of 0.31) and bilateral (by a factor of 0.64) double ovulation. Logistic regression analysis indicated no significant effects of synchronization, days in milk, lactation number and service number on pregnancy rate. Collectively, our results indicate that cows showing estrus in conditions of heat stress had a high risk of ovulation failure. The effect of milk production on double ovulation was negative, whereas lactation number was positively correlated with this factor; the highest incidence of double ovulation occurring during the mid-lactation period.

The ovaries of 12 mature wapiti hinds were studied by transrectal ultrasonography during the anovulatory season to characterize follicular dynamics and to test the hypothesis that follicle development occurs in a wave-like fashion. The hinds were examined daily, standing without sedation. Follicle size and numbers were recorded, and individual follicles were identified serially. Follicle development was considered wave-like if periodic changes in follicle numbers could be associated temporally with the development of a dominant follicle. There were non-random changes (P0.01) in the number of folliclesor =4 mm in diameter detected per day. Each peak in follicle numbers was associated with the development of a single dominant follicle. The dominant follicle of the cohort was larger (P0.05) than the other follicles 1 day after its emergence. Intervals between successive peaks (6.8 +/- 0.4 day) and troughs (6.8 +/- 0.4 day) in follicle numbers, and emergence of sequential dominant follicles (7.1 +/- 0.5 day) were not different (P=0.86). Results confirmed the hypothesis that ovarian follicles develop in a wave-like fashion in wapiti during the anovulatory season.

The primary objective of this study was to investigate the effects of abnormal ovarian cycles during the pre-service postpartum period on subsequent reproductive performance of high-producing Holstein cows. The study was conducted in a commercial dairy farm with approximately 150 lactating cows, in a subtropical region of Japan. Animals were kept in free-stall barn, and fed a total mixed ration. Cows that calved from June 2001 to July 2002 were included in the study. Milk samples were collected twice weekly from 2 to 11 weeks postpartum, and progesterone concentrations in skim milk were determined by ELISA. After a voluntary waiting period of 40 days, cows detected in estrus were bred by artificial insemination (AI). Pregnancy was confirmed by palpation per rectum 40-70 days after AI. Out of a total of 91 cases, 39 (42.9%) had normal ovarian cycles (ovulation within 45 days after calving, followed by normal ovarian cycles), 32 (35.2%) had prolonged luteal phase (i.e. luteal activity for >20 days), and 12 (13.2%) had anovulation or delayed first ovulation (i.e. first ovulation did not occur until >45 days after calving). The remaining (8.8%) had other types of abnormalities. When compared with cows with a normal ovarian cycle, prolonged luteal phase cows had a lower 100 days AI submission rate, conception rate and pregnancy rate (84.2% versus 56.3%; P