Luteal function of induced corpora lutea in the bitch

Nineteen anestrous bitches with a mean of 22 kg body weight and ranging from 2 to 4 years of age were induced to exhibit estrus and ovulate using PMSG and HCG. Twelve days after the first day of estrus, bitches were assigned to four treatment groups. Group (A) consisted of six bitches, Group (B) of five bitches and Groups (C) and (D) of four bitches each. At this time, bitches in Groups (A), (B) and (C) were laparotomized and those assigned to Groups (A) and (B) were bilaterally hysterectomized leaving the cervix and oviducts intact. Although bitches in Group (C) were laparotomized, they were not hysterectomized. Group (D) bitches were not subjected to any surgical procedures. Homologous uterine extract was prepared from each bitch in Group (A) and administered intramuscularly beginning on day 25 (day 0 = first day of estrus) and continued every other day for 61 days post-estrus. Bitches in Group (B) were similarly injected with equal volumes of 0.9% saline. Blood samples, obtained prior to laparotomy and every other day for 85 days thereafter, were assayed for plasma progesterone concentrations using radioimmunoassay. One bitch in each of Groups (A) and (D) did not form luteal tissue following treatment with PMSG and HCG although both bitches exhibited estrus following treatment. All other bitches showed an increase in progesterone levels (4 to 19 ng/ml) between the first day of estrus and 10 days post-estrus. Thereafter, progesterone levels progressively declined in all groups with levels below 1 ng/ml between 38 to 40 days post-estrus. Results of this study suggested that CL formed in the bitch following PMSG and HCG treatment have a reduced function compared to non-induced CL of a normal, non-fertile estrous cycle. Such premature CL regression appears to be independent of the presence or absence of the uterus.     

Premature luteal regression in goats superovulated with PMSG: effect of hCG or GnRH administration during the early luteal phase

Twenty-two goats were superovulated with PMSG; 84 h after the onset of estrus the goats were treated with saline solution (control group n = 7), hCG (hCG group, n = 7), or GnRH (GnRH group, n = 8). The ovaries of all the goats were laparoscopically examined 3 and 6 d after the onset of estrus. In each case the CL were counted and classified according to their appearance as normal-looking or as regressing. Blood samples for progesterone determination were collected every 12 h from Day 1 to Day 6. Premature luteal regression was considered to have occurred if progesterone concentrations declined to less than 1 ng/mL by Day 6. According to progesterone concentrations, 57.5, 0 and 37.5% of the goats underwent premature luteal regression in the control, hCG and GnRH groups, respectively. Progesterone concentrations were higher in the hCG group than in the other groups on Days 5 and 6 post estrus (P < 0.05). The control group was the only one in which there was a significant (P < 0.05) increase in the number of regressing CL between Day 3 (1.6 +/- 1.4) and Day 6 (7.3 +/- 1.4). It was also the only group in which there was a significant decrease in the number of normal-looking CL between Day 3 (12.6 +/- 2.1) and Day 6 (2.6 +/- 2.1). On Day 6 the animals treated with hCG had significantly more normal-looking CL (12.0 +/- 2.3) than those in the control group (2.6 +/- 2.1). The number of large follicles present on the ovaries on Day 6 post estrus had negative correlations with progesterone concentrations (P = 0.05) and with the number of normal-looking CL (P < 0.05). It is concluded that the administration of hCG 84 h after the onset of estrus prevents premature luteal regression in goats superovulated with PMSG.     

Assessment of superovulatory responses in terms of palpable corpora lutea and embryo recovery using milk progesterone

Milk progesterone profiles were used to assess superovulatory responses in cyclic lactating buffalo (n = 9) in terms of the number of ovulations and the number of embryos recovered. All of the buffalo received a total of 30 ml of folltropin divided into morning and evening doses and spread over 5 days, beginning on Day 10 of the estrous cycle (day of expected estrus = Day 0). Milk samples for progesterone determination were collected on alternate days from all nine animals from Day 1 prior to the expected synchronized estrus to 5 days after flushing for embryo recovery. All animals were palpated per rectum 1 day prior to flushing in order to record the number of corpora lutea. Of an estimated 23 ovulations from the nine buffalo, only 12 embryos were recovered, of which one was an unfertilized oocyte. Milk progesterone profiles from individual buffalo suggested that a poor superovulatory response in terms of embryo recovery in some buffalo was caused by a failure to respond optimally to lutalyse treatment for the induction of estrus. It was hypothesized that ova trapping by the fimbriae of the fallopian tubes may not be efficent in this species especially in the superovulated ovaries.     

Estrus synchronization with lower dose of PGF2 alpha and subsequent fertility in subestrous buffalo

Two experiments were conducted to determine luteal regression, estrous response and fertility in buffalo receiving cloprostenol via 2 routes of administration. In Experiment 1, cyclic buffalo (n = 10) were assigned to 2 equal groups receiving either 500 micrograms i.m. cloprostenol (Estrumate, ICI) or 125 micrograms cloprostenol injected intravulvosubmucosal (ivsm) ipsilateral to the side of the corpus luteum (CL) on Day 11 of an induced estrous cycle. Serum progesterone (P4) concentrations were evaluated immediately before treatment and at 24, 48, 72, 96 and 120 h after PGF2 alpha administration. The decline in serum P4 concentrations was significantly different (P < 0.05) between groups up to 48 hrs after treatment. However, no significant difference (P > 0.05) was observed for the interval from treatment to the onset of estrus (94.9 +/- 10.7 vs 96.0 +/- 15.9 h) for 500 or 125 micrograms of cloprostenol groups, respectively. In Experiment 2, multiparous, lactating subestrous buffaloes (n = 137) were treated either with 125 micrograms ivsm cloprostenol or 500 micrograms i.m. cloprostenol (n = 28 vs 33, respectively) during peak breeding (September-February) or low breeding (March-August) season (n = 37 vs 39, respectively). Buffalo observed in estrus were inseminated twice with frozen-thawed semen at 12 and 22 h after the onset of estrus. Buffalo that failed to exhibit estrus were given a second equal dose of cloprostenol at an 11-d interval and underwent fixed-time insemination at 72 and 96 h. The interval to the onset of estrus was 85.0 +/- 4.4 vs 73.2 +/- 2.6 h during peak breeding and 96.1 +/- 2.6 vs 92.1 +/- 3.8 h during the low breeding season for buffalo treated with 125 and 500 micrograms cloprostenol, respectively. These intervals were different (P < 0.05) between seasons but not between treatments in the same season. Conception rates of 47.8 vs 53.1% during peak breeding and 23.5 vs 25.6% during low breeding season were also different (P < 0.05) between seasons but not between the treatments in the same season for buffalo treated with 125 and 500 micrograms cloprostenol, respectively. These results indicated that 125 micrograms ivsm and 500 micrograms i.m. cloprostenol were equally effective for synchronizing estrus in subestrous buffalo. No negative effect of a lower dose of cloprostenol was observed on estrus synchrony and subsequent fertility; however, season of treatment had a significant effect on conception rates.     

Ovarian superstimulation after follicular wave synchronization with GnRH at two different stages of the estrous cycle in cattle

The objective of this study was to evaluate superovulatory programs based on synchronization of follicular waves with GnRH at 2 different stages of the estrous cycle. Sixteen Holstein cows were randomly assigned to 1 of 3 groups and administered GnRH (Cystorelin, 4 ml i.m.) between Days 4 and 7 (Groups 1 and 3) or between Days 15 and 18 (Group 2) of the estrous cycle (estrus = Day 0). Four days after GnRH treatment, > or = 7-mm follicles were punctured in Groups 1 (n = 6) and 2 (n = 6) or were left intact in Group 3 (n = 4). All cows were superstimulated 2 d later (i.e., from Days 6 to 10 after GnRH treatment) with a total of 400 mg NIH-FSH (Folltropin-V) given twice daily in decreasing doses. The GnRH treatment caused a rapid disappearance of large follicles (P < 0.005), rapid decrease in estradiol concentrations (P < 0.003), and increase in the number of recruitable follicles (4 to 6 mm; P < 0.04), indicative of the emergence of a new follicular wave within 3 to 4 d of treatment. Between 4 and 6 d after GnRH treatment, the mean number of 4- to 6-mm follicles decreased (4.7 +/- 1.8 to 1.5 +/- 3.3) in the nonpunctured group but increased (3.9 +/- 1.0 to 7.3 +/- 1.9) in the punctured group of cows (P < 0.05). In response to FSH treatment, the increase in the number of > or = 7-mm follicles was delayed by approximately 2 d in the nonpunctured group (P < 0.006). Moreover, the mean number of > or = 7-mm follicles at estrus was higher (16.9 +/- 1.7 vs 11.5 +/- 3.0; P < 0.1) in the punctured than the nonpunctured group. The increase in progesterone concentration after estrus was delayed in the nonpunctured group (P < 0.1) compared with the punctured follicles. Mean numbers of CL as well as freezable (Grade 1 and 2) and transferable (Grade 1, 2 and 3) embryos were similar (P > 0.1) in punctured and nonpunctured groups. Spontaneous estrus did not occur prior to cloprostenol-induced luteolysis in any group, and stage of the estrous cycle during which GnRH was given did not affect (P > 0.1) hormonal and follicular responses in the punctured groups. In conclusion, GnRH given at different stages of the estrous cycle promotes the emergence of a follicular wave at a predictable time. Puncture of the newly formed dominant follicle increases the number of recruitable follicles (4 to 6 mm) 2 d later and, in response to superstimulation with FSH, causes a greater number and faster entry of recruitable follicles into larger classes (> or = 7 mm) and a faster postovulatory increase in progesterone concentrations.     

Ultrasonographic determination of ovarian follicular. Development in superovulated heifers pretreated with FSH-P at the beginning of the estrous cycle

On Day 3 of the estrous cycle (estrus = Day 0), dairy heifers were given either 10 mg i.m. FSH-P (FSH-P primed; n = 9) or a saline vehicle (saline primed; n = 9). On Day 10, all heifers were superovulated with FSH-P (total = 27.7 mg i.m.) in declining doses over 5 d. Heifers were inseminated artificially at estrus. From Day 2 until estrus, the number and size of follicles >2 mm were monitored daily by ultrasonography. The mean (+/- SEM) number of corpora lutea (CL) (6.2 +/- 1.5 vs 10.7 +/- 0.9; P<0.05) and the mean number of recovered embryos and unfertilized ova (3.6 +/- 1.7 vs 8.4 +/- 2.2; P<0.05) were lower in FSH-P-primed than in saline-primed heifers. Prior to initiation of superovulation, follicles >10 mm appeared on Days 6 to 7 in saline-primed heifers but only on Days 8 to 10 in FSH-P-primed heifers (P<0.05). Also, until Day 10, the mean number of follicles 4 to 6 mm and 7 to 10 mm was higher (P<0.05) in FSH-P-primed than in saline-primed heifers. After initiation of the superovulatory treatment (Day 10 to estrus), saline-primed heifers had a greater and faster increase in the mean number of follicles >10 mm (P<0.02) than FSH-P-primed heifers did. Depletion in the number of follicles 2 to 3 mm (P<0.001) between Day 10 and estrus and in the number of follicles 4 to 6 mm (P<0.05) between Day 12 and estrus occurred in both groups of heifers. Decreased superovulatory response and embryo recovery in FSH-P-primed heifers may have been due to the presence of large follicles (>10 mm) prior to the initiation of the superovulatory treatment which reduced the ability of small follicles to grow into larger size classes during superovulatory treatment.     

Superovulatory and endocrine responses in heifers treated with FSH-P at different stages of the estrous cycle

Forty-two Holstein heifers were superovulated with FSH-P (total dose, 30 mg) and cloprostenol. Treatment was initiated on Day 3 (Group D3, n = 11), Day 6 (Group D6, n = 11), Day 9 (Group D9, n = 10) or Day 12 (Group D12, n = 10) of the estrous cycle. Heifers were bled daily for serum progesterone and estradiol-17beta determinations and every 6 h for a 48-h duration at the expected time of estrus for luteinizing hormone (LH) assay. Ova and embryos were flushed from the reproductive tracts and the number of corpora lutea (CL) were recorded after slaughter on Day 7 post-estrus. Mean (+/- SEM) numbers of observed CL were higher (P < 0.05) in Group D9 (33.3 +/- 4.8) than in Group D3 (15.3 +/- 3.8), with Group D6 (17.0 +/- 2.9) and Group D12 (23.9 +/- 7.3) being intermediate. Similarly, mean (+/- SEM) numbers of fertilized embryos were highest (P < 0.05) in Group D9 (13.3 +/- 2.2). There was also a nonsignificant trend for the number of transferable embryos to be greatest in Group D9. Neither serum progesterone concentrations 3 d after the LH peak nor peak serum estradiol 17beta concentrations differed among groups, but both were significantly correlated with numbers of observed CL and total ova and embryos.     

Effect of timing of prostaglandin PGF 2 alpha injection subsequent to embryo collection on the resumption of normal follicular development following superovulatory treatment in cattle

Nonlactating Holstein and Jersey cows (n = 24) were superovulated and ovarian follicular development was monitored by transrectal ultrasound during the period after embryo recovery. Luteolysis was induced by two injections of prostaglandin F(2)alpha (PGF; 25 mg Lutalyse; 12-h interval) at specific times after superovulatory induced estrus (Treatment 1, Day 9; Treatment 2, Day 12; Treatment 3, Day 17; Treatment 4, Day 25; superovulatory estrus = Day 0 of Cycle 1). Follicular development was monitored during Cycle 1 before and after PGF injection and continued through the ensuing estrous cycle (Cycle 2). Superovulation led to more than one embryo collected in 14 cows (mean = 8.71 embryos: positive superovulatory response [PSR] cows), while 10 cows were not successfully superovulated (mean = 0.1 embryo; negative superovulatory response [NSR] cows). These cows differed in terms of number of unovulated follicles detected at embryo collection (4.21 vs 17.2, PSR vs NSR) and plasma progesterone during the superovulatory estrous cycle (32.3 ng/ml PSR vs 8.6 ng/ml NSR). Follicular development during Cycle 1 started sooner in NSR than in PSR cows (day by class by response P<0.03) and was initiated on Days 11 to 12 in NSR cows and on Days 19 to 20 in PSR cows. Interval to estrus after PGF averaged 6.3 d. Cows having short intervals to estrus had follicles at the time of PGF injection. Treatment influenced the length of Cycle 1, but it did not affect the interval to estrus after PGF, the length of Cycle 2, or follicular development during Cycle 2. The results indicate that 1) the timing of PGF injection after embryo collection does not influence subsequent follicular populations, 2) elongated estrous cycles and intervals to estrus after PGF in superovulated cattle are a function of decreased follicular activity, and 3) the presence of numerous corpora lutea and not the superovulatory treatment, per se, seem to attenuate follicular growth.     

Premature regression of the corpora lutea in superovulated cows

Morphological and functional regression of the CL was shown by $\text{15}\text{55}$ (27%) superovulated dairy cows at slaughter on D 14. Neither the routine injection of a PMSG-antiserum at the induced superovulatory oestrus, nor intrauterine infections proved to be responsible. Animals with regressed CL however had significantly lower progesterone levels in the peripheral blood at the time PMSG (D 10, P = 0,05) and prostaglandin (D 12, P = 0,02) were injected, as compared to superovulated animals with normal CL. At the induced superovulatory heat, the differences between the 2 groups disappeared. From D 4 after superovulation the differences in progesterone concentration between the 2 groups became significant again (P = 0,02 – 0,05). It is not yet clear whether the observed luteal dysfunction is due to an inadequate luteotrophic stimulus or to a premature luteolysis. The luteal regression could be caused either by a genuine luteal insufficiency of the midcyle CL or by poor heat detection.     

Effects of oxytocin on follicular development and duration of the estrous cycle in heifers

Holstein heifers were used to study effects of exogenous administration of oxytocin on luteal function and ovarian follicular development. Twelve heifers were monitored for 1 estrous cycle to confirm normal ovarian function. At the subsequent estrus, these animals were randomly assigned to 1 of 3 treatments: saline control, (Group 1, n=4), oxytocin (Group 2, n=4) and saline pregnant (Group 3, n=4). Group 2 received continuous infusion of oxytocin (1.9 mg/d) from Days 14 to 26 after estrus, while Groups 1 and 3 received saline infusion during the same period. Group 3 were artificially inseminated at estrus. Daily blood samples were collected for oxytocin and progesterone assay. Ovarian follicles and corpus luteum (CL) development were monitored daily by transrectal ultrasonography until Day 32 after estrus. Plasma progesterone (P4) concentrations prior to initiation of infusion were 7.6+/-1.3 ng/mL on Day 14. They then decreased to <1 ng/mL on Day 19 for Group 1 and on Day 28 for Group 2. The interestrous interval was longer (P <0.05) for heifers that received oxytocin infusion. During the infusion period P4 concentrations were not different (P >0.05) between Group 2 and 3 but declined gradually from Day 20 in Group 2 despite the presence of high plasma oxytocin concentrations. Control heifers had 2 waves of follicular growth, with the second dominant follicle ovulating. Three of the 4 oxytocin-infused animals had an additional wave, with the third dominant follicle ovulating. Oxytocin infusion had no effect on size of the ovulating follicle (P >0.05) and the number of Class 1 follicles (3 to 5 mm, P >0.1). Differences in the number of Class 2 follicles (6 to 9 mm) among treatments on Days 15 to 22 after estrus were not detected (P >0.1) except on Days 23 to 26, when Group 2 had fewer follicles than Group 3 (P <0.05). The results show that continuous infusion of oxytocin during normal luteolysis delays luteal regression without inhibiting follicular development.     

Follicular dynamics in water buffalo superovulated in presence or absence of a dominant follicle

The ovaries of 12 buffalo were examined daily by ultrasound beginning at Day 3 of the estrous cycle, followed by superovulation between Days 10 and 13 of the cycle. The buffalo were divided into 2 groups on the basis of the presence (dominant, n = 7) or absence (nondominant, n = 5) of a dominant follicle at the start of superovulation. Daily ultrasonographic observations of the ovaries were recorded on a videotape and were used to assess the progression of both the large (dominant) follicle and the next-to-the-large (subdominant) follicle as well as the numbers of follicles in the small (4 to 6 mm), medium (7 to 10 mm), and large (>10 mm) size categories, before and during the superovulation treatment. A greater number of small size (P < 0.05) follicles was available before the start of the superovulatory treatment in the buffalo superovulated in the absence of a dominant follicle. The turnover of follicles from medium to large size classes also occurred sooner (P < 0.01), and was of higher magnitude (P < 0.01) during treatment in buffalo of the nondominant follicle group. The number of corpora lutea at palpation per rectum was higher (P < 0.05) in buffalo of the nondominant than the dominant group (4.6 +/- 0.6 vs 2.7 +/- 0.5). However, there was no significant difference among the groups in the means of serum progesterone concentration (3.6 +/- 1.3 vs 2.2 +/- 0.6 ng/ml), total number of embryos (2.0 +/- 0.6 vs 1.1 +/- 0.7), transferable embryos (1.6 +/- 0.5 vs 1.0 +/- 0.6) and unfertilized ova recovered (0.4 +/- 0.2 vs 0) on Day 6. It is concluded that in buffalo, the superovulatory response could possibly be improved by ultrasongraphic observation of the status of follicular dominance prior to treatment.     

Plasma progesterone levels during the estrous cycle of Holstein and Brahman cows, Carora type and cross-bred heifers

Daily plasma progesterone (P(4)) was determined during one estrous cycle of 19 cows and 18 heifers of four different breeds: Holstein (H), Brahman (B), Carora-type (C) and crossbred (CB) females. Estrus detection was made by visual observation and using a teaser bull with a chin-ball marker. The P(4) profiles showed no differences among groups. In Group 1 (H), P(4) levels ranged from 0.5 ng/ml plasma on the day of estrus (Day 0) to 5.1 ng/ml at the luteal phase peak (Day 13). In Group 2 (B), P(4) levels ranged from 0.5 ng/ml on Day 0 to 9.2 ng/ml on Day 13. In Groups 3 (C) and 4 (CB), P(4) levels ranged from 0.5 ng/ml, on Day 0, to 13.7 ng/ml on Day 12 and 8.8 ng/ml on Day 13. These last two groups were moved to the same location and then compared. It was found that P(4) concentrations were significantly higher (P < 0.025) in Group 3 between Days 7 and 14 of the estrous cycle. In all groups, P(4) levels were lower than 1 ng/ml one day before the next estrus, and levels of 0.4, 0.5, 0.4 and 0.4 ng/ml were obtained the day of estrus in Groups 1 to 4, respectively. Results indicated that the pattern of P(4) for each one of the groups was similar to those reported by other investigators.     

Superovulatory response of river bufalo (Bubalus bubalis )

The ovarian response of 25 buffalo-cows was visually assessed, and their oviducts and uteri separately flushed 3 to 6 d post superovulatory estrus at slaughter. Ten buffalo-cows slaughtered on Days 5 and 6 were examined per rectum for corpora lutea (CL) and follicles > 8 mm prior to slaughter, and the estimate was compared later with the actual ovarian response. Five out of the ten buffalo-cows were nonsurgically flushed in vivo on Day 5 of the estrous cycle, a day before slaughtering, and as a result, six ova/embryos were recovered. After the flushing of the reproductive tract at slaughter, one more ovum was recovered from the uterus of each of the three buffalo-cows. As a result of treatment of three groups of five buffalo with 3000 IU pregnant mare serum gonadotrophin (PMSG) on Days 6, 10 or 14 of the estrous cycle, 3.8, 6.2 and 3.4 CL on the average were recovered, respectively (Experiment I). A mean number of 8.8 and 9.0 CL, respectively, was obtained in two groups of five buffalo each, after treatment with 40 mg of follicle stimulating hormone (FSH) on Day 10 of the stage of the estrous cycle (Experiment II) and 3000 IU PMSG regardless of the stage of cycle (Experiment III). The percentage of ova/embryos recovered in the three experiments was 32.8, 20.4 and 22.2, respectively.     

Effects of estradiol-17β and hCG supplementation on superovulatory responses and embryo quality in swamp buffalo (Bubalus bubalis) implanted with norgestomet

Twenty-four cycling swamp buffaloes with normal reproductive histories and 2–3 months postpartum were used to investigate the effect of addition of estradiol-17β and human chorionic gonadotrophin (hCG) to the superovulation regime on the level of ovarian stimulation and embryo production.The estrous cycles of buffaloes were synchronized by prostaglandin injection and then divided into two groups for superovulatory treatment. Those in Group 1 (n = 12) received a implant containing 3 mg norgestomet (Syncro-Mate-B) for 9 days (insertion day is Day 0), with 4000 IU of equine chorionic gonadotrophin (eCG) and 500 μg cloprostenol i.m. given at Day 7. Group 2 (n = 12) received the same regime as Group 1, together with 7.5 mg estradiol-17β given in three intramuscular injections on Days 3, 5 and 7 in decreasing doses (4.0, 2.5 and 1.0 mg, respectively) and 5000 I.U hCG i.v. coincidentally with the first insemination. Estrus was monitored visually and by placing treated animals with bulls. Each animal was inseminated twice with frozen sperm after standing estrus. The numbers of corpora lutea (CL) and follicles greater than 8 mm in diameter were recorded via palpation per rectum at 6 days after implant removal. Two days later 11 animals from Group 2 and two from Group 1 were slaughtered for direct observation of ovarian responses and for embryo collection.The mean number of CL were 0.91 ± 0.66 and 9.08 ± 5.0 for Groups 1 and 2, respectively. The average recovery rate based on CL counts at slaughter was 60% in Group 2. No embryos were recovered from the two animals in Group 1. Seventy-nine percent of the collected ova were fertilized and more than 60% of them had developed into hatched blastocysts. The percentages of buffalo with excellent and good estrus were 41.6 and 91.6% for Groups 1 and 2, respectively.These results showed that the supplementation of estradiol-17β and the hCG treatment significantly improved the level of ovarian stimulation in swamp buffalo.     

Ovarian response to gonadotropin treatment initiated relative to wave emergence in ultrasonographically monitored ewes

Follicular recruitment and luteal response to superovulatory treatment initiated relative to the status of the first wave of the ovine estrous cycle (Wave 1) were studied. All ewes (n = 25) received an intravaginal progestagen sponge to synchronize estrous cycles, and ewes were monitored daily by transrectal ultrasonography. Multiple-dose FSH treatment (total dose = 100 mg NIH-FSH-P1) was initiated on the day of ovulation (Day 0 group) in 16 ewes. In the remaining 9 ewes, FSH treatment was started 3 d after emergence of the largest follicle of Wave 1 (Day 3 group). Ewes received PGF(2alpha) with the last 2 FSH treatments to induce luteolysis. Daily blood samples were taken to determine progesterone profiles and to evaluate the luteal response subsequent to superovulation. The ovulation rate was determined by ultrasonography and correlated with direct observation of the ovaries during laparotomy 5 to 6 d after superovulatory estrus when the uterus was flushed to collect embryos. Results confirmed that follicular recruitment was suppressed by the presence of a large, growing follicle. In the Day 0 and Day 3 groups, respectively, mean numbers (+/- SEM) of large follicles (>/= 4 mm) recruited were 6.4 +/- 0.6 and 2.7 +/- 0.7 (P < 0.01) at 48 h after the onset of treatment, and 6.7 +/- 0.5 and 5.1 +/- 0.6 (P = 0.08) at 72 h after the onset of treatment. Ovulation rates were 5.6 +/- 0.8 and 3.3 +/- 0.8 in the respective groups (P < 0.05). The number of transferable embryos was 1.8 +/- 0.5 and 0.3 +/- 0.2 in the respective groups (P < 0.05). Short luteal phases (相似文献   

Rate of transport and development of preimplantation embryo in the superovulated buffalo (Bubalus bubalis)

This study was designed to ascertain the rate of transport and development of preimplantation embryo in the superovulated buffalo in order to determine the optimum time for their nonsurgical collection. Eighteen Murrah-type buffalo were superovulated with 600 mg NIH-FSH-P1. Luteolysis was induced by administration of PGF2 alpha at 72 (PG + 72) and 84 h (PG + 84) after initiating gonadotrophin treatment and fixed-time AI was done beginning at 36 h post PG + 72 administration and at 12-h intervals thereafter, upto 72 h. Six control buffalo received treatment similar to experimental group except that in place of FSH they received normal saline. For embryo collection, experimental animals were humanely killed at 6-h intervals corresponding to 156 (n = 2), 162 (n = 2), 168 (n = 2), 174 (n = 3), 180 (n = 3), 186 (n = 3) and 192 h(n = 3) after PG + 72 treatment, whereas the control animals were humanely killed at 156 (n = 2), 174 (n = 2) and 192 h (n = 2). Superovulated buffalo had higher number of ovulations than untreated controls (8.78 +/- 5.00 vs 0.67 +/- 0.51) and total ova/embryos recovered was 4.11 +/- 2.46 and 0.67 +/- 0.51, respectively. The high estradiol-17 beta (E2) levels with its prolonged rise may, by leading to reverse peristalsis in the oviduct with a consequent loss of some embryos in the peritoneal cavity, be one of the reasons for our inability to recover nearly 84/158 ova/embryos in the superovulated buffalo. In superovulated animals, nearly all the ova/embryos reached the uterus between 168 and 174 h post PG + 72 treatment or about 134 h (circa 5.5 d) after the onset of superovulatory estrus, suggesting that the ideal time for non-surgical embryo collection in the buffalo is between Days 7 to 8 after PG + 72 treatment or Days 5.5 to 6.0 of the superovulated cycle (estrus = Day 0). Embryo development of superovulated buffalo showed considerable variation as various stages of embryos (8 cell to expanded blastocyst) were recovered from the same donor buffalo, and the rate of development appeared to be 24 to 36 h faster than in cattle.     

Is slow follicular growth the cause of silent estrus in water buffaloes?

The present experiment was conducted to study the growth profile of the ovulatory follicle in relation to the expression of estrus following administration of PGF(2alpha) to subestrus buffaloes. After detection of a mature corpus luteum by examination per rectum, confirmed by ultrasound scanning, subestrus buffaloes (n=20) were treated (Day 0) with single dose of Dinoprost tromethamin (25 mg, i.m.). Blood samples were collected at 0, 24 and 48 h after treatment for estimation of plasma progesterone concentration. Growth profile of the ovulatory follicle was monitored daily through ultrasound scanning starting from Day 0 until ovulation and the regression profile of CL was monitored at 0, 24 and 48 h of treatment. Estrus was detected by exposure to a fertile buffalo bull three times a day until expression of overt estrus or ovulation. Behavioral estrus was recorded in 14 animals and 6 animals ovulated silently. Sixteen animals including six animals with silent estrus ovulated from the dominant follicle present at treatment (Group A) and remaining four animals ovulated from the dominant follicle of succeeding follicular wave (Group B). The intervals from treatment to estrus (6.5+/-0.25 versus 3.2+/-0.27 days, P<0.001) and treatment to ovulation (7.5+/-0.25 versus 5.4+/-0.46 days, P<0.005) were significantly longer in animals of Group B compared with animals of Group A. Significant differences were observed in growth profile of the ovulatory follicle between animals of Groups A and B with respect to size of the follicle on Day 0 (9.8+/-0.7 versus 5.3+/-0.45 mm, P<0.001), daily growth rate (0.97+/-0.07 versus 1.6+/-0.2 mm/day, P<0.01) and increase in diameter (4.1+/-0.6 versus 7.8+/-0.7 mm, P<0.01). The animals with silent estrus (subgroup A-2) had significantly smaller diameter of the ovulatory follicle on Day 0 (7.7+/-0.4 versus 11.0+/-0.7 mm, P<0.005), its daily growth rate was significantly slower (0.7+/-0.02 versus 1.1+/-0.1 mm/day, P<0.01) and they recorded significantly longer interval from treatment to ovulation (7.3+/-0.56 versus 4.2+/-0.27 days, P<0.001) compared with the animals that showed overt estrus (subgroup A-1). The corpus luteum area (CL area) and plasma progesterone (P(4)) concentration declined continuously from 0 to 48 h after PGF(2alpha) treatment in the animals of both the Groups A and B. Non-significant differences were observed in mean CL area and plasma P(4) concentration at 0, 24 and 48 h post-treatment between animals of Groups A and B and also between animals of subgroups A-1 and A-2. The small size and the slow growth rate of the ovulatory follicle were identified as the possible cause of silent estrus in subestrus buffaloes after PGF(2alpha) treatment.     

Superovulation of dairy cows with purified FSH supplemented with defined amounts of LH

This study investigated the effects of a purified follicle stimulating hormone (FSH) preparation supplemented with three different amounts of bovine luteinizing hormone (bLH) and a commercially available FSH with a high LH contamination on superovulatory response, plasma LH and milk progesterone levels in dairy cows. A total of 112 lactating Holstein-Friesian crossbred dairy cows were used for these experiments; the cows were randomly assigned to treatment groups consisting of purified porcine FSH (pFSH) supplemented with bLH. Group 1 was given 0.052 IU LH 40 mg armour units (AU) FSH (n = 6); Group 2 was given 0.069 IU LH (n = 32); Group 3 received 0.423 IU LH (n = 34); while Group 4 cows (n = 36) were superovulated with a commercially available FSH-P((R)). This compound appeared to contain 8.5 IU LH 40 mg AU FSH according to bioassay measurement. All animals received a total of 40 mg AU FSH at a constant dose twice daily over a 4-d period. Levels of milk progesterone and plasma LH were determined during the course of superovulatory treatment. The Group 1 treatment did not reveal multiple follicular growth, and no embryos were obtained. Superovulation of Group 3 cows resulted in significantly (P<0.05) more corpora lutea (CL; 12.6+/-1.1) and fertilized ova (5.1+/-1.3) compared with Groups 2 and 4 (10.1+/-0.9 and 2.6+/-0.6, 9.0+/-0.9 and 2.7+/-0.5, respectively). Due to a high percentage of degenerated embryos (33%) Group 3 yielded only one more transferable embryo than Groups 2 and 4. Among groups, LH levels differed in the period prior to induction of luteolysis and were similar thereafter. The progesterone pattern following FSH LH administration reflected the amount of LH supplementation. Milk progesterone levels on the day prior to embryo collection were correlated to the number of CLs and recovered embryos. It is concluded that under the conditions of our experiment superovulation with 0.423 IU LH 40 mg AU FSH may yield a significantly improved superovulatory response in dairy cows. It is further suggested that LH supplementation exerts its effects mainly on follicular and oocyte maturation during the period prior to luteolysis.     

Uterine involution and postpartum ovarian activity in Nili-Ravi buffaloes

Uterine involution and postpartum ovarian activity were studied in 53 Nili-Ravi buffaloes. Mean intervals to uterine involution (26 days), regression of the corpus albicans of pregnancy (22 days), resumption of follicular activity (21 days) and first postpartum estrus (56 days) were not affected by the month of calving or age. Mean interval to formation of first corpus luteum (CL) after calving as indicated by progesterone in plasma (>/= 1.5 ng/ml) was 23.8 +/- 1.7 days, but only 52% of these CL were palpable. The number of CL formed before first postpartum estrus ranged from zero to five per buffalo; mean values based upon progesterone and palpation were 1.6 +/- 1.3 and 0.8 +/- 0.2, respectively. Based upon either progesterone or palpation, length of first postpartum luteal phase (7.9 or 6.6 days) was shorter than the luteal phase immediately preceeding the first estrus (12.1 or 8.9 days). Intervals from regular cyclic ovarian activity was not established until first estrus and intervals from the end of one luteal phase to the onset of the next were as long as three weeks. High concentrations of progesterone (>/= 1.5 ng/ml) on the day of behavioral estrus were seen in 23% of the buffaloes studied.     

Effects of oxytocin on cloprostenol-induced luteolysis, follicular growth, ovulation and corpus luteum function in heifers

Twenty-five normally cyclic Holstein heifers were used to examine the effects of oxytocin on cloprostenol-induced luteolysis, subsequent ovulation, and early luteal and follicular development. The heifers were randomly assigned to 1 of 4 treatments: Group SC-SC (n=6), Group SC-OT (n=6), Group OT-SC (n=6) and Group OT-OT (n=7). The SC-SC and SC-OT groups received continuous saline infusion, while Groups OT-SC and OT-OT received continuous oxytocin infusion (1:9 mg/d) on Days 14 to 26 after estrus. All animals received 500 microg, i.m. cloprostenol 2 d after initiation of infusion (Day 16) to induce luteolysis. Groups SC-OT and OT-OT received oxytocin twice daily (12 h apart) (0.33 USP units/kg body weight, s.c.) on Days 3 to 6 of the estrous cycle following cloprostenol-induced luteolysis, while Groups SC-SC and OT-SC received an equivalent volume of saline. Daily plasma progesterone (P4) concentrations prior to cloprostenol-induced luteolysis and rates of decline in P4 following the induced luteolysis did not differ between oxytocin-infused (OT-OT and OT-SC) and saline-infused (SC-SC and SC-OT) groups (P >0.1). Duration of the estrous cycle was shortened in saline-infused heifers receiving oxytocin daily during the first week of the estrous cycle. In contrast, oxytocin injections did not result in premature inhibition of luteal function and return to estrus in heifers that received oxytocin infusion (OT-OT). Day of ovulation, size of ovulating follicle and time of peak LH after cloprostenol administration for oxytocin and saline-treated control heifers did not differ (P >0.1). During the first 3 d of the estrous cycle following luteal regression, fewer (P <0.01) follicles of all classes were observed in the oxytocin-infused animals. Day of emergence of the first follicular wave in heifers treated with oxytocin was delayed (P <0.05). The results show that continuous infusion of oxytocin during the mid-luteal stage of the estrous cycle has no effect on cloprostenol-induced luteal regression, timing of preovulatory LH peak or ovulation. Further, the finding support that an episodic rather than continuous administration of oxytocin during the first week of the estrous cycle results in premature loss of luteal function. The data suggest minor inhibitory effects of oxytocin on follicular growth during the first 3 d of the estrous cycle following cloprostenol-induced luteolysis.