The influence of ovarian status on response to estrus synchronization treatment in dairy goats during the breeding season

The influence of ovarian status (presence of a corpora lutea and follicles) on the times of the onset of estrus, LH peak and ovulation rate at a synchronized estrus was evaluated in 73 Alpine and Saanen cyclic goats. Does were treated for 11 d with 3 mg norgestomet implants or 45mg fluorogestone acetate (FGA) sponges. They also received 400 IU of PMSG and 50 μg of a PGF_2α analog on Day 9 of progestagen priming. Follicles (1 to 7 mm) and corpora lutea (CL) were counted by laparoscopy on Days 0 and 9 of progestagen treatment and 5 or 6 d after the synchronized estrus. Estrus was detected every 4 h from 16 to 60 h after the end of progestagen treatment using a vasectomized buck. The LH concentration was determined by radioimmunoassay (RIA) in blood samples collected every 4 h for 24 h beginning at the time of the onset of estrus. The number of follicles on Days 0 and 9 of progestagen treatment was not related to the time of the onset of estrus and occurrence of the LH peak or to ovulation rate. The number of CL on Day 9 influenced the time of occurrence of the LH peak but not the time of the onset of estrus. Thus, in does with 2 or 3 CL on Day 9, the LH peak occurred at 46.9 h after the end of progestagen treatment, and in does with 1 or 0 CL at 42.2 and 42.5 h, respectively, after treatment, suggesting that the number of CL at luteolysis is a factor in the variability of response after the synchronization of estrus.     

Time of ovulations in dairy goats induced to superovulate with porcine follicle stimulating hormone during and out of the breeding season

Alpine dairy goats were induced to superovulate at the end of a progestagen treatment with porcine follicle stimulating hormone (pFSH) during the breeding season (n = 10 goats) and out of the breeding season (n = 10 goats). Occurrence of estrus and of the luteinizing hormone (LH) peak were checked every 4 h. Ovulations were determined every 6 h by ovarian laparoscopic examination. Among the parameters studied, the mean interval from sponge removal to the onset of estrus did not differ whatever the season of treatment, but the variability was higher for females treated out of the breeding season. Ovulations began during the laparoscopic control period for nine of ten goats during the breeding season vs seven of ten goats out of the breeding season. For these 16 females, on which the LH peak and beginning of ovulation were known, the season did not affect the intervals between the onset of estrus and the LH peak and between the LH peak and the beginning of ovulation. When ovulations are observed by laparoscopy every 6 h, for any given goat 54.9% of total ovulations (counted 7 d after estrus) occurs in less than 6 h, and 87.1% in less than 12 h. Although the interval between the LH peak and the ovulation is quite constant, the additive variabilities of the intervals between the sponge removal and the onset of estrus and between the onset of estrus and the LH peak precluded the determination of an optimal time for artificial insemination (AI) by timing sponge removal or onset of estrus.     

Synchronization of estrus in goats: The relationship between eCG binding in plasma,time of occurrence of estrus and fertility following artificial insemination

Radioimmunoassay (RIA) was used to measure plasma eCG binding in dairy goats (n = 524) at the beginning of a progestagen/eCG treatment and 25 d after eCG administration. The eCG binding was not dependent on the age of the females but increased with the number of treatments they had previously received (3.4 % ± 4.8, n = 47 vs 9.6 % ± 13.2, n = 249; mean ± SD; P < 0.01 for goats treated 0 and 1 time vs those treated 2 to 5 times, respectively). The synchronization treatment led to an increase in the binding of eCG (7.1 % ± 10.9 before vs 28.3 ± 24.5 after treatment; P < 0.01). When eCG binding before treatment was higher than 5 % the onset of estrus was delayed: 37.9 % of goats came into estrus more than 30 h after sponge removal vs 7.4 % when eCG binding was lower than 5 % (P < 0.01). Fertility was significantly decreased when eCG binding was higher than 10 %. These results show that the repetition of treatment with eCG to induce estrus in goats increases eCG binding. This could explain the lowered efficiency of the hormonal treatment to synchronize estrus and the associated decrease in fertility when goats are inseminated at a predetermined time.     

Induction of estrus with intramuscular injections of GnRH or PMSG in lactating goats (Capra hircus ) primed with a progestagen during seasonal anestrus

In Experiment 1, goats in seasonal anestrus (n=154) were treated with sponges impregnated with 1 of 2 types of progestagen (MAP or FGA) followed by PMSG (400 IU im) 48 h before sponge removal. The type of progestagen used had no effect on kidding, abortion, pseudogestation, multiple births, stillbirths, number of live births per doe or gestation length. In Experiment 2, lactating goats (n=24) in seasonal anestrus were treated with progestagen sponges (MAP). At sponge removal they received one of the following treatments: 1 injection of PMSG (400 IU im), 1 injection of GnRH (125 mug im; GnRH-1), or 2 injections of GnRH (125 mug/injection im; GnRH-2) at a 48 h interval. Serum samples were taken at 6-h intervals for 96 h, starting 12 h after sponge removal. Heterologous radioimmunoassays were validated for the measurements of goat FSH, LH, E(2) and P(4). The onset of estrus (P=0.004), mean doe receptivity (P=0.0006), maximum preovulatory E(2) concentrations (P=0.0001) and LH peak concentrations (P=0.08) occurred significantly later for GnRH-1 and GnRH-2 than for PMSG treatment. The PMSG treatment induced a preovulatory LH peak in a greater number of goats (P=0.05) and gave a higher gestation rate than GnRH-1 and GnRH-2 treatments (57 vs 0 vs 12%; P=0.03). It is likely that the GnRH treatments administered did not reactivate the hypothalamo-pituitary-gonadal axis. Thus, intramuscular injections of GnRH in lactating goats primed with a progestagen were not as effective in regulating reproductive performance during seasonal anestrus as were injections of PMSG.     

Four years of induction/synchronization of estrus in dairy goats: effect on the evolution of eCG binding rate in relation with the parameters of reproduction

Ninety-eight Alpine goats of two herds were followed over 4 years in a program of annual artificial insemination after estrus induction/synchronization, including progestagen administration (vaginal sponge) followed by prostaglandin analog and equine chorionic gonadotrophin (eCG) 48 h before sponge removal. Goats were sampled every 4 hours from the 16th to the 56th following sponge removal, for determination of LH surge and tested for estrus by the presence of a buck. Seven days after AI, endoscopic examination of the ovaries was performed to determine the number of corpus lutea. Pregnancy diagnosis was performed at day 21-22 post AI by determination of plasma progesterone and at day 40-45 by ultrasonography. Parturition, number and sex of kids were recorded. All the goats were sampled before and after each treatment, for anti-eCG antibodies screening. Statistical analysis of the results clearly established a significant effect of the treatments on anti-eCG antibodies. Time of estrus and LH surge were significantly different between herd. The antibodies significantly delayed the time of coming out of estrus as well as the time of LH surge. Two antagonistic effects were evidenced: first, the delayed of time of estrus and time of LH surge in relation with the immune reaction to eCG; secondly, the ahead of time of estrus and time of LH surge during the years of treatment, identical to both herd. The antibodies negatively influenced the percentage of ovulating females as well as kidding rate. Finally, no effect of antibodies on prolificacy was found.     

Progesterone and behavioral features when estrous is induced in Alpine goats

The objective of the present study was to evaluate the endocrine and behavioral features of estrous-induced Alpine goats. A total of 36 nulliparous, 40 non-lactating and 42 lactating does were treated with intravaginal 60 mg medroxyprogesterone acetate sponges for 9 d plus 200 IU eCG and 22.5 microg d-cloprostenol 24 h before sponge removal. Plasma progesterone concentration was analyzed from blood sampled on days 0 (sponge insertion), 5, 8 (cloprostenol administration) and 9 (sponge removal) in 11 nulliparous, 13 non-lactating and 11 lactating does. Estrous response did not differ (P>0.05) among nulliparous (97.2%), non-lactating (90.00%) and lactating does (85.7%). Interval to estrus and duration of estrus did not differ (P>0.05) among nulliparous (22.8+/-9.9 and 25.6+/-6.8h), non-lactating (23.7+/-15.8 and 25.0+/-6.0 h) and lactating does (22.2+/-10.4 and 24.9+/-4.2h). The accumulative percentage of does in estrus during the first 36 h after sponge removal was 88.1%. The correlation between interval to estrus and duration of estrus was r=-0.32 (P<0.001). Endogenous progesterone production is decreased until day 8 or suppressed by MAP on day 9. Conception rate was greater (P<0.01) in lactating (77.8%) than non-lactating (44.4%) but similar (P>0.05) to nulliparous (60.0%) goats. Estrus can be efficiently induced by means of hormonal treatment in goats and acceptable fertility can be obtained regardless of animal category.     

Synchronization of estrus in goats: the relationship between time of occurrence of estrus and fertility following artificial insemination

The fertility rate for goats following artificial insemination (AI) is usually analyzed according to herd or treatment groups. However, these general information are insufficient to allow identification of specific factors which affect this individual reproductive performance. In the present experiment 640 dairy goats were used to analyze to what extent the interval from sponge removal to estrus affects the results of AI, performed at a predetermined time following sponge removal. Estrus occurred in 98.1% of experimental animals between 24 and 72 hours after sponge removal. The fertility rate was lower for goats that came into estrus later than 30 hours after sponge removal (33.3%, n = 108 than for goats that exhibited estrus earlier (65.0%, n = 520; P<0.001). The occurrence of late estrus is not age dependent, but it increases with the number of treatments that an individual animal has previously received. These results show that the low fertility rate observed in some herds after synchronization of estrus and AI may be related to the high proportion of goats with a late occurrence of estrus, and this phenomenon increases in animals that are treated repeatedly.     

Ovulation of aged follicles does not affect embryo quality or fertility after a 14-day progestagen estrus synchronization protocol in ewes

The aim was to examine the effect of ovulation of aged follicles on embryo quality and fertility in ewes. In Experiment 1, ewes (n = 39) received a prostaglandin analogue on Day 6 of the cycle and then received either a progestagen sponge from Day 6 to 20 after estrus (Single sponge) or a progestagen sponge on Day 6 that was replaced on Day 11 and 16 and removed on Day 20 (Multiple sponges). In a subgroup of ewes, the growth of ovarian follicles was characterised using ultrasonography. Fertile rams were introduced 48 hours after sponge withdrawal; we slaughtered the ewes on Day 5 of pregnancy and recovered the embryos. The mean age of the ovulatory follicles was greater in ewes that received a single sponge compared with multiple sponges (8.7+/-0.8 days, range 4 to 14, versus 4.5+/-0.7 days, range 3 to 6; P<0.05). However, the groups did not differ (P>0.05) in ovulation rate (2.4+/-0.3 corporal lutea per ewe) or the proportion of good quality embryos recovered (71 to 82%; developed to the early morula stage or further). In Experiment 2, ewes (570 in total) received treatments similar to those in Experiment 1 but were kept until lambing. Ewes that received a single sponge came into heat earlier (P<0.05) than those that received multiple sponges, but > or = 97% of ewes in all groups (P>0.05) were bred by 48 to 72 hours after ram introduction. There was no difference (P>0.05) between groups for the proportion of ewes that lambed to first service (80 to 86%) or the number of lambs per ewe (1.94+/-0.08 lambs). We conclude that when luteolysis occurs at the beginning of progestagen synchronisation, ewes will ovulate aged follicles, but that compared to shorter duration follicles, these follicles produce oocytes that are equally competent to be fertilised and develop into good quality embryos and full-term lambs.     

Endocrine responses of goats after induction of superovulation with PMSG and FSH

Goats in Group A were pretreated for 9 days with a synthetic progestagen, administered via intravaginal sponge, and 1000 i.u. PMSG s.c. on Day 12 of the oestrous cycle. Goats in Group B had the same PMSG treatment, but not the progestagen pretreatment. Group C goats received a s.c. twice daily injection of a porcine FSH preparation (8 mg on Day 12, 4 mg Day 13, 2 mg Day 14 and 1 mg Day 15). Oestrus was synchronized in all animals by 50 micrograms cloprostenol, 2 days after the start of gonadotrophin treatment. The vaginal progestagen sponges were removed from Group A at the same time. Mean ovulation rate was slightly higher in FSH-treated than in the PMSG-treated animals, whereas the incidence of large follicles that failed to ovulate was significantly elevated in PMSG-treated animals in Group B. More goats in Groups A and B than in Group C exhibited premature luteal failure. Progestagen pretreatment appeared to suppress both follicular and luteal activity, as indicated by numbers of large non-ovulating follicles and by the magnitude and duration of elevated plasma oestradiol levels following PMSG stimulation, and by decreased plasma progesterone levels before and after PMSG treatment. Oestrogenic response to FSH was considerably less than that to PMSG, as indicated both by a considerably shorter duration of elevation of circulating oestradiol levels during the peri-ovulatory period, and by lower maximal oestradiol levels. Differences in the ovarian responses to PMSG and FSH may be attributed primarily to differences in the biological half-life of each preparation.     

Induction of estrus in non-lactating dairy goats with different estrous synchrony protocols

The objective of this study was to evaluate two protocols of estrous synchronization in non-lactating Toggenburg goats. Nineteen goats were allocated, according to body condition score and weight, into two groups (A and B) and evaluated utilizing two treatments (T1 and T2). Animals in the T1 and T2 groups received an intravaginal sponge (day 0) containing 60 mg medroxyprogesterone acetate for 6 and 9 days, respectively, plus 200 IU equine chorionic gonadotrophin (eCG) and 22.5 microg cloprostenol 24 h before sponge removal. Females were bred only at the second estrus and received 22.5 microg cloprostenol 7 days later to prevent pregnancy. Percentages of animals in estrus did not differ (P > 0.05) between T1 (89.5%) and T2 (84.2%). From 33 females in estrus (T1 + T2), 28 (84.8%), 2 (6.1%), and 3 (9.1%) were identified in estrus at 06:00, 12:00 and 18:00 h, respectively. Additionally, 6 (18.2%), 0 (0.0%) and 27 (81.8%) were no longer detected to be on estrus at 06:00, 12:00 and 18:00 h, respectively. Interval from sponge removal and the onset of estrus (IE) did not differ (P > 0.05) between T1 (46.1 +/- 15.0 h) and T2 (53.6 +/- 16.1 h). Duration of estrus did not differ (P > 0.05) between T1 (30.0 +/- 12.0 h) and T2 (27.2 +/- 11.2 h). Both protocols were effective in inducing estrus in non-lactating goats. The onset and end of the estrus relative to hour of the day should be considered in estrous detection, natural breeding, and artificial insemination in goats.     

The efficacy of estrus detection and fertility following synchronization with PGF2a or synchro - mate- B in Zebu cattle

Two experiments were carried out to assess the efficacy of estrus detection and fertility in Zebu cattle after synchronization with prostaglandin F2a or a progestagen. The first experiment compared estrus detection rates and fertility following insemination in 42 cows previously synchronized with either 25 mg of PGF2a or with a 6 mg of Norgestomet implant plus 5 mg i.m. of estradiol valerate (SMB). Differences were observed in the percentage of cows detected in estrus (54 vs 95%, respectively, P < 0.05), but not in fertility at the first synchronized estrus (26 vs 15%), nor in the detection rate and fertility at the subsequent estrous period (38 v 47%). The second experiment evaluated the efficacy of estrus detection at different time intervals in 30 cows, comparing estrus synchronized with PGF2a with the subsequent estrous period. The observation periods were continuous, day and night, for 100 h both after PGF2a treatment and from Day 18 of the treatment cycle (Period 1). In addition, the animals were administered PGF2a again on Day 10 of the second cycle and observed continuously from 0600 to 1800 h, and from Day 18 of the treatment cycle (Period 2). Finally, the same treatment regimen was used except that the observation was between 0600 to 0700 h and 1800 to 1900 h (Period 3). No differences were obtained in the percentage of cows detected in estrus in the synchronized and nonsynchronized groups (average 75%); however, accuracy in the detection of estrus in Period 3 differed in the nonsynchronized and synchronized estrus groups by 40% (P < 0.05) compared with the other two, more intense observation periods.     

Plasma hormone profliles and fertility in ewe lambs given progestagen supplementation after mating

Clun Forest ewe lambs (n = 124) were used to investigate the effects of post-mating progestagen supplementation on fertility. The animals were assigned to 1 of 3 three treatments: Group A (n = 41) served as the controls, Group B (n = 42) received 3 weekly injections of 6 mg of medroxyprogesterone acetate (MAP), while Group C (n = 41) was treated with intravaginal sponge containing 60 mg of MAP; all treatments were administered from Day 5 to Day 26 post mating. Supplementation did not increase the percentage of animals pregnant or those lambing: Group A, 72.2 and 66.6%; Group B, 57.5 and 50.0%; and Group C, 67.5 and 60.0%, respectively. Furthermore, there was no effect of supplementation on plasma progesterone, prolactin, cortisol, growth hormone, insulin, or glucose concentrations (P>0.05). However, pre- and post- mating hormone profiles differed significantly between the animals that lambed or aborted and the animals which were found to be barren at lambing. In the barren animals, progesterone concentrations were lower 4 days before and 9 to 33 days after mating (P<0.01), while overall prolactin concentrations were higher throughout the trial (P<0.01). But there was no difference between barren and fertile lambs in cortisol, growth hormone, insulin or glucose concentrations (P>0.05). These results indicate that progestagen supplementation does not increase the reproductive performance of ewe lambs. However, infertility is associated with reduced luteal function and increased prolactin concentration before and after mating.     

Influence of GnRH administration on timing of the LH surge and ovulation in dwarf goats

This study was conducted to determine whether or not exogenous gonadotropin releasing hormone (GnRH) alters the timing or improves the synchrony of estrus, the LH surge, and ovulation following estrous synchronization in dwarf goats, and to assess the effects of season on these parameters. In January and June, estrus was synchronized in 12 Pygmy and Nigerian Dwarf goats with a 10-day progestagen sponge, 125 microg cloprostenol i.m. 48 h before sponge removal, and 300 IU equine chorionic gonadotrophin (eCG) i.m. at sponge removal. Six of the 12 goats were given 50 microg GnRH i.m. 24h after sponge removal. Onset of estrus was monitored using two males. Samples for plasma LH were collected at 2 h intervals beginning 22 h after sponge removal and ending at 48 h in January and at 58 h in June. Time of ovulation time was confirmed by laparoscopy at 36, 50, 60, and 74 h in January and at 50, 60, and 74 h in June. Administration of GnRH had no significant effect on the onset of estrus; however, it reduced the interval from sponge removal to the LH surge and improved the synchrony of the LH surge (P<0.05). Treatment with GnRH also reduced the interval from sponge removal to ovulation and improved the synchrony of ovulation (P<0.05). Season had a significant effect on the timing and the synchrony of estrus with and without GnRH treatment (P<0.05). A seasonal shift was also observed in the timing of the LH surge in the absence of GnRH treatment (P<0.05). Further research is required to determine the optimum time for GnRH administration and the minimum effective dose in dwarf goats.     

The effects of buck teasing on synchronization of estrus in goats after intravulvo-submucosal administration of cloprostenol

A study was conducted on 35 East African shorthorned female goats to determine if a combination of buck teasing and low doses of a prostaglandin (PGF(2) alpha) analogue, cloprostenol, given intravulvo-submucosally (i.v.s.m.) would be suitable for synchronization of estrus. Goats were allotted, with the onset of estrus, to seven groups (n = 5 goats per group). Five of the seven groups received varying doses of cloprostenol: Group 1 (125 mug cloprostenol i.m. per goat); Group 2 (62.5 mug cloprostenol i.v.s.m. per goat); Group 3 (62.5 mug cloprostenol i.v.s.m. per goat plus buck teasing); Group 4 (31.25 mug cloprostenol i.v.s.m. per goat); Group 5 (31.25 mug cloprostenol i.v.s.m. per goat plus buck teasing); Group 6 (buck teasing); Group 7, (2 ml physiological saline i.v.s.m. per goat, control group). Plasma progesterone concentration was measured on day of treatment and for 6 d thereafter. All goats in groups 1, 2, 3 and 5 exhibited estrus within 68 h. Thus, the number of goats receiving low doses of PG-cloprostenol intravulvo-submucosally observed in estrus increased (P < 0.05) with exposure to bucks. Exhibition of behavioral signs of estrus was maximal between 2 and 20 h after onset of signs of estrus. The exposure of females to males prior to intrauterine penetration was an advantage because copious mucus eased penetration.     

Preliminary report on induction of estrus with multiple eCG injections in Colored Mohair goats during the anestrus season

This trial was conducted to evaluate the effectiveness of multiple eCG injections in the induction of estrus and pregnancy in Colored Mohair goats during the anestrus season. It was also aimed to determine total dose of eCG required for induction of estrus. Ten multiparous and lactating goats were used. The goats were randomly divided into two groups and treatments were started on May 22. Group eCG (n=5) was treated with eCG intramuscularly for 6 days. Daily dosages of eCG from May 22 to May 27 were 300 IU, 200 IU, 200 IU, 100 IU, 100 IU and 50 IU, respectively. Goats in control group received no treatment. Blood samples were taken from animals in each of the two groups just before and after the beginning of the treatments and serum progesterone concentrations were assayed by RIA. Starting on the fourth day after the first treatments, goats were exposed to fertile bucks twice daily for 30 min to detect standing heat. The estrus goats were allowed to be mated by the bucks. Pregnancies were determined 40 days after mating by real-time ultrasonography. One goat on day 5 and three goats on day 7 exhibited behavioral estrus in eCG group (80%) after the first eCG injection. Three of them (75%) became pregnant. None of the goats in the control group exhibited behavioral estrus. Mean serum progesterone concentrations had prominent elevations indicating ovulation in eCG group, but not in control group, after 20 days from the first treatments. Progesterone concentrations of eCG group were significantly different than those of control group on days 20 and 28 (P<0.05). The results suggest that divided multiple injections of a total 950 IU eCG are effective without progestagen pretreatment in the induction of estrus and obtaining successful pregnancy and live kids in Colored Mohair goats during the anestrus season.     

Use of Chronogest implants and Folltropin for estrus synchronization and superovulation in goats.

Six Barbari goats each were assigned randomly to treatments 1,2 or 3, comprising im injections of FSH (folltropin) at 12, 14 or 16 mg dose level respectively. Estrus was synchronized with intravaginal sponge impregnated with flugestone acetate (30 mg; chronogest) inserted for 12 days and cloprostenol (125 micrograms) im at the insertion as well as at removal of sponge. FSH treatment started 48 hr before the sponge removal as 4-day declining dose scheme. Estrus could be effectively synchronized in all goats under the study, with significant difference (P less than 0.05) in the onset of estrus between the treatment groups. All goats were administered with 750 IU hCG i.v. at estrus. Recording of ovarian response and embryo recovery was done 45 hr after the onset of estrus. The prime aim of superovulation was effectively achieved in Barbari goats with the use of chronogest implants and folltropin. There was no difference (P greater than 0.05) between the treatment groups in recovery of transferable embryos, however, 14 mg folltropin appeared to be near optimal dose. There was no adverse effect on the quality of recovered embryos with high doses of folltropin.     

Effects of time of PMSG and fixed-time GnRH injections on estrus incidence and fertility in physiologically different ewes pre-treated with progestogen-impregnated vaginal sponge during the nonbreeding season

A 2 × 2 factorial study for hormonal treatment was designed in 85 seasonally anestrous ewes with physiologically different status (nonparous, dry, and postpartum). All ewes were pre-treated with 60 mg of 6-methyl-17-acetoxy-progesterone (MAP) vaginal sponge for nine days and divided into four groups: Group I (22 ewes) — an i. m. injection of 600 i.u. pregnant mare's serum gonadotropin (PMSG) at the sponge removal (Day 0) and a single i.m. injection of 100 ug synthetic gonadotropin releasing hormone (GnRH) at 36 h after the sponge removal; Group II (21 ewes) — a PMSG injection at Day 0 and a saline injection at 36 h after the sponge removal; Group III (21 ewes) — a PMSG injection two days before the sponge removal and the GnRH injection at 24 h after the sponge removal; and Group IV (21 ewes) — a PMSG injection at Day -2 and a saline injection at 24 h after the sponge removal. The treated ewes were allowed to mate once with rams for five days after treatment. Estrus incidence and lambing rates were low (69.4% and 27.1%, respectively), probably due to the mating system and poor body condition of ewes used in the study. No effect of PMSG injection two days before with-drawal of MAP sponge and the fixed-time GnRH injection were observed in estrus incidence, fertility, and prolificacy. The present study indicates that the physiological status of ewes combined with management systems including feeding and mating would be important for out-of-season breeding with hormonal treatment.     

Fertility and blood progesterone levels following LHRH-induced superovulation in FSH-treated anestrous goats

Twenty mature, mixed-breed, seasonally anestrous female goats were used to study the effects of luteinizing hormone releasing hormone (LHRH) on ovulation rate, fertility, and blood progesterone levels following norgestomet-induced estrus and follicle stimulating hormone (FSH) treatments. Each goat received 6 mg norgestomet by subcutaneous (sc) implant and 3 mg intramuscularly, along with an intramuscular (im) injection of 5 mg estradiol valerate. Four injections of FSH were given for 2 d in divided doses of 10, 10, 5 and 5 mg im every 12 h, starting at 24 h before implant removal. The goats were randomly assigned to 1 of 2 equal treatment groups, and were treated with 2 intravenous (iv) injections of either 0.9% saline (control) or 300 ug LHRH at 24 and 48 h after the removal of the implants. All the goats exhibited estrus within 24 or 36 h of implant withdrawal and were mated to bucks of proven fertility. At laparotomy on Day 7 or 8 after the removal of the implants, the mean number of unovulated follicles was higher (P<0.05) in Group I than in Group II. The mean number of corpora lutea (ovulation rate), the total number of embryos and the number of normal embryos recovered were higher (P<0.05) in LHRH-treated does than in the controls. Treatment with LHRH resulted in 72.14% fertility (mean number of CL = 14) as compared with the controls with 64.29% fertility (mean number of CL = 2.8). The embryos obtained from goats in Group II were of more uniform developmental age regardless of the day of embryo collection, as compared with those of the controls. Plasma progesterone levels were significantly increased on Days 4 to 6 in both treatment groups. The results of this study have demonstrated that the FSH and LHRH treatment regimen increased follicular development, ovulation rate and blood progesterone levels in norgestomet-treated anestrous goats. Moreover, LHRH treatment enhanced fertility, and improved embryo quality as indicated by the significantly higher total number of embryos as well as the higher (P<0.05) number of normal recoverable embryos.     

Follicular recruitment and ovulatory response to FSH treatment initiated on day 0 or day 3 postovulation in goats

The present study evaluates the effect of the presence of a large growing follicle at the onset of superovulatory treatment on follicular recruitment and ovulatory response in dairy goats. The treatment consisted of six equal doses of pFSH given every 12 h (total dose: 200 mg NIH-FSH-P1) which was initiated at Day 0 (Group D0) or Day 3 (Group D3) postovulation. Two half-doses of an analogue of prostaglandin F2alpha (delprostenate, 80 microg each) were administered together with the last two FSH doses to ensure luteolysis. A dose of a GnRH analogue (busereline acetate, 10.5 microg) was administered at the onset of estrus. Ovarian changes were evaluated twice a day by transrectal ultrasonography. Follicles were classified according to follicular diameter as small (3 to < 4 mm), medium (4 to < 5 mm) and large follicles (> or = 5 mm). The number of corpora lutea (CL) was recorded after laparotomy performed 6 days after estrus. The work was conducted in replicates. In the first trial, the does were assigned to either the D0 (n = 4) or D3 group (n = 4) and in the second replicate, each goat was assigned to the alternate group. No large follicles were recorded and the diameter of the largest follicle was 3.3 +/- 0.1 mm (mean +/- S.E.M.) at the initiation of the treatment in D0-treated goats. In contrast, a growing large follicle was present (6.7 +/- 0.4 mm, P < 0.01) when the treatment was initiated in D3-treated goats. In these goats, the number of small follicles increased 24 h after ovulation but then declined 48 h later, temporally correlated with the growth of the largest follicle of the first follicular wave. The number of small follicles recruited by the FSH treatment was significantly higher and occurred earlier in D0- than in D3-treated goats (9.0 +/- 1.3 versus 5.6 +/- 1.1 follicles; P < 0.05; and 24 h versus 48 h from the onset of the treatment, respectively). The number of large follicles at the onset of estrus was higher in D0- than in D3-treated goats (14.4 +/- 1.9 versus 10.3 +/- 1.3; P < 0.05). Consequently, the number of CL recorded 6 days after estrus were higher in D0- than in D3-treated goats (13.6 +/- 1.9 versus 10.4 +/- 1.9; P < 0.05, respectively). These results demonstrate that the presence of a dominant follicle at the time of initiation of super-stimulatory treatment is detrimental to ovulatory response. This study supports the advantages of the so-called Day 0 protocol, e.g. treatment starting soon after ovulation, when the emergence of the first follicular wave takes place and there are no dominant follicles.     

A new strategy for superior reproductive performance of ewes bred out-of-season utilizing progestagen supplement prior to withdrawal of intravaginal pessaries

Two experiments were conducted to examine the effect of progestagen supplement 24h prior to intravaginal pessary withdrawal on reproductive performance of seasonal anestrous ewes. Ewes in each experiment were allocated to treatment and control and all were induced to estrus using either intravaginal MAP (Exp. 1; n=24) or CIDR-G (Exp. 2; n=28) pessaries for 12 days. Half of the ewes in each experiment were supplemented 24h before withdrawal of pessaries with either 10mg oral MAP tablets (Exp. 1) or 25mg i.m. progesterone (P(4)) administration (Exp. 2; P(4)-supplement-treated group). Fertile rams were allowed with the ewes at sponge removal (Day 0, 0h) and estrus was monitored at 6-h intervals for 3 days. Blood samples were collected for measurements of P(4) (Exp. 1 and Exp. 2) and LH (Exp. 2). In both experiments, the percent of ewes in estrus was greater (P<0.05) and intervals to estrus were longer (P<0.05) in progestagen-supplement-treated than control ewes. In Exp. 2, the occurrence and magnitude of LH surges were greater (P<0.01) and intervals to onset of LH surge were longer (P<0.01) in P(4)-supplement-treated than control ewes. In Exp. 2, P(4) supplement elevated P(4) levels from 1.8+/-0.1ng/mL on Day -1 to 4.2+/-0.3 on Day 0 (P<0.001). Following pessaries removal, P(4) concentrations fell to basal values on Day 1 in both groups and remained low until Day 5. Then, P(4) concentrations increased and remained elevated through Day 19 in all (100%) progestagen-supplement-treated in Exp. 1 (12/12) and Exp. 2 (14/14) and in only 5/12 (41.7%) and 6/14 (42.9%) control ewes, respectively. These ewes were confirmed pregnant by ultrasonography and lambed on Day 149.2+/-0.2 following Day 0. In conclusion, progestagen supplement 24h prior to removal of pessary can be used successfully to improve reproductive performance of ewes bred out-of-season.