Ultrasound and endocrine evaluation of the ovarian response to a single dose of 500 IU of eCG following a 12-day treatment with progestogen-releasing intravaginal sponges in the breeding and nonbreeding seasons in ewes

A standard dose of 500 IU of eCG is commonly given to progestogen pre-treated anestrous ewes for induction of estrus. Twelve seasonally anestrous and 12 cyclic Western White Face ewes were treated for 12 days with intravaginal sponges impregnated with medroxyprogesterone acetate (MAP). In trials in both the breeding and nonbreeding seasons, six randomly selected ewes were given 500 IU of eCG at sponge removal to determine the effects of low dose of eCG on ovarian antral follicular dynamics and ovulation. Ultrasound scanning and blood sampling were done daily. Treatment with eCG did not have marked effects on antral follicular growth. All ewes ovulated, except for five of six control anestrous ewes. Luteal structures and progesterone secretion were confirmed in all but the control anestrous ewes. In the breeding season, peak progesterone concentrations were greater (P<0.05) in eCG-treated compared to control ewes. Daily serum estradiol concentrations were greater in the periovulatory period in eCG-treated compared to control ewes (treatment-by-day interaction; P<0.05), particularly in anestrus. Progestogen-treated ewes ovulated follicles from several follicular waves, in contrast to ovulations of follicles from the final wave of the cycle in untreated, cyclic ewes. Anestrous ewes exhibited more frequent follicular waves and FSH peaks compared to cyclic ewes after a progestogen/eCG treatment. In conclusion, 500 IU of eCG given after 12 days of progestogen treatment had limited effects on the dynamics of ovarian follicular waves. However, eCG treatment increased serum concentrations of estradiol during the periovulatory period, particularly in anestrous ewes; this probably resulted in the synchronous estrus and ovulation in anestrous ewes.     

The effects of progesterone priming on reproductive performance of GnRH-PGF2alpha-treated anestrous goats

The objective of this experiment was to determine the effect of a 5-day progesterone priming prior to a GnRH-PGF2alpha treatment on reproductive performance of anestrous goats. Thirty-six Mountain Black goats were randomly assigned in a 2 x 2 factorial arrangement and were administered intravaginally on day -12, either with 300 mg progesterone inserts (CGPE and CGP) or with 0 mg progesterone (GPE and GP) for 5 days. On day -6, the goats were injected with 100 microg GnRH, followed 6 days later by 15 mg PGF2alpha (day 0), the time at which the goats in the CGPE and GPE groups were administered 300 IU eCG injections and those in CGP and GP groups were administered the control solution. The goats were exposed to four fertile bucks at 0 h and were checked for breeding marks at 6-h intervals for 72 h. Blood samples were collected from all goats for progesterone analysis. Progesterone concentrations increased only in CGPE and CGP during the period of device insertion but remained low in GPE and GP groups (P < 0.001). Progesterone levels at the time of GnRH injection on day -6 were basal (0.2 +/- 0.04 ng.mL-1) among the groups and began to increase starting on day -2. Day 0 progesterone concentrations differed (P < 0.05) among groups and were significantly influenced by CIDR-G (P < 0.001). A similar proportion of goats expressed estrus and intervals to detected estrus were shorter (P < 0.05) in the CGPE and GPE groups than in GP with no difference between the CGPE, CGP and GPE or between CGP and GP groups. The number of goats ovulating based upon elevated progesterone levels on day 0 was significantly greater (P = 0.002) in CGPE (9/9) and CGP (9/9) than GPE (6/9) and GP (5/9) groups and was significantly influenced by CIDR-G (P = 0.03). All pregnant goats had elevated progesterone concentration on day 0 and none of the goats with basal progesterone levels became pregnant. Pregnancy and kidding rates, twinning percentage and the number of kids born per goat exposed were greater (P < 0.05) among goats treated with progesterone and eCG. In conclusion, progesterone priming and eCG are essential for producing higher rates of pregnancy and kidding in GnRH-PGF2alpha-treated anestrous goats.     

Autoclaved, previously used intravaginal progesterone devices induces estrus and ovulation in anestrous Toggenburg goats

Intravaginal progesterone devices are used worldwide for estrus induction in goats. Reused devices are able to induce estrus; however, this can be a health risk within a flock. The objective was to compare new and previously used (and autoclaved) progesterone-releasing intravaginal devices for induction of estrus and ovulation in seasonally anestrous Toggenburg goats. Anestrous goats (n=42) received new intravaginal devices containing 0.3g progesterone (CONTROL), or similar devices previously used for either 6 (USED6) or 12d (USED12) and subsequently autoclaved. All goats received 5mg dinoprost at device insertion and 200 IU eCG 5d later, and all devices were removed after 6d. After device removal, estrus was monitored and females displaying signs of estrus were mated by fertile bucks. Transrectal ovarian ultrasonography was performed after device removal until detection of ovulation. Blood samples were collected for determination of plasma progesterone concentration at different times. There was no difference (P>0.05) among groups CONTROL, USED6 or USED12 for: estrus response (87, 100 or 100%, respectively); duration of estrus (32.3±2.3, 25.2±3.4 or 27.3±4.1h); ovulation rate (100, 88 or 100%); number of ovulations (1.5±0.2, 1.9±0.3 or 1.7±0.3); and pregnancy rate (60, 58 or 67%). Plasma progesterone (P4) concentrations were greater (P<0.05) in CONTROL than in USED6-treated and USED12-treated goats (7.2±1.2, 4.7±0.7 and 4.3±0.6 ng/mL, respectively) at 6h after device insertion; these differences were maintained until 4d after device insertion (3.4±0.4, 2.3±0.2, and 2.5±0.2 ng/mL). Overall, plasma progesterone concentrations were greater (P<0.05) in nulliparous than in lactating goats (3.1±0.8 compared to 2.4±0.6 ng/mL, respectively). In conclusion, autoclaved, previously used intravaginal progesterone-releasing devices resulted in significant lesser plasma progesterone concentrations than new devices, but were similarly effective in inducing estrus and ovulation in anestrous goats.     

A new approach to enhance reproductive performance in sheep using royal jelly in comparison with equine chorionic gonadotropin

The objective was to compare the effects of royal jelly (RJ) and eCG treatments on reproductive performance of ewes synchronized using intravaginal progesterone-releasing devices. Forty-two cycling Awassi ewes were treated intramuscularly (i.m.) with 15 mg PGF2alpha. On the following day, all ewes were administered with CIDR-G for 12 days and were randomly allocated to three (RJ, eCG and control) groups of 14 ewes each. Ewes in the RJ-treated group received daily i.m. treatments of 400mg RJ during the period of CIDR-treatment. Each ewe in the eCG-treated group received an i.m. treatment of 500 IU eCG at the time of CIDR-G removal (day 0) and no further treatment was given to ewes in the control group. Ewes were exposed to four fertile rams for 72 h, from the time of CIDR-G removal, and checked for breeding marks at 6-h intervals. Blood samples were collected from day -13 until day 0 and thereafter until day 19 for progesterone analysis. Royal jelly treatment resulted in a greater rate of decline and lower (P<0.02) progesterone concentrations between days -10 and 0 than eCG-treated and control ewes. Expression of estrus was similar among the three groups and intervals to onset of estrus were shorter (P<0.01) in RJ-treated (31.3h) and eCG-treated (29.8h) than control (41.3h) ewes. First-cycle pregnancy and lambing rates were greater (P<0.05) in RJ-treated (71.4 and 71.4%) and eCG-treated (85.7 and 78.6%) than in control (42.9 and 35.7%) ewes, respectively. Results demonstrate that the treatments of RJ and eCG in conjunction with CIDR-G were similarly effective in induction of estrus and improvement of pregnancy and lambing rates.     

Effect of presence of the male on initiation of estrous cycle activity of goats

Serum progesterone concentrations and behavioral estrus were determined in two groups of 17 mixed breed dairy does at the beginning of the breeding season. The treatment group was pastured adjacent to two mature bucks while two teaser bucks ran with the group. The control group was pastured without exposure to bucks. Goats were observed for estrus daily for 35 days and samples of jugular blood were collected every other day for radioimmunoassay of progesterone. Signs of estrus were observed in 16 of 17 does in the treatment group within a mean +/- S.E. of 5.5 +/- 1.3 days after introduction of the bucks. Thirteen does demonstrated a progesterone profile characteristic of a normal estrous cycle with peak progesterone concentrations of 5.9 +/- 0.5 ng/ml. Signs of behavioral estrus were not observed in the control group. One control doe demonstrated a progesterone profile characteristic of a normal estrous cycle attaining a peak progesterone concentration of 3.9 ng/ml. Progesterone concentrations in the remaining 16 control does were at or near the lower limits of sensitivity of the assay for the duration of the experiment. Fifteen of the control does exhibited estrus within 7 +/- 1.5 days after exposure to bucks at the end of the experiment. These results clearly demonstrated a profound influence of the male on estrous cycle activity during the beginning of the breeding season.     

Resynchronization of estrous cycle with eCG and temporary calf removal in lactating Bos indicus cows

The aim of this study was to compare four methods of estrus resynchronization performed 23 days after timed artificial insemination (TAI) plus estrus observation in Bos indicus cows. Eight hundred fourteen lactating Nelore cows were submitted to TAI and then randomly assigned to one of the five following treatments: R23 (resynchronization without eCG), R23/200 (resynchronization with 200 IU of eCG), R23/300 (resynchronization with 300 IU of eCG), R23/TCR (resynchronization with temporary calf removal [TCR]), and a control group, with estrus observation followed by AI (with no resynchronization). Treatment consisted of a progesterone device plus administration of estradiol benzoate on Day 0; on Day 8, the device was removed and cloprostenol was applied, together with estradiol cypionate. Also on Day 8, either eCG was administered or TCR was performed in the resynchronized groups, except for R23. The females were inseminated 48 hours after device removal or TCR (33 days after the first TAI). The control group was kept under estrus observation from 18 to 23 days after the first TAI and was inseminated 12 hours after detection of estrus. The first pregnancy evaluation was performed using ultrasound examination 31 days after the first TAI. After 30 days of the resynchronization, a second pregnancy evaluation was performed and the animals in the R23/300 and R23/TCR groups achieved the highest conception rates, 76.6% and 74.0%, respectively (P < 0.05). There were no differences between the conception rates of the animals in the R23/200 (63.3%), R23 (61.3%), and control (54.3%) groups (P > 0.05). These results suggest that estrus resynchronization at 23 days after TAI can effectively improve the conception rate of lactating Bos indicus cows in a short time period. Furthermore, resynchronization with 300 IU of eCG or with TCR provided the best results.     

The negative effect of repeated equine chorionic gonadotropin treatment on subsequent fertility in Alpine goats is due to a humoral immune response involving the major histocompatibility complex

In dairy goats, the use of eCG as a convenient hormone for the induction of ovulation is necessary for out-of-season breeding and artificial insemination. However, repeated eCG treatments are followed by decreased fertility in goats inseminated at a fixed time after treatment. In this report, we show the presence of anti-eCG antibodies in plasma of treated goats. A 500 IU eCG injection induces a humoral response, with variable concentrations of anti-eCG antibody being produced in individual goats. The analysis of successive anti-eCG immune responses over several years has demonstrated the existence of different populations of goats, defined as low, medium, and high responders. By the use of two caprine microsatellites located inside (OLADRB) and outside (BM1258) the major histocompatibility complex (MHC), a significant association (p < 0.05) between the anti-eCG antibody response and some MHC-DRB alleles was found. Goats with high antibody concentrations at the time of eCG injection (> 2.5 microg/ml) exhibited a much lower kidding rate than did other females (41.3% vs. 66.7%). Lower fertility of these goats, inseminated at a fixed time after eCG treatment, might be due to the observed delay in estrus occurrence and the preovulatory LH surge.     

Pharmacokinetics of eCG and induction of fertile estrus in bitches using eCG followed by hCG

The aim was to design a protocol combining eCG followed by hCG for estrus induction in the bitch. In Experiment 1, three ovariohysterectomized bitches received 10 000 IU of eCG iv, and 15 days later 10 000 IU of eCG im. Blood samples were taken up to 144 h after each injection to measure eCG concentrations. In Experiment 2, 25 healthy, intact late anestrous bitches were assigned to one of five doses of eCG (5, 10, 15, 20, 44, or 50 IU/kg eCG im; [TRT5-TRT50]). Sexual behavior (SB), clinical signs of estrus (CSE) and vaginal cytology (VC) samples were obtained and scored before eCG administration and every other day until onset of estrus, or for 14 days. In Experiment 3, intact late anestrous bitches were assigned to a treatment group (TRT; n = 16) and received eCG (50 IU/kg im) followed by hCG (500 IU im) 7 days later; or to a placebo group (PLA; n = 8) where they received 1 mL saline solution im. All bitches that were induced in estrus were mated or AI with fresh semen. In Experiment 1, maximum observed concentration (C_max) eCG were similar between im and iv routes (6.1 ± 0.9 vs. 8.6 ± 0.5 IU/mL, P > 0.08), whereas time for maximum observed concentration (T_max.) was longer for im compared to iv routes (17.5 ± 0.5 vs. 11.6 ± 0.3 h, P < 0.01). The area under the curve (AUC) was similar for im and iv routes (P > 0.48), and eCG was detectable in serum for at least 144 h for both routes. In Experiment 2, 3 days or 3 to 5 days after treatment, all bitches in TRT50 had higher scores compared to TRT5-44 animals (P < 0.01). In TRT50, the mean interval from treatment to estrus was 4.0 ± 0.4 days. In Experiment 3, the mean interval from treatment to estrus was shorter in the TRT group compared to the PLA group (4.1 ± 3.3 vs. 68.5 ± 4.4 days, P < 0.01). The previous interestrus interval was similar for TRT and PLA groups (199.6 ± 7.2 vs. 197.5 ± 10.2 days), but the new interestrus interval was shorter for the TRT compared to the PLA group (164.0 ± 7.2 vs. 212.2 ± 10.2 days; treatment by interval interaction, P < 0.007). Serum P₄ concentrations increased on the first day of cytologic diestrus after treatment in bitches in TRT (0.7 ± 0.3 vs. 22.8 ± 4.2 ng/mL; P < 0.01); but did not change in PLA (P > 0.84). Ninety-four percent of animals were bred (15/16; AI, n = 7; natural mating, n = 8), and 80% (12/15) became pregnant. None of the bitches had any side effects from the eCG and hCG therapy. We concluded that 50 IU/kg of eCG combined 7 days later with 500 IU of hCG was effective to induce normal and fertile estrus in bitches at 164 days post estrus, with an 80% pregnancy rate, with no side effects, and with a reduction of 48 days of the interestrus interval.     

Do high progesterone concentrations decrease pregnancy rates in embryo recipients synchronized with PGF2alpha and eCG?

The objective of this study was to evaluate the effects of equine chorionic gonadotropin (eCG) treatment on the number of induced accessory corpora lutea (CL), plasma progesterone concentrations and pregnancy rate in cross-bred heifers after transfer of frozen-thawed (1.5M ethylene glycol) embryos. All recipients received 500 microg PGF2alpha (dl-cloprostenol, i.m.) at random stages of the estrous cycle (Day 0) and were observed for estrus for 7 days. On Day 14, heifers detected in estrus between 2 and 7 days after PGF2alpha treatment were randomly allocated to four groups ( n=83 per group) and given 0 (control), 200, 400, or 600 IU of eCG. Two days later (Day 16), these recipients were given PGF2alpha and observed for estrus. Six to eight days after detection of estrus, plasma samples were collected to determine progesterone concentration and ultrasonography was performed to observe ovarian structures. Heifers with multiple CL or a single CL >15 mm in diameter received an embryo by direct transfer. Embryos of excellent and good quality were thawed and transferred to the recipients by the same veterinarian. Pregnancy was diagnosed by ultrasonography and confirmed by transrectal palpation 21 and 83 days after embryo transfer (ET), respectively. Plasma progesterone concentrations on the day of transfer (Day 7 of the estrous cycle) were 3.9+/-0.7, 4.2+/-0.4,6.0+/-0.4 and 7.8+/-0.6 ng/ml for groups Control, 200, 400, and 600, respectively (Control versus treated groups P=0.009; 200 versus 400 and 600 groups P=0.0001; and 400 versus 600 P=0.012 ). Conception rates 83 days after ET were 41.9, 50.0, 25.0, and 20.9% for groups Control, 200, 400, and 600, respectively (200 versus 400 and 600 groups P=0.0036 ). In conclusion, an increase in progesterone concentration, induced by eCG treatment, did not improve pregnancy rates in ET recipients. Conversely, there was a decline in conception rates in the animals with the highest plasma progesterone concentrations.     

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.     

The effects of a low dose of cabergoline on induction of estrus and pregnancy rates in anestrous bitches

This is the first report of successful induction of normal estrus and ovulation in breeder bitches with as a low dose as 0.6 microg/kg/day of cabergoline formulation marketed for use in women. Sixty-one pure breed bitches from various breeds were used in the study at their already determined periods of anestrus. Twenty-four dogs formed the control group, while 37 bitches were administered with two different doses of cabergoline (recommended dose group, n=10, 5 microg/kg/day and low dose group, n=27, 0.6 microg/kg/day). Induced estrus rates and mean treatment and proestrus durations of dogs in these two dose groups were compared. At the second phase of the study, the effects of 500 IU human chorionic gonadotropin (hCG) administered on days 1 and 3 of estrus induced by the low dose of cabergoline, on the duration of behavioral estrus, ovulation rates, pregnancy rates and the number of offspring were investigated. For this purpose, the dogs with signs of proestrus (22/27) following the treatment in the low dose group were assigned into two subgroups. Five hundred IU of hCG (Pregnyl, Organon, Turkey) was intramuscularly administered to eight of these dogs [low dose (hCG+) group] on days 1 and 3 of estrus. The remaining 14 dogs were not treated with hCG [low dose (hCG-) group]. An aqueous solution of cabergoline (Dostinex, Pharmacia, Italy) was orally administered until 2 day after the onset of proestrus or for a maximum of 42 days. Blood samples were taken daily from all treatment and 11 control bitches during the first five days of behavioral estrus to measure progesterone concentrations. In the recommended dose and low dose groups, estrus was induced between days 8-45 and 4-48 (mean: 23.63+/-14.33 and 24.41+/-14.31 days), in the ratio of 80.0 and 81.5%, respectively (p>0.05). In both dose groups, post-treatment interestrous intervals were significantly shorter than both those of the control group and their own pre-treatment interestrous intervals (p<0.05). Ovulation rates, pregnancy rates and mean number of offspring delivered by the dogs in the recommended dose, low dose (hCG-), low dose (hCG+) and control groups were found to be similar (p>0.05). However, the mean duration of behavioral estrus of the dogs in the low dose (hCG+) group was found to be significantly longer compared to dogs in all other groups (p<0.05). In both dose groups, no correlation could be found between the anestrus stages and treatment durations (p>0.05). Shortly, it has been concluded from the study that (1) normal and fertile estrus can be induced more economically in bitches during different stages of anestrus using as a low dose of 0.6 microg/kg of cabergoline formulation marketed for use in women, and that (2) hCG injections on days 1 and 3 of the estrus induced by this method has no positive effects on the ovulation rates, pregnancy rates and the number of offspring per pregnancy.     

Reproductive hormone secretions in pony mares subsequent to ovulation control during late winter

Beginning in December, pony mares were placed under a schedule of increasing light. Starting in February, onset of estrus was checked by daily teasing with a stallion. Mares were randomly assigned to one of three treatments (6 mares per group) administered in March. Treatments were: Group I — 75 mg progesterone injected intramuscularly every day for 10 days in combination with a 1.25 mg injection of PGF₂α on day 7 of progesterone treatment and a 2,000 IU injection of HCG on day 2 of estrus; Group II — a norgestomet ear implant inserted for 10 days in combination with 1.25 mg PGF₂α given 7 days after insertion and 2,000 IU HCG administered on day 2 of estrus; and Group III — same as II except that 2 mg of GnRH rather than HCG were administered on day 2 of estrus. Blood plasma for radioimmunoassay of progesterone, LH and estradiol was collected from the first day of treatment until 14 days after the end of estrus. Also in March, 6 mares were bled daily from the first day of estrus until subsequent estrus or day 21 (control estrus). Although estrus was detected in all mares, 14 of 18 mares ovulated subsequent to treatments and four of the six control estrus mares ovulated. Only among HCG treated mares was the ovulation rate higher (P < .05) than it was in the control estrus group. The interval from last progesterone injection or norgestomet implant removal to estrus did not differ between treatment groups. Concentrations of estradiol and LH were increased for several days around the time of ovulation and tended to be positively correlated with each other. In the mares that did not ovulate, concentrations of LH and estradiol appeared to be lower than in mares that ovulated. In summary, progestins in combination with PGF₂α and increasing light will synchronize estrus in mares during late winter and HCG will hasten ovulation in some mares.     

Embryo yield and plasma progesterone profiles in superovulated dairy cows and heifers.

This study was conducted to compare the superovulatory (SOV) response of dairy cows (n=172) and heifers (n=172), with two SOV treatments started at the mid-luteal-phase of the estrus cycle. Donors were randomly treated either with equine chorionic gonadotrophin (eCG) plus neutra-eCG serum (eCG+N group, n=167) or follicle stimulating gonadotrophin (FSH-P group, n=177).No significant differences were observed among groups in the percentage of superovulatory responsive donors (SR donors; corpora lutea (CL) >/=2), the mean number of total ova, fertilized ova and viable embryos recovered. Cows yielded significantly less total ova and less fertilized ova (P<0.05) and tended to yield less viable embryos (P<0.06) than heifers.Plasma progesterone (P4) concentrations (n=135 donors) on the day of PGF(2alpha) (PGF) injection and on the day of SOV estrus were significantly higher (P<0.01) in eCG+N than in FSH-P donors and, the increase between those 2 days was also significantly higher (P<0.05) in group eCG+N than in group FSH-P, suggesting a higher luteotrophic effect of eCG than FSH-P. SR donors had P4 levels significantly higher (P<0.001) than non-SR donors only on day 5 after the SOV estrus and on the day of embryo recovery. Plasma P4 concentrations at 5 days after the SOV estrus and at embryo recovery correlated significantly (r=0.76, P<0.001).Heifers had significantly higher P4 levels than cows at gonadotrophin injection (P<0.01), PGF injection (P<0.001), 5 days (P<0.01) and 7 days (P<0.001) after the SOV estrus. At day 7 after the SOV estrus, P4 concentrations per ova recovered were significantly higher in heifers than in cows (P<0.01). The increase of plasma P4 per ova recovered, between days 5 and 7 after the SOV estrus, was significantly (P<0.01) higher in heifers than in cows. Also, the increase of plasma P4 between injections of gonadotrophin and PGF was significantly higher (P<0.05) in heifers than in cows.These results suggest that heifers have higher plasma P4 concentrations at diestrus (either before or after the SOV treatment) and this is associated with a higher embryo yield and quality, as compared to lactating cows. These higher plasma P4 concentrations reflect not only differences in ovulation rate as well as the competence of the corpus luteum, which is potentialized by gonadotrophin stimulation.     

Endocrine, luteal and follicular responses after the use of the short-term protocol to synchronize ovulation in goats

The effect of the so-called Short-Term Protocol (5-day progesterone treatment+PGF(2)alpha) on ovarian activity and LH surge was studied in goats. The goats received 250IU eCG at the time of device withdrawal (eCG group; n=7), or 200microg of EB (estradiol benzoate) 24h after device withdrawal (EB group; n=8), or received neither eCG nor EB (control group; n=8). The Short-Term Protocol induced greater (4.1+/-1.1ng/ml) progesterone serum concentrations at 24h after start of the treatment, that declined to 0.2+/-0.1ng/ml at 12h after device withdrawal. In all of the groups, the maximum concentration of estradiol-17beta was reached at about 36h after device withdrawal. Maximum concentration was greater in the EB group (76.9+/-24.6pmol/l) than in the control group (41.8+/-9.0pmol/l; P<0.01), with the eCG group showing intermediate concentration (70.3+/-32.5pmol/l; P=NS). The LH peak occurred earlier in the eCG group (38.4+/-2.0h after device withdrawal) and in the EB group (41.0+/-4.1h), than in the control group (46.3+/-5.1h; P<0.05). Ovulation occurred earlier in the eCG group (5/7) and in the EB group (8/8) (58.8+/-2.7h and 63.0+/-5.6h, respectively), than in the control group (7/8) (70.2+/-8.3h; P<0.05). In summary, the Short-Term Protocol induced similar concentrations of progesterone among treated goats. In addition, eCG or EB resulted in a similar increase in estradiol-17beta and a similar LH surge, which induced ovulation in most females (86.7%) in a consistent interval (about 60h) after the end of progesterone exposure.     

Male effect in seasonally anovulatory lactating goats depends on the presence of sexually active bucks,but not estrous females

A study was conducted in subtropical northern Mexico (26 degrees N) to determine whether the presence of estrous females can improve the response of seasonally anovulatory goats to the introduction of bucks in the group. The induction of estrous activity was studied in three groups of anovulatory lactating goats during seasonal anestrus. These females were of the Mexican Creole breed. In the control group (sexually inactive (SI), n = 20), two control (SI) bucks exposed to normal seasonal daylength variations were used. In the second group (SI + E, n = 20 + 3), two control males were also used, but in addition, three females of the group were in estrus at the time of male introduction. In the third group (sexually active, SA + E, n = 19 + 4), anovulatory females were exposed to two bucks made sexually active by exposure to 2.5 months of long days (16L:8D) followed by two subcutaneous 18 mg melatonin implants, and four estrous females were also present when introducing the bucks. In all groups, males were introduced on 15 March and estrous detection was conducted twice daily for 15 days. The sexual activity of the bucks was observed from 08:00 to 10:00 h during the first five days of exposure to females. More females displayed estrous behavior in the first 15 days following the introduction of the males in the SA + E group (18/19) as compared with the SI or SI + E groups (2/20 and 0/20, respectively; P < 0.001). No difference was observed between the two latter groups. Thirteen females of SA + E group showed a second estrus between days 6 and 11 (short estrous cycle duration: 5.4 +/- 0.4 days). By contrast, in the SI group none showed a second estrus. The sexual behavior of the males in the SA + E group was greater as compared with that of the males in SI and SI + E groups (over 80% of the total sexual activity recorded in the three groups; P < 0.001). By contrast, no differences were found between SI and SI + E males. These results indicate that the presence of estrous females alone at the time of buck introduction is not sufficient to induce an adequate stimulation of seasonally inactive males. The use of sexually active bucks is necessary to induce reproductive activity in anovulatory females, whereas preparation of the bucks with long days followed by melatonin implants allows them to gain such a capacity.     

Effect of prior FSH treatment on the estrus and ovulation responses to eCG in prepubertal gilts

The objective of this study was to determine the effect of pre-treatment of prepubertal gilts with FSH on the estrus and ovulatory responses to eCG injection at two ages. A total of 149 prepubertal Hypor gilts were selected at 150 days (n=76) or 180 days (n=73) of age and assigned to injection of 400 IU eCG plus 200 IU hCG (PG600), 600IU eCG alone (Folligon), pre-treatment with 72 mg FSH (Folltropin) administered as 6 x 12 mg injections at 12 h intervals with 600 IU Folligon 12h after last FSH injection, or non-injected controls. To facilitate detection of estrus, gilts were exposed to a mature boar for 15 min daily for 7 days. To determine ovulatory responses, blood samples were obtained on the day of injection and 10 days later and assayed for progesterone content. Following treatment at 150 days, one control gilt (5.3%) was deemed estrus but ovulation did not occur. Compared to treatment with Folligon alone, PG600 injection tended (P=0.1) to increase the estrus response (52.6% compared with. 26.3%) and increased (P<0.01) the ovulatory response (89.5% compared with. 47.4%). The estrous response in gilts pretreated with Folltropin was intermediate (42.1%) but the ovulatory response (47.4%) was the same as for Folligon alone. Following treatment at 180 days, two control gilts (10.5%) were deemed estrus and ovulation did occur in these gilts. There was no difference between hormone-treated groups for estrus or ovulatory responses, although the ovulatory response of PG600-treated gilts tended (P=0.1) to be greater than for the Folligon-treated group (89.5% compared with 66.7%), with Folltropin-pretreated gilts being intermediate (76.5%). These data demonstrate that the estrus and ovulatory responses of gilts were greater for PG600 than for Folligon and that while responses to PG600 were not affected by gilt age, for the combined Folligon groups, estrous response (P<0.02) and ovulatory response (P<0.05) improved with increased gilt age.     

Male reproductive condition is the limiting factor of efficiency in the male effect during seasonal anestrus in female goats

Two experiments were conducted to determine whether the failure of males to induce sexual activity in goats during seasonal anestrus is due to unresponsiveness of females to male stimulus or insufficient stimulation from males. In the first study, one group of males (sexually inactive, SI; n = 4) was kept under natural photoperiod while the other (sexually active, SA; n = 4) was subjected to 2.5 mo of long days (16L:8D) and received 2 s.c. implants of melatonin. Two mo later, 2 different flocks of anovulatory goats previously separated from bucks were exposed to either SI (n = 34) or SA (n = 40) bucks. Progesterone assays and estrous behavior were used to determine ovarian and behavioral responses of the females to teasing. Of the goats exposed to SI males, only 2 ovulated, and none showed estrous behavior during the 35 days of the study. In contrast, all females (40 of 40) in contact with SA males ovulated and showed at least one estrous behavior during the first 11 days following male introduction (P < 0.001). Overall, 38 of 40 females stimulated with SA bucks were diagnosed pregnant at Day 35, according to progesterone assay (versus 0 in SI-treated group: P < 0.001). To control for a possible difference of responsiveness between flocks, the experiment was repeated 1 yr later using a single flock of goats divided into 2 groups. Again, over the first 14 days, 1 of 33 goats showed estrous behavior in the SI-treated group versus 27 of 33 in the SA-treated group (P < 0.001). Therefore, treating bucks with long days and melatonin increased their teasing capacity to induce sexual activity in females during anestrus. These results indicate that the absence of response to teasing at this time of the year is not due to female unresponsiveness, but to insufficient stimulation from the male.     

Effects of melatonin supplementation prior to Ovsynch protocol on ovarian activity and conception rates in anestrous Murrah buffalo heifers during out of breeding season

Buffalo heifers have tendency to show anestrus during summer season. Melatonin has been used for correcting summer dependent anestrous via inducing resumption of ovarian activity. Therefore, the investigation was conducted to compare efficacy of melatonin for induction of estrus and conception rate with Ovsynch protocol in summer anestrous Murrah buffalo heifers. Thirty, summer anestrous Murrah buffalo heifers were selected and divided into two groups- treatment (n?=?20; 12 melatonin implants) and control (n?=?10; no treatment). On day 28 post-implant insertion, animals of both the groups were subjected to Ovsynch protocol. Blood sampling and ovarian ultrasonography were conducted to measure plasma melatonin, progesterone concentration and ovarian dynamics, respectively. No animal in either group showed estrus during first 28?days post-implant insertion. However, estrus induction rate was 100% after Ovsynch protocol in both groups. As compared to controls, treatment group exhibited higher (p?<?0.05) plasma melatonin on days 1, 4, 8, 15, 22 and 28 post-melatonin, with highest concentration on day 4. The progesterone concentration increased (p?<?0.05) on days 15 and 22 post-melatonin treatment. The treatment group had larger (p?<?0.05) preovulatory follicle on day of AI, subsequently developed larger (p?<?0.05) corpus luteum and higher plasma progesterone concentrations by day 12 post-AI as compared to the control group. The overall conception rate was 50 and 20% in treatment and control groups, respectively. In conclusion, melatonin treatment along with Ovsynch protocol improved the luteal profiles as well as the conception rate in buffalo heifers when compared with animals treated with Ovsynch protocol alone during summer season.