Effect of hCG vs. GnRH at the beginning of the Ovsynch on first ovulation and conception rates in cyclic lactating dairy cows

Ovulatory response to the first GnRH of Ovsynch is a very important factor for determining the outcome of a successful synchronization. The aim of the present study was to develop a protocol to increase the percentage of cows that ovulated in response to the first administration of Ovsynch. This study was designed to compare ovulation rates in response to GnRH or hCG at the beginning of Ovsynch and to evaluate the effects of this manipulation on pregnancy. Cows (n = 371) with corpus luteum (CL) and at least one follicle greater than 10 mm diameter size on either ovary were included in the study. Cows were divided into two groups. The Ovsynch protocol began with GnRH (10 μg) in the GPG group (n = 161; GnRH-7d-PGF2α-56h-GnRH-18h-AI), whereas in the HPG group, the first GnRH of the Ovsynch was replaced with 1500 IU hCG (n = 210; hCG-7d-PGF2α-56h-GnRH-18h-AI). Ovarian ultrasonography was performed at the times of GnRH or hCG and of PGF2α administration, at the time of artificial insemination (AI) and seven days after AI, to determine ovulation. Maximal follicle size at the beginning of the Ovsynch did not affect on response to the first GnRH/hCG treatment. Conception rate (31 d) was 0.6 times more likely to be higher (P < 0.001) in cows that responded to the first hormonal administration of Ovsynch than in those that did not respond (95% CI = 0.29-0.71). Conception rate was found to be different between the HPG (37.6%, 79/210) and the GPG groups (48.4%, 78/161). Thus, beginning of the Ovsynch protocol with hCG did not increase ovulation and conception rate in lactating dairy cows, suggesting that hCG is not a suitable replacement of the first GnRH of Ovsynch. However, our results do show that increasing the ovulation rate in response to the first hormonal administration of Ovsynch can have a significant effect on conception rate.     

Efficacy of intermittent or continuous administration of GnRH in inducing ovulation in early and late seasonal anoestrus in the Père David's deer hind (Elaphurus davidianus)

Père David's deer hinds were treated with GnRH, administered as intermittent i.v. injections (2.0 micrograms/injection at 2-h intervals) for 4 days, or as a continuous s.c. infusion (1.0 micrograms/h) for 14 days. These treatments were given early (February-March) and late (May-June) in the period of seasonal anoestrus. The administration of repeated injections of GnRH increased mean LH concentrations from pretreatment values of 0.54 +/- 0.09 to 2.10 +/- 0.25 ng/ml over the first 8 h of treatment in early anoestrus, and from 0.62 +/- 0.11 to 2.73 +/- 0.49 ng/ml in late anoestrus. The mean amplitude of GnRH-induced LH episodes was greater (P less than 0.01) in late (4.03 +/- 0.28 ng/ml) than in early (3.12 +/- 0.26 ng/ml) anoestrus, but within each replicate (early or late anoestrus), neither mean LH episode amplitude nor mean plasma LH concentrations differed significantly between the four periods of intensive blood sampling. On the basis of their progesterone profiles, 6/12 hinds had ovulated in response to treatment with injections of GnRH (1/6 in early anoestrus and 5/6 in late anoestrus), and oestrus and a preovulatory LH surge were recorded in all of these animals. Oestrus and a preovulatory LH surge were also recorded in one other animal treated in early anoestrus in which progesterone concentrations remained low. The mean times of onset of oestrus (91.0 +/- 1.00 and 62.4 +/- 0.98 h) and of the preovulatory LH surge (85.8 +/- 3.76 and 59.4 +/- 0.25 h) both occurred significantly earlier (P less than 0.001) in animals treated in late anoestrus. Continuous infusion of GnRH to seasonally anoestrous hinds resulted in an increase in mean plasma LH concentrations, but this response did not differ significantly between early (2.15 +/- 0.28 ng/ml) and late (2.48 +/- 0.26 ng/ml) anoestrus. Ovulation, based on progesterone profiles, occurred in 2/7 hinds in early anoestrus and in 4/6 hinds in late anoestrus. Oestrus was detected in all except one of these hinds. The mean time of onset of oestrus occurred earlier in animals treated in late anoestrus (66.2 +/- 0.32 h and 46.7 +/- 0.67 h, P less than 0.01). The administration of GnRH, given either intermittently or continuously, will induce ovulation in a proportion of seasonally anoestrous Père David's deer. However, more animals ovulate in response to this treatment in late than in early anoestrus (75% compared with 23%).     

Efficacy of decreasing the dose of GnRH used in a protocol for synchronization of ovulation and timed AI in lactating dairy cows

To determine the efficacy of reducing the dosage of GnRH used in a protocol for synchronization of ovulation and timed AI, primiparous and multiparous lactating Holstein cows (n=237) were randomly assigned to 1 of 2 treatment groups. Ovulation was synchronized for cows in the first group using intramuscular injections of GnRH and PGF₂ as follows: Day 0, 100 μg GnRH; Day 7, 25 mg PGF₂; Day 9, 100 μg GnRH. Ovulation was synchronized in the second group of cows using the same injection schedule and dosage of PGF₂ but only 50 μg GnRH per injection. All cows underwent a timed AI at 12 to 18 h after the second GnRH injection. The proportion of cows ovulating in response to the second GnRH injection (synchronization rate) and pregnancy status at 28 and 56 d post AI were determined using transrectal ultrasonography. The synchronization rate, double-ovulation rate, conception rate at 28 and 56 d post AI, and pregnancy loss from 28 to 56 d post AI did not differ statistically between treatment groups. For all cows, synchronization rate was 84.0%, and double-ovulation rate was 14.1%. Conception rates calculated using all cows receiving synchronization of ovulation were 41.1% at 28 d and 34.4% at 56 d post AI. Conception rates calculated for only synchronized cows were 47.6% at 28 d and 40.1% at 56 d post AI. For all cows, pregnancy loss from 28 to 56 d post AI was 13.5%, with an attrition rate of 0.5% per day. Estimated savings in hormone costs using 50 rather than 100 μg GnRH per injection for synchronizing ovulation were $6.40 per cow and $20.27 per pregnancy. Thus, decreasing the dosage of GnRH used for synchronization of ovulation and timed AI in lactating dairy cows reduces synchronization costs per cow and per pregnancy without compromising the efficacy of the synchronization protocol.     

Reproductive performance of dairy cows with ovarian cysts after synchronizing ovulation using GnRH or hCG during the warm or cool period of the year

This study was designed to compare the reproductive response to timed AI of lactating dairy cows with cystic ovarian follicles treated with GnRH or hCG to synchronize ovulation. The effectiveness of treatment during the warm or cool period of the year was also compared. Cows were given 12 microg GnRH-agonist i.m. on day 0 of the protocol, 15 mg PGF(2alpha) i.m. on day 7, and either GnRH-agonist (GPG treatment) or 3000 IU hCG i.m. (GPH treatment) on day 9, followed by timed AI. The cows were randomly chronologically assigned to GPG (n=130) or GPH (n=136) group. All cows were inseminated at fixed time 16-22 h after the end of treatment. During the warm period the pregnancy rate to first AI was 12% (7/60) and 21% (14/68) for the GPG and GPH groups, respectively, there being no significant differences between groups; the cumulative pregnancy rate was 22% (13/60) and 21% (14/68) for the GPG and GPH groups, respectively, again with no significant intergroup differences. During the cool period pregnancy rate to first AI was not different between groups: 29% (20/70) for GPG and 32% (22/68) for GPH, respectively; whereas the cumulative pregnancy rate was significantly higher (P<0.05) for the GPH groups than for the GPG group: 56% (39/70) and 78% (53/68), respectively. These findings indicate that during the warm period, the pregnancy rates of the cystic cows were similar whether they received GPG or GPH treatment, during the cool period, there is a beneficial effect to use hCG at day 9 of the ovsynch protocol compared GnRH on cumulative pregnancy rate.     

Optimal dose of human chorionic gonadotropin for inducing ovulation in the ferret

The optimal dose of human chorionic gonadotropin (hCG) for induction of ovulation was determined by comparing the ovulatory response of 119 mated ferrets (controls) with that of estrous females induced to ovulate with five different dosages of hCG. Copulation induced formation of 12.7 ± 4.5 corpora lutea (CL) in all 119 females and resulted in a 90.7% conception rate as evidenced by finding approximately eight blastocysts/female in the uteri of 108 ferrets. All doses of hCG tested induced ovulation; however, the lower doses (50 and 75 IU) resulted in a lesser percentage of females ovulating. The highest doses of hCG (150 and 300 IU) resulted in fewer CL/female being formed. The optimal dose of hCG for simulating copulation induced ovulation was 100 IU. Tubal transport of unfertilized oocytes in pseudopregnant females was found to be significantly retarded when compared to the rate of transport of embryos in the control group.     

The efficacy of different hCG dose rates and the effect of hCG treatment on ovarian activity: ovulation, multiple ovulation, pregnancy, multiple pregnancy, synchrony of multiple ovulation; in the mare

Despite the widespread use of hCG to advance ovulation in the mare there is little information on efficacy of dose rates and any contraindications of its use. This study aims to investigate the effect of dose of hCG on ovulation within 48h and the effect of hCG on: ovulation, multiple ovulation (MO), pregnancy, multiple pregnancy (MP) rates and synchrony of MO; additionally whether any seasonal effect is evident. Sequential ultrasonic scanning was used to monitor the occurrence of ovulation, within 48h of treatment, in 1291 Thoroughbred mares treated with either 750iu hCG or 1500iu hCG s.c. Ovulation rate, type (single ovulations (SO), MO, synchronous, asynchronous) and subsequent pregnancy were then monitored in 1239 Thoroughbred mares on a commercial stud over 3 years, 536 of which were treated with 750iu hCG at mating, all mares were also allocated into groups according to month of mating. No significant difference existed between the two dose levels of hCG and no significant difference existed between treated and untreated mares in overall ovulations (1.32 and 1.28 respectively), MO (31.7% and 27.7%), pregnancy (65.1% and 65.6%) or MP rates (10.8% and 11.8%). There was no significant association between month of year and pregnancy or MP rates for either treated or control mares, nor for MO for untreated mares. A significant (p<0.05) association was evident between month and MO in treated mares, MO being lowest in April (22.3%). 95.9% of treated mares multiple ovulated within 48h compared with 90.7% controls, a near significant difference. In conclusion this study demonstrates that: (i) hCG dose of 750iu s.c. is just as effective in inducing ovulation within 48h as 1500iu, (ii) 750iu hCG has no significant effect on ovulation, MO, pregnancy or MP rates; (iii) a significant (p<0.05) association exists between season and MO in hCG treated mares; (iv) a tighter synchrony (ovulation within 48h) of MO is evident in hCG treated compared with control mares (p=0.052).     

Follicular Development and Ovulation in Sows: Effect of hCG and GnRH Treatment

Follicular growth, chronology of ovulation and embryo morphology were compared in sows ovulating spontaneously and sows, in which the ovulation was attempted induced by hCG or GnRH. Indwelling catheters were placed on day 1 (weaning = day 0) in the ear veins of 18 sows, which were then randomly divided into 3 groups: a control group (N = 6), a group (N = 6) given 750 iu hCG (Physex®) im 76h after weaning (hCG group) and a group (N = 6) given 500 µg GnRH (Fertagyl®) im 76h (N = 3) or 100h after weaning (N = 3) (GnRH group). Follicular diameter and time of ovulation were monitored by ultrasonography every 4h from day 3 until ovulation or development of cysts by means of a sector scanner fitted with a 5.0/7.5 MHz multiangle probe. Heat detection was performed every 8h from day 3 until ovulation. On day 13, the sows were slaughtered, the number of corpora luteae (CL) was counted, and embryos were flushed from the uteri. The control group showed clear heat symptoms, and on day 3, the follicles were typically 3–7 mm and grew up to 7–10 mm over 2 days, where they remained for approximately 24h until ovulation took place 41h ± 9h after first sign of standing heat. The hCG group exhibited no signs of heat, and the follicles only reached 5–8 mm in diameter at time of ovulation, which occurred 40h ± lh after hCG-injection. The GnRH group exhibited inconsistent signs of heat, and the follicles reached a maximum size of 7–12 mm in diameter where they remained for more than 24h. Only 2 sows in this group ovulated within 84–92h after the GnRH injection, and development of bursa cysts and cystic follicles was a common finding. The average number of CL was 18.2 ±5.7 per sow (N = 16, range: 3–27) with no significant difference between the groups. Total embryo recovery was 79 ± 13 % with no significant difference between groups. The embryo diversity calculated as standard deviation of the maximum diameter was higher in the hCG group as compared with the control group. It is concluded that (1) transrectal ultrasonography can be used in sows for accurate assessment of follicular growth and ovulation; (2) the use of hCG results in lack of heat symptoms and reduced follicle size at the time of ovulation when injected 76h after weaning; (3) administration of a single injection of GnRH, if given before the first signs of heat, results in inconsistent heat symptoms and no or late ovulations.     

Control of ovulation with a GnRH analog in gilts and sows

Methods for the control of ovulation with GnRH or the GnRH analog D-Phe6 -LHRH (GnRH-A), were evaluated in gilts and sows as the last step in development of a fixed-time Al protocol. This involved 3 field trials using 2,744 gilts (10 units) and 71,628 sows (33 units). In Trial 1, the GnRH-A (75 microg) was given subsequent to treatment with altrenogest for cycle control or eCG for the stimulation of uniform follicle development in gilts. The release of LH was followed by ovulations which commenced within 36.4 +/- 3.3 hr and were terminated at 39.0 +/- 2.8 hr after administration of GnRH-A. This degree of synchronization of ovulations enabled the use of fixed-time AI. Consequently, subsequent to pretreatment with altrenogest and eCG, in 10 production units 1,285 gilts received 50 microg GnRH-A and 1,459 gilts 500 IU hCG serving as positive controls (Trial 2); all the gilts were inseminated 24 and 42 hr after treatment. Pregnancy rate and piglet index (n of piglets per 100 first inseminations) following GnRH-A vs hCG were 78.8% and 779 vs 74.4% and 728, respectively (P < 0.05). In field trials with first litter gilts and multiparous sows (33 units holding from 250 to 6,000 sows), 1,000 IU eCG was used for estrus control after weaning and 25 microg or 50 microg GnRH-A were given 55 to 58 hours after eCG (n = 19,954 and 20,701) (Trial 3). Sows treated during the same time period with 300 microg GnRH plus 300 IU. hCG (n = 30,973) served as positive controls; all sows were inseminated 24 and 42 hours after treatment. Pregnancy rates for 50 microg GnRH-A, 25 microg GnRH-A and 300 microg GnRH plus 300 IU hCG were 83.0%, 81.7% and 80.7%, and the piglet indices 913, 899 and 880, respectively (P < 0.05). Unit size and parity had significant effects on fertility and productivity. In all studies, results with 50 microg GnRH-A were superior. In year-long studies, highest levels of fertility in response to these treatments were seen from December to May.     

Inhibition of hCG, alpha hCG and progesterone release from human placental tissue in vitro by a GnRH antagonist

A dramatic suppression of hCG, alpha hCG and progesterone release from midgestation, human placentas in vitro was effected when incubated with 1 microgram/ml of an antagonist to GnRH. This inhibition of hormonal release occurred rapidly and was partially restored by the addition of GnRH. Human chorionic somatomammotropin was also suppressed, but only two days following the decline of the other hormones. These data demonstrate that an antagonist to GnRH can rapidly inhibit human placental hormone release.     

Effect of dose of GnRH analog on ovulation in mares

Proper timing of insemination for optimal conception is accomplished by frequent palpations per rectum, by ultrasonography of the preovulatory follicle and/or by treatment with hCG or GnRH. Sustained release of GnRH from implants has been shown to hasten ovulation. Therefore, 2 studies were conducted to evaluate the efficacy of a GnRH analog, deslorelin, for hastening ovulation in nonlactating cyclic mares. The GnRH implant was 2.3 x 3.7 mm and released deslorelin for 2 to 3 days. In Experiment 1, 60 nonlactating, cycling mares were assigned to 1 of 5 doses: 0, 1.2, 1.7, 2.2 and 2.7 mg per implant. Mares were assigned sequentially on the first day of estrus (Day 1). Ovaries were examined per rectum and with ultrasonography every 12 h until ovulation. Once the mares obtained a follicle >30 mm, they were injected subcutaneously with a GnRH implant. The mares were inseminated every other day during estrus with semen from 1 of 3 stallions. Pregnancy was determined with ultrasonography. Experiment 2, 40 nonlactating, cyclic mares were assigned to 1 of 5 treatments (same treatments as in Experiment 1). Data were obtained on interval to ovulation, duration of estrus and pregnancy rates at 12, 18 and 35 d after ovulation. Time to ovulation was shorter (P<0.05) in GnRH-treated mares than in control mares in the Experiment 1. Mean time to ovulation was 68, 49, 48, 47, 44 h in Experiment 1, and 91, 66, 58, 46, 58 h in Experiment 2 for mares given 0, 1.2, 1.7, 2.2 and 2.7 mg/mare in the 2 trials. Averaged for both experiments, the proportion of mares ovulating within 48 h of treatment was 40, 75, 85, 90 and 90% for 0, 1.2, 1.7, 2.2 and 2.7 mg/mare. For both experiments, there was no effect of GnRH on pregnancy rate. In summary, a subcutaneous implant containing GnRH analog induced ovulation in most mares by 48 h of injection, and there was no advantage of doses higher than 2.2 mg/mare.     

Variations in rabbit oviduct microvascular architecture after ovulation induced by hCG

Rabbits were induced to ovulate by injection with hCG and vascular corrosion casts of the oviducts were examined by scanning electron microscopy after 24 and 48 h, when the ova would be expected to be at the ampullary-isthmic junction, and traversing the isthmus respectively. At 24 h there was dilatation of the isthmic subserosal venous plexus. It is suggested that venous distension in the isthmic subserosal venous plexus, due to raised venous pressure or to reduced venous wall tone, may occlude the isthmic lumen to ova, and thus explain the known pre-isthmic delay in ovum transport. By 48 h after hCG, distension was no longer evident, consistent with the possibility of ovum transport.     

Synchronization of ovulation in dairy cows using PGF2alpha and GnRH

This paper reports a new method for synchronizing the time of ovulation in cattle using GnRH and PGF(2alpha). In Experiments 1 and 2, lactating dairy cows (n=20) ranging from 36 to 280 d postpartum and dairy heifers (n=24) 14 to 16 mo old were treated with an intramuscular injection of 100 mug GnRH at a random stage of the estrous cycle. Seven d later the cattle received PGF(2alpha) to regress corpora lutea (CL). Lactating cows and heifers received a second injection of 100 mug GnRH 48 and 24 h later, respectively. Lactating cows were artificially inseminated 24 h after the second GnRH injection. Ovarian morphology was monitored daily by trans-rectal ultrasonography from 5 d prior to treatment until ovulation. In Experiment 3, the flexibility in the timing of hormonal injections with this synchronization protocol was evaluated by randomly assigning 66 lactating dairy cows to 3 different treatment groups. Lactating cows received the injection of PGF(2alpha) 48 (Group 1), 24 (Group 2), and 0 h (Group 3) prior to the second injection of GnRH, which was administered at the same time in each group to ensure the second injection of GnRH was given when follicles were at a similar stage of growth. In Experiments 1 and 2, the first injection of GnRH caused ovulation and formation of a new or accessory CL in 18 20 cows and 13 24 heifers. In addition, this injection of GnRH initiated or was coincident with initiation of a new follicular wave in 20 20 lactating cows and 18 24 heifers. Corpora lutea regressed after PGF(2alpha) in 20 20 cows and in 18 24 heifers. All cows and 18 24 heifers ovulated a newly formed dominant follicle between 24 and 32 h after the second injection of GnRH. Ten of 20 cows conceived to the timed artificial insemination. In Experiment 3, the conception rate in Groups 1 and 2 were greater than in Group 3, (55 and 46 % vs 11%, respectively). In summary, this protocol could have a major impact on managing reproduction in lactating dairy cows, because it allows for AI to occur at a known time of ovulation and eliminates the need for detection of estrus.     

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.     

Inducing ovulation with hCG improves the fertility of dairy cows during the warm season

This study was designed to assess the effects of human chorionic gonadotrophin (hCG), given within a timed artificial insemination program, on plasma progesterone concentrations and subsequent fertility in lactating dairy cows during the warm and cold seasons of the year. Cows were treated intramuscularly with GnRH-agonist (Day 0) and PGF₂ (Day 7) followed by either GnRH-agonist (GPG treatment; 60 animals) or hCG (GPH treatment; 60 animals) on Day 9. All cows were fixed-time inseminated (TAI) 16–22 h after the end of treatment. To determine plasma progesterone levels, blood was withdrawn from all animals on Days 3, 6, 9, 12 and 15 after TAI. During the warm period, the pregnancy rate recorded at TAI was similar for the GPG and GPH groups (20% vs. 23%) while the cumulative pregnancy rate within 30 days of TAI was lower (P < 0.05) for the GPG than the GPH group (36% vs. 63%). No differences were observed during the cold period. During the warm period, embryo losses between Days 28 and 45 after TAI were greater (P < 0.05) for the GPG group compared to the GPH group (36% vs. 5%) while again no differences emerged during the cold period. Mean plasma progesterone levels were higher (P < 0.05) in the GPH group than GPG group on Days 3, 6 and 9 post-insemination. Our findings indicate that the use of hCG to induce ovulation in a timed artificial insemination protocol increases plasma progesterone levels and improves fertility in dairy cows during the warmer period of the year.     

Induction of ovulation and spermatogenesis by hMG/hCG in hypogonadotropic GH-deficient patients.

Nine female and 20 male hypogonadotropic GH-deficient patients were studied for sexual development by hCG/hMG. In the female patients, gonadotropin therapy was started at the mean age of 22.7 +/- 2.1 years. The administration of progesterone induced withdrawal bleeding at an average of 2.77 +/- 1.94 years after the initiation of hMG/hCG therapy in 8 of the 9 patients studied. Of 6 patients who had been confirmed as positive in a gestagen test, induction of ovulation by hMG/hCG was observed in 5 patients at an average of 5.58 +/- 1.23 years after the onset of therapy, but not in the remaining patient who had been given estrogen and progesterone 4 years 9 months prior to the initiation of the gonadotropin therapy. In male patients, gonadotropin therapy was started at the mean age of 23.6 +/- 5.7 years. Seminal fluid was obtained by masturbation and brought to our clinic in the morning. Of the 20 patients, 19 patients could be observed once a month regularly. Of the 19 patients, spermatozoa could be detected at a mean period of 2.19 +/- 0.87 years after initiation of hCG/hMG therapy in 18, but not in the remaining patient, after 5 years of therapy, who did not receive hCG/hMG regularly. The sperm count exceeded 20 x 10(6)/ml and more in 12 and was lower than that in 8 patients after 3 years of the therapy. No side effects were observed in female patients, but gynecomastia developed in 2 of the 20 male patients. These data suggest that gonadotropin therapy for hypogonadotropic GH-deficient patients is effective in promoting ovulation and spermatogenesis despite the initial replacement therapy with sex hormones.     

Delayed treatment with GnRH agonist,hCG and progesterone and reduced embryonic mortality in buffaloes

The present study examined the effect of delayed treatment with tropic hormones and progesterone (P₄) on embryonic mortality in buffaloes. Buffaloes with a conceptus on Day 25 after AI were assigned to the following treatments: Control (n = 41), i.m. physiological saline; GnRH agonist (n = 36), i.m. 12 μg buserelin acetate; hCG (n = 33), i.m. 1500 IU hCG; P₄ (n = 38), i.m. 341 mg P₄ every 4 days on three occasions. Control buffaloes had an embryonic mortality of 41.4% (17/41) between Days 25 and 45, and this was reduced (P < 0.01) by treatment with GnRH agonist (11.1%, 4/36), hCG (9.0%, 3/33) and P₄ (13.1%, 5/38). On Day 45, buffaloes treated with hCG and which ovulated had greater (P < 0.05) concentrations of P₄ in whey (453 ± 41 pg/ml) than buffaloes in the same treatment that did not ovulate (297 ± 32 pg/ml). A similar but non-significant trend was observed for buffaloes treated with GnRH agonist. It was concluded from the findings that the treatment of buffaloes on Day 25 after AI with tropic hormones or P₄ is beneficial to processes associated with embryonic implantation.     

Delayed treatment with GnRH agonist, hCG and progesterone and reduced embryonic mortality in buffaloes

The present study examined the effect of delayed treatment with tropic hormones and progesterone (P₄) on embryonic mortality in buffaloes. Buffaloes with a conceptus on Day 25 after AI were assigned to the following treatments: Control (n = 41), i.m. physiological saline; GnRH agonist (n = 36), i.m. 12 μg buserelin acetate; hCG (n = 33), i.m. 1500 IU hCG; P₄ (n = 38), i.m. 341 mg P₄ every 4 days on three occasions. Control buffaloes had an embryonic mortality of 41.4% (17/41) between Days 25 and 45, and this was reduced (P < 0.01) by treatment with GnRH agonist (11.1%, 4/36), hCG (9.0%, 3/33) and P₄ (13.1%, 5/38). On Day 45, buffaloes treated with hCG and which ovulated had greater (P < 0.05) concentrations of P₄ in whey (453 ± 41 pg/ml) than buffaloes in the same treatment that did not ovulate (297 ± 32 pg/ml). A similar but non-significant trend was observed for buffaloes treated with GnRH agonist. It was concluded from the findings that the treatment of buffaloes on Day 25 after AI with tropic hormones or P₄ is beneficial to processes associated with embryonic implantation.