Effect of administration of eCG to postpartum cows on folliculogenesis in the ovary ipsilateral to the previously gravid uterine horn and uterine involution

This study tested the hypothesis that increased oestradiol secretion by large follicles in the ovary ipsilateral to the previously gravid uterine horn has a local effect to increase the rate of uterine involution. Cows were administered an i.m. water placebo (n = 19), 250 iu equine chorionic gonadotrophin (eCG) (n = 18) or 750 iu eCG (n = 20) 14 days post partum (day 0). Transrectal ultrasonography at the time of treatment and 2, 4 and 6 days later monitored uterine horn diameter and ovarian structures. Blood samples collected contemporaneously were assayed for 15-keto-13, 14-dihydro-prostaglandin F(2alpha) and oestradiol concentration. For control cows, accumulated diameter of the largest follicle in the ovary ipsilateral to the previously gravid uterine horn, compared with the contralateral ovary, was smaller on day 0 (P < 0.05) and days 2, 4 and 6 (P < 0.001). There were no significant differences in the eCG-treated animals. There were 12, 8 and 11 cows with a plasma oestradiol concentration < 1 pg ml(-1) on day 0 in the control, 250 and 750 iu eCG treatment groups, respectively. For control cows, the peripheral oestradiol concentrations were higher on day 6 compared with days 0, 2 and 4 (P < 0.05); for cows treated with 250 iu eCG, concentrations were higher on days 4 and 6 compared with day 0 (P < 0.05); and for cows treated with 750 iu eCG, concentrations were higher on days 2 and 4 compared with day 0 (P < 0.01). Treatment with eCG, or the presence of a follicle > 8 mm in diameter in the ovary ipsilateral to the previously gravid uterine horn, did not affect the rate of uterine involution or plasma 15-keto-13,14-dihydro-prostaglandin F(2alpha) concentration. In conclusion, administration of eCG to increase follicular growth and oestradiol production overcame the inhibition of follicular growth in the ovary ipsilateral to the previously gravid uterine horn, but did not affect uterine involution.     

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.     

Effect of eCG on early resumption of ovarian activity in postpartum dairy cows

The purpose of the present study was to hasten the resumption of ovarian activity early postpartum in lactating dairy cows, using equine chorionic gonadotropin (eCG), to enhance follicular growth, followed by hCG, to induce ovulation. Primiparous Holstein dairy cows (n=21) were assigned equally into eCG, eCG-hCG and Control groups. Cows in the eCG and eCG-hCG groups received an i.m. injection of eCG (500 IU Folligon?) on Day 6 postpartum. Cows in the eCG-hCG group were also given an i.m. injection of hCG (500 IU Chorulon?), once dominant follicle reached the diameter of 13-16 mm following eCG injection. Cows in Control group did not receive any treatment. Daily blood sampling and ultrasound examination were conducted, starting at Day 6 postpartum until confirming the third ovulation. Follicles ≥10 mm in diameter were detected on Day 11.5±1.48, 10.1±0.52 and 11.1±1.36 after calving in Control, eCG and eCG-hCG groups, respectively (P>0.05). The first wave dominant follicle ovulated in 71.4% of cows treated with eCG and eCG-hCG. In contrast, none of the first wave dominant follicles ovulated in Control cows. By Day 20 postpartum, all cows in eCG group, 6/7 cows in eCG-hCG group and none of the cows in Control group ovulated (P<0.05). Short estrous cycles (≤16 days) were detected in 2/7, 1/7 and 6/7 cows in eCG, eCG-hCG and control groups, respectively (P<0.05). In conclusion, injection of eCG on Day 6 postpartum could assist the early resumption of ovarian activity by enhancing ovarian follicle growth and early ovulation in postpartum cows. In this context, subsequent hCG injection may not provide any more beneficial effect.     

The effect of administering equine chorionic gonadotropin (eCG) and human chorionic gonadotropin (hCG) post artificial insemination on fertility of lactating dairy cows

The objective was to evaluate the effect of equine chorionic gonadotropin (eCG) and hCG post artificial insemination (AI) on fertility of lactating dairy cows. In Experiment 1, cows were either treated with eCG on Day 22 post AI (400 IU; n = 80) or left untreated (n = 84). On Day 29, pregnant cows were either treated with hCG (2500 IU; n = 32) or left untreated (n = 36). Pregnancy and progesterone were evaluated on Days 29 and 45. In Experiment 2, cows (n = 28) were either treated with eCG on Day 22 (n = 13) or left untreated (n = 15) and either treated with hCG on Day 29 (n = 14) or left untreated (n = 14). Blood sampling and ultrasonography were conducted between Days 22 and 45. In Experiment 3, cows were either treated with eCG on Day 22 post AI (n = 229) or left untreated (n = 241). Pregnancy was evaluated on Days 36 and 85. In Experiment 1, eCG on Day 22 increased (P < 0.02) the number of pregnant cows on Day 29 (50.0 vs. 33.3%) and on Day 45, the increase was higher (P < 0.01) in cows with timed AI (41.2 vs. 6.5%) than in cows AI at detected estrus (50.0 vs. 37.8%). Pregnancy losses were reduced by eCG and hCG, but increased in cows that did not receive eCG but were given hCG (P < 0.01). Treatment with hCG tended (P < 0.06) to increase progesterone in control cows, but not in cows treated with eCG. In Experiment 2, hCG increased (P < 0.01) the number of accessory CLs on Day 35 (28.5 vs. 0.0%) and tended (P < 0.07) to increase progesterone. In Experiment 3, eCG increased the number of pregnant cows (P < 0.05) on Days 36 and 85, but only in cows with low body condition (eCG = 45.6 and 43.5%; Control = 22.9 and 22.9%). In conclusion, eCG at 22 days post insemination increased fertility, primarily in cows with low body condition and reduced pregnancy losses when given 7 days before hCG; hCG induced accessory CLs and slightly increased progesterone, but hCG given in the absence of a prior eCG treatment reduced fertility.     

Evolution of anti-eCG antibodies in response to eCG doses and number of injections. Relationship with productivity of rabbit does

The aim of this experiment was to study the kinetics of anti-eCG (equine chorionic gonadotrophin) antibodies in relation to eCG dose (8 or 25 IU) and number of injections (n = 11) in comparison with a control group (no injection), and to relate antibody production to sexual receptivity and productivity of rabbit does. In all, 124 lactating primiparous rabbit does were inseminated every 35 days for a year. Just before eCG injection (48 h before insemination), blood samples were collected from all the does to assay anti-eCG antibodies. The anti-eCG antibody binding rate, regardless of the injected dose, shows that none of the does developed detectable anti-eCG antibodies before the 7th injection. The level of detectable anti-eCG antibodies began to show an increase at the 7th injection and was significant only for the 25 IU dose at the 11th injection. At the end of the experiment, 15% and 39% of does treated with 8 and 25 IU, respectively, developed immunity to eCG (binding rate >6%: higher binding rate of the control group). Consequently, the immune response depends on the eCG dose and on the number of injections. Moreover, productivity of does estimated from the number of weaned rabbits produced per insemination is not influenced by the level of eCG antibodies (7.0 and 6.9 for binding rate <6% and binding rate 6%, respectively). Only 19 inseminations (n = 6 and n = 13 for 8 and 25 IU, respectively) were made on hyperimmune does. Consequently, the immune response to eCG seems to be marginal for rabbit does. Moreover, under the described experimental conditions, reproductive performances of hyperimmune does were not affected.     

Effects of temporary calf removal and eCG on pregnancy rates to timed-insemination in progesterone-treated postpartum Nellore cows

The objective was to evaluate the effects of temporary calf removal (TCR), eCG administration, or both, in a progesterone-based protocol. Suckled Nellore cows (40-80 d postpartum, n=443) with body condition scores from 2.0 to 3.5 (5-point scale) on three farms were all given a synchronizing protocol (PEPE). At the start (designated Day 0), cows were given an intravaginal device (1.0 g of progesterone) and 2.5mg of estradiol benzoate (EB) im. On Day 8, the device was removed and cows were given PGF(2 alpha) (150 microg of D-cloprostenol im), followed in 24h by 1.0mg EB im, and 30-36 h thereafter, fixed-time AI. The design was a 2 x 2 factorial; main effects were TCR (54-60 h; from device removal to FTAI) and eCG treatment (300 IU im, concurrent with PGF(2 alpha)). Transrectal ultrasonography was done on Days -10 and 0 to detect anestrus (absence of a CL at both examinations) and approximately 30 d after FTAI (pregnancy diagnosis). Data were analyzed by logistic regression. The following variables did not significantly affect pregnancy rates: farm, postpartum interval, cyclicity, inseminators, and semen (sire). Overall, 77% of the cows were deemed anestrus. Pregnancy rates were similar (P>0.05) among treatment groups: Control (54/108=50.0%), TCR (44/106=41.5%), eCG (63/116=54.3%), and TCR+eCG (49/113=43.4%). Pregnancy rate was higher in multiparous than primiparous cows (186/360, 51.7% vs. 24/83, 28.9%, P<0.01), but was not significantly affected by cyclicity status or body condition score. In conclusion, temporary calf removal, eCG, or both, did not significantly increase pregnancy rate to timed-insemination in a progesterone-based synchronization protocol in postpartum Nellore cows with acceptable body condition.     

The fertility of autumn calving suckler beef cows is increased by the addition of prostaglandin to progesterone and eCG estrus synchronization treatment

The objective of this study was to determine the efficacy of PGF2 alpha treatment on pregnancy and calving rates in autumn-calving suckler beef cows synchronized with progesterone and eCG. The population studied consisted of 124 Charolais and 130 Limousin cows in 13 and 12 beef herds, respectively. In each herd, pairs of cows were formed according to parity, body condition score and calving difficulty. Group 1 received a progesterone releasing intravaginal device (PRID) for 12 d with a capsule containing 10 mg estradiol benzoate at implant insertion and 500 IU eCG at PRID removal (Day 0). Group 2 received the same treatment plus 25 mg i.m. dinoprost at Day -2. Each cow was artificially inseminated 56 h after PRID removal (Day 3). Plasma progesterone concentrations were measured to determine cyclicity prior to treatment in samples take on Days -22 and -12, to confirm the occurrence of ovulation (Day 13) and to determine the early pregnancy rate (Day 26). Serum pregnancy-specific protein B (PSPB) concentrations were determined to assess pregnancy rate at Day 39. The effects of variation factors on pregnancy and calving rates after treatment were studied using logistic mixed models and a Cox model, respectively. There were no significant differences between groups or breeds for the rate of cyclicity before treatment nor for ovulation rate (means, 74.1 and 95.7%, respectively). Cyclicity was, however, influenced by individual factors such as body condition score (OR = 3.36, P = 0.001), parity (OR = 5.4, P = 0.001) and herd factors such as stocking rate (OR = 5.62, P = 0.001). The use of a prostaglandin injection increased pregnancy rate at Day 26 (71.7 vs 56.7%, P = 0.01) and at 39 d (67.7 vs 54.3%, P = 0.02) and the calving rate at induced estrus (64.5 vs 48.5%, P = 0.01). We observed 9 twin calvings (5.6%) which occurred in cyclic cows only before treatment. Cows in Group 2 had a 1.5 greater chance of calving before 300 d following the first AI than cows in Group 1 (P = 0.03). In conclusion, the addition of PGF2 alpha injection, 48 h before PRID removal, increased reproductive efficiency in autumn-calving Charolais and Limousin suckler beef cows compared to a classical estrus synchronization treatment using a PRID + eCG.     

Decreased pulsatile LH secretion in heifers superovulated with eCG or FSH

This study was designed to test the hypothesis that treatment with super-ovulatory drugs suppresses endogenous pulsatile LH secretion. Heifers (n=5/group) were superovulated with eCG (2500 IU) or FSH (equivalent to 400 mg NIH-FSH-P1), starting on Day 10 of the estrous cycle, and were injected with prostaglandin F(2alpha) on Day 12 to induce luteolysis. Control cows were injected only with prostaglandin. Frequent blood samples were taken during luteolysis (6 to 14 h after PG administration) for assay of plasma LH, estradiol, progesterone, testosterone and androstenedione. The LH pulse frequency in eCG-treated cows was significantly lower than that in control cows (2.4 +/- 0.4 & 6.4 +/- 0.4 pulses/8 h, respectively; P<0.05), and plasma progesterone (3.4 +/- 0.4 vs 1.8 +/- 0.1 ng/ml, for treated and control heifers, respectively; P<0.05) and estradiol concentrations (25.9 +/- 4.3 & 4.3 +/- 0.4 pg/ml, for treated and control heifers, respectively; P<0.05) were higher compared with those of the controls. No LH pulses were detected in FSH-treated cows, and mean LH concentrations were significantly lower than those in the controls (0.3 +/- 0.1 & 0.8 +/- 0.1, respectively; P<0.05). This suppression of LH was associated with an increase in estradiol (9.5 +/- 1.4 pg/ml; P<0.05 compared with controls) but not in progesterone concentrations (2.1 +/- 0.2 ng/ml; P>0.05 compared to controls). Both superovulatory protocols increased the ovulation rate (21.6 +/- 3.9 and 23.0 +/- 4.2, for eCG and FSH groups, respectively; P>0.05). These data demonstrate that super-ovulatory treatments decrease LH pulse frequency during the follicular phase of the treatment cycle. This could be explained by increased steroid secretion in the eCG-trated heifers but not in FSH-treated animals.     

Reproductive responses in ewes treated with eCG or increasing doses of royal jelly

This experiment was conducted to evaluate the effect of administering increasing doses of royal jelly (RJ) on reproductive parameters in ewes. Additionally, this study compared using RJ vs. equine chorionic gonadotropin (eCG) in estrous cycle control. In May (transitional period between anestrous and the breeding season) 37 multiparous, winter-lambing Awassi ewes 3-6 years of age (average body weight of 53+/-1.2 kg) were fitted with intravaginal flourogestone acetate-impregnated sponges (FGA, 40 mg) for 12 days. Ewes were randomly assigned into five treatment groups to receive no RJ (CON, n=7), 250 mg RJ/d (RJ250, n=8), 500 mg RJ/d (RJ500, n=8), 750 mg RJ/d (RJ750, n=7), or 600IU eCG (eCG, n=7). Royal jelly was administrated orally on daily basis when sponges were in place while eCG was administered on the day of sponge withdrawal (d 0). Behavioral estrus was checked using fertile Awassi rams at 6h intervals for 5 days beginning on d 1. Interval from d 0 to onset of estrus was shorter (P<0.05) in eCG than in CON and RJ250 groups. No differences in the onset of estrus were detected among the RJ-treated groups. The intervals from d 0 to first progesterone rise were shorter (P<0.05) in the eCG-treated compared with RJ-treated and control ewes (100+/-15.3, 138.4+/-14, 135.7+/-15, 155.6+/-15, 154.4+/-15.1h in eCG, CON, RJ250, RJ500, and RJ750, groups, respectively). The overall pregnancy rate from mating at induced estrus was 75.7% (28/37). Of these ewes, 23/37 (64.8%) lambed within 155 days following d 0. Lambing rate was higher (P<0.05) in the RJ500 group compared with controls. Lambing rate from mating at induced estrus was 2/7 (28.5%), 4/8 (50%), 8/8 (100%), 4/7 (57%), and 5/7 (71%) in CON, RJ250, RJ500, RJ750, and eCG groups, respectively. Results of the present study demonstrate that eCG but not RJ was effective in improving estrus expression in ewes during the transition between the non-breeding and breeding seasons. Royal jelly may be effective in improving pregnancy and lambing rates but further studies are required to confirm such findings.     

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.     

Superovulatory response in anestrous ewes is affected by the presence of a large follicle

Superovulatory response to conventional treatment with eCG (1200 IU) and progestagen sponges (MAP, n = 9; FGA, n = 9; or controls without sponge, n = 6) was studied in Corriedale anestrous ewes. The follicular population just before the administration of eCG and the total ovarian response (large anovulatory follicles plus normal CL and prematurely regressing CL) to treatment were determined after laparotomy. Pretreatment with progestagen did not modify the number or class of follicles greater than 1 mm observed on the ovarian surface at the time of eCG administration (19 +/- 2.2 follicles vs 19 +/- 2.9 follicles, for pooled progestagen-treated groups and control groups, respectively; mean +/- SEM) but significantly decreased the number of large anovulatory follicles (4.7 +/- 1.0 vs 10.2 +/- 2.6; P < or = 0.01) observed following treatment. Progestagen-treated animals were classified according to the presence (n = 13) or absence (n = 5) of a large follicle (LF: > or = 4 mm diameter) on the ovarian surface at the time of eCG treatment; a qualitatively better superovulatory response was observed in ewes without large follicle (large anovulatory follicles: 1.6 +/- 0.7 vs 5.8 +/- 1.3, P < or = 0.05; normal CL: 7.0 +/- 1.4 vs 3.8 +/- 1.0, P < or = 0.1; normal CL/total ovarian response: 78.7 +/- 10.1 % vs 34.9 +/- 8.2 %, P < or = 0.01; for ewes without LF and ewes with 1 to 2 LF respectively). No differences were observed in the individual ovulatory response when comparing ovaries ipsilateral or contralateral to LF in a same animal, indicating that the effect of LF on the superovulatory response would be fundamentally systemic. This work shows that, similar to what occurs in cows, the presence of a large follicle at the time of gonadotropin administration decreases the superovulatory response in anestrous ewes.     

In vitro and in vivo viability of vitrified and non-vitrified embryos derived from eCG and FSH treatment in rabbit does

This study aimed to evaluate the in vitro and in vivo viability of vitrified and non-vitrified embryos derived from eCG and FSH treatments in rabbit does. Ninety-six nulliparous does were randomly subjected to consecutive superovulation treatments with eCG (20 IU/kg body weight intramuscularly (i.m.), eCG group), FSH (3 x 0.6 mg/doe at 24 h intervals i.m., FSH group), or without superovulation treatment (control group). Does were artificially inseminated 3 days later and ovulation was induced immediately by hCG (75 IU/doe intravenous). Seven experimental groups were differentiated: first FSH and eCG treatment, second FSH and eCG treatment, eCG-interchanged group (does with previous FSH treatment), FSH-interchanged group (does with previous eCG treatments) and control group. Embryos were collected in vivo by laparoscopy 76-80 h post-insemination in the first and second recovery cycles and post mortem in the third recovery cycles. The ovulation rate was significantly higher in does treated with the first-FSH than in those treated with eCG or in control does (25.2+/-2.0 versus 19.2+/-1.4 to 11.0+/-1.5, and 12.2+/-1.2, first-FSH, first-eCG to second-eCG and control groups, respectively, P < 0.05). Significant differences were observed in the total recovery influenced by ovulation rate in each group (20.3+/-2.2 to 9.4+/-1.2, first-FSH to control groups). Embryo donor rate (donor with at least one normal embryo) was similar among groups with an overall of 75.1%. The number of normal embryos recovered per doe with at least one normal embryo increased significantly in relation to ovulation rate (17.7+/-2.2 to 8.41+/-3, first-FSH and control groups). The vitrification of embryos negatively affected their in vitro development to hatched blastocyst in all groups (88.1% versus 48%, P > 0.05). However, after embryo transfer, this negative effect was only observed in superovulated vitrified embryos (16.8 and 12.8% versus 39.4% total born rate from eCG, FSH and control vitrified groups, P < 0.05). Results indicated that the primary treatments with eCG or FSH increased the number of normal embryos recovered per donor doe, but these embryos are more sensitive to vitrification protocols.     

Fixed-time AI protocols replacing eCG with a single dose of FSH were less effective in stimulating follicular growth, ovulation, and fertility in suckled-anestrus Nelore beef cows

The aim of the present study was to evaluate the effects of a single treatment with FSH on diameter of the largest follicle and on conception rates of suckled Bos indicus beef cows submitted to timed artificial insemination (TAI). Four hundred fifty-six suckled anestrous Nelore beef cows at 30-60 days postpartum were assigned to treatments. At the first day of the estrous synchronization protocol (Day 0), all cows received a progesterone-releasing intravaginal device plus 2mg of estradiol benzoate. On Day 8, cows were assigned to blocks according to the diameter of the largest follicle and then allocated to one of three treatment groups (Control, FSH, or eCG) within each block. Simultaneously to progesterone device withdrawal on Day 8, cows in the eCG treatment group (n=150) received 300 IU of eCG and cows in FSH treatment group (n=153) received 10mg of FSH, and Control cows (n=153) did not receive any additional treatment. Additional treatments with 150 μg of cloprostenol and 1mg of estradiol cypionate (EC) were also administered concurrently to progesterone device removal in all cows on Day 8. Two days later (D10), TAI and ovarian ultrasonic examinations to evaluate follicle size were performed in all cows. On Day 12, a subset of cows (n=389) were submitted a second ultrasonic exam to confirm ovulation. Final follicular growth (mm/day) was less (P=0.006) in both Control (0.95±0.11) and in FSH-treated cows (0.90±0.10) than in eCG-treated cows (1.40±0.13). Interestingly, there was a treatment-by-BCS interaction in ovulation results (P=0.03), in which, eCG treatment increased percentage of cows having ovulations with a lesser BCS. Similarly, there was a treatment-by-BCS interaction for conception (P=0.04), where the eCG treatment increased fertility in cows with a lesser BCS. In conclusion, FSH failed to stimulate final follicular growth, ovulation, and conception rate in sucked-anestrous beef cows submitted to TAI as effectively as eCG. However, physiological effects of eCG seem to be more evident in cows with a lesser BCS.     

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.     

Sheep embryos derived from FSH/eCG treatment have a lower in vitro viability after vitrification than those derived from FSH treatment

In the non breeding period, the effect of two superovulatory treatments (eCG/FSH in single dose or FSH alone in four decreasing doses) on the production of embryo quality following in vitro viability after vitrification procedures was investigated using forty-four adult Sarda breed ewes. In sheep treated with eCG/FSH, the mean number of corpora lutea was significantly (P < 0.05) higher (11.8+/-4.0 vs. 8.05+/-3.8), although the recovery rate was significantly (P < 0.01) lower (74.6 vs. 59.9) than with FSH alone. After vitrification (ethylene glycol and glycerol) was repeated three times, the rates of re-expansion at first and second warming were significantly (P < 0.01) higher in embryos derived from FSH alone than in those with both gonadotrophins (94.9 and 41.9 vs. 72.8 and 18.6) and after the last vitrification the hatched blastocyst rates were 22.5 and 7.6. After differential stain, blastocysts derived from FSH alone showed a mean number of cells significantly higher than blastocysts from eCG/FSH (184.2 vs. 157.7). It was concluded that superovulatory treatment with eCG/FSH may increase the ovarian responses compared with FSH alone, but these embryos showed a reduction in viability rates after repeated vitrification.     

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 effect of equine chorionic gonadotropin (eCG) on pregnancy rates of white-tailed deer following fixed-timed artificial insemination

Control of the white-tailed doe's reproductive cycle is not well documented. The objective was to determine the effects of giving equine chorionic gonadotropin (eCG) at progesterone device removal on fixed time artificial insemination (FTAI) pregnancy rates in white-tailed does. All does (n = 74) were synchronized with a vaginal progesterone implant (CIDR; 0.3 g progesterone), inserted on Day 0 (without regard to stage of estrous cycle), removed 14 days later, and subjected to FTAI, on average, 60 h post-CIDR removal. Of these, 34 were given 200 IU (im) of eCG at CIDR removal. Overall, FTAI pregnancy rate was 50% across 2 yrs (effect of year, P = 0.35). Administration of eCG at CIDR removal did not affect (P = 0.16) pregnancy rate (eCG = 59%; no eCG = 43%). Pregnancy rates were not affected by vulva score or doe disposition. Does that were ≤ 4 yrs old were more likely (P = 0.01) to become pregnant than does > 4 yrs of age. Does inseminated ≥ 60.5 h after CIDR removal were 22 times more likely (P = 0.002) to become pregnant to FTAI than does inseminated < 60.5 h. When frozen-thawed semen was deposited in the cervix or uterus, does were 17 times more likely (P = 0.005) to become pregnant compared with those receiving intravaginal insemination. Fecundity was not different (P = 0.73) across treatment groups (1.6 ± 0.11; no eCG vs. 1.7 ± 0.10; eCG). Furthermore, fecundity of does pregnant to FTAI was not different (P = 0.72) compared with does pregnant to clean-up bucks (1.7 ± 0.08; AI does vs. 1.7 ± 0.09; clean-up bucks). In summary, white-tailed does were successfully inseminated using a 14 days FTAI protocol, eCG may not be essential for acceptable pregnancy rates, and increased pregnancy rates may result when FTAI is done ≥ 60.5 h after progesterone device removal.     

The effect of eCG or estradiol at or after norgestomet removal on follicular dynamics, estrus and ovulation in early post-partum beef cows nursing calves

In post-partum anestrous beef cows suckling calves, neither the choice of hormonal regime to ensure the presence of a healthy dominant follicle at the end of a progestagen treatment nor the optimum hormone to induce estrus and ovulation is clear. Twenty-eight beef cows, in good body condition, 25-30 days post-partum, were assigned to one of four treatments: (i) 3mg norgestomet (N) implant with 5mg estradiol valerate (EDV) and 3mg N injection at the time of insertion (Crestar) for 5 days followed by 600 IU eCG at the time of implant removal; (ii) Crestar for 5 days as in (i) followed by 0.75 mg estradiol benzoate (EDB) 24h later; (iii) Crestar for 9 days followed by 600 IU eCG at the time of implant removal; and (iv) Crestar for 9 days followed by 0.75 mg EDB 24h later. Ovarian scanning was preformed from 4 days before implant insertion until ovulation and 4 days postovulation to detect the CL. Daily blood samples were collected from day 20 post-partum until second ovulation for FSH and E(2) assay. Data were analyzed using analysis of variance. There was no effect of the stage of follicle wave at the time of implant insertion on interval to new follicle wave emergence (range 1-7 days; mean 4.7 days). FSH concentrations were decreased to 5.9+/-2.0 and 7.7+/-1.1 ng/ml for pre- and post-selection cows 1 day after start of treatment; thereafter, they increased on Day 2 to 7.9+/-2.0 and 11.0+/-1.1 ng/ml and on Day 3 to 10.3+/-2.7 and 11.4+/-1.7 ng/ml for pre- and post-selection cows, respectively, despite high-estradiol concentrations at that time. There was no effect of treatment on the interval from implant removal to ovulation (3.2-4.0 days) or on the number of cows detected in estrus (26 of 27 cows). The size of the ovulatory follicle in cows given 0.75 mg EDB 24h post implant removal was decreased in animals at the pre-selection stage (12.2+/-0.1mm) of the follicle wave compared with those at the post-selection stage (15.3+/-0.9 mm) at implant removal. Cows given 600 IU eCG at the pre-selection phase of follicular growth had multiple ovulations (4.0+/-1.1). Cows given EDV at the start of a 5-day implant period had higher estradiol concentrations before and on the day of implant removal than those given EDV at the start of a 9-day implant period. The injection of 0.75 mg EDB 1 day after implant removal tended to increase concentrations of estradiol one day later. In conclusion, 5mg EDV and 3mg N at insertion of a 3mg N implant resulted in variable new follicle wave emergence 1-7 days later in post-partum beef cows nursing calves (22 of 27); both eCG and EDB were equally effective at inducing estrus after implant removal in cows in good BCS, but eCG resulted in a significant increase in ovulation rate in cows treated before dominant follicle selection.     

Effects of progesterone presynchronization and eCG on pregnancy rates to GnRH-based, timed-AI in beef cattle

Three experiments were conducted to determine the effects of low-dose progesterone presynchronization and eCG on pregnancy rates to GnRH-based, timed-AI (TAI) in beef cattle (GnRH on Day 0, PGF_2α on Day 7, with GnRH and TAI on Day 9, 54-56 h after PGF_2α). Experiments 1 and 2 were 2 × 2 factorials with presynchronization (with or without a once-used CIDR; Days −15 to 0 in Experiment 1 and Days −7 to 0, with PGF_2α at insertion, in Experiment 2), and with or without 400 IU eCG on Day 7 in suckled cows. In Experiment 3, suckled cows and nulliparous heifers were either presynchronized with a twice-used CIDR (Days −5 to 0) and PGF_2α at insertion, or no treatment prior to insertion of a new CIDR (Days 0-7). Presynchronization increased (P < 0.05) ovulation rate to GnRH on Day 0 (75.0% vs 48.7%, 76.7% vs 55.0%, and 60.0% vs 36.1% for Experiments 1, 2, and 3, respectively), increased the diameter of the preovulatory follicle in Experiments 1 and 2, and increased the response to PGF_2α (regardless of parity) in Experiment 1 (P < 0.01), and in primiparous cows in Experiment 2 (P < 0.01). Effects of presynchronization on pregnancy rates (53.4% vs 54.1%, 57.7% vs 45.3%, and 54.3% vs 44.4% for Experiments 1, 2, and 3, respectively) were influenced by parity and eCG (P < 0.05). Treatment with eCG had no effect (P > 0.05) on the diameter of the preovulatory follicle (Experiment 1), or the response to PGF_2α (Experiments 1 and 2), but tended (P = 0.08) to improve pregnancy rates, especially in primiparous cows that were not presynchronized (P < 0.01). However, the effects of eCG and presynchronization were not additive.     

Efficiency of superstimulatory protocol P-36 associated with the administration of eCG and LH in Nelore cows

Recent work with P-36 demonstrates that the replacement of the last two doses of Follicle-Stimulating Hormone (FSH) with equine chorionic gonadotropin (eCG) increases embryo yields. However, it is unclear if the positive effect of eCG is related to its FSH-like activity, LH-like activity, or both. This study aimed to verify the replacement of eCG with pLH on the last day of superstimulatory treatment. Twenty-five Nelore cows were allocated to four groups: P-36 (control), P-36/eCG, P-36/LH2, and P-36/LH4. All animals underwent four treatments in a crossover design. The control group cows were superstimulated with decreasing doses of porcine Follicle-Stimulating Hormone (pFSH, 133 mg, im). In the P-36/eCG, P-36/LH2, and P-36/LH4 groups, the last two doses of pFSH were replaced in the former group by two doses of eCG (200 IU each dose, im) and in the latter two groups by two doses of pLH (1 and 2 mg each dose, im), respectively. Donors received fixed-time artificial insemination 12 and 24 hours after pLH. Embryo flushing was performed on D16. Data were analyzed by ANOVA (Proc Mixed, SAS). There was a trend of decreasing ovulation rate when comparing groups LH2 and eCG (P = 0.06). However, there was no significant difference in the mean number of viable embryos among groups P-36 (3.3 ± 0.7), P-36/eCG (4.5 ± 0.5), P-36/LH2 (3.7 ± 0.8), and P-36/LH4 (4.2 ± 1.0). It is concluded that the replacement of eCG by pLH on the last day of superstimulatory treatment can be performed with no significant variation in the production of viable embryos.