Mg Of Estradiol Cypionate Research Articles

Effects of small dose estradiol cypionate after artificial insemination on reproductive performance in Holstein cows

The goals of this study were to assess whether the injection of 1 mg of estradiol cypionate (ECP) at 13 days after service of artificial insemination (AI) increases fertility in the study subject and if the same dose injected in the near estrus (20 ± 1 days) after artificial insemination services changed the diagnosis in empty cows without affecting the ongoing gestation. Two experiments were conducted with Holstein cows: (1) In the first experiment, 110 animals were used in summer season and were inseminated and divided randomly in injected and non-injected groups (n = 55). At 13 days post-service, animals in injected group received intramuscularly 1 mg of ECP. (2) The other experiment was conducted during both summer and winter. Four hundred lactating Holstein cows were selected from first and second services. The pregnancy diagnosis were performed by rectal palpation on day 43, only in cows that had not repeated the artificial insemination. The injection of 1 mg ECP at 13 days after IA service does not affect ongoing pregnancy and increases fertility (p < 0.05). In Holstein cows that repeated the heat due the treatment, decreased significantly the proportion of cows that arrive empty to the diagnosis during the summer but not in winter.

A comparison of two different esters of estradiol for the induction of ovulation in an estradiol plus progestin-based timed artificial insemination protocol for suckled Bos indicus beef cows

The abilities of two different estradiol esters to induce ovulation in a timed AI (TAI) synchronization protocol in suckled Bos indicus cows were evaluated. In Experiment 1 (synchrony of ovulation), 31 cows were submitted to an estradiol/progestin-based synchronization protocol (Day 0) and randomly assigned to one of three treatments at the time of progestin removal on Day 8: 0.5 or 1.0mg of estradiol cypionate (EC) at that time or 1.0mg of estradiol benzoate (EB) 24h later (Day 9). To determine the timing of ovulation, ultrasound examinations were performed every 12h from ear implant removal to 96h after the removal. Orthogonal comparisons were performed to determine the effects of estradiol ester and the effects of the dose of EC on reproductive parameters. Although neither the E2 ester (P=0.83) nor the dose of EC (P=0.55) affected the ovulation rate, the interval from progestin removal to ovulation was longer (P=0.04) in EC-treated cows (1.0mg EC=71.1±3.6 and 0.5mg EC=78.0±3.5) than EB-treated cows (EB=66.0±2.3) was detected. Ovulation in 0.5-mg-EC-treated cows was less synchronous than that in 1.0-mg-EC-treated cows (distribution curves compared using kurtosis). In Experiment 2 (pregnancy per AI; P/AI), 660 cows at two different locations received the same synchronization protocol (n=361 at Farm A and n=299 at Farm B) and were treated with estradiol esters as in Experiment 1 [0.5mg EC (n=220) or 1.0mg EC (n=219) at the time of progestin removal or 1.0mg EB (n=221) 24h later]. The cows were inseminated 54 to 56h after progestin removal. As applied in the Experiment 1, orthogonal comparisons were performed to evaluate the effect of estradiol ester and the dose of EC on P/AI. Although the type of estradiol ester used did not affect the P/AI (P=0.57; EB – 43.0% vs. EC – 44.6%), the P/AI was higher (P=0.03) in cows treated with 1.0mg EC (55.7%) than in those treated with 0.5mg EC (38.6%). In summary, the administration of 0.5mg EC at the time of progestin removal altered the distribution of ovulation and resulted in a lower P/AI when compared with the use of 1.0mg EC in suckled B. indicus cows. However, the P/AI following the administration of 1.0mg EC at the time of progestin removal did not differ from that after the administration of 1.0mg EB 24h later.

Ovulatory response and luteal function after eCG administration at the end of a progesterone and estradiol’ based treatment in postpartum anestrous beef cattle

The objective of this study was to evaluate the effect of equine chorionic gonadotropin (eCG) administration associated to fixed-time AI (FTAI) on follicular dynamics, ovulation, corpus luteum (CL) development and serum progesterone concentrations. Multiparous suckled Hereford cows (n=46) in anestrus with 60–75 days postpartum were used. Females received an intravaginal device containing 0.5g of progesterone during 8 days and 2mg of estradiol benzoate i.m. at device insertion. At device removal 500μg of cloprostenol and 0.5mg of estradiol cypionate were administered i.m., and FTAI was performed 52–56h later. Cows were divided into two experimental groups to receive 400IU of eCG i.m. at device removal (n=23), while control group did not receive eCG (n=23). Daily ovarian ultrasonography (7.5MHz transducer) and progesterone concentrations determined by RIA were assayed from device removal until 30 or 14 days after FTAI, respectively. Treatment with eCG increased ovulation rate [65.2% (15/23) vs. 30.4% (7/23); P=0.018], ovulatory follicle diameter (14.5±0.4 vs. 13.1±0.7mm, mean±SEM; P=0.081), CL area from 6 to 14 days after FTAI (344.3±25.1 vs. 274.2±23.9mm2; P=0.045) and mean serum progesterone concentrations from FTAI to 14 days later (3.0±0.2 vs. 1.8±0.2ng/ml; P=0.001), in comparison with control cows. In conclusion, the addition of eCG to a progesterone and estradiol’ based treatment for FTAI improves ovulation rate and luteal function in anestrous cows. These findings have implications in order to increase pregnancy rates in FTAI treatments in Bos taurus beef cattle.

Effect of estradiol cypionate and amount of progesterone in the intravaginal device on synchronization of estrus, ovulation and on pregnancy rate in beef cows treated with FTAI based protocols

Three experiments were conducted to evaluate the effect of estradiol cypionate (ECP) and amount of progesterone in the intravaginal device (PID) on synchronization of estrus and ovulation, follicular dynamics, luteal dynamics and function and on pregnancy rate in beef cows treated with fixed-time artificial insemination (FTAI) based protocols. In Experiment 1, we evaluated the synchronization of ovulation using 1mg of ECP at PID removal (day 8 after PID insertion) or 1mg of estradiol benzoate (EB) 24h later, in cows treated with 0.558 or 1g of progesterone (P4). The final subgroups were: 0.558g+ECP: n=10; 0.558g+EB: n=11; 1g+ECP: n=10; 1g+EB: n=10. Ovarian ultrasonic examinations were performed to detect the dominant follicle and ovulation. There was no effect of treatments on the diameter of dominant follicle at any time, and on the mean interval to estrus and to ovulation (P>0.05); however, ECP treated cows had scattered distribution of estrus (P<0.03) and ovulation (P<0.03). In Experiment 2, cows received the following treatments: 0.558gP4+ECP: n=52; 0.558gP4+EB: n=52; 1gP4+ECP: n=50; 1gP4+EB: n=52; and FTAI. Pregnancy rate did not differ (P>0.05) between progesterone content (0.558g: 52.9%, 55/104; 1g: 56.9%, 58/102) but differed between estradiol esters (P<0.05; ECP: 48.9%, 49/102; EB: 61.5%, 64/104). In Experiment 3, cows received: 0.558gP4+ECP: n=55; 0.558gP4+EB: n=53; 1gP4+ECP: n=54; 1gP4+EB: n=53; and FTAI. Pregnancy rate did not differ (P>0.05) between progesterone content (0.558g: 48.1%, 52/108; 1g: 53.3%, 57/107) and estradiol esters (ECP: 47.7%, 52/109; EB: 53.8%, 57/106). In conclusion, ECP administration at device removal and progesterone content of PID has no influence on the synchronization of estrus, follicular dynamics, luteal dynamics and function. However, ECP administration affected the synchronization of ovulation and pregnancy rate in non-suckling beef cows, but did not affected pregnancy rate in suckling beef cows. Future studies should evaluate the distribution of ovulations in suckling Bos taurus beef cows.

Increasing length of an estradiol and progesterone timed artificial insemination protocol decreases pregnancy losses in lactating dairy cows

Our hypothesis was that increasing the length of an estradiol and progesterone (P4) timed artificial insemination (TAI) protocol would improve pregnancy per artificial insemination (P/AI). Lactating Holstein cows (n=759) yielding 31±0.30kg of milk/d with a detectable corpus luteum (CL) at d −11 were randomly assigned to receive TAI (d 0) following 1 of 2 treatments: (8d) d −10 = controlled internal drug release (CIDR) and 2.0mg of estradiol benzoate, d −3 = PGF2α(25mg of dinoprost tromethamine), d −2 = CIDR removal and 1.0mg of estradiol cypionate, d 0 = TAI; or (9d) d −11 = CIDR and estradiol benzoate, d −4 = PGF2α, d −2 CIDR removal and estradiol cypionate, d 0 TAI. Cows were considered to have their estrous cycle synchronized in response to the protocol by the absence of a CL at artificial insemination (d 0) and presence of a CL on d 7. Pregnancy diagnoses were performed on d 32 and 60. The ovulatory follicle diameter at TAI (d 0) did not differ between treatments (14.7±0.39 vs. 15.0±0.40mm for 8 and 9 d, respectively). The 9d cows tended to have greater P4 concentrations on d 7 in synchronized cows (3.14±0.18ng/mL) than the 8d cows (3.05±0.18ng/mL). Although the P/AI at d 32 [45 (175/385) vs. 43.9% (166/374) for 8d and 9d, respectively] and 60 [38.1 (150/385) vs. 40.4% (154/374) for 8d and 9d, respectively] was not different, the 9d cows had lower pregnancy losses [7.6% (12/166)] than 8d cows [14.7% (25/175)]. The cows in the 9d program were more likely to be detected in estrus [72.0% (269/374)] compared with 8d cows [62% (240/385)]. Expression of estrus improved synchronization [97.4 (489/501) vs. 81% (202/248)], P4 concentrations at d 7 (3.22±0.16 vs. 2.77±0.17ng/mL), P/AI at d 32 [51.2 (252/489) vs. 39.4% (81/202)], P/AI at d 60 [46.3 (230/489) vs. 31.1% (66/202)], and decreased pregnancy loss [9.3 (22/252) vs. 19.8% (15/81)] compared with cows that did not show estrus, respectively. Cows not detected in estrus with small (<11mm) or large follicles (>17mm) had greater pregnancy loss; however, in cows detected in estrus, no effect of follicle diameter on pregnancy loss was observed. In conclusion, increasing the length of the protocol for TAI increased the percentage of cows detected in estrus and decreased pregnancy loss.

DIÂMETRO DO FOLÍCULO NO MOMENTO DA INSEMINAÇÃO ARTIFICIAL EM TEMPO FIXO E TAXA DE CONCEPÇÃO EM VACAS NELORE

The objective of this study was to evaluate the influence of the diameter of the largest follicle at the time of TAI (DFOL) on conception rate of Nellore cows submitted to TAI protocol. Therefore, 348 females were synchronized on day 0 (D0) with an intravaginal progesterone device (P4) associated with 2.0mg of estradiol benzoate intramuscularly (im). On day 8 (D8), after P4 removal, 500?g Sodium cloprostenol (im), 0.6mg of estradiol cypionate (im) and 300UI equine chorionic gonadotropin (eCG) (im) were administered. On day 10 (D10), immediately before each TAI, DFOL was measured in all animals by transrectal ultrasonography. Pregnancy diagnosis was performed 30 days after TAI by transrectal ultrasonography. Data were analyzed by SPSS (version 19) and DFOL means were compared by Student's t-test. The overall conception rate was 57.47% and DFOL overall average was 12.43±2.84mm. There were differences (P=0.0001) in the comparison of DFOL of pregnant (13.33±2.40mm) and nonpregnant (11.27±2.75mm) cows. The results showed a positive effect of DFOL on fertility of cows submitted to synchronization protocol.KEYWORDS: Artificial insemination; cattle; synchronization.

Prostaglandin treatment at the onset of norgestomet and estradiol-based synchronization protocols did not alter the ovarian follicular dynamics or pregnancy per timed artificial insemination in cyclic Bos indicus heifers

The aim of the present study was to evaluate the effects of the PGF2α treatment given at the onset of a synchronization of ovulation protocol using a norgestomet (NORG) ear implant on ovarian follicular dynamics (Experiment 1) and pregnancy per AI (P/AI; Experiment 2) in cyclic (CL present) Bos indicus heifers. In Experiment 1, a total of 46 heifers were presynchronized using two consecutive doses of PGF2α 12 days apart. At first day of the synchronization protocol the heifers received implants containing 3mg of NORG and 2mg of estradiol benzoate (EB). At the same time, heifers were randomly assigned to receive 150mg of d-cloprostenol (n=23; PGF2α) or no additional treatment (n=23; Control). When the ear implants were removed 8 days later, all heifers received a PGF2α treatment and 1mg of EB was given 24h later. The follicular diameter and interval to ovulation were determined by transrectal ultrasonography. No effects of PGF2α treatment on the diameter of the largest follicle present were observed at implant removal (PGF2α=9.8±0.4 vs. Control=10.0±0.3mm; P=0.73) or after 24h (PGF2α=11.1±0.4 vs. Control=11.0±0.4mm; P=0.83). No differences in the time of ovulation after ear implant removal (PGF2α=70.8±1.2 vs. Control=73.3±0.9h; P=0.10) or in the ovulation rate (PGF2α=87.0 vs. Control=82.6%; P=0.64) between treatments were observed. In Experiment 2, 280 cyclic heifers were synchronized using the same experimental design described above (PGF2α; n=143 and Control; n=137), at random day of the estrous cycle. All heifers received 300 IU of equine chorionic gonadotropin (eCG) and 0.5mg of estradiol cypionate (as ovulatory stimulus) when the NORG ear implants were removed. Timed artificial insemination (TAI) was performed 48h after implant removal and the pregnancy diagnosis was conducted 30 days later. No effects on the P/AI due to PGF2α treatment were observed (PGF2α=51.7 vs. Control=57.7%; P=0.29). In conclusion, PGF2α treatment at the onset of NORG-based protocols for the synchronization of ovulation did not alter the ovarian follicular responses or the P/AI in cyclic Bos indicus beef heifers synchronized for TAI.

Resynchronization with unknown pregnancy status using progestin-based timed artificial insemination protocol in beef cattle

Two experiments were designed to evaluate the use of resynchronization (RESYNCH) protocols using a progestin-based timed artificial insemination (TAI) protocol in beef cattle. In experiment 1, 475 cyclic Nelore heifers were resynchronized 22 days after the first TAI using two different inducers of new follicular wave emergence (estradiol benzoate [EB; n = 241] or GnRH [n = 234]) with the insertion of a norgestomet ear implant. At ear implant removal (7 days later), a pregnancy test was performed, and nonpregnant heifers received a dose of prostaglandin plus 0.5 mg of estradiol cypionate, with a timed insemination 48 hours later. The pregnancy rate after the first TAI was similar (P = 0.97) between treatments (EB [41.9%] vs. GnRH [41.5%]). However, EB-treated heifers (49.3%) had a greater (P = 0.04) pregnancy per AI (P/AI) after the resynchronization than the GnRH-treated heifers (37.2%). In experiment 2, the pregnancy loss in 664 zebu females (344 nonlactating cows and 320 cyclic heifers) between 30 and 60 days after resynchronization was evaluated. Females were randomly assigned to one of two groups (RESYNCH 22 days after the first TAI [n = 317] or submitted only to natural mating [NM; n = 347]). Females from the NM group were maintained with bulls from 15 to 30 days after the first TAI. The RESYNC-treated females were resynchronized 22 days after the first TAI using 1 mg of EB on the first day of the resynchronization, similar to experiment 1. No difference was found in P/AI (NM [57.1%] vs. RESYNC [61.5%]; P = 0.32) or pregnancy loss (NM [2.0%] vs. RESYNC [4.1%]; P = 0.21) after the first TAI. Moreover, the overall P/AI after the RESYNCH protocol was 47.5%. Thus, the administration of 1 mg of EB on day 22 after the first TAI, when the pregnancy status was undetermined, promotes a higher P/AI in the resynchronized TAI than the use of GnRH. Also, the administration of 1 mg of EB 22 days after the TAI did not affect the preestablished pregnancy.

Timed artificial insemination should be performed early when used norgestomet ear implants are applied for synchronizing ovulation in beef heifers

The present study evaluated the effect of the type of norgestomet ear implant (new vs. used) on the ovarian follicular response (experiment 1) and pregnancy per artificial insemination (AI) (P/AI; experiment 2) of beef heifers subjected to an estradiol plus progestin timed artificial insemination (TAI) program. In experiment 1, 57 cyclic beef heifers were randomly assigned to one of two groups according to the type (new or previously used for 9 days) of norgestomet ear (NORG) implant. At the time of NORG implant insertion, the heifers were treated with 2 mg of intramuscular estradiol benzoate. Eight days later, the NORG implants were removed, and the heifers received an intramuscular administration of 150 μg of d-cloprostenol, 300 IU of equine chorionic gonadotropin, and 0.5 mg of estradiol cypionate. The heifers had their ovaries scanned every 12 hours from the time of NORG implant removal to 96 hours after verifying the occurrence and timing of ovulation. No difference (P = 0.89) was observed in the ovulation rates between the two treatments (new = 80.0%; 24/30 vs. used = 81.5%; 22/27). However, the heifers treated with a used NORG implant had (P = 0.04) higher proportion (36.4%; 8/22) of early ovulation (between 36 and 48 hours after NORG implant removal) compared with the heifers treated with a new NORG implant (8.3%; 2/24). In experiment 2, at the beginning of the synchronization protocol, 416 beef heifers were randomly assigned into two groups, as described in the experiment 1. Two days after the NORG implant removal, the heifers were reassigned to be inseminated at 48 or 54 hours after NORG implant removal. There was an interaction (P = 0.03) between the type of NORG implant and the timing of TAI on P/AI. The timing of insemination only had an effect (P = 0.02) on the P/AI when the heifers were treated with a used NORG implant [(TAI 54 hours = 41.9% (44/105) vs. TAI 48 hours = 58.6% (58/99)]. In conclusion, beef heifers synchronized with a used NORG implant plus estradiol exhibited a higher proportion of earlier ovulations, and TAI in these heifers should be performed 48 hours after removal of used NORG implants.

Repeatability of Prolactin Responses to a Small Dose of Sulpiride in Estrogen-Primed Geldings in Spring and in Mares During the Estrous Cycle in Summer

Two experiments were conducted to assess the repeatability of prolactin responses to a small dose of sulpiride in estrogen-primed geldings in spring and in mares during the estrous cycle in summer. Six long-term geldings each received a single intramuscular injection of 100 mg of estradiol cypionate on March 31, 2011, and were then challenged with an intravenous injection of dl-sulpiride (5 μg/kg of body weight of the racemic mixture) every other day for a total of 8 days. Jugular blood was collected at 0, 10, 20, 40, and 60 minutes after the injection of sulpiride for prolactin measurement. The experiment was repeated with six mares during the summer (July), except that the number of challenges was extended to 15 over 30 days so that any effect of estrous cycle stage could be assessed. Prolactin responses in geldings during April were robust and were varied in a quadratic manner (P < .003) over the eight sulpiride injections, increasing linearly to a plateau by the fourth injection. Mares also displayed robust prolactin responses to sulpiride injections in July, and there was no effect (P > .1) of day of injection and no effect of stage of estrous cycle (follicular phase, early diestrus, or late diestrus). We concluded that prolactin responses to this dose of sulpiride were sufficiently robust and repeatable for use as a paradigm for studies of the relative competitive efficacy and duration of action of various dopaminergic compounds and their vehicular formulations.

Timing of prostaglandin F2α treatment in an estrogen-based protocol for timed artificial insemination or timed embryo transfer in lactating dairy cows

Objectives were to investigate progesterone concentrations and fertility comparing 2 different intervals from PGF2α treatment and induced ovulation in an estrogen-based ovulation synchronization protocol for timed artificial insemination (TAI) or timed embryo transfer (TET) in lactating dairy cows. A total of 1,058 lactating Holstein cows [primiparous (n=371) and multiparous (n=687)], yielding 34.1±0.33 kg of milk/d at various days in milk were randomly assigned to receive treatment with PGF2α on either d 7 or 8 of the following protocol: d 0: 2mg of estradiol benzoate + controlled internal drug release device; d 8: controlled internal drug release device removal + 1.0mg of estradiol cypionate; d 10: TAI or d 17: TET. Only cows with a corpus luteum at d 17 received an embryo and all cows received GnRH at TET. Pregnancy diagnoses were performed by detection (transrectal ultrasonography) of an embryo on d 28 or a fetus on d 60. Fertility [pregnancy per artificial insemination (P/AI) or pregnancy per embryo transfer (P/ET)] was affected by breeding technique (AI vs. ET) and time of PGF2α treatment (d 7 vs. 8) at the 28-d pregnancy diagnosis for TAI [32.9% (238) vs. 20.6% (168)] and TET cows [47% (243) vs. 40.7% (244)] and at the 60-d pregnancy diagnosis for TAI [30% (238) vs. 19.2% (168)] and TET cows [37.9% (243) vs. 33.5% (244)]. The progesterone (P4) concentration at d 10 altered fertility in TAI cows, with higher P/AI in cows with P4 concentration <0.1 ng/mL compared with cows with P4 concentration ≥0.1 ng/mL, and in ET cows, with higher P/ET in cows with P4 concentration <0.22 ng/mL compared with cows with P4 concentration ≥0.22 ng/mL. Prostaglandin F2α treatment at d 7 increased the percentage of cows with P4 <0.1 ng/mL on d 10 [39.4 (85) vs. 23.2 (54)]. Reducing the period between PGF2α and TAI from 72 to 48h in dairy cows resulted in a clear reduction in fertility in cows bred by TAI and a subtle negative effect in cows that received TET. The earlier PGF2α treatment benefits are most likely mediated through gamete transport, fertilization, or early embryo development and a more subtle effect of earlier PGF2α treatment that may be mediated through changes in the uterine or hormonal environment that manifests itself after ET on d 7.

Effects of Equine Chorionic Gonadotropin on Follicular, Luteal and Conceptus Development of Non-Lactating Bos Indicus Beef Cows Subjected to a Progesterone Plus Estradiol-Based Timed Artificial Insemination Protocol

The aim of this study was to evaluate the effects of equine chorionic gonadotropin (eCG) on ovarian follicular responses, corpus luteum (CL) development and conceptus length on day 16 after timed artificial insemination (TAI). A total of 124 cows at day 0 (D0) received 2 mg of estradiol benzoate (EB) and the insertion of a progesterone (P4) intravaginal device. Eight days later, the device was removed, and cows received 0.15 mg of prostaglandin and 0.5 mg of estradiol cypionate (EC), and were randomly assigned to 1 of 2 treatments: eCG (n=60), in which cows received 300 U of eCG; and control (n=64). Cows were TAI 48 h after P4 device removal. The diameter of the largest follicle (LF) present on D8 and D10 and of CL on D15 and D26 were measured. Conceptus recovered rate, conceptus length, CL diameter and weight were determined at slaughter on D26. Plasma P4 concentration was determined on D15 and D26. Follicular growth from D8 to D10 (P=0.03), the diameter of CL at D15 (P=0.03) and D26 (P=0.003) and the CL weight at day 26 (P=0.04) were greater in the eCG group than the control. However, there was no effect of eCG treatment on oestrus occurrence, conceptus recovery rate and length, or P4 concentrations on either D15 or D26. In conclusion, although eCG increases follicular responses and the diameter of the CL, this gonadotropin treatment does not influence the length of the conceptus or the P4 concentration on the subsequent oestrus cycle.

24 EVALUATION OF THE PREGNANCY RATE OF FIXED-TIME ARTIFICIALLY INSEMINATED BOS INDICUS COWS USING HETEROSPERMIC AND MONOSPERMIC SEMEN

The aim of this study was to establish a comparison between heterospermic and monospermic semen on the pregnancy rate of fixed-time AI Bos indicus cows. The experiment was conducted in the state of Mato Grosso, Brazil, during December 2010 and February 2011. Multiparous (n = 173) and primiparous (n = 204) Nelore cows, 45 ± 15 days postpartum, were evaluated on body condition score (BCS; score 1 to 9), and those that presented BCS between 5 and 8 were selected. Two protocols of estrous cycle synchronization were performed (PeCG and Pshang). Synchronization of the estrous cycle was achieved with the aid of the following protocol: on Day 0, all animals were treated with a progesterone vaginal implant with 1.9 g of progesterone combined with an IM injection of 2 mg of estradiol benzoate. On Day 7, an IM injection of 12.5 mg of dinoprost was administered. On Day 9, implants were withdrawn and the animals received an IM injection of 0.5 mg of estradiol cypionate. On Day 9, part of the animals (n = 222) received an IM injection of 300 IU mg of eCG (PeCG) and the other part (n = 155) had their calves removed for 48 hours (Pshang). All animals were inseminated 46 to 52 h after the end of the protocol. Cows were allocated randomly in 4 groups according to the donor male sample in the semen straw and groups were designated as MA (monospermic straw from bull A; n = 110), MB (monospermic straw from bull B; n = 102), MC (monospermic straw from bull C; n = 108), and HT (heterospermic sample from bulls A, B, and C; n = 57). Commercially available semen straws from Aberdeen Angus donors were used (ABS Pecplan, Brazil). Pregnancy diagnosis was performed 35 days after AI using real-time ultrasonography. Results are summarized in Table 1. There was no statistical difference between MA, MB, MC, and HT in any group according to the chi-square test (P &gt; 0.05). However, there was a remarkable difference in pregnancy rates among the 3 bulls tested considering both protocols, probably due to the variation in the ovulation moment. Table 1.Pregnancy rates of Nelore cows submitted to FTAI protocol inseminated with monospermic (bull A, B, or C) or heterospermic (HT) semen

Dose-Response of Prolactin to Increasing Doses of the Dopamine Receptor Antagonist, Sulpiride, in Horses: Effect of Season in Mares and Stallions of Estradiol Pretreatment in Geldings

Two experiments were performed to determine whether dopaminergic input to the adenohypophysis (1) differs across seasons in mares and stallions proportionally with changes in prolactin secretion and (2) is altered by estradiol administration in geldings. In experiment 1, prolactin responses to increasing doses of l-sulpiride in eight mares and eight stallions in March, June, September, and December were used to estimate the theoretical dose equivalent to 50% of maximal response. Prolactin areas increased (P < .001) with increasing doses of sulpiride and were greatest (P < .05) in March for stallions, but in June for mares. Mean half-maximal dose, which was assumed to be proportional to the dopaminergic input to the pituitary, was lowest (P < .05) in June and greatest in September. Experiment 2 used the same approach to determine whether the stimulatory effect of estradiol pretreatment on prolactin secretion was associated with an alteration of the half-maximal response. Geldings (n = 6/group) were administered 100 mg of estradiol cypionate in oil, or oil alone, on day 0 (October 3) and increasing doses of l-sulpiride starting on day 6. Estradiol treatment increased (P < .08) the prolactin response to l-sulpiride at 0.41 μg/kg body weight and all higher doses (P < .05); mean half-maximal dose did not differ (P > .1) between groups. We conclude that dopaminergic input to the adenohypophysis of mares and stallions varies with season and that the stimulatory effect of estradiol on prolactin secretion is not associated with a decrease in dopaminergic input to the adenohypophysis.

Fertility-associated antigen on Nelore bull sperm and reproductive outcomes following first-service fixed-time AI of Nelore cows and heifers

The objective was to determine whether the presence of fertility-associated antigen (FAA) on sperm collected from Nelore ( Bos indicus) bulls can be used to assess potential fertility of sperm for use at first-service fixed-time AI (TAI). Six Nelore bulls were selected based on FAA status (FAA-negative: N = 3; FAA-positive: N = 3) and the ability to produce neat semen with ≥ 70% morphologically normal sperm and 60% estimated progressive motility before cryopreservation. In Experiment 1, suckled multiparous Nelore cows (N = 835) were evaluated for body condition score (BCS) and received an intravaginal progesterone device (CIDR) and 2.0 mg of estradiol benzoate (Day 0). On Day 9 the CIDR was removed, 12.5 mg of PGF 2α and 0.5 mg of estradiol cypionate were administered, and calves were removed for 48 h. All cows received TAI on Day 11 (48 h after CIDR removal). Pregnancy per TAI (P/TAI) was not different between FAA-positive and FAA-negative bulls (41.5% vs. 39.3%, respectively). There was an effect of AI technician on P/TAI (36.0% vs. 43.9%; P < 0.05) and BCS tended to affect P/TAI (P = 0.09), as cows with BCS ≥ 2.75 were 1.4 times more likely to become pregnant compared with cows with BCS < 2.75. In Experiment 2, nulliparous Nelore heifers (N = 617) were evaluated for BCS and received a CIDR and estradiol benzoate (2.0 mg) on Day 0. On Day 7, all heifers received PGF 2α (12.5 mg). On Day 9, CIDR inserts were removed and all heifers received estradiol cypionate (0.6 mg) and 200 IU eCG. All heifers received TAI on Day 11 (48 h after CIDR removal). Pregnancy/TAI was different (P = 0.04) between FAA-positive and FAA-negative bulls (33.7% vs. 40.7%, respectively). Presence of FAA on sperm was unsuccessful in assessing the potential fertility of sperm for use in TAI.

Stimulation of prolactin after estradiol pretreatment: Comparison of polymer formulations for domperidone and sulpiride and oral administration of sulpiride in horses

Stimulation of prolactin after estradiol pretreatment: Comparison of polymer formulations for domperidone and sulpiride and oral administration of sulpiride in horses

Importance of estrus on pregnancy per insemination in suckled Bos indicus cows submitted to estradiol/progesterone-based timed insemination protocols

The objective was to evaluate the effect of estrus occurrence (based on removal of tail-head marks) on ovarian responses and pregnancy per AI (P/AI; 30 d after AI) in suckled Bos indicus beef cows submitted to timed AI (TAI) protocols. Cows received an intravaginal device containing 1.0 g progesterone, and 2.0 mg estradiol benzoate im; 8 d later, the intravaginal device was removed, and they were given PGF2α (0.25 mg of cloprostenol sodium) and 300 IU of eCG, with TAI 48 to 52 h later. In Experiment 1, cows were assigned to receive one of three treatments: 1 mg of estradiol cypionate (ECP) im at progesterone (P4) device removal (N = 178); 10 μg of GnRH im at TAI (N = 190); or both treatments (N = 172). In cows given estradiol (ECP or ECP + GnRH), more displayed estrus (P = 0.002) and became pregnant (P < 0.0001) compared with those receiving only GnRH. In Experiment 2, the effect of the occurrence of estrus on ovarian responses was evaluated in cows (N = 53) synchronized using ECP at device removal. Cows that displayed estrus had a greater diameter of the largest follicle (LF) at device removal (P < 0.0001), a greater diameter at TAI (P < 0.0001), a greater ovulation rate (P = 0.02), a larger CL (P = 0.02), and a greater P4 concentration (P < 0.0001) than cows that did not display estrus. In Experiment 3, the effect of GnRH treatment on P/AI at TAI was evaluated in cows that received ECP at device removal, and either displayed, or did not display, estrus (N = 726). There was no estrus by GnRH interaction (P = 0.22); the P/AI was greater (P < 0.0001) in cows that displayed estrus (61.9%) than cows that did not display estrus (41.4%). However, GnRH did not improve (P = 0.81) P/AI (GnRH = 53.7% vs. no GnRH = 52.6%). In conclusion, exogenous estradiol at device removal increased both the proportion of suckled Bos indicus cows that displayed estrus and P/AI. Cows that displayed estrus had better ovarian responses (i.e., larger follicles at TAI, a greater ovulation rate, larger CL, and greater P4 concentrations) following an estradiol/P4-based synchronization protocol. Although occurrence of estrus improved pregnancy outcomes, GnRH at TAI did not improve P/AI in suckled Bos indicus cows treated with ECP, regardless of estrus occurrence.

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 2 mg 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 10 mg of FSH, and Control cows ( n = 153) did not receive any additional treatment. Additional treatments with 150 μg of cloprostenol and 1 mg 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.

Stimulation of Ovulation in Seasonally Anovulatory and Vernal Transitional Mares with Estradiol and Domperidone: Dose and Combination Studies

Three experiments were conducted to test the efficacy of different doses of estradiol cypionate (ECP) and domperidone for inducing ovulation in seasonally anovulatory (January; Experiments 1 and 2) and transitional period (March; Experiment 3) mares. In the first two experiments, mares in Kentucky and Louisiana were administered domperidone (3 g in biodegradable particles) alone or after pretreatment with 100 or 150 mg of ECP; another group received ECP, domperidone, and progesterone, and a fifth group received ECP and progesterone only (the latter two in Kentucky). Control mares in both states received no treatment. The proportion of mares ovulating within 35 days (for mares treated in January) was greater ( P = .0002) for those receiving any combination of ECP plus domperidone relative to mares not receiving the combined treatment. Addition of progesterone to ECP plus domperidone did not enhance ( P = .7) the response relative to the combination alone; domperidone by itself, or ECP plus progesterone, did not alter the response relative to controls ( P > .24). Experiment 3 was conducted in Louisiana as a 2 × 3 factorial, with two doses of domperidone (1.5 or 3 g) and three doses of ECP (0, 75, or 150 mg). There was no main effect of domperidone or ECP dose; a greater proportion ( P = .055) of mares receiving any combination of ECP plus domperidone ovulated in 21 days compared with those receiving no ECP. In conclusion, pretreatment with ECP before injection of domperidone 10 days later can be used to increase the proportion of mares ovulating early in the year; within the limits of the present experiments, there appears to be no difference in doses of ECP of 75, 100, or 150 mg, and no difference in doses of domperidone of 1.5 or 3 g.

20 PREGNANCY RATES IN SUCKLED BEEF COWS SYNCHRONIZED WITH PROGESTERONE INTRAVAGINAL DEVICES AND RECEIVING eCG FOURTEEN DAYS AFTER BREEDING

An experiment was designed to test the following hypotheses: (1) the administration of 400IU of eCG (Novormón, Syntex SA, Buenos Aires, Argentina) 14 days after fixed-time artificial insemination (FTAI) increases pregnancy rates in cross-breed Zebu × Bonsmara suckled cows synchronized with progesterone releasing devices (DIB 0.5, 0.5 g of progesterone, Syntex SA); and (2) pregnancy rates in cows treated with estradiol or GnRH, combined with a DIB device, are not different. Primiparous suckled cows (n = 260), between 60 and 120 days postpartum (DPP) and with a body condition score between 2.0 and 2.5 (1 to 5 scale) were used. At the beginning of the experiment (Day 0), all cows were examined by rectal palpation (only 11% had a CL), received a DIB device, and were randomly allocated to 1 of 3 treatment groups. Cows in the E2 group received 2 mg of estradiol benzoate (EB) intramuscularly (i.m.) at DIB insertion and those in the two GnRH groups received 100 μg of gonadorelin (GDR Gonasyn, Syntex SA) at the same time. On Day 7, DIB devices were removed and all cows received 500 μg of cloprostenol (Ciclase DL, Syntex SA) plus 400 IU of eCG (i.m.). Cows in the E2 group received 0.5 mg of estradiol cypionate (ECP, Cipiosyn, Syntex SA) and underwent FTAI administered by one technician, using semen from 1 of 2 bulls between 52 and 56 h later. Cows in the GnRH groups received a dose of 100 μg of gonadorelin (full GnRH group) or 50 μg of gonadorelin (1/2 GnRH group) at the time of the FTAI (52 to 56 h after DIB removal). Fourteen days after FTAI cows in the 3 groups were further subdivided (3 × 2 factorial) to receive or not 400 IU of eCG i.m. Pregnancy was determined 30 days after FTAI using real-time ultrasonography. Data were analyzed by logistic regression, taking into account the effect of the synchronization treatment, eCG or noteCG, 14 days after FTAI and sire used. No differences in pregnancy rates were found (P = 0.16) among treatment groups (E2: 39/87, 43.7%, full GnRH: 38/92, 41.3%, and 1/2 GnRH: 25/81, 30.9%). However, there was a significant (P = 0.02) effect of eCG treatment 14 days after FTAI (eCG: 60/127, 47.2% v. no eCG: 41/133, 30.8%). Furthermore, bull A (77/155, 47.1%) resulted in higher pregnancy rate (P = 0.009) than bull B (28/107, 26.2%), but there were no significant interactions between bull and synchronization treatment or eCG administration 14 days after FTAI (P &gt; 0.1). We conclude that the application of 400 IU of eCG 14 days after FTAI increases pregnancy rates in suckled Bos taurus × Bos indicus primiparous cows with fair to poor body condition score synchronized with progesterone releasing devices. Furthermore, the use of estradiol ester or GnRH at DIB insertion and removal did not affect pregnancy rates.