Biomedical subjects

R J Mapletoft

Publications and source records attributed to R J Mapletoft.

At least 19 recordsLinked to original sources

PubMed2006

Effects of estradiol on gonadotrophin release, estrus and ovulation in CIDR-treated beef cattle.

The effects of estradiol-17beta (E-17beta) or estradiol benzoate (EB) on gonadotrophin release, estrus and ovulation in beef cattle were evaluated in two experiments. In experiment 1, 16 ovariectomized cows received a previously used CIDR insert from days 0 to 7 and 1mg of EB on day 8; they also received 5mg of E-17beta on days 0 or 1, or 5mg of E-17beta+100mg of progesterone on day 0. There was only an effect of time (P<0.0001) on plasma concentrations of progesterone, estradiol, FSH, and LH. Following treatment with E-17beta, plasma FSH concentrations were suppressed for approximately 36 h, whereas plasma LH concentrations were reduced (P<0.05) for 6 h, but surged within 24 h. Injecting 1mg of EB 24 h after CIDR removal decreased (P<0.02) plasma LH concentrations for 6h, followed by an LH surge at 18 h. In experiment 2, ovary-intact heifers (n=40) received a used CIDR and 5mg of E-17beta+100mg of progesterone on day 0. On day 7, CIDR were removed, PGF given, and heifers received nothing (control) or 1mg of EB 12, 24, or 36 h later. In these groups, plasma LH peaked (mean+/-SEM) 78.0+/-23.0, 37.8+/-8.5, 44.4+/-10.3, and 51.0+/-5.1 h after CIDR removal (means, P<0.001; variances, P<0.001) and intervals from CIDR removal to ovulation were 102.0+/-6.7, 63.6+/-3.6, 81.6+/-3.5, and 78.0+/-4.1h (P<0.05). The interval from CIDR removal to ovulation was shorter and less variable in EB-treated groups; the interval from EB to ovulation was shortest (P<0.05) in the 12-h group. In summary, E-17beta or EB decreased both FSH and LH, but LH increased after 6h (despite elevated progesterone concentrations). Following CIDR removal, 1mg of EB effectively synchronized LH release, and ovulation (in intact cattle), but the interval from CIDR removal to EB treatment affected the time of ovulation.

Animals↗

PubMed2005

Resynchronization of previously timed-inseminated beef heifers with progestins.

The objective was to determine the efficacy of a previously used CIDR or melengestrol acetate (MGA; 0.5mg/head/day) for resynchronization of estrus in beef heifers not pregnant to timed-AI (TAI). In three experiments and a field trial, heifers were reinseminated 6-12 h after first detection of estrus. Pregnancy diagnosis was done from approximately 25-43 days after either TAI or reinsemination. In Experiment 1, 79 heifers received a once-used CIDR from 13 to 20 days after TAI and 80 heifers were untreated controls. For these two groups, there were 34 and 35 heifers, respectively, not pregnant to TAI; median +/- S.E. intervals from TAI to onset of estrus were 22 +/- 0.2 days versus 20 +/- 0.6 days (P < 0.001); estrus rates were 70.6% versus 85.7% (P = 0.1); conception rates were 62.5% versus 76.7% (P < 0.3); and pregnancy rates were 44.1% versus 65.7% (P = 0.07), for CIDR and untreated (control) groups, respectively. In Experiment 2, heifers (n = 651) were TAI (Day 0) and 13 days later randomly assigned to one of seven groups (n = 93 per group) to receive a once-used CIDR (three groups; Days 13-20), MGA (three groups; Days 13-19), or no treatment (control group). Groups given a CIDR or MGA also received: no further treatment (CIDR or MGA alone); 1.5mg estradiol-17beta (E-17beta) and 50 mg progesterone (P4) in 2 mL canola oil on Day 13; or E-17beta and P4 on Day 13 and 0.5 mg E-17beta on Day 21 (24 h after CIDR removal or 48 h after the last feeding of MGA). Pregnancy rate to TAI was lowest (P < 0.05) for the group given a CIDR plus E-17beta and P4 on Day 13 and E-17beta on Day 21. Variability in return to estrus was greater (P < 0.001) in the control and MGA groups than in CIDR groups. Conception and pregnancy rates in heifers given a CIDR (65.1 and 61.4%) were higher (P<0.01) than those fed MGA (49.6 and 40.4%), but not different from controls (62.2 and 54.9%, respectively). In Experiment 3, 616 heifers received a once- or twice-used CIDR for 7 days, beginning 13+/-1 days after TAI, with or without a concurrent injection of 150 mg of P4 (2 x 2 factorial design). Pregnancy rate to TAI was 47.2%. In heifers that returned to estrus, there was no significant difference between a once- or twice-used CIDR for rates of estrus (68.8%, P < 0.3), conception (65.9%, P < 0.6) and pregnancy (45.3%, P < 0.8). Injecting progesterone at CIDR insertion increased the median interval from CIDR removal to onset of estrus (P < 0.05) and reduced rates of estrus (63.8% versus 73.8%, P<0.05), conception (60.5% versus 70.6%, P = 0.1) and pregnancy (38.6% versus 52.2%, P < 0.02). In a field trial, 983 heifers received a once-used CIDR for 7 days, beginning 13 +/- 1 days after TAI. Pregnancy rate to TAI was 55.2%. The median (and mode) of the interval from CIDR removal to estrus was 2.5 days. Estrus, conception and pregnancy rates were 78.2, 70.3 and 55.0% (overall pregnancy rate to TAI and rebreeding, 78.7%). In summary, a once- or twice-used CIDR for 7 days, starting 13 +/- 1 days after TAI resulted in the majority of nonpregnant heifers detected in estrus over a 4-day interval, with acceptable conception rates; however, injecting progesterone at CIDR insertion significantly reduced both estrus and pregnancy rates, and estradiol treatment after CIDR removal was associated with a decreased pregnancy rate to TAI. Fertility was higher in heifers resynchronized with a once-used CIDR than with MGA.

Animals↗

PubMed2005

Effect of estradiol valerate on ovarian follicle dynamics and superovulatory response in progestin-treated cattle.

Three experiments evaluated the effects of estradiol valerate (EV) on ovarian follicular and CL dynamics, intervals to estrus and ovulation, and superovulatory response in cattle. Experiment 1 compared the efficacy of two norgestomet ear implants (Crestar and Syncro-Mate B; SMB) for 9 d (with PGF at implant removal), combined with either 5 mg estradiol-17beta and 100 mg progesterone (EP) or 5 mg EV and 3mg norgestomet (EN) im at the time of implant insertion on CL diameter and follicular wave dynamics. Ovaries were monitored by ultrasonography. There was no effect of norgestomet implant. Diameter of the CL decreased following EN treatment (P < 0.01). Mean (+/- S.D.) day of follicular wave emergence (FWE) was earlier (P < 0.0001) and less variable (P < 0.0001) in EP- (3.6 +/- 0.5 d) than in EN- (5.7 +/- 1.5 d) treated heifers. Intervals from implant removal to estrus (P < 0.001) and ovulation (P < 0.01) were shorter in EN- (45.7 +/- 11.7 and 74.3 +/- 12.6 h, respectively) than in EP- (56.4 +/- 14.1 and 83.3 +/- 17.0 h, respectively) treated heifers. Experiment 2 compared the efficacy of EP versus EN in synchronizing FWE for superovulation in SMB-implanted cows. At random stages of the estrous cycle, Holstein cows (n = 78) received two SMB implants (Day 0) and were randomly assigned to receive EN on Day 0 or EP on Day 1. Folltropin-V treatments were initiated on the evening of Day 5, with PGF in the morning and evening of Day 8, when SMB were removed. Cows were inseminated after the onset of estrus and embryos were recovered 7 d later. Non-lactating cows had more CL (16.7 +/- 11.3 versus 8.3 +/- 4.9) and total ova/embryos (14.7 +/- 9.5 versus 7.9 +/- 4.6) than lactating cows (P < 0.05). EP-treated cows tended (P = 0.09) to yield more transferable embryos (5.6 +/- 5.2) than EN-treated cows (4.0 +/- 3.7). Experiment 3 compared the effect of dose of EV on ovarian follicle and CL growth profiles and synchrony of estrus and ovulation in CIDR-treated beef cows (n = 43). At random stages of the estrous cycle (Day 0), cows received a CIDR and no further treatment (Control), or an injection of 1, 2, or 5 mg im of EV. On Day 7, CIDR were removed and cows received PGF. Follicular wave emergence occurred within 7 d in 7/10 Control cows and 31/32 EV-treated cows (P < 0.05). In responding cows, interval from treatment to FWE was longer (P < 0.05) in those treated with 5 mg EV (4.8 +/- 1.2 d) than in those treated with 1 mg (3.2 +/- 0.9 d) or 2 mg (3.4 +/- 0.8 d) EV, while Control cows were intermediate (3.8 +/- 2.0 d). Diameter of the dominant follicle was smaller (P < 0.05) at CIDR removal and tended (P = 0.08) to be smaller just prior to ovulation in the 5 mg EV group (8.5 +/- 2.2 and 13.2 +/- 0.6 mm, respectively) than in the Control (11.8 +/- 4.6 and 15.5 +/- 2.9 mm, respectively) or 1mg EV (11.7 +/- 2.5 and 15.1 +/- 2.2 mm, respectively) groups, with the 2mg EV group (10.7 +/- 1.5 and 14.3 +/- 1.7 mm, respectively) intermediate. Diameter of the dominant follicle at CIDR removal was less variable (P < 0.01) in the 2 and 5mg EV groups than in the Control group, and intermediate in the 1mg EV group. In summary, treatment with 5mg EV resulted in a longer and more variable interval to follicular wave emergence than treatment with 5mg estradiol-17beta, which affected preovulatory dominant follicle size following progestin removal, and may have also affected superstimulatory response in Holstein cows. Additionally, 5 mg EV appeared to induce luteolysis in heifers, reducing the interval to ovulation following norgestomet removal. Conversely, intervals to, and synchrony of, follicular wave emergence, estrus and ovulation following treatment with 1 or 2 mg EV suggested that reduced doses of EV may be more useful for the synchronization of follicular wave emergence in progestogen-treated cattle.

Animals↗

PubMed2005

Effects of oestradiol and some of its esters on gonadotrophin release and ovarian follicular dynamics in CIDR-treated beef cattle.

Three experiments were conducted to: (1) compare the effect of three oestradiol formulations on gonadotrophin release in ovariectomised cows; (2) compare the effects of either oestradiol-17beta (E-17beta) or oestradiol benzoate (EB), given at two doses, on the synchrony of ovarian follicular wave emergence in CIDR-treated beef cattle; and (3) determine the timing of ovulation of the dominant follicle of a synchronised follicular wave following administration of E-17beta or EB 24h after progesterone withdrawal. In Experiment 1, ovariectomised cows (n = 16) received a once-used CIDR on Day 0 (beginning of the experiment) and were allocated randomly to receive 5mg of E-17beta, EB or oestradiol valerate (EV) plus 100mg progesterone i.m. The CIDR inserts were removed on Day 7. There were effects of time, and a treatment-by-time interaction (P < 0.0001) for plasma concentrations of both oestradiol and FSH. Plasma oestradiol concentrations peaked 12h after treatment, with highest (P < 0.01) peak concentrations in cows given E-17beta; estradiol concentrations subsequently returned to baseline by 36 h in E-17beta-treated cows and by 96 h in EB- and EV-treated cows. Plasma FSH concentrations decreased by 12h after oestradiol treatment in all groups (P < 0.0001), reached a nadir at 24h, and increased by 60 h in all groups; plasma FSH reached higher (P < 0.02) concentrations in E-17beta-treated than in EB- or EV-treated cows. In Experiment 2, non-lactating Hereford cows (n = 29) received a new CIDR on Day 0 (beginning of the experiment), and were assigned randomly to receive 1 or 5mg of E-17beta or EB i.m. on Day 1. On Day 8, CIDR were removed and PGF was given. Transrectal ultrasonography was done once daily from 2 days before CIDR insertion to 2 days after CIDR removal, and then twice-daily to ovulation. Although there was no difference among groups in the interval from oestradiol treatment to follicular wave emergence (4.2 +/- 0.3 days; P = 0.5), 5mg of E-17beta resulted in the least variable interval to wave emergence (P < 0.005), compared with the other treatment groups which were not different (P = 0.1). For the interval from CIDR removal to ovulation, there were no differences among groups for either means (P = 0.5) or variances (P = 0.1). In Experiment 3, beef heifers (n = 32) received a once-used CIDR on Day 0 (beginning of the experiment) plus 100mg progesterone i.m. and were assigned randomly to receive 5mg E-17beta or 1mg EB i.m. On Day 7, CIDR were removed and all heifers received PGF. On Day 8 (24h after CIDR removal), each group was subdivided randomly to receive 1mg of either E-17beta or EB i.m. There was no effect of oestradiol formulation on interval from treatment to follicular wave emergence (4.1 +/- 0.2 days; P = 0.7) or on the median interval (76.6h; P = 0.7) or range (72-120 h; P = 0.08) from CIDR removal to ovulation. In summary, oestradiol treatments suppressed FSH in ovariectomised cows, with the duration of suppression dependent on the oestradiol formulation. Both E-17beta and EB effectively synchronised ovarian follicular wave emergence and ovulation in CIDR-treated cattle, and the interval from CIDR removal to ovulation did not differ in heifers given either E-17beta or EB 24h after CIDR removal.

Animals↗

PubMed2005

Assisted reproductive technologies in cattle: a review.

Over a period of approximately thirty years, commercial bovine embryo transfer has become a large international business. The technology is well established, and more than 500,000 embryos are produced annually from superovulated cows world wide. Since bovine embryos with intact zonae pellucidae can be specified pathogen-free through washing procedures, thousands of frozen embryos are routinely sold and transferred between countries. Throughout the world, approximately 15% of bovine embryos are produced by in vitro technology. Polymerase chain reaction technology is currently being used for sexing embryos on a small scale, and it is likely that this technology will be used for 'embryo diagnostics' in the future. Semen sexing is an established technology and is likely to be used on a small scale in the near future, especially in in vitro embryo production systems. The cloning of adult cattle through nuclear transfer and the production of cloned, transgenic cattle has been technically achieved. However, this is an expensive and inefficient technology, which is being used primarily by the pharmaceutical industry. Benefits in agriculture are likely to be minimal in the near future.

Animals↗

PubMed2004

Fertility following fixed-time AI in CIDR-treated beef heifers given GnRH or estradiol cypionate and fed diets supplemented with flax seed or sunflower seed.

The objectives were to determine pregnancy rates following fixed-time AI (FTAI) in heifers: (1). given GnRH or estradiol cypionate (ECP) to synchronize follicular wave emergence and ovulation in a CIDR-based protocol; and (2). fed diets supplemented with flax or sunflower seeds. At two locations, Angus and crossbred Angus heifers (n=983) were examined ultrasonically to confirm reproductive maturity and randomly allocated to six synchronization groups in a 2 x 3 factorial design. On Day 0 (start of synchronization treatments), heifers received a CIDR and either 100 microg GnRH i.m. (n=492) or 1mg ECP plus 50 mg progesterone i.m. (n=491); in these groups, CIDR removal and PGF treatment were done concurrently on Days 7 and 8.5, respectively. Heifers were re-randomized to receive 0.5 mg ECP i.m. at CIDR removal or 24 h later (with FTAI 58-60 h after CIDR removal in both groups), or 100 microg GnRH i.m. concurrent with FTAI (52-54 h after CIDR removal). The heifers were fed a barley silage-based diet for 50 days (from Day -25 to 25) supplemented with 1kg/heifer per day of flax seed (n=321), sunflower seed (n=324), or no oilseed (n=338). Pregnancy rate to FTAI (overall, 56.2%) was not affected by treatment at CIDR insertion (P = 0.96) but was higher (P < 0.05) in heifers given ECP 24h after CIDR removal (216/330, 65.4%) than in those given either ECP at CIDR removal (168/322, 52.1%) or GnRH at AI (169/331, 51.1%). Overall, there was no effect of diet on pregnancy rates (P = 0.46). In summary, pregnancy rate to FTAI was not significantly affected by treatment at CIDR insertion to synchronize follicular wave emergence, but 0.5mg ECP 24h after CIDR removal (to synchronize ovulation) resulted in the highest pregnancy rate.

Animals↗

PubMed2004

Fertility in beef cattle given a new or previously used CIDR insert and estradiol, with or without progesterone.

The objective was to compare pregnancy rates following fixed-time AI (FTAI) in beef cattle given a new or previously used CIDR insert and injections of estradiol, with or without progesterone, to synchronize follicular wave emergence. In Experiment 1, heifers (n=616) received a new or once-used CIDR insert for 9 days and were given 1mg estradiol cypionate (ECP), with or without 100 mg of a commercial progesterone preparation (CP4), at CIDR insertion. Heifers were treated with PGF at CIDR removal and 0.5 mg ECP i.m. 24h later, with FTAI 55 to 60 h after CIDR removal. Pregnancy rate was not affected by either the number of CIDR uses (P=0.59; 48.3% versus 46.2% for new versus once-used CIDRs, respectively) or the addition of progesterone (P=0.42; 45.6% versus 48.8% for ECP+CP4 and ECP, respectively). In Experiment 2 (replicated at two locations), heifers (n=56) and lactating beef cows (n=307) received a once- or twice-used CIDR and an i.m. injection of 1mg estradiol benzoate (EB), with or without 100 mg progesterone, at CIDR insertion. Cattle received PGF in the ischiorectal fossa at CIDR removal (Day 7) and 1mg EB i.m. 24h later, with FTAI 52 to 56 h after CIDR removal. Pregnancy rate was affected by location (P<0.002; 46.0% versus 61.1% for Locations A and B, respectively), parity (P<0.04; 67.9% versus 53.1% in heifers and cows, respectively), and numbers of times the CIDR had been used (P<0.03; 62.4% versus 48.4% for once- and twice-used CIDRs, respectively). However, the addition of progesterone to the injection of EB at CIDR insertion did not affect pregnancy rate (P=0.6). In Experiment 3, heifers (n=187) received one new, one once-used, one twice-used or two twice-used CIDRs for 7 days and 2 mg EB plus 50 mg of CP4 at the time of CIDR insertion. Heifers were treated with PGF at CIDR removal and 1mg EB i.m. 24 h later, with FTAI 52-56 h after CIDR removal. Pregnancy rate was not affected by treatments (P=0.28, 57.5, 63.8, 47.9, 47.9% for one new, one once-used, one twice-used, or two twice-used CIDRs, respectively). In summary, pregnancy rate to FTAI did not differ between cattle synchronized with a new or once-used CIDR, but pregnancy rate was lower in cattle synchronized with a twice-used CIDR; however, the insertion of two twice-used CIDRs did not affect pregnancy rates. The addition of an injection of progesterone to the estradiol treatment at CIDR insertion did not enhance pregnancy rate to FTAI.

Administration, Intravaginal↗

PubMed2004

The use of estradiol and/or GnRH in a two-dose PGF protocol for breeding management of beef heifers.

The objective was to determine reproductive performance following AI in beef heifers given estradiol to synchronize ovarian follicular wave emergence and estradiol or GnRH to synchronize ovulation in a two-dose PGF-based protocol. In Experiment 1, 561 cycling (confirmed by ultrasonography), Angus heifers received 500 microg cloprostenol, i.m. (PGF) twice, 14 days apart (days 0 and 14) and were equally allocated to four groups in a 2 x 2 factorial design. On Day 7, heifers received either 2 mg estradiol benzoate (EB) and 50 mg progesterone (P), i.m. in oil (EBP group) or no treatment (NT group). Half the heifers in each group received 1mg EB, i.m. in oil on Day 15 (24h after the second PGF treatment) with TAI 28 h later (52 h after PGF), and the other half received 100 microg GnRH, i.m. on Day 17 (72 h after PGF) concurrent with TAI. All heifers were observed for estrus twice daily from days 13 to 17; those detected in estrus more than 16 h before scheduled TAI were inseminated 4-16 h later and considered nonpregnant to TAI. Overall pregnancy rate (approximately 35 days after AI) was higher in heifers that received EBP than those that did not (61.6% versus 48.2%, respectively; P < 0.002); but was lower in heifers that received EB after PGF than those that received GnRH (50.0% versus 59.8%; P < 0.02). Although estrus was detected prior to TAI in 77 of 279 heifers (27.6%) treated with EBP (presumably due to induced luteolysis), they were inseminated and 53.2% became pregnant. Overall pregnancy rates were 51.4, 68.3, 45.0, and 55.0% in the NT/GnRH, EBP/GnRH, NT/EB, and EBP/EB groups, respectively (P < 0.05). In Experiment 2, 401 cycling, Angus heifers were used. The design was identical to Experiment 1, except that 1.5mg estradiol-17beta (E-17beta) plus 50mg progesterone (E-17betaP) and 1mg E-17beta were used in lieu of EBP and EB, respectively. All heifers receiving E-17beta 24h after the second injection of PGF (NT/E-17beta and E-17betaP/E-17beta) were TAI 28 h later without estrus detection, i.e. 52 h after PGF. Heifers in the other two groups received 100 microg GnRH, i.m. 72 h after PGF and were concurrently TAI; heifers in these two groups that were detected in estrus prior to this time were inseminated 4-12h later and considered nonpregnant to TAI. Estrus rate during the first 72 h after the second PGF treatment was higher (P < 0.05) in the E-17betaP/GnRH group (45.0%; n = 100) than in the NT/GnRH group (16.0%; n = 100), but conception rate following estrus detection and AI was not different (mean, 57.4%; P = 0.50). Overall pregnancy rate was not significantly different among groups (mean, 46.9%; P = 0.32). In summary, the use of EB or E-17beta to synchronize follicular wave emergence and estradiol or GnRH to synchronize ovulation in a two-dose, PGF-based protocol resulted in acceptable fertility to TAI. However, when 2mg EB was used to synchronize follicular wave emergence, early estrus occurred in approximately 28% of heifers, necessitating additional estrus detection. A combination of estrus detection and timed-AI in a two-dose PGF protocol resulted in highly acceptable pregnancy rates.

Animals↗

PubMed2003

Ultrasound image characteristics of ovarian follicles in relation to oocyte competence and follicular status in cattle.

Assessment of the quality of the female gamete has become paramount for in vitro procedures. There is a need to identify reliable indicators of oocyte competence and develop a simple, non-invasive method to assess competence. The aim of this study was to investigate the relationships among ultrasonographic attributes of a follicle, its stage of development and the competence of the oocyte that it contains. We tested the hypotheses that follicular echotexture characteristics are related to: (1) the phase of development of the follicle, (2) the presence of the corpus luteum (CL) and/or the dominant follicle in the ovary, and (3) developmental competence of cumulus oocyte complexes (COC) from the same ovary. Crossbred beef cows (n=143), age 4-14 years, were given a luteolytic dose of dinoprost to cause ovulation. Ultrasound-guided ablation of all follicles > or = 4mm was done 8 days later to induce new follicular wave emergence during a luteal phase. Ultrasonographic images of dominant follicles and the three largest subordinate follicles (n=402 follicles; 84 cows) were acquired on Days 2, 3, 5 or 7 of the follicular wave (Day 0: wave emergence), i.e. growing, early-static, late static, and regressing phases of subordinate follicle development, respectively. From a subset of these animals (n=33), ovaries were collected within 30 min of slaughter and COC from subordinate follicles > or = 3mm underwent in vitro maturation, fertilization and culture to the blastocyst stage.Image analysis revealed differences in echotexture between dominant and subordinate follicles among Days 2-7 of the follicular wave. Images of dominant and subordinate follicles at Day 7 of the wave displayed consistently lower grey-scale values (P<0.05) in the peripheral antrum, follicular wall and perifollicular stroma than all other days. Follicle images displayed a consistent pattern of variation in echotexture among follicular phases. Data did not support the hypothesis of a local effect of the CL or dominant follicle on follicular echotexture. Echotexture values of the perifollicular stroma were lower in ovaries that did not produce embryos compared to ovaries that produced embryos. Our results showed that the changes in follicular image attributes are consistent with changes in follicular status. The sensitivity of the technique is not yet sufficient for use in a diagnostic setting, but results provide rationale for further development of image analysis as a tool for evaluating oocyte competence in situ.

Animals↗

PubMed2002

The control of follicular wave development for self-appointed embryo transfer programs in cattle.

Our expanding knowledge of the control of follicular wave dynamics during the bovine estrous cycle has resulted in renewed enthusiasm for the prospects of precisely controlling the follicular and luteal dynamics and finely controlling the time of ovulation. Follicular wave development can be controlled mechanically by ultrasound-guided follicle ablation or hormonally by treatments with GnRH or estradiol and progestogen/progesterone in combination. Treatment of cattle with GnRH in combination with prostaglandin F2 alpha (PGF) 7 d later and a second GnRH 48 h after PGF (known as Ovsynch) has resulted in acceptable pregnancy rates after fixed-time AI in lactating dairy cows and in recipients in which embryos were transferred without estrus detection. Alternatively, treatments with estradiol and progestogen/progesterone-releasing devices resulted in synchronous emergence of a new follicular wave and, when a second estradiol treatment was given 24 h after device removal, synchronous ovulation and high pregnancy rates to fixed-time AI. Self-appointed embryo transfer (without estrus detection) using estradiol and progesterone treatments have resulted in pregnancy rates comparable with those obtained with recipients transferred 7 d after estrus. Furthermore, estradiol and progesterone treatments combined with PGF and eCG (given 1 d after the expected time of wave emergence) have resulted in high rates of recipients selected for transfer (84.6%) and an overall pregnancy rate of 48.7% (recipients pregnant/recipients treated). Estradiol and progestogen/progesterone treatments have also been widely used for self-appointed superstimulation protocols with equivalent embryo production to that of donor cows superstimulated using the traditional approach beginning 8 to 12 d after estrus. In summary, exogenous control of luteal and follicular development facilitates the application of assisted reproductive technologies in cattle by offering the possibility of planning the superstimulation of donors and synchronization of recipients at a self-appointed time, without the necessity of estrus detection and without sacrificing results.

Animals↗

PubMed2002

The use of a progesterone-releasing device (CIDR-B) or melengestrol acetate with GnRH, LH, or estradiol benzoate for fixed-time AI in beef heifers.

The objective of this experiment was to compare two progestins and three treatments for synchronizing follicular wave emergence and ovulation in protocols for fixed-time AI in beef heifers. On d 0 (beginning of the experiment), Angus and Angus-Simmental cross beef heifers at random stages of the estrous cycle either received a CIDR-B device (n = 257) or were started on 0.5 mg x anima(-1) x d(-1) melengestrol acetate (MGA; n = 246) and were randomly assigned to receive i.m. injections of 100 microg GnRH, 12.5 mg porcine LH (pLH), or 2 mg estradiol benzoate (EB) and 50 mg progesterone (P4). The last feeding of MGA was given on d 6 and on d 7, CIDR-B devices were removed and all heifers received 500 microg cloprostenol (PG). Consistent with their treatment groups on d 0, heifers were given either 100 microg GnRH or 12.5 mg pLH 48 h after PG (and were concurrently inseminated) or 1 mg EB 24 h after PG and were inseminated 28 h later (52 h after PGF). Estrus rate (combined for both progestins) in heifers receiving EB (92.0%) was greater (P < 0.05) than that in heifers receiving GnRH and pLH (combined) and a CIDR-B device (62.9%) or MGA (34.3%). Although the mean interval from PG treatment to estrus did not differ among groups (overall, 47.8 h; P = 0.85), it was less variable (P < 0.01) in MGA-fed heifers (SD = 2.5 h) than in CIDR-B-treated heifers (SD = 8.1 h). Pregnancy rates (determined by ultrasonography approximately 30 d after AI) did not differ (P = 0.30) among the six treatment groups (average, 58.0%; range, 52.5 to 65.0%). Although fixed-time AI was done, pregnancy rates were greater in heifers detected in estrus than in those not detected in estrus (62.6 vs 51.9%; P < 0.05). In conclusion, GnRH, pLH, or EB treatment in combination with a CIDR-B device or MGA effectively synchronized ovulation-for fixed-time AI, resulting in acceptable pregnancy rates in beef heifers.

Animals↗

PubMed2001

The use of GnRH or estradiol to facilitate fixed-time insemination in an MGA-based synchronization regimen in beef cattle.

Two experiments were conducted to compare pregnancy rates when GnRH or estradiol were given to synchronize ovarian follicular wave emergence and ovulation in an MGA-based estrus synchronization program. Crossbred beef cattle were fed melengestrol acetate (MGA, 0.5 mg per day) for 7 days (designated days 0-6, without regard to stage of the estrous cycle) and given cloprostenol (PGF; 500 microg intramuscular (im)) on day 7. In Experiment 1, lactating beef cows (n=140) and pubertal heifers (n=40) were randomly allocated to three groups to receive 100 microg gonadorelin (GnRH), 5 mg estradiol-17beta and 100 mg progesterone (E+P) in canola oil or no treatment (control) on day 0. All cattle were observed for estrus every 12 h from 36 to 96 h after PGF. Cattle in the GnRH group that were detected in estrus 36 or 48 h after PGF were inseminated 12 h later; the remainder were given 100 microg GnRH im 72 h after PGF and concurrently inseminated. Cattle in the E+P group were randomly assigned to receive either 0.5 or 1.0 mg estradiol benzoate (EB) in 2 ml canola oil im 24 h after PGF and were inseminated 30 h later. Cattle in the control group were inseminated 12 h after the first detection of estrus; if not in estrus by 72 h after PGF, they were given 100 microg GnRH im and concurrently inseminated. In the absence of significant differences, all data for heifers and for cows were combined and the 0.5 and 1.0 mg EB groups were combined into a single estradiol group. Estrus rates were 57.6, 57.4 and 60.0% for the GnRH, E+P and control groups, respectively (P=0.95). The mean (+/-S.D.) interval from PGF treatment to estrus was shorter (P<0.001) and less variable (P<0.001) in the E+P group (49.0+/-6.1 h) than in either the GnRH (64.2+/-15.9 h) or control (66.3+/-13.3 h) groups. Overall pregnancy rates were higher (P<0.005) in the GnRH (57.6%) and E+P (55.7%) groups than in the control group (30.0%) as were pregnancy rates to fixed-time AI (47.5, 55.7 and 28.3%, respectively). In Experiment 2, 122 crossbred beef heifers were given either 100 microg GnRH or 2 mg EB and 50 mg progesterone in oil on day 0 and subsequently received either 100 microg GnRH 36 h after PGF and inseminated 14 h later or 1 mg EB im 24 h after PGF and inseminated 28 h later in a 2 x 2 factorial design. Pregnancy rates were not significantly different among groups (41.9, 32.2, 33.3 and 36.7% in GnRH/GnRH, GnRH/EB, EB/GnRH and EB/EB groups, respectively). In conclusion, GnRH or estradiol given to synchronize ovarian follicular wave emergence and ovulation in an MGA-based synchronization regimen resulted in acceptable pregnancy rates to fixed-time insemination.

Animals↗

PubMed2001

The use of in vitro fertilization techniques to investigate the fertilizing ability of bovine sperm with proximal cytoplasmic droplets.

The objective of this experiment was to determine the effect of proximal droplets on sperm-oocyte binding, zona penetration, fertilization, and the developmental competence of oocytes fertilized by sperm with proximal droplets (PD) in an in vitro fertilization (IVF) and culture system. Frozen semen from three bulls (PD1, PD2 and PD3) with varying proportions of normal appearing sperm with proximal droplets and semen from a normal control bull (C) were used in this experiment. The mean number of sperm bound to the zona pellucida (26.8 +/- 2.0, n=100; 15.2 +/- 1.1, n=100; 16.2 +/- 1.0, n=100) for bulls PD1, PD2, and PD3, respectively, were significantly lower (P<0.05) than that of the control bull C (47.4+/- 1.9; n=114). No spermatozoa with PD were found bound to the zona pellucida and this finding was consistent among the three bulls. The percentage penetration of zonae for the bulls PD1, PD2 and PD3 (74%, 74/100; 71%, 71/100 and 69%, 69/100, respectively) were not different than that of bull C (72%, 179/245). Similarly, the mean number of sperm penetrating the zona pellucida (1.43+/- 1.2, 1.24 +/- 1.1 and 1.20 +/- 1.1, for bulls PD1, PD2 and PD3, respectively) were not different than that of bull C (1.45 +/- 1.1). However, fertilization rates (8.8%, 8/90; 16.8%, 16/95; and 10.6%, 11/103, for bulls PD1, PD2 and PD3, respectively) were lower (P<0.001) than that of bull C (68.7%; 77/112). Similarly, cleavage rates (5%, 10/200; 8%, 8/100 and 14%, 15/111) for the bulls PD1, PD2 and PD3, respectively, were lower than that of the control bull, C (60.7%; 79/130). Cleaved zygotes resulting from the fertilization of oocytes by apparently normal sperm from bulls with PD did not develop beyond cleavage, whereas, 43.8% (57/130) morulae and 20% (26/130) blastocysts were produced by oocytes fertilized by sperm from bull C. In summary, normal appearing sperm with PD did not bind to the zona pellucida. Apparently normal sperm with out proximal droplets co-existing in the semen along with sperm containing PD were also functionally deficient, resulting in reduced zonae binding and zygotes resulting from insemination with semen with a high percentage of PD did not develop beyond cleavage.

Animals↗

PubMed2000

Transvaginal collection and ultrastructure of llama (Lama glama) oocytes.

Ultrasound-guided transvaginal follicle aspiration has been described as a noninvasive and repeatable procedure for oocyte collection in several species, but its use has not been described for any of the members of the family, Camelidae. A study was designed to determine the feasibility of an ultrasound-guided transvaginal approach for oocyte collection in llamas. Fifteen non-pregnant, adult female llamas (10 non-stimulated and 5 superstimulated) were examined by transrectal ultrasonography with a 7.5-MHz linear-array transducer to determine the number and diameter of follicles available for aspiration. After caudal epidural anesthesia was induced, the 7.5-MHz linear-array transducer was fastened to a long rigid handle and inserted intravaginally. The free hand was placed into the rectum to manipulate the ovaries, one at a time, in position against the vaginal wall over the face of the transducer. A 20-gauge, 55-cm-long, single-lumen needle was advanced through the vaginal fornix and into follicles > or = 3 mm in diameter. Follicular contents were aspirated using a regulated vacuum pump (flow rate = 33 mL/min; approximately 150 mm Hg) into a tube containing 3 mL of phosphate buffered saline and 0.2% BSA. Fluid was filtered (75 microm mesh), and oocytes were located and morphologically evaluated using a stereomicroscope. Overall, 134 follicles were aspirated, and 76 oocytes were collected (collection rate = 57%). Thirty-two oocytes (42%) were surrounded by multiple layers of compacted granulosa cells and had homogenous dark ooplasm; 13 oocytes (17%) were surrounded by the corona radiata layer only and had heavily granulated ooplasm; 9 oocytes (12%) were denuded and had homogenous dark ooplasm; and 22 oocytes (29%) were denuded and displayed signs of ooplasm degeneration. The ultrastructure of llama oocytes was similar to that of cattle except for conspicuous accumulation of large lipid droplets in the cytoplasm. Twenty-four hours after follicle aspiration, the ovaries were examined by transrectal ultrasonography and intrafollicular hematomas were detected in 3 llamas (9 of 48 follicles aspirated). Results demonstrate the potential utility of a transvaginal ultrasound-guided technique for oocyte collection and in vitro embryo production in llamas. Oocytes of llamas bear an ultrustructural resemblance to those of cattle, but are distinguished by a predominance of cytoplasmic lipid.

Animals↗

PubMed2000

Effect of the knobbed acrosome defect in bovine sperm on IVF and embryo production.

An IVF and culture system was used to determine the effect of the knobbed acrosome defect in bovine spermatozoa on fertilization and early embryonic development. Three bulls affected with knobbed acrosomes were identified as K+ (flattened acrosome), K2+ (indented acrosome) or K3+ (deep indentation of the acrosome) based on the predominant type of acrosomal aberration present in sperm of the respective bulls. After swim-up, all semen traits, except for acrosome morphology, were similar between bulls with varying degrees of the knobbed acrosome defect and a control bull, C. The mean number of spermatozoa bound to the zona pellucida was lower (P< 0.05) for the bulls with the knobbed acrosome defects (40.3 +/- 2.3, 29.5 +/- 1.6, 14.6 +/- 1.3, respectively, for Bulls K+, K2+ and K3+) than for Bull C (52.3 +/- 2.3). The percentages of zonae pellucidae penetrated by spermatozoa from Bulls K+ (51.2%), K2+ (49.5%) and K3+ (37.1%) were lower than that of Bull C (84.5%). No sperm with knobbed acrosome defects were found to have penetrated the zona pellucida. Fertilization rates for bulls with the knobbed acrosome defect, K+ (63.0%), K2+ (62.7%) and K3+ (22.6%), were significantly lower than that of the control bull (82.8%). Percentages of cleaved embryos, morulae and blastocysts produced were also lower for the bulls with knobbed acrosomes than that of the control bull. Results indicate that sperm with the knobbed acrosome defect had a reduced ability to bind to the zona pellucida, depending upon the severity of the defect, and that these aberrant spermatozoa did not penetrate the zona pellucida. The apparently normal spermatozoa coexisting in the inseminate of bulls with a high percentage of knobbed spermatozoa were also functionally deficient; oocytes penetrated by these spermatozoa had a reduced potential for fertilization, and resulting zygotes had a reduced ability for cleavage and embryonic development to the blastocyst stage. The results of the present study do not support the hypotheses that the knobbed acrosome defect is compensable.

Acrosome↗

PubMed2000

Induction of follicular wave emergence for estrus synchronization and artificial insemination in heifers.

The objective was to synchronize follicular wave emergence among cattle for synchronization of estrus and ovulation, and to determine pregnancy rate after AI at observed estrus. At random stages of the estrous cycle, a controlled internal drug release device (CIDR-B) was inserted intravaginally (Day 0) in 67 cross-bred beef heifers, and they were randomly allocated to receive either no further treatment (Control; n = 18); 5 mg of estradiol-17beta and 100 mg of progesterone im (E/P; n = 16); 100 microg im of GnRH (GnRH; n = 16); or transvaginal ultrasound-guided follicular ablation of all follicles > or = 5 mm (FA; n = 17). All heifers received a luteolytic dose of PGF (repeated 12 h later), and CIDR-B were removed on Days 9, 8, 6 or 5, in Control, E/P, GnRH or FA groups, respectively, so the dominant follicle of the induced wave was exposed to exogenous progesterone for a similar period of time in each group. Mean (+/- SEM) intervals (and range, in days) from treatment to follicular wave emergence in these groups were 3.5 +/- 0.6 (-2 to 8), 3.4 +/- 0.1 (3 to 4), 1.5 +/- 0.3 (-1 to 4), and 1.0 +/- 0.1 (0 to 2), respectively. Although the interval was longest (P<0.01) in the E/P and Control groups, it was least variable (P<0.01) in the E/P and FA groups. Intervals (and range, in days) from CIDR-B removal (and first PGF treatment) to estrus were 2.3 +/- 0.2 (1.5 to 4.5), 2.2 +/- 0.2 (1.5 to 3.0), 2.1 +/- 0.1,(1.5 to 3.5), and 2.5 +/- 0.1 (2.0 to 3.5), and to ovulation were 3.5 +/- 0.2 (2.5 to 5.5), 3.4 +/- 0.1 (3.0 to 4.5), 3.5 +/- 0.1 (2.5 to 4.5), and 3.8 +/- 0.1 (3.0 to 4.5), for Control, E/P, GnRH and FA groups, respectively (ns). The proportion of heifers displaying estrus was higher in the Control than in the FA group (94% versus 65%, P<0.05) and intermediate in EP and GnRH groups (87% and 75%). Heifers were inseminated approximately 12 h prior to ovulation (based on estrous behavior and ultrasound examinations). Pregnancy rates were 78%, 80%, 69% and 65% for Control, E/P, GnRH and FA groups, respectively (P=0.73). Results support the hypothesis that synchronous follicular wave emergence results in synchronous follicle development and, following progesterone removal, synchronous estrus and ovulation with high pregnancy rates to AI. The synchrony of estrus and ovulation in the E/P, GnRH and FA groups suggest that these treatments, in combination with CIDR-B, could be adapted to fixed-time insemination programs.

Animals↗

PubMed2000

Local versus systemic effects of exogenous estradiol-17 beta on ovarian follicular dynamics in heifers with progestogen implants.

Two experiments were designed to determine if the suppressive effect of estradiol treatment on ovarian follicles in progestogen-implanted heifers is mediated directly at the ovary or systemically, at a higher level. The purpose of Experiment 1 was to determine a minimal effective dose of estradiol-17beta (E-17beta) that would induce follicle regression in progestogen-implanted heifers. Beef heifers were implanted with progestogen on Day 2 (Day 0=ovulation) and were assigned randomly to five groups: control (sesame seed oil, n=9); 0. 1 mg of E-17beta (n=8); 0.5 mg of E-17beta (n=8); 1 mg of E-17beta (n=8); or 5 mg of E-17beta (n=8) by intramuscular (im) injection on Day 3. Treatment with 5 and 1 mg of E-17beta resulted in smaller (P<0.05) day-to-day diameter profiles of the dominant follicle compared with controls, whereas 0.1 mg of E-17beta did not have an apparent effect on follicle growth. The effect of a dose of 0.5 mg was intermediate and tended (P<0.06) to result in a smaller diameter profile of the dominant follicle compared with control heifers. Experiment 2 was designed to utilize a subminimal dose of E-17beta (0.1 mg), locally, to determine whether estradiol treatment induces follicle regression through a direct action on the ovary. Beef heifers received a progestogen ear implant on Day 2 and were assigned randomly to five groups on Day 3: control (sesame seed oil, n=8); 5 mg of E-17beta im (n=8); 0.1 mg of E-17beta im (n=8); 0.1 mg of E-17beta given into the wall of the uterus, near the tip of the horn ipsilateral to the dominant follicle (intrauterine (iu), n=8); or 0.1 mg of E-17beta given into the stroma of the ovary, immediately adjacent to the dominant follicle (intraovarian (io), n=6). Local (iu and io) treatments were given via a transvaginal ultrasound-guided needle injection. Treatment with 5 mg of E-17beta im resulted in suppression of the dominant follicle of the first follicular wave and early emergence of the second follicular wave (P<0.05). Diameter profiles of the dominant follicle in heifers treated with 0.1 mg im or 0.1 mg iu differed from those of control heifers on Day 5, whereas diameter profiles of the dominant follicle in heifers treated with 0.1 mg io did not differ from the controls. Daily changes in diameter of the dominant follicle did not differ among the three groups treated with 0.1 mg of E-17beta (im, iu and io). Hourly changes in circulating concentrations of FSH and LH were not detected following estradiol treatment either before or after the results were combined for all estradiol-treated groups. Results are supportive of the hypothesis that the suppressive effect of estradiol in cattle is exerted indirectly through a systemic route rather than directly at the ovary. Although low plasma concentrations of FSH and LH were not detected, systemic treatments with high E-17beta dosages resulted in follicular suppression whereas local treatments with subminimal dosages, within the ovary bearing the dominant follicle, were without effect.

Animals↗

PubMed2000

Superovulatory response following transvaginal follicle ablation in cattle.

A study was designed to compare superovulatory responses in cattle when gonadotropin treatment followed 1 of 3 different treatments to synchronize follicular wave emergence. Animals at unknown stages of the estrous cycle were randomly assigned to 3 groups: ablation of the 2 largest follicles per pair of ovaries (n = 21); ablation of all follicles > or = 5 mm (n = 19); or intramuscular administration of 5 mg estradiol-17beta plus 100 mg progesterone (n = 23). All animals were given a CIDR-B intravaginally at the time of the respective treatments. Gonadotropin treatment, initiated 1 d after follicle ablation or 4 d after estradiol plus progesterone treatment, in the respective groups, consisted of 200 mg of pFSH divided in decreasing doses twice daily over 4 d. Cloprostenol (500 microg) was given at 48 and 60 h after the first pFSH treatment; CIDR-B devices were removed at the time of the second cloprostenol treatment. Ovarian ultrasonography was done on the days of CIDR-B insertion, first gonadotropin treatment, and at 36 and 72 h after CIDR-B removal. Cattle were inseminated twice, at 60 and 72 h after the first injection of cloprostenol. Ovarian and ova/embryo data were collected at slaughter 5, 6 or 7 d after insemination. No differences were detected among groups in the number of follicles > or = 8 mm at the time of first insemination (20.4 +/- 1.7 vs 16.6 +/- 2.0 vs 19.9 +/- 2.3; P > 0.05). At slaughter, no differences were detected among groups in the numbers of CL (23.3 +/- 1.9 vs 17.9 +/- 1.9 vs 20.1 +/- 2.6; P < 0.05), unovulated follicles > or = 8 mm (2.2 +/- 0.5 vs 2.1 +/- 0.3 vs 3.7 +/- 0.9; P < 0.05), ova/embryos (11.0 +/- 1.4 vs 12.2 +/- 1.3 vs 8.5 +/- 1.3; P < 0.05), fertilized ova (9.4 +/- 1.3 vs 10.1 +/- 1.2 vs 7.5 +/- 1.1; P < 0.05) or transferable embryos (8.2 +/- 1.2 vs 8.4 +/- 1.3 vs 6.5 +/- 0.9; P < 0.05). Variation in the numbers of CL (P = 0.1) and unovulated follicles > or = 8 mm (P < 0.01) was lower in the ablation groups than in the steroid-treated group. Results suggest that follicle ablation is as effective as estradiol plus progesterone in synchronizing follicular wave emergence for superstimulation in cattle, and that ablation of the 2 largest follicles is as efficacious as ablating all follicles > or = 5 mm.

Animals↗