Time Of Controlled Internal Drug Release Removal Research Articles

CIDR estrous synchronization in the Arabian Oryx (Oryx leucoryx)

In Jordan, the Arabian Oryx (Oryx leucoryx) is considered among the most important wild ungulates. The Arabian Oryx is listed as vulnerable species according to the International Union for Conservation of Nature (IUCN). Based on author’s knowledge, estrus synchronization in the Arabian Oryx has never been investigated. Therefore, the current study aimed to validate a Controlled Internal Drug Release (CIDR) estrus synchronization technique for the first time in 7 Arabian Oryx females. Prior to CIDR application, animals were subjected to transabdominal ultrasonic examination twice, two weeks apart to exclude pregnancies. A single CIDR was inserted (Day 0) for a period of 7 days. At the time of CIDR removal (Day 7), animals were administered a single injection of prostaglandin F2α (PF2α) and equine chorionic gonadotropin (eCG). Blood samples were collected from all animals before, during and after CIDR removal for progesterone (P4) analysis. Animals were monitored for estrus behavior for 8 days starting 24 h after CIDR removal. All animals were considered to be anestrous at the start of the study as defined by having blood progesterone <1 ng/ml prior to insertion of the CIDR. All animals displayed estrous behavior between Day 1–3 after CIDR removal and the average interval from CIDR removal to estrus and length of estrus were 53.71 ± 5.59 h and 55.43 ± 6.19 h, respectively. On Day 14 (6 days after CIDR removal) P4 concentrations rose above 1 ng/ml indicated ovulation. It is possible to synchronize estrus in Arabian Oryx using CIDRs. The success of CIDR estrous synchronization in female Arabian Oryx, as described in the current study, opens new perspectives towards the possible application of assisted reproductive techniques for the propagation and conservation englishEnglishof this vulnerable species.

260 The induction and synchronization of estrus in sheep during the fall and late spring (season and out of season) using controlled internal drug release (CIDR) devices on Delmarva

Changing U.S. demographics have increased lamb demand, which usually follows holidays, changing from year-to-year coinciding with traditions/festivals. In 2013, >80,000 t (metric tons) of lamb were imported to USA. A chief constraint to continuous year-round lamb supply is the influence of season on sheep reproduction. The purpose of this project was not to determine FDA approved CIDRs' (2009) efficacy in sheep but to resolve applicability and practicality of CIDR use in commercial flocks to condense lambing periods and target peak lamb demands. From 2012 to 2015, purebred and crossbred Katahdin ewes (n = 201) were separated into two groups, synchronized (CIDR) or not (CONTROL), for breeding in late Spring (anestrus-season) or Fall (natural-breeding-season). At each breeding event, CIDRs were inserted for 12 to 18 d, and at the time of CIDR removal, ewes were grouped for mating in single sire groups of no more than 6 ewes/group. The FDA approved protocol (12 to 18 d) was followed because pre-trials at this station gave inconsistent results following the label's CIDR insertion and removal time (5 d). At birth, lambs were tagged, weighed, and sexed, and litter size was recorded (LSZ) (lambs/ewe exposed). Data were analyzed using Chi-square and analysis of variance (SAS software package) for effect of synchronization and season on pregnancy rates (PR) (pregnant ewes/exposed ewes) and LSZ at birth. Overall PR did not differ from one year to the other in CIDR or CONTROL ewes. PR was higher (P < 0.0001) in CIDR ewes (63.4%) than in CONTROL ewes (34.3%) but was similar between breeding seasons (62.4% and 37.6% for CIDR and 52.8% and 47.2% for CONTROL in Fall and Spring, respectively). During Spring, PRs were higher (P < 0.0001) in CIDR ewes (71.4%) than in CONTROL ewes (17.6%). During Fall, PRs were similar (58.5% and 49.1% for CIDR and CONTROL, respectively). Overall, ewe LSZ was influenced by season bred and use of CIDRs, with CONTROL Spring-bred ewes having a lower (P < 0.0001) litter size (0.3 ± 0.1) compared to CONTROL-Fall, CIDR-Fall, and CIDR-Spring bred ewes (1.0 ± 0.1, 1.2 ± 0.1, and 1.3 ± 0.1, respectively). The results encourage using CIDRs in commercial sheep flocks to increase pregnancy rate and litter size. Additionally, CIDR synchronization in our station reduced a 60 to 90 d lambing period to 10 d, allowing operators to arrange facilities, labor, and supplies accordingly, enhancing lamb survival and ewe welfare. Project funded by Evans-Allen grant USDA/NIFA MDX-AS1012001.

Effects of estradiol and oxytocin injection on the efficiency of artificial insemination in Iranian Zel ewes during the breeding season

In sheep industry, pregnancy rate after artificial insemination (AI) declines due to the complex anatomy of the cervix in ewes, such that it might prevent effective intrauterine insemination. At estrus, cervical relaxation occurs to some degree in ewes, which is regulated by the changes in the levels of reproductive hormones. This study aimed to evaluate the effects of estradiol and intravenous (IV) or intramuscular (IM) oxytocin injection at different doses on the cervical opening and pregnancy rate of Iranian Zel ewes during the breeding season. For this purpose, three experiments were conducted on 120 ewes (3-4 years old, weighing 47±2.5 kg). In the first experiment, ewes were equally assigned to two groups to receive estradiol (100-200 µg). After 12 h, each group was equally divided into six subgroups (n=20) and received 50, 100 and 150 IU oxytocin via IV and IM injection. Cervical opening was measured before and 15 min and 12 h after estradiol injection and 20 min after oxytocin administration. In the second experiment, we only assessed the effect of oxytocin administration on cervical opening similar to the first experiment. In the third experiment, controlled internal drug release (CIDR) was used in all the ewes for 12 days to induce estrus synchronization. Afterwards, the ewes received 550 IU intrauterine equine chorionic gonadotropin at the time of CIDR removal. Before AI, ewes were equally categorized into three groups (n=40); the first group was considered as control, and the other two groups received 100 IU oxytocin via IM or IV injection. At 54 h after CIDR removal, all ewes were inseminated transcervically using diluted fresh semen. Pregnancy was detected via ultrasound 50 days after insemination, and lambing and twinning rates were measured after parturition. Results of the first and second experiment indicated that estradiol injection had no effect on cervical opening (P>0.05), while the administration of 100 or 150 IU oxytocin (IV or IM) could dilate the cervix with or without estradiol (P 0.05). According to the results, IV or IM injection of oxytocin could improve the pregnancy rate in Iranian Zel ewes through the dilation of cervical canal. Therefore, it is suggested that this method be applied to enhance the pregnancy rate of ewes during the breeding season.

The effect of equine chorionic gonadotrophin (ecg) injection combined with prostaglandin F2α (pGF2α) and gonadotrophin releasing hormone (GnRH) treatment on reproductive performance of Zandi ewes during non-breeding season

In this study, we aimed to investigate reproductive performance in estrus-induced Zandi ewes treated with equine chorionic gonadotrophin (eCG) injection in combination with prostaglandin F2α (PGF2α)and gonadotrophin releasing hormone (GnRH) during non-breeding season. The estrous cycle was synchronized using controlled internal drug release (CIDR) for 12 days. The ewes were randomly assigned to five groups (n=100 in each group). The first group (control) did not receive hormone injection, the second group (eCG) received 400 IU of eCG at the time of CIDR removal, the third group (eCG+PGF2α) received 400 IU of eCG and 1 ml of PGF2α at the time of CIDR removal, the fourth group (eCG+GnRH) received 400 IU of eCG at the time of CIDR removal and 1 ml of GnRH injection on the day of insemination, and the fifth group (eCG+PGF2α+GnRH) received 400 IU of eCG, 1 ml of PGF2α at the time of CIDR removal, and 1 ml of GnRH on the day of insemination. The results showed that the heat response rate was higher in all the groups receiving hormonal injections compared with the control group (P 0.05). In conclusion, use of eCG at the time of CIDR removal and GnRH on the day of insemination increased reproductive performance. Therefore, it can be applied as a strategy for increasing lambing rate in ewes.

Comparison of 4- versus 5-day Co-Synch + controlled internal drug release (CIDR) + timed artificial insemination protocols in dairy heifers

The objective of this study was to compare the pregnancy rate after timed artificial insemination (P/TAI) in dairy heifers treated with 4- versus 5-day Co-Synch + controlled internal drug release (CIDR) protocols. A total of 120 Holstein heifers were randomly assigned to one of two groups. The heifers received an intravaginal CIDR insert containing 1.38 g of progesterone for 4 days (Monday–Friday 4-day Co-Synch + CIDR; n = 60) or 5 days (5-day Co-Synch + CIDR; n = 60). At the time of CIDR removal, 25 mg of PGF2α was injected intramuscularly, and 72 hours after CIDR removal, the heifers received 100 μg of GnRH intramuscularly and were artificially inseminated. Artificial insemination was performed by an experienced technician, using commercial frozen–thawed semen from a single sire. Pregnancy diagnosis was performed by ultrasonography per rectum 32 days after TAI. Categorical data were analyzed using proc logistic and the chi-square test, whereas continuous variables were analyzed using the t-test of Statistical Analysis Systems. Heifers in the 4-day Co-Synch + CIDR group had an acceptable P/TAI32 (55.0%, 33 of 60), which was not different (P = 0.35) from that observed in the 5-day Co-Synch + CIDR group (63.3%, 38 of 60). Progesterone concentration at CIDR insertion or estradiol concentration at TAI did not influence the pregnancy outcomes. Interestingly, estradiol concentration at TAI was greater in the 4-day Co-Synch + CIDR group compared to the 5-day Co-Synch + CIDR group (P < 0.01). In conclusion, the Monday to Friday 4-day Co-Synch + CIDR protocol resulted in adequate P/TAI in dairy heifers, which was similar to that of the 5-day Co-Synch + CIDR protocol. This novel protocol might represent a promising hormonal treatment for TAI in dairy heifers, facilitating their reproductive management routine, while maintaining an adequate fertility.

Estrous and ovulatory responses following cervical artificial insemination in Thai-native goats given a new or once-used controlled internal drug release with human chorionic gonadotropin.

The study was conducted to compare estrous rate, ovulatory response, plasma progesterone concentrations, and conception rate following cervical artificial insemination in goats given a new or once-used controlled internal drug release (CIDR) device with human chorionic gonadotropin (hCG). Fifty-six Thai-native goats with the average age and body weight of 11 months and 17.3 kg received a 14-day treatment with a new CIDR device (Eazi-Breed(TM)CIDR®, Pfizer, NY, USA) or a once-used CIDR device. All goats received a 300-IU injection of hCG (Chorulon®, Intervet International B.V., New Zealand) at the day of CIDR removal to induce ovulation. All goats displaying signs of Estrous behavior were artificially inseminated at 12 h after the onset of estrus with frozen semen. No differences in percentage of estrus and ovulation rates were observed; however, goats that received once-used CIDR devices exhibited shorter (P < 0.05) duration of estrus in comparison with new devices (21.4 ± 1.4 h vs. 26.1 ± 1.1 h) and delayed the onset of estrus (47.0 ± 3.6 h vs. 36.5 ± 1.9 h) and the time of ovulation (74.9 ± 3.9 h vs. 64.5 ± 1.3 h), respectively. Progesterone (P4) concentrations were not significantly different (P > 0.05) between treatments during CIDR device insertion and at the time of CIDR removal except on day 4. No significant differences were found in overall conception rates between the treatments. This study indicates that the once-used CIDR device with hCG could be applied to synchronize the estrus and ovulation in small-size Thai-native goats without negative effects on Estrous behavior, ovulatory response, and plasma P4 concentration.

Restablecimiento de la actividad reproductiva posparto en ovejas de pelo

The purpose of this study was to determine the effect of suckling, postpartum (PP) synchro-nization protocol and the ram effect on repro-ductive performance of hairy sheep. Isolated from the rams, 96 ewes were randomly assigned to one of two groups at lambing (n=48): continuous suckling for 18 h (Ac) and controlled suckling for 30 minutes twice a day (Lc). On day 35 PP, both groups were synchronized with CIDR (Controlled Internal Drug Release) for 10 days, 48 hours before CIDR removal, 7,5 mg of dinoprost was administered and the effect of the ram (Ca) 48 hours before and at the time of CIDR removal were tested. We determined progesterone (P4) por radioimmunoassay at 30, 35, 50, 55 y 64 days PP. The ewes were inseminated intrauterine by abdominal laparoscopy 12 to 15 hours after estrus onset. The response variables were: percentage of ovulation before 35 days PP, time of estrus onset, pregnancy rate, prolificacy, fecundity and live weight of the ewes and their lambs. The information obtained was analyzed using logistic regression and Poisson, chi-square test, survival curves and repeated measures analysis. The percentage of ewes that ovulated before 35 days PP was higher (p 0.05) between treatments. The weight of lambs was higher (p<0.05) in Ac after 41 days PP and there was no mortality during lactation. After CIDR removal all ewes showed estrus, being those of Lc (p<0.05) the first to manifest estrous behavior (50 hours). Pregnancy rate, prolificacy and fecundity were not different between treatments and averaged 82.3, 1.84 and 1.51 %, respectively. The results indicate that controlling lactation increases and concentrates the number of ewes that ovulated before 35 days PP. All ewes responded to the synchronization postpartum and the ram effect showing estrous behavior and only one ewe presented corpora lutea of shortened lifespan.

Is GnRH necessary at CIDR insertion using a 7-Day CIDR synchronization protocol for beef heifers?

The EAZI-BREED CIDR is commonly used in estrous synchronization protocols for both beef heifers and cows. The label calls for insertion of a progesterone-impregnated controlled internal drug release (CIDR) for 7 consecutive days with an injection of prostaglandin F2αgiven a day before CIDR removal. Animals should display estrus 1 to 3 days after CIDR removal. Modifications to this protocol include administration of gonadotropin-releasing hormone (GnRH) at the time of CIDR insertion and administration of the prostaglandin injection at the time of CIDR removal on day 7. Use of GnRH in conjunction with a CIDR may improve estrous synchronization in beef cows and fertility at fixed-time insemination but may not be necessary when synchronizing beef heifers. Our objective was to compare heat response and fertility in heifers with or without GnRH administration at the time of CIDR insertion. Our hypothesis was that heifer fertility would be similar between treatments.

A CIDR-Based Timed Embryo Transfer Protocol Increases the Pregnancy Rate of Lactating Repeat Breeder Dairy Cows

This study evaluated the pregnancy rates following either a controlled internal drug release (CIDR)-based timed artificial insemination (TAI) or an embryo transfer (TET) protocol compared with that following a single PGF(2alpha) injection and AI after estrus (AIE) in lactating repeat breeder dairy cows. Fifty-three lactating dairy cows diagnosed as repeat breeders were used in this study and were randomly assigned to the following three treatments. (1) Cows, at random stages of the estrous cycle, received a CIDR device and 2 mg estradiol benzoate (EB; Day 0), a 25 mg PGF(2) (alpha) injection at the time of CIDR removal on Day 7 and a 1 mg EB injection on Day 8. The cows then received TAI 30 h (Day 9) after the second EB injection using dairy semen (TAI group, n=13). (2) Cows, at random stages of the estrous cycle, received the same hormonal treatments as in the TAI group. The cows then received TET on Day 16 using frozen-thawed blastocysts or morula embryos collected from Korean native cattle donors (TET group, n=13). (3) Cows, at the luteal phase, received a 25 mg injection of PGF(2alpha) and AIE using dairy semen (control group, n=27). The ovaries of the cows in the TET group were examined by transrectal ultrasonography to determine ovulation of the preovulatory follicles, and blood samples were collected for serum progesterone (P4) analysis. The pregnancy rate was significantly higher in the TET group (53.8%) than in the control (18.5%) or TAI (7.7%) groups (P<0.05). The ultrasonographic observations demonstrated that all the cows in the TET group ovulated the preovulatory follicles and concomitantly formed new corpora lutea. Accordingly, the mean serum P4 concentration remained constant between Day 0 and Day 7 of the luteal phase, decreased dramatically on Day 8 (P<0.01) and subsequently increased by Day 16 (P<0.01). These data suggest that the CIDR-based TET protocol can be used to effectively increase the pregnancy rate in lactating repeat breeder dairy cows.

Treatment of Cycling and Noncycling Lactating Dairy Cows with Progesterone During Ovsynch

Our objective was to determine whether progesterone (P4) supplementation during an Ovsynch protocol would enhance fertility in lactating dairy cows. Lactating dairy cows (n = 634) at 6 locations were assigned randomly within lactation number and stage of lactation to receive the Ovsynch protocol [OVS; synchronization of ovulation by injecting GnRH 7 d before and 48h after PGF2α, followed by one fixed-time AI (TAI) 16 to 20h after the second GnRH injection] or Ovsynch plus a controlled internal drug release (CIDR) P4-releasing insert for 7 d, beginning at the first GnRH injection (OVS + CIDR). Blood was sampled to quantify P4 10 d before the first GnRH injection, immediately before the first GnRH injection, at the time of CIDR removal, before the PGF2α injection (1 to 2h after CIDR insert removal), and 48h after the PGF2α injection to determine cyclicity status before initiation of treatment, luteal status at the PGF2α injection, and incidence of luteal regression. Overall, conception rates at 28 (40 vs. 50%) and 56 d (33 vs. 38%) after TAI differed between OVS and OVS + CIDR, respectively; but a treatment×location interaction was detected. Compared with OVS, pregnancy outcomes were more positive for OVS + CIDR cows at 4 of 6 locations 28 d after TAI and at 3 of 6 locations 56 d after TAI. An interaction of luteal status (high vs. low) before CIDR insert removal and PGF2α injection with pretreatment cycling status indicated that cows having low P4 at PGF2α injection benefited most from P4 supplementation (OVS + CIDR = 36% vs. OVS = 18%), regardless of pretreatment cycling status. Pregnancy loss between 28 and 56 d after TAI was greater for noncycling cows (31%) compared with cycling cows (16%). Pregnancy loss for cows receiving P4 (21%) did not differ from that for cows not receiving P4 (21%). Supplementation of P4, pretreatment cycling status, and luteal status before PGF2α injection altered follicular diameters at the time of the second GnRH injection, but were unrelated to pregnancy outcomes. Incidence of multiple ovulation was greater in noncycling than in cycling cows. Further, cows having multiple ovulations had improved pregnancy outcomes at 28 and 56 d after TAI. In summary, a CIDR insert during the Ovsynch protocol increased fertility in lactating cows having low serum P4 before PGF2α injection. Improved pregnancy outcomes were observed at some, but not all locations.

Comparison of the effect of estradiol benzoate plus progesterone and GnRH on the follicular wave emergence and subsequent follicular development in CIDR-treated, lactating dairy cows with follicular cysts

This study examined the effect of estradiol benzoate (EB) plus progesterone (P4) as compared with GnRH on follicular wave emergence and follicular development, and synchrony of ovulation and pregnancy rates following a second injection of GnRH in a controlled internal drug release (CIDR)-based timed AI (TAI) protocol in lactating dairy cows with follicular cysts. Lactating dairy cows diagnosed with follicular cysts received a CIDR device, with an injection of 2 mg EB plus 50 mg P4 (EB + P4 group) or with an injection of 100 μg GnRH (GnRH group) at the beginning of the experiment (day 0). Thereafter, all received PGF 2α at the time of CIDR removal on day 7, GnRH on day 9, and TAI 16 h later. Follicular wave emergence occurred within 7 days in 12/15 EB plus P4-treated and 14/15 GnRH-treated cows ( P > 0.05). The interval to wave emergence was longer in the EB + P4 group (4.8 ± 0.4 days) than in the GnRH group (2.0 ± 0.2 days). The mean diameters of preovulatory follicles and the proportion of cows with preovulatory follicles greater than 12 mm on day 9 did not differ between groups ( P > 0.05). The proportion of cows with synchronized ovulations by 40 h after the GnRH injection on day 11 and pregnancy rates to TAI did not differ between the EB + P4 (13/15 and 36.7%) and the GnRH (14/15 and 53.3%) groups, respectively. Results suggest that a single treatment with EB plus P4 as compared with GnRH simultaneously with CIDR insertion in lactating dairy cows with follicular cysts will result in relatively asynchronous emergence of a new follicular wave, but subsequently similar sizes of preovulatory follicles and synchronous ovulation, resulting in similar pregnancy rates to TAI.

A CIDR-based timed AI protocol can be effectively used for dairy cows with follicular cysts

The present study evaluated whether a controlled internal drug release (CIDR)-based timed AI (TAI) protocol could be used as an efficient tool for the treatment of ovarian follicular cysts in lactating dairy cows. In the first experiment, lactating dairy cows diagnosed with follicular cysts were randomly assigned to two treatments: (1) a single injection of GnRH at diagnosis (Day 0) and AI at estrus (AIE) within 21 days (GnRH group, n = 70), or (2) insertion of a CIDR device containing progesterone and an injection of GnRH on Day 0, PGF 2α injection at the time of CIDR removal on Day 7, GnRH injection on Day 9, and TAI 16 h after the GnRH injection (CIDR-based TAI group, n = 65). Conception rate after the CIDR-based TAI protocol (52.3%) was greater ( P < 0.05) than that after AIE following a single GnRH injection (26.9%). In the second experiment, lactating dairy cows diagnosed with follicular cysts (Cyst group, n = 16) and cows having normal estrous cycles (CYC group, n = 15) received the same treatment: a CIDR device containing progesterone and an injection of GnRH on Day 0, PGF 2α injection at the time of CIDR removal on Day 7, and GnRH injection on Day 9. The proportion of cows with follicular wave emergence and the interval from treatment to follicular wave emergence did not differ ( P > 0.05) between groups. The mean diameters of dominant follicles on Days 4 and 7 as well as preovulatory follicles on Day 9, and the synchrony of ovulation following the second injection of GnRH did not differ ( P > 0.05) between groups. These data suggest that the CIDR-based TAI protocol results in an acceptable conception rate in dairy cows with follicular cysts.

235 FOLLICULAR WAVE EMERGENCE AND DEVELOPMENT FOLLOWING ESTRADIOL PLUS PROGESTERONE AT A GROWING OR A STATIC PHASE OF THE DOMINANT FOLLICLE IN CIDR-TREATED, LACTATING DAIRY COWS

Treatment with estradiol benzoate (EB), compared to GnRH, in a controlled internal drug release (CIDR)-based timed AI protocol induced relatively asynchronous follicular wave emergence, resulting in ovulation of smaller ovulating follicles (Kim et al. 2005 Theriogenology 63, 260-268). In this study, we compared new follicular wave emergence and development following treatment with EB (2 mg) plus progesterone (50 mg) at a growing (Day 3 after ovulation) or a static (Day 8) phase of the dominant follicle during the first follicular wave in CIDR-treated, lactating dairy cows. Previously synchronized, lactating dairy cows received CIDRs (InterAg, Hamilton, New Zealand; Day 0) 3 days after ovulation and were assigned to two treatment groups and a control group. Cows in the T1 group (n = 11) received 2 mg EB (SY Esrone; Samyang, Seoul, Korea) and 50 mg P4 (SY Ovaron; Samyang) i.m., and those in the control group (n = 10) received no treatment at that time. Other previously synchronized cows received a CIDR (Day 0) with injections of 2 mg EB plus 50 mg P4 i.m. 8 days after ovulation (T2 group, n = 10). Thereafter, all cows received PGF2� (Lutalyse; Pharmacia &amp; Upjohn, Puurs, Belgium) at the time of CIDR removal on Day 7, and GnRH (Conceral; Dongbang Co., Seoul, Korea) on Day 9. Ovaries of each cow were examined by transrectal ultrasonography (Sonoace 600 with 7.5 MHz linear-array transducer; Medison Co., Ltd, Seoul, Korea) every 24 h from Days 0 to 9, on Day 11, and on Day 14 of treatment to observe changes in ovarian structures (follicles and corpora lutea (CL)). Data were analyzed by Fisher's exact test, Kruskal-Wallis test, and ANOVA using an SAS program (SAS Institute, Inc., Cary, NC, USA). Follicular wave emergence occurred within 7 days in 3/10 of the control group, 9/11 of the T1 group, and 9/10 of the T2 group (P &lt; 0.05). The interval to wave emergence did not differ (P &gt; 0.05) among groups (3.7 � 1.2, 4.8 � 0.5, 5.9 � 0.3 days, respectively). While the diameters of dominant follicles on Day 0 were greater (P &lt; 0.01) in the T2 group (14.3 � 1.2 mm) than in the control (9.4 � 0.6 mm) and T1 (10.5 � 0.7 mm) group, diameters of preovulatory follicles on Day 9 were significantly smaller (P &lt; 0.01) in the T1 (13.6 � 0.7 mm) and T2 (12.3 � 0.5 mm) groups than in the control group (16.4 � 0.8 mm). Synchronized ovulation by 40 h after the GnRH injection (Day 11) occurred in 10/10 of the control group, 10/11 of the T1 group, and 9/10 of the T2 group (P &gt; 0.05). In conclusion, administration of 2 mg EB plus 50 mg P4 at both a growing and a static phase of the dominant follicle during the first follicular wave results in synchronous follicular wave emergence and development and also synchronized ovulation in CIDR-treated, lactating dairy cows.

17 COMPARISON OF FOLLICULAR WAVE EMERGENCE AND FOLLICULAR DEVELOPMENT FOLLOWING ESTRADIOL BENZOATE PLUS PROGESTERONE OR GnRH AT THE FIRST FOLLICULAR WAVE IN A CIDR-TREATED, LACTATING HOLSTEIN COWS

Treatment with GnRH in a controlled internal drug release (CIDR)-based timed AI protocol induced synchronized follicular wave emergence, a large ovulatory follicle, and synchronous ovulation following a second injection of GnRH, while follicular wave emergence was relatively asynchronous in the estradiol benzoate (EB)-treated cows resulting in ovulation of smaller ovulatory follicles (Kim et al. 2004 Theriogenology, in press). In this study, we compared new follicular wave emergence and follicular development following treatment with EB plus progesterone (P4) or GnRH at the first follicular wave in CIDR-treated, lactating Holstein cows. Previously synchronized, lactating Holstein cows (n = 20) received a CIDR (CIDR™, InterAg, Hamilton, New Zealand, Day 0) 3 to 8 days after ovulation and were randomly assigned to two treatments: cows in the GnRH group (n = 10) received 100 μg fertirelin acetate i.m. (GnRH, Conceral, Dongbang Co., Seoul, Korea) and those in the E/P group (n = 10) received 2 mg EB (SY Esrone, Samyang, Seoul, Korea) and 50 mg P4 i.m. (SY Ovaron, Samyang, Seoul, Korea) at that time. Thereafter, all animals received PGF2α (Lutalyse, Pharmacia &amp; Upjohn, Puurs, Belgium) at the time of CIDR removal on Day 7, and GnRH on Day 9. Ovaries of each cow were examined by transrectal ultrasonography (Sonoace 600 with 5.0 MHz linear-array transducer; Medison Co., Ltd., Seoul, Korea) every 24 h from Days 0 to 9, on Day 11, and on Day 14 of treatment to observe changes in ovarian structures (follicles and CL). Data were analyzed by Fisher's exact test, Wilcoxon Rank-Sum test and Student's t-test using an SAS program. Follicular wave emergence occurred within 7 days in 9/10 GnRH- and 8/10 E/P-treated cows (P &gt; 0.05). The interval to wave emergence was longer (P &lt; 0.01) in the E/P group (5.9 ± 0.5 days) than in the GnRH group (2.9 ± 0.4 days). While diameters of dominant follicles on Day 0 were not different (P &gt; 0.05) between groups, diameters on Day 7 and Day 9 in the E/P group (9.4 ± 0.4 and 13.1 ± 0.7 mm, respectively) were significantly smaller (P &lt; 0.01) than those in the GnRH group (12.9 ± 0.5 and 15.8 ± 0.7 mm, respectively). Growth rates of preovulatory follicles in the E/P group (2.1 ± 0.2 mm/day) were greater (P &lt; 0.01) than in the GnRH group (1.2 ± 0.1 mm/day), while the duration of dominance of the preovulatory follicle was longer (P &lt; 0.01) in the GnRH group (6.3 ± 0.4 days) than in the E/P group (3.3 ± 0.5 days). Synchronized ovulation by 40 h after the GnRH injection (Day 11) occurred in 10/10 GnRH- and 9/10 E/P-treated cows (P &gt; 0.05). Results suggest that estradiol benzoate plus progesterone administered at the first follicular wave in CIDR-treated, lactating Holstein cows delays new follicular wave emergence, resulting in ovulation of smaller ovulatory follicles than GnRH. Endocrine changes during treatment and fertility following timed AI has been investigated in this study.

Follicular wave emergence, luteal function and synchrony of ovulation following GnRH or estradiol benzoate in a CIDR-treated, lactating Holstein cows

This study evaluated the effect of GnRH or estradiol benzoate (EB) on follicular wave emergence and progesterone concentrations, and following a second injection of GnRH, synchrony of ovulation, and pregnancy rates in a controlled internal drug release (CIDR)-based timed AI (TAI) protocol in lactating Holstein cows. Cows received a CIDR device without hormone (controls), with an injection of 100 μg GnRH or with an injection of 4 mg EB. Thereafter, all received PGF 2α at the time of CIDR removal on Day 7, GnRH on Day 9, and TAI 16 h later. Follicular wave emergence occurred within 7 days in 19/20 GnRH-treated, 14/20 EB-treated and 5/20 control cows ( P < 0.05). The interval to wave emergence was the shorter and less variable ( P < 0.01) in the GnRH group (2.9 ± 0.2 days) than in the EB (4.7 ± 0.5 days) or control (4.8 ± 1.0 days) groups. Serum progesterone concentrations from Days 4 to 7 were higher ( P < 0.01) in the GnRH-treated cows that ovulated than in those that did not ovulate, or in control and EB-treated cows. The diameters of dominant follicle on Day 7 differed among groups ( P < 0.01), and the diameters of the preovulatory follicle on Day 9 were larger ( P < 0.01) in the control and GnRH groups than in the EB group. The proportion of cows with synchronized ovulations did not differ among groups, but pregnancy rate to TAI was higher ( P < 0.05) in the GnRH group (65%; 13/20) than in the control (30%; 6/20) or EB (35%; 7/20) groups. Results suggest that GnRH treatment of CIDR-treated lactating Holstein cows will result in synchronous follicular wave emergence, large preovulatory follicles and synchronous ovulation, resulting in an acceptable pregnancy rates to TAI.