Inhibitory effects of CIDR-based ovulation-synchronization protocols on uterine PGF2alpha secretion at the following luteal phase in early postpartum non-cycling beef cows

We investigated whether CIDR-based ovulation-synchronization protocols inhibit secretion of prostaglandin (PG) F2alpha from the uterus in the following luteal phase in non-cycling beef cows. Ten early (a month) postpartum non-cycling Japanese Black beef cows were treated with (1) Ovsynch (GnRH analogue on Day 0, PGF2alpha analogue on Day 7, and GnRH analogue on Day 9; n=3), (2) Ovsynch+CIDR (Ovsynch protocol plus a CIDR for 7 days from Day 0; n=4), or (3) estradiol benzoate (EB) Ovsynch+CIDR (EB on Day 0 in lieu of the first GnRH treatment followed by the Ovsynch+CIDR protocol; n=3). An oxytocin challenge was administered on Day 24 to examine uterine PGF2alpha secretion. Plasma concentrations of 13,14-dihydro-15-keto- PGF2alpha were lower at 30-120 min after oxytocin administration in the Ovsynch+CIDR group and 75 min after administration in the EB Ovsynch+CIDR group than in the Ovsynch group (P<0.05). Plasma progesterone concentrations were higher from Days 1 to 7 in the Ovsynch+CIDR group and from Days 1 to 5 in the EB Ovsynch+CIDR group than in the Ovsynch group (P<0.05). The progesterone concentrations were higher on Days 27 and 29 in both CIDR-treated groups than in the Ovsynch group (P<0.05). In conclusion, in non-cycling beef cows, CIDR-based ovulation-synchronization protocols inhibit uterine PGF2alpha secretion in the following luteal phase and prevent premature luteolysis as is seen with the Ovsynch protocol.     

Comparison of plasma concentrations of estradiol-17β and progesterone, and conception in dairy cows with cystic ovarian diseases between Ovsynch and Ovsynch plus CIDR timed AI protocols

The objectives of this study were 1) to determine the effects of adding a CIDR to the Ovsynch protocol on plasma concentrations of estradiol-17β and progesterone and conception in dairy cows with cystic ovarian diseases and 2) to examine associations among the estradiol-17β and progesterone concentrations and conception. Cows were diagnosed as having cystic ovarian diseases if they were found to have a cystic follicle (diameter ≥25 mm) without a corpus luteum by two palpations per rectum with an interval for 7 to 14 days. They were treated with either the Ovsynch (GnRH on Day 0, PGF(2α) on Day 7 and GnRH on Day 9, with AI on Day 10; n=15) or Ovsynch+CIDR protocol (Ovsynch protocol plus a CIDR from Day 0 to Day 7; n=23). Plasma estradiol-17β concentrations were determined on Days 0, 7 and 9, and plasma progesterone concentrations were determined on Days 0, 7, 9 and 17. The plasma estradiol-17β and progesterone concentrations at all of the days examined and conception rates did not differ significantly between the two timed AI protocols. The progesterone concentrations on Day 17 and conception rates were lower (P<0.05) for cows with low concentrations of estradiol-17β (<2 pg/ml) on Day 9 than for cows with high concentrations of estradiol-17β (≥2 pg/ml). The present study suggests that, in dairy cows with cystic ovarian diseases, addition of a CIDR to the Ovsynch protocol had no remarkable effects on plasma estradiol-17β and progesterone concentrations during and after the treatments or on conception after timed AI. This study indicates that the low plasma estradiol-17β concentration at the second administration of GnRH in the protocols can be a predictor for impaired luteal formation and lower likelihood of pregnancy in dairy cows with cystic ovarian diseases.     

Ovsynch plus CIDR protocol for timed embryo transfer in suckled postpartum Japanese Black beef cows

We compared synchronization and pregnancy rates, and the increase in blood progesterone concentrations during luteal development, between (1) Ovsynch plus an intravaginal controlled internal drug release (CIDR) device protocol followed by timed embryo transfer (timed ET), and (2) a conventional estrus synchronization method using PGF(2 alpha) and ET in suckled postpartum Japanese Black beef cows. Cows in the PGF group (n=18) received a PGF(2 alpha) analogue when a CL was first palpated per rectum at 10-d intervals after 1 to 2 month postpartum. Cows (n=11), which showed estrus (Day 0) within 5 d of the PGF(2 alpha), and had a CL on Day 7, received ET. Cows in the Ovsynch+CIDR group (n=19) underwent the Ovsynch protocol plus a CIDR for 7 d (GnRH analogue and CIDR on Day-9, PGF(2alpha) analogue with CIDR removal on Day-2, and GnRH analogue on Day 0), with ET on Day 7. The ovulation synchronization (100%) and embryo transfer (100%) rates in the Ovsynch+CIDR group were greater (P<0.01) than the estrus synchronization (66.7%) and the embryo transfer (61.1%) rates in the PGF group. The postpartum interval at ET in the Ovsynch+CIDR group (62.5 +/- 2.5 d) was shorter (P<0.01) than in the PGF group (74.9 +/- 3.9 d). The pregnancy rate in the Ovsynch+CIDR group (57.9%) did not differ significantly from that in the PGF group (50.0%). Plasma progesterone concentrations were not significantly different in the two groups on Days 0, 1, 2, 5, 7, 14 and 21. In summary, higher synchronization and transfer rates, and shorter postpartum interval to ET, can be achieved with timed ET following the Ovsynch plus CIDR protocol than after estrus with the single PGF(2 alpha) treatment followed by ET in suckled postpartum recipient beef cows. Pregnancy rates were similar. Also, the increase in blood progesterone concentrations during luteal development following ovulation synchronized by the Ovsynch plus CIDR protocol was similar to that after estrus induced by the PGF(2 alpha) treatment.     

Preventive effects of CIDR-based protocols on premature ovulation before timed-AI in Ovsynch in cycling beef cows

Ovsynch is a program developed to synchronize ovulation for timed breeding. In this paper, the authors investigate whether controlled internal drug release (CIDR)-based protocols prevent premature ovulation before timed-artificial insemination (AI) when Ovsynch is started a few days before luteolysis in cycling beef cows. Nine beef cows at 16 days after oestrus were treated with (1) Ovsynch, i.e. gonadotropin releasing hormone (GnRH) analogue on day 0, prostaglandin (PG) F(2alpha) analogue on day 7 and GnRH analogue on day 9 with timed-AI on day 10, (n=3); (2) Ovsynch+CIDR (Ovsynch protocol plus a CIDR for 7 days from day 0, n=3), or (3) oestradiol benzoate (OB)+CIDR+GnRH (OB on day 0 in lieu of the first GnRH treatment, followed by the Ovsynch+CIDR protocol, n=3). In the Ovsynch group (1) plasma progesterone concentrations fell below 0.5 ng/mL earlier (day 5) than in both CIDR-treated groups (2) and (3), where this occurred on day 8. Plasma oestradiol-17beta concentrations peaked on day 8 in the Ovsynch group and on day 9 in both CIDR-treated groups. The dominant follicle ovulated on day 10 in the Ovsynch group and on day 11 in both CIDR-treated groups. Thus, both CIDR-based protocols prevented premature ovulation before timed-AI in Ovsynch when the protocol was started a few days before luteolysis. This reflects the fact that progesterone levels remained high until the beef cattle were treated with PGF(2alpha).     

Pregnancy Rates in Angus Cross Beef Cows Bred at Observed Oestrus With or Without Second GnRH Administration in Fixed‐Time Progesterone‐Supplemented Ovsynch and CO‐Synch Protocols

Crossbred cows (n = 1073) from five locations had oestrous cycles synchronized with 100 μg of GnRH IM and insertion of controlled internal drug release device (CIDR) on Day 0 followed by 25 mg of PGF_2α IM and CIDR removal on Day 7. Kamar^® patches were placed on all cows at CIDR removal. Cows were observed three times daily for oestrus after PGF_2α administration. In the Ovsynch‐CIDR group, cows detected in oestrus (n = 193) within 48 h after PGF_2α were inseminated using the AM–PM rule. Among these cows, 80 received and 113 did not receive a second GnRH at 48 h after PGF_2α. Cows (n = 345) not detected in oestrus received a second GnRH at 48 h after PGF_2α on Day 9, and fixed‐time AI 16 h after the GnRH on Day 10. In the CO‐Synch‐CIDR group, cows detected in oestrus (n = 224) within 48 h after PGF_2α were inseminated using the AM–PM rule. Among these cows, 79 received and 145 did not receive a second GnRH at 64 h after PGF_2α. Cows (n = 311) not detected in oestrus received a second GnRH on Day 10 at the time of AI, 64 h after PGF_2α. The AI pregnancy rates were not different between the Ovsynch‐CIDR and CO‐Synch‐CIDR groups (p = 0.48). There were no differences in the AI pregnancy rates for cows inseminated at a fixed time (p = 0.26) or at detected oestrus (p = 0.79) between the treatment groups. Among cows inseminated in oestrus, there were no differences in the AI pregnancy rates between cows that received or did not receive the second GnRH (p = 0.47). In conclusion, acceptable AI pregnancy rates can be achieved with or without inclusion of oestrus detection in the Ovsynch‐CIDR and CO‐Synch‐CIDR protocols. Among cows detected in oestrus, cows that received a second GnRH yielded similar pregnancy rates when compared with cows that did not receive the second GnRH.     

Intravaginal progesterone devices in synchronization protocols for artificial insemination in beef heifers

Two experiments were designed to investigate the administration of intravaginal progesterone in protocols for oestrus and ovulation synchronization in beef heifers. In Experiment 1, cyclic Black Angus heifers (n = 20) received an Ovsynch protocol and were randomly assigned to receive (CIDR‐Ovsynch) or not (Ovsynch) a progesterone device between Days 0 and 7. Treatment with a controlled internal drug release (CIDR) device significantly increased the size of the dominant follicle prior to ovulation (12.8 ± 0.4 CIDR‐Ovsynch vs 11.4 ± 0.4 Ovsynch) (p < 0.02). Plasma progesterone concentrations throughout the experiment were affected by the interaction between group and day effects (p < 0.004). In Experiment 2, cyclic Polled Hereford heifers (n = 382) were randomly assigned to one of the six treatment groups (3 × 2 factorial design) to receive a CIDR, a used bovine intravaginal device (DIB), or a medroxiprogesterone acetate (MAP) sponge and GnRH analogues (lecirelin or buserelin). All heifers received oestradiol benzoate plus one of the devices on Day 0 and PGF on Day 7 pm (device withdrawal). Heifers were detected in oestrus 36 h after PGF and inseminated 8–12 h later, while the remainder received GnRH 48 h after PGF and were inseminated on Day 10 (60 h). The number of heifers detected in oestrus on Day 8 and conception rate to AI on Day 9 were higher (p < 0.01) in the used‐DIB than in the CIDR or MAP groups, while the opposite occurred with the pregnancy rate to FTAI on Day 10 (p < 0.01). There was no effect of progesterone source, GnRH analogue or their interaction on overall pregnancy rates (64.9%). Progesterone treatment of heifers during an Ovsynch protocol resulted in a larger pre‐ovulatory follicle in beef heifers. Progesterone content of intravaginal devices in synchronization protocols is important for the timing of AI, as the use of low‐progesterone devices can shorten the interval to oestrus.     

Comparison of two types of CIDR-based timed artificial insemination protocols for repeat breeder dairy cows

This study compared two types of controlled internal drug release (CIDR)-based timed artificial insemination (TAI) protocol for treatment of repeat breeder dairy cows. In the first trial of the experiment, 55 repeat breeder cows were randomly assigned to the following two treatments. (1) In the EB group, a CIDR device was inserted into the cows, and then the cows were administered an injection of 1 mg estradiol benzoate (EB) plus 50 mg progesterone (P4; Day 0). On Day 7, they were given an injection of PGF(2alpha) and the CIDR device was removed. The cows were given an injection of 1 mg EB on Day 8 and were subjected to TAI 30 h later (n=27). (2) In the gonadotrophin releasing hormone (GnRH) group, a CIDR device was inserted into the cows, and then the cows were administered an injection of 250 microg gonadorelin (GnRH; Day 0). On Day 7, they were given an injection of PGF(2alpha) and the CIDR device was removed. The cows were given an injection of 250 microg GnRH on Day 9 and were subjected to TAI 17 h later (n=28). In the second trial, 41 repeat breeder cows that were confirmed as not pregnant in the first trial were randomly assigned to the same two treatments used in the first trial (an EB group of 20 cows and a GnRH group of 21 cows). The ovaries of 15 cows from each group were examined by transrectal ultrasonography in order to observe the changes in ovarian structures, and blood samples were collected for analysis of serum P4 concentrations. The pregnancy rates following TAI in the first (18.5 vs. 32.1%) and second (40.0 vs. 38.1%) trials and the combined rates (27.7 vs. 34.7%) did not differ between the EB and GnRH groups. The proportions of cows with follicular wave emergence within 7 days did not differ between the EB (12/15) and GnRH groups (13/15). The interval to wave emergence was shorter (P<0.01) in the GnRH group than in the EB group, but there was no difference in the mean diameters of dominant follicles on Day 7 between the groups. Moreover, the proportions of cows with synchronized ovulation following a second EB or GnRH treatment did not differ between the groups. In conclusion, treatment with either EB or GnRH in a CIDR-based TAI protocol results in synchronous follicular wave emergence, follicular development, synchronous ovulation, and similar pregnancy rates for TAI in repeat breeder cows.     

Induction of ovulation with GnRH and PGF2alpha in lactating Bos taurus x Bos indicus cows

Induction of ovulation for timed artificial insemination (TAI) with the Ovsynch protocol was evaluated in 49 anoestrous and lactating Bos taurus x Bos indicus cows. Palpation per rectum and transrectal ultrasonography were used on Days -30, -20, -10 and 0 (start of treatment) to confirm anoestrus but with the presence of follicles > or = 10 mm, and every other day during treatment to determine ovarian activity. Cows were randomly assigned to: (1) Ovsynch (n = 24; Day 0, 200 microg GnRH; Day 7, 150 microg PGF2alpha; Day 9, 200 microg GnRH + TAI 16 to 20 h later) and (2) control (n = 25; no treatment). Rates of ovulation for the first GnRH injection, detection of a corpus luteum (CL) at PGF2alpha injection, pregnancy and induction of cyclicity were greater (P < 0.05) with Ovsynch. There was no effect of body condition score (P > 0.05). In conclusion, the Ovsynch protocol was not effective in obtaining acceptable pregnancy rate for TAI, but it was effective for induction of cyclicity in anoestrous and lactating Bos taurus x Bos indicus cows under tropical conditions.     

The effects of administering estradiol benzoate plus progesterone during the growth or static phases of the dominant follicle in CIDR-treated lactating dairy cows

We studied the effects of administering estradiol benzoate (EB) plus progesterone (P4) as part of a CIDR-based protocol during the growth or static phases of dominant follicle development on follicular wave emergence, follicular growth, synchrony of ovulation and pregnancy rate following CIDR withdrawal, treatment with PGF(2alpha) and GnRH, and fixed-time artificial insemination (TAI). Forty-one previously synchronized lactating Holstein dairy cows were randomly allocated to three treatment groups. The control group (n=14) received a CIDR on the third day after ovulation only (Day 0). The two treatment groups were administered CIDRs comprising 2 mg EB and 50 mg P4 either on the third (T1, n=14) or eighth day (T2, n=13) after ovulation (Day 0). All cows received PGF(2alpha) after CIDR removal on Day 7, GnRH on Day 9, and TAI 16 h after GnRH treatment. The proportion of cows with follicular wave emergence within 8 days of treatment differed (P<0.01) among the control (14.3%), T1 (85.7%), and T2 groups (92.9%). However, the mean intervals between treatment and wave emergence were not significantly different. There were significant differences in the diameters of the dominant follicles on Day 7 (P<0.01) and in preovulatory follicles on Day 9 (P<0.01), with the largest follicles observed in the control group and the smallest follicles observed in the T2 group. In contrast, the numbers of cows showing synchronous ovulation after GnRH treatment (92.9 to 100.0%) and pregnancy following TAI (46.2 to 50.0%) were similar between the treatment groups. The results showed that, irrespective of the phase (growth or static) of the dominant follicle, administration of 2 mg EB plus 50 mg P4 to CIDR-treated lactating dairy cows induced consistent follicular wave emergence and development, synchronous ovulation after GnRH administration, and similar pregnancy rates following TAI.     

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.     

Calf removal improves conception rates to the Ovsynch and CO-Synch protocols

Beef cows (n = 473) from two locations were stratified by breed, postpartum interval, age, and AI sire and were randomly allotted to one of four treatments for synchronization of ovulation. Ovulation synchronization protocols included the Ovsynch protocol with (n = 114) or without (n = 123) 48-h calf removal from d 7 to 9 (d 0 = 1st GnRH injection) or the CO-Synch protocol with (n = 119) or without (n = 117) 48-h calf removal from d 7 to 9. The Ovsynch protocol included administration of GnRH (100 microg; i.m.) on d 0, PGF2alpha (25 mg; i.m.) on d 7, GnRH (100 microg; i.m.) on d 9, and timed insemination on d 10. The CO-Synch protocol included administration of GnRH (100 microg; i.m.) on d 0, PGF2alpha (25 mg; i.m.) on d 7, and GnRH (100 microg; i.m.) with timed insemination on d 9. Blood samples were collected from all cows on d -10 and d 0 for analysis of serum progesterone. Cows with at least one serum progesterone concentration greater than 1 ng/mL were considered to be cyclic at the time of treatment. Conception rates of cows that received the CO-Synch + calf removal, Ovsynch + calf removal, CO-Synch, or Ovsynch protocol (63, 61, 54, and 52%, respectively) were not different (P = 0.50). Conception rates were not different (P = 0.80) among CO-Synch- and Ovsynch-treated cows; however, both estrual status and 48-h calf removal affected conception rates. Conception rates of cyclic cows (66%) were greater (P = 0.01) than those of anestrous cows (53%), regardless of which synchronization protocol was used. When data were pooled across synchronization protocol, conception rates of cows with 48-h calf removal (62%) were greater (P = 0.09) than conception rates of cows without calf removal (53%). The CO-Synch + calf removal protocol induces a fertile ovulation in cyclic and anestrous cows, requires handling cattle just three times, results in high conception rates from timed insemination, and should be a useful program for synchronization of ovulation in beef cows.     

Effect of estrus synchronization protocols on plasma progesterone profile and fertility in postpartum anestrous Kankrej cows

The study was aimed at induction/synchronization of estrus in postpartum anestrous Kankrej cows of zebu cattle maintained at an organized farm. The study included use of different hormone protocols, viz., Ovsynch, CIDR (controlled internal drug release), Ovsynch plus CIDR, and Heatsynch with estimation of plasma progesterone on days 0, 7, 9/11 (artificial insemination--AI) and on day 20 post-AI following fixed time insemination. Thirty selected anestrous animals were divided into five equal groups (four treatment and one control), and the findings were compared with the normal cyclic control group of six cows. All the protocols were initiated in cows with postpartum anestrous period of more than 4 months, considering the day of first GnRH injection or CIDR insertion as day 0. The animals were bred by fixed time artificial insemination. Pregnancy was confirmed per rectum on day 60 post-AI in non-return cases. The conception rates at induced/first heat in Ovsynch, CIDR, Ovsynch + CIDR, and Heatsynch protocols were 33.33, 66.66, 50.00 and 16.67%, respectively. The corresponding overall conception rates of three cycles post-treatment were 50.00% (3/6), 100.00% (6/6), 66.66% (4/6), and 50.00% (3/6). In normal cyclic and anestrous control groups, the pooled pregnancy rates were 83.33% (5/6) and 16.67% (1/6), respectively. The pooled mean plasma progesterone (nanograms per milliliter) concentrations were significantly (P < 0.05) higher on day 7 in Ovsynch (5.727 ± 1.26), CIDR (4.37 ± 0.66), Ovsynch plus CIDR (3.55 ± 0.34), and Heatsynch (5.92 ± 1.11) protocols as compared with their corresponding values obtained on days 0, 9/11 (AI), and on day 20 post-AI. In anestrous control group, the mean progesterone concentration at the beginning of experiment was 0.67 ± 0.33 ng/ml, which was at par with values of all other groups. The overall plasma progesterone levels on the day of initiating treatment were low in all groups, with smooth small inactive ovaries palpated per rectum twice at 10 days interval, suggesting that most of the animals used in the study were in anestrous phase. Mean (± SE) values of plasma progesterone (nanograms per milliliter) on day 20 post-AI were higher in conceived cows than the non-conceived cows of all the groups, but differed significantly (P < 0.05) only in normal cyclic group. These results suggest that use of different hormone protocols particularly Ovsynch, CIDR, and Ovsynch + CIDR may serve as an excellent tool for induction and synchronization of estrus and improvement of conception rate in postpartum anestrous Kankrej cows.     

Evaluation of the effect of a 3rd GnRH injection administered six days after the 2nd GnRH injection of Ovsynch on the reproductive performance of Japanese black cows

This study was designed to evaluate the reproductive performance of Japanese black cows following the 3rd injection of gonadotropin releasing hormone (GnRH) analogue administered concurrently with Ovsynch-based treatment on day 6 (day 1 = the day of ovulation). In Experiment 1, 12 cows were allocated into three groups: a control group that was subjected to Ovsynch treatment and then injected with a placebo on day 6; group 1 (Ovsynch + GnRH), which was subjected to Ovsynch treatment and was injected with GnRH analogue on day 6, and group 2 (Ovsynch + controlled internal drug-release (CIDR) + GnRH), which received Ovsynch-CIDR treatment and was injected with GnRH analogue on day 6. Blood collection and ultrasonographic observation of the ovaries were conducted daily. Both treatments induced the formation of an accessory corpus luteum and significantly increased the cross-sectional area of the luteal tissue when compared to the control. However, plasma progesterone (P₄) was significantly higher in the treatment groups than in the control group on days 11, 12, 17 and 18 in the group 1 and from day 10 to 21 in the group 2. In Experiment 2, 41 cows were assigned to the same three groups described above and then artificially inseminated on day 1. The pregnancy rates on day 45 did not differ among groups. In conclusion, administration of GnRH analogue on day 6 following Ovsynch-based treatment did not improve the reproductive performance of Japanese black cows, even though the P₄ concentration was higher in groups that received the GnRH.     

Insemination at the second of two induced oestrous periods in anoestrous dairy cows increases conception rates to first service

AIM: To determine whether mating previously anoestrous cows on their second, rather than first, oestrus post pm-turn could increase conception rates to that service. METHODS: Cows diagnosed as anovulatory anoestrus were allocated to two groups, starting treatment on Day -17 (OES2) or on Day -7 (OESI) where the date of the planned start of mating = Day 0. All cows were treated with intravaginal progesterone (CIDR device) for 6 days and an injection of 1 mg oestradiol benzoate 24 h after removal of the device. Cows in the OES2 group were also injected with prostaglandin F2alpha on Day 0. RESULTS: During the first 7 days of mating, 61.8% (207/335) and 88.2% (328/372) of cows in the OES2 and OESl groups, respectively, were inseminated on detection of oestrus (p <0.001). Oestrus without ovulation occurred in 1.5% of cows in the OES2 group and 6.2% of cows in the OESl group during this period (p <0.01). Of those cows inseminated in the first week of mating, conception rates were 54.0% in the OES2 group and 45.5% in the OESl group (p = 0.05). There was no significant difference in median interval from start of mating to conception between the two groups (24 and 22 days for OES2 and OESl, respectively, p >0.05). CONCLUSION: Mating previously anoestrous cows on their second, rather than first oestrus post partum increased conception rates to that service. However, median intervals from start of mating to conception were not altered.     

Supplementing treated anoestrous dairy cows with progesterone does not increase conception rates

AIM: To determine whether conception rates of anoestrous dairy cows treated with progesterone and oestradiol benzoate (ODB) could be increased by treating them with additional progesterone following insemination at the induced oestrus. METHODS: Cows which had not been detected in oestrus for at least 21 days after calving in 18 herds were confirmed anovulatory anoestrus (AA) by veterinary examination, due to the absence of a detectable corpus luteum in the ovaries. All cows were treated with intra-vaginal progesterone (CIDR insert) for 6 days and injected with 1 mg ODB 24 h after insert removal (Day 0). Only cows which were seen in oestrus on Days 0, 1 or 2 were enrolled in the trial. These cows were either treated with a second CIDR insert on Day 8, for 7 days (P4+; n=422), or remained untreated (Control; n=756). Milk progesterone concentrations were measured in a subset of enrolled cows (n=669) on Day 8 to determine the proportion of cows that ovulated following the induced oestrus. RESULTS: Conception rates to first insemination were similar in P4+ and Control cows (40.3% and 37.2%, p=0.59). Of cows which had milk progesterone concentrations measured on Day 8, 78.6% displayed oestrus and ovulated, (range: 53.8% to 94.6% among herds). Of the cows that ovulated, conception rate to first insemination was 46.8% and 43.5% in P4+ and Control cows, respectively (p=0.86). CONCLUSION: Conception rates to first insemination in AA cows treated with progesterone and ODB were not increased by progesterone supplementation using CIDR inserts following insemination. KEY WORDS: dairy cattle, postpartum anoestrus, reproduction, progesterone treatment, CIDR insert.     

Comparison of effects of GnRH and prostaglandin in combination, and prostaglandin on conception rates and time to conception in dairy cows

OBJECTIVE: To assess the effectiveness of a gonadotrophin-releasing hormone (GnRH) / prostaglandin program (GnRH-PG-GnRH, Ovsynch) on conception rates and time to conception of lactating dairy cows compared with a PG program (double prostaglandin injection). DESIGN: A randomised multi-centre cohort study was conducted with 778 cows from nine dairy herds. Cows at different stages of lactation were randomly assigned, after matching for days open at the time of treatment, to either the PG or Ovsynch program. PROCEDURE: Cows on the PG program received two intramuscular injections of prostaglandin (2 mL, Prosolvin) 11 days apart. The Ovsynch program consisted of two intramuscular injections of GnRH (1 mL, Fertagyl) 9 days apart, separated by one injection of prostaglandin 40 h before the second GnRH injection. Milk samples were taken at the time of artificial insemination and assayed for progesterone by radioimmunoassay. RESULTS: The Ovsynch program was not significantly different to PG in achieving conception, with overall conception rates of 37.6% and 41.4%, respectively, for each program. There was, however, a significant interaction between the effects of parity and treatment (P = 0.03), because conception rates were higher in older cows (parity 5 or more) on the PG program than for older cows on the Ovsynch program. There was no significant effect of treatment (P > 0.5) on time to conception after treatment, but older cows were slower to conceive (P < 0.0001). Conception rates differed (P < 0.0001) among herds. CONCLUSION: The median days to conception for both groups was 22 and mean days from treatment to conception were 36.3 +/- 3.3 and 31.6 +/- 2.7 for the Ovsynch and PG programs respectively, indicating that reproductive performance of cows was not significantly different with Ovsynch program or PG program. There appears to be a need to evaluate causes of reproductive failure in older cows.     

Administration of human chorionic gonadotropin to suckled beef cows before ovulation synchronization and fixed-time insemination: replacement of gonadotropin-releasing hormone with human chorionic gonadotropin

Two experiments were conducted to evaluate whether hCG administered 7 d before initiating the CO-Synch + controlled internal drug release (CIDR) ovulation synchronization protocol (Exp. 1 and 2), or replacing GnRH with hCG at the time of AI (Exp. 1), would improve fertility to a fixed-time AI (TAI) in suckled beef cows. In addition, the effects of hCG on follicle dynamics, corpus luteum development, and concentrations of progesterone (P4) were evaluated. In Exp. 1, cows were stratified by days postpartum, age, and parity and assigned randomly to a 2 × 2 factorial arrangement of 4 treatments: 1) cows received 100 μg of GnRH at CIDR insertion (d -7) and 25 mg of PGF(2α) at CIDR removal (d 0), followed in 64 to 68 h by a TAI plus a second injection of GnRH at TAI (CG; n = 29); 2) same as CG but the second injection of GnRH at the time of insemination was replaced by hCG (CH; n = 28); 3) same as CG, but cows received hCG 7 d (d -14) before CIDR insertion (HG; n = 28); and 4) same as HG, but cows received hCG 7 d (d -14) before CIDR insertion (HH; n = 29). Pregnancy rates were 52, 41, 59, and 38% for GG, GH, HG, and HH, respectively. Cows receiving hCG (39%) in place of GnRH at TAI tended (P = 0.06) to have poorer pregnancy rates than those receiving GnRH (56%). Pre-CO-Synch hCG treatment increased (P < 0.05) the percentage of cows with concentrations of P4 >1 ng/mL at d -7, increased (P < 0.02) concentration of P4 on d -7, and decreased (P < 0.001) the size of the dominant follicle on d 0 and 3, compared with cows not treated with hCG on d -14. In Exp. 2, cows were stratified based on days postpartum, BCS, breed type, and calf sex and then assigned to the CG (n = 102) or HG (n = 103) treatments. Overall pregnancy rates were 51%, but no differences in pregnancy rates were detected between treatments. Pre-CO-Synch hCG treatment increased (P < 0.05) the percentage of cows cycling on d -7 and increased (P < 0.05) concentrations of P4 on d -7 compared with pre-CO-Synch controls. Therefore, pretreatment induction of ovulation after hCG injection 7 d before initiation of CO-Synch + CIDR protocol failed to enhance pregnancy rates, but replacing GnRH with hCG at the time of AI may reduce pregnancy rates.     

Estrous synchronization using an intravaginal progesterone device in combination with gnrh or estradiol benzoate characterized by the initial ovarian conditions in Japanese black cows

Estrous synchronization using a Controlled Internal Drug Releasing device (CIDR) in combination with GnRH or estradiol benzoate (EB) treatment was investigated in Japanese black cows characterized with initial ovarian conditions. A total of 142 cows were allocated to one of four treatments: insertion of CIDR for eight days (Group A: n=34), CIDR with 100 microg of GnRH on d 0 (Group B: n=54, d 0=CIDR insertion), CIDR with GnRH on d 0 and 1 mg of EB on d 10 (Group C: n=20) or CIDR with 2 mg of EB on d 0 and 1 mg of EB on d 9 (Group D: n=34). All cows received 25 mg of PGF(2alpha) on d 7 and blood was collected for progesterone (P4) analysis on d 0, 8, and 21. AI was performed at estrus, but in Group D timed AI was set following a day of EB treatment. Estrus was induced in 141/142 cows, and the majority of which occurred on d 10 and 11 (98 cows, 34 cows). GnRH treatment induced more intermediate ovulation than EB treatment in cows with CL on d 0 (19.0% vs. 0%). Ovulation after CIDR removal was significantly higher in cows with CL on d 0 compared to those without CL (87.0% vs. 71.4%). Group B showed higher conception rates than those combined with Groups C and D where EB was injected after CIDR removal (51.1% vs. 38.9%). Conception had no correlation with either CL existence on d 0 or intermediate ovulation on d 8. P4 concentrations on d 8 were significantly lower compared to those on d 0 or d 21. On d 21 in cows without intermediate ovulation, Group A showed significantly lower P4 concentrations than the other 3 groups. The data suggests that CIDR insertion with PGF(2alpha) treatment is an effective method for estrous synchronization irrespective of initial ovarian conditions, and GnRH treatment at CIDR insertion induces intermediate ovulation and improves the conception rate in Japanese black cows.     

The reproductive performance of dairy cows with anovulatory anoestrus that were injected with either gonadotrophin-releasing hormone or oestradiol benzoate as part of a re-treatment process after insemination

This experiment compared the reproductive performance of synchronised anoestrous dairy cows that were treated initially with a combination of progesterone and oestradiol benzoate and then with either gonadotrophin-releasing hormone (GnRH) or oestradiol benzoate to resynchronise returns to service. It was hypothesised that injecting anoestrous dairy cows with GnRH 12-15 days after insemination and coinciding with the time of insertion of a controlled intravaginal progesterone-releasing (CIDR) device would increase conception rates to the preceding 1st insemination compared with oestradiol benzoate treated cows; both GnRH and oestradiol benzoate would resynchronising the returns to service of those cows that did not conceive to the preceding insemination. Groups of cows in 11 herds were presented for a veterinary examination after they had not been seen in oestrus postpartum. Those cows diagnosed with anovulatory anoestrus (n = 1112) by manual rectal palpation and/or ultrasonography were enrolled in the trial. Each enrolled cow was injected with 2 mg oestradiol benzoate i.m. on Day -10, (where Day 0 was the 1st day of the planned insemination) concurrently with vaginal insertion of a CIDR device. The device inserted was withdrawn on Day -2 and then each cow injected i.m. with 1 mg of oestradiol benzoate on Day -1 unless it was in oestrus. Observation for oestrus preceded each insemination. Every cow that had been inseminated on Days -1,0,1 or 2 was presented for treatment for resynchrony on Day 14 (n = 891). They were divided into 2 groups; those with an even number were each injected i.m. with 250 microg of a GnRH agonist (Treatment group n = 477); each of the cows with an odd number injected i.m. with 1 mg of oestradiol benzoate (control group, n = 414). Each GnRH or oestradiol benzoate injection preceded reinsertion of a CIDR device previously inserted from Days -10 to -2. It was withdrawn on Day 22, 24 hours before injecting 1 mg oestradiol benzoate. Cows observed in oestrus were submitted for a 2nd insemination. Every enrolled cow still present in the herd was pregnancy tested by palpation of uterine contents per rectum about 6 weeks later and again at the end of a herd's seasonal breeding programme. The alternative use of GnRH instead of oestradiol benzoate did not affect the percentage of cows conceiving within 3 days of the mating start date (MSD) (35.6 % vs 35.3 %, P = 0.90), resubmission rates for a 2nd insemination among cows not pregnant to the 1st insemination (81.6 % vs 83.5 %, P = 0.41), 6-week pregnancy rate (59.3 % vs 60.6 %, P = 0.65), 21-weekpregnancy rate (86.6 vs 85.0, P = 0.36), mean interval from MSD to conception (32.5 +/- 1.8 days vs 29.9 +/- 1.8 days, P = 0.26) or conception rate of cows reinseminated by Day 28 (43.3 % vs 38.8 %, P = 0.39). When GnRH was compared with oestradiol benzoate, it did not increase conception rates to the 1st service; it was as effective as oestradiol benzoate in synchronising returns to service in previously treated anoestrous cows that did not conceive to the 1st service. Its use affected neither conception rates to the preceding 1st inseminations nor to the following 2nd inseminations.     

GnRH treatment at CIDR insertion influences ovarian follicular dynamics in Japanese black cows

Ovarian follicular dynamics and estrous synchronization after Gonadotropin-releasing hormone (GnRH) treatment at Controlled Internal Drug Releasing device (CIDR) insertion were investigated in Japanese Black cows. CIDR was inserted for eight cows at 7 days after estrus. Cows were allocated to either Group A: 8-day CIDR insertion with GnRH treatment on d 0 (n=4, d 0=CIDR insertion) or Group B: 8-day CIDR insertion (n=4). Both groups were injected with prostaglandin F2alpha (PGF2alpha) on d 7. Ultrasonography and blood sampling were performed twice daily. Intensive sampling was performed every 15 min for 8 hr to determine the pulsatile release of LH on d -1, d 5 and d 10. Three of four cows showed intermediate ovulation within 2 days after GnRH treatment during CIDR insertion in Group A, whereas no ovulation was found in Group B. Three of four cows in Group A and all four cows in Group B ovulated after CIDR removal. Plasma progesterone concentrations from d 3 to d 7 in three intermediate ovulatory cows in Group A (8.4 +/- 1.6 ng/ml) was significantly higher than those in Group B (4.1 +/- 1.2 ng/ml; 4 cows) during CIDR insertion (P<0.01). Interval to estrus and ovulation after CIDR removal was observed at 60.0 +/- 12.0 hr and 76.0 +/- 6.9 hr in three cows in Group A, and 75.0 +/- 15.1 hr and 93.0 +/- 20.5 hr in Group B, respectively. There was a significant increase in LH pulse frequency on d 10 compared on d -1 or d 5 in both groups (P<0.05), in addition those on d 10 in Group A tended to be higher than in Group B. As a result, GnRH treatment at CIDR insertion at 7 days after estrus induced intermediate ovulation with formation of corpus luteum (CL) and rather synchronized emergence of ovulatory follicle during CIDR insertion. These induced CL increased plasma progesterone concentrations and contributed to precise synchronization.