Comparison of an oestrus synchronisation protocol with oestradiol benzoate and PGF2alpha and insemination at detected oestrus to a timed insemination protocol (Ovsynch) on reproductive performance of lactating dairy cows

A total of 226 out of 245 postpartum lactating dairy cows in a commercial dairy farm were allocated to two groups of oestrous synchronisation protocols in order to evaluate reproductive performance. One group was treated with oestradiol benzoate (ODB) and PGF2alpha on day 10 of the oestrous cycle with insemination at the detected oestrus, the second group underwent the Ovsynch (OVS) protocol (GnRH + PGF2alpha + GnRH) with timed AI. Pregnancy was diagnosed by ultrasonography on day 28 after AI and confirmed by rectal palpation on day 45. A higher (P < 0.001) proportion of cows in OVS (100%) were inseminated within (19.2 +/- 3.8 h) following the second GnRH injection than those of cows in EPE (ODB + PGF2alpha + ODB) (70.6%) inseminated at the detected oestrus within (35.6 +/- 5.2 h) following the second ODB injection. Pregnancy rates for the first AI at day 28 (64.0 +/- 4.6, 62.4 +/- 5.5%) and at day 45 post-insemination (40.4 +/- 4.7, 40.0 +/- 5.6%) for OVS and EPE cows respectively, did not differ between the two treatments, whereas, the overall pregnancy rates tended to be higher (P < 0.08) for the OVS (85.1 +/- 3.8%) cows than the EPE cows (74.1 +/- 4.5%). No differences were observed in pregnancy rates for first AI and overall up to fourth AI between primiparous (34.7 +/- 5.8 and 85.3 +/- 4.7%) and multiparous cows (43.5 +/- 4.5 and 77.4 +/- 3.6%). Days open for pregnant cows tended to be lower (P < 0.08) for OVS (76.2 +/- 3) than for EPE cows (84.7 +/- 4), while days open were higher (P < 0.05) in primiparous cows (85.3 +/- 4) than in multiparous cows (75.6 +/- 3). The results indicate that pregnancy rates for first AI were similar, but overall pregnancy rates up to the fourth AI tended to be higher for OVS than EPE cows, while days open was tended to be lower for OVS than EPE cows.     

Effect of treatment with progesterone and oestradiol benzoate on ovarian follicular turnover in postpartum anoestrous cows and cows which have resumed oestrous cycles.

Two experiments were carried out to determine the effect of a low dose of progesterone (P) with and without the addition of an injection of oestradiol benzoate (ODB) on ovarian follicle dynamics, oestradiol production and LH pulsatility in postpartum anoestrous cows, compared with cows which had resumed oestrous cycles (cycling cows). In the first experiment, anoestrous Jersey cows were treated with (AN+P, n=8) or without (AN-3, n=3) a previously used intravaginal progesterone releasing (CIDR) device for 10 days, commencing 3 or 4 days after emergence of a new dominant follicle (DF1) as determined by transrectal ultrasonography. Contemporary cycling cows (CYC+P, n=8) were similarly treated with used CIDR devices and injected with prostaglandin F(2alpha) (PGF) at the time of device insertion. Follicle turnover was monitored by daily ultrasonography and pulsatile release of LH was measured on the ninth day after device insertion. During the period of CIDR device insertion, a second dominant follicle emerged in 4/8 of the CYC+P group and 7/8 of the AN+P group (P=0.14). Maximum diameter of DF1 was greater in cows in the CYC+P compared with the AN+P group (P=0.02), but did not differ between cows in the AN+P and AN-P groups (P>0.1). Frequency of LH pulses was greater in cows in the CYC+P than AN+P group (P=0.06), and in cows in the AN+P than AN-P group (P=0.02).In the second experiment, anoestrous (n=20) and cycling (n=11) Friesian cows were treated with a new CIDR device for 6 days commencing 3 days after emergence of a new dominant follicle (DF1). Cycling cows were also injected with PGF on the day of device insertion. Half of the cows in each group were injected with 2mg ODB on the day of device insertion. Daily ultrasonography was used to monitor follicular dynamics throughout the experimental period. Follicular turnover was increased by ODB in cycling (5/5 versus 1/6; P<0.05), but not anoestrous cows (5/9 versus 4/11). Persistence of DF1 was reduced by ODB treatment in both cycling and anoestrous cows (P<0.001). Maximum diameter of DF1 was influenced by ODB treatment and reproductive status (P<0.05). In anoestrous cows in which a second dominant follicle did not emerge during the period of device insertion, the interval from emergence of DF1 to emergence of a second dominant follicle was significantly delayed by treatment with ODB (P=0.04).In conclusion, P treatment of anoestrous cows increased pulsatile release of LH, but did not induce the development of persistent follicles. Injection of ODB in association with P treatment reduced the persistence of dominant follicles in both cycling and anoestrous cows, but delayed subsequent follicular development in a proportion of anoestrous cows.     

Effects of maturity of the potential ovulatory follicle on induction of oestrus and ovulation in cattle with oestradiol benzoate

The effect of maturity of the dominant follicle (DF) on the capacity of oestradiol benzoate (ODB) to induce oestrus and ovulation was examined in cattle. In experiment 1, 31 prepubertal heifers each received an intravaginal progesterone insert (IPI) and 1mg ODB i.m./500kg BW (ODB1). Daily ovarian ultrasonography detected emergence of a new follicular wave 3.1+/-0.1 days after ODB1. The IPI was removed when newly emerged DF were "young" (1.3+/-0.1 days after emergence; YDF; n=15) or "mature" (4.2+/-0.1 days; MDF; n=16), and 24h later, heifers received 0.75mg ODB/500kg BW (ODB2; n=16) or no further treatment (NoODB2; n=15). Most of the heifers receiving ODB2 were observed in oestrus (15/16) and ovulated (12/16), as compared to 0/15 and 1/15 in the NoODB2 group, respectively (P<0.01). In experiment 2, 32 heifers received ODB1 on day 6 of the oestrous cycle, and new follicular wave emergence was detected 3.2+/-0.1 days later. Heifers received an injection of prostaglandin-F2alpha (PGF) when the DF was young (1.1+/-0.1 days after emergence; YDF; n=16) or mature (4 days; MDF; n=16), and then ODB2 24h later or no further treatment (NoODB2). The interval from PGF to oestrus was greater (P<0.01) in the YDF-NoODB2 (70+/-3.9h) as compared to MDF-NoODB2 group (57+/-1.8h). Inclusion of ODB2 reduced (P<0.01) this interval to 47.0+/-0.7h without regard to the maturity of the DF (maturityxODB2, P<0.05) and also reduced (P<0.05) the interval to ovulation. In experiment 3, 21 suckling anoestrous cows received an IPI and ODB1 at 29.3+/-1.7 days postpartum. The IPI were removed either 1 day (YDF; n=9) or 3.9+/-0.1 days (MDF; n=9) after emergence of a new follicular wave and every cow received ODB2. Oestrus was subsequently detected in all but one animal. Ovulation of the newly emerged DF was detected within 48h of ODB2 in nine of nine cows of the MDF group, and in four of nine of the YDF group (P<0.05). During the subsequent ovulatory cycle, luteal size and plasma concentrations of progesterone were greater (P<0.01) in the MDF group compared to the YDF group. We conclude that behavioural oestrus is readily induced by 0.75mg ODB i.m./500kg BW. Maturity of the DF appeared to have little influence on the ability of the DF to ovulate in heifers. In contrast, young DF in lactating anoestrous cows were less likely to respond to the ovulatory cue provided, and luteal development was compromised in those that did ovulate.     

Efficacy of intermittent or continuous administration of GnRH in inducing ovulation in early and late seasonal anoestrus in the Père David's deer hind (Elaphurus davidianus)

Père David's deer hinds were treated with GnRH, administered as intermittent i.v. injections (2.0 micrograms/injection at 2-h intervals) for 4 days, or as a continuous s.c. infusion (1.0 micrograms/h) for 14 days. These treatments were given early (February-March) and late (May-June) in the period of seasonal anoestrus. The administration of repeated injections of GnRH increased mean LH concentrations from pretreatment values of 0.54 +/- 0.09 to 2.10 +/- 0.25 ng/ml over the first 8 h of treatment in early anoestrus, and from 0.62 +/- 0.11 to 2.73 +/- 0.49 ng/ml in late anoestrus. The mean amplitude of GnRH-induced LH episodes was greater (P less than 0.01) in late (4.03 +/- 0.28 ng/ml) than in early (3.12 +/- 0.26 ng/ml) anoestrus, but within each replicate (early or late anoestrus), neither mean LH episode amplitude nor mean plasma LH concentrations differed significantly between the four periods of intensive blood sampling. On the basis of their progesterone profiles, 6/12 hinds had ovulated in response to treatment with injections of GnRH (1/6 in early anoestrus and 5/6 in late anoestrus), and oestrus and a preovulatory LH surge were recorded in all of these animals. Oestrus and a preovulatory LH surge were also recorded in one other animal treated in early anoestrus in which progesterone concentrations remained low. The mean times of onset of oestrus (91.0 +/- 1.00 and 62.4 +/- 0.98 h) and of the preovulatory LH surge (85.8 +/- 3.76 and 59.4 +/- 0.25 h) both occurred significantly earlier (P less than 0.001) in animals treated in late anoestrus. Continuous infusion of GnRH to seasonally anoestrous hinds resulted in an increase in mean plasma LH concentrations, but this response did not differ significantly between early (2.15 +/- 0.28 ng/ml) and late (2.48 +/- 0.26 ng/ml) anoestrus. Ovulation, based on progesterone profiles, occurred in 2/7 hinds in early anoestrus and in 4/6 hinds in late anoestrus. Oestrus was detected in all except one of these hinds. The mean time of onset of oestrus occurred earlier in animals treated in late anoestrus (66.2 +/- 0.32 h and 46.7 +/- 0.67 h, P less than 0.01). The administration of GnRH, given either intermittently or continuously, will induce ovulation in a proportion of seasonally anoestrous Père David's deer. However, more animals ovulate in response to this treatment in late than in early anoestrus (75% compared with 23%).     

Effect of artificial insemination on submission rates of lactating dairy cows synchronised and resynchronised with intravaginal progesterone releasing devices and oestradiol benzoate

This study investigated the hypothesis that a reduction in submission rates at a resynchronised oestrus is not due to the resynchrony treatment involving intravaginal progesterone releasing devices (IVDs) and oestradiol benzoate (ODB) but is associated with artificial insemination (AI) at the first synchronised oestrus. In Experiment 1, cows were synchronised for first oestrus with IVDs, with ODB administered at the time of device insertion (Day 0, 2 mg IM) and 24 h after removal (Day 9, 1 mg IM) and PGF(2alpha) injected at the time of device removal. Cows were then either inseminated (I) for 4 days or not inseminated (NI) following detection of oestrus (first round of AI). Every animal was resynchronised for a second round of AI by reinsertion of IVDs on Day 23 with administration of ODB (1 mg IM) at the time of insertion as well as 24 h after removal (Day 32). Cows detected in oestrus and inseminated for 4 days at the second round of AI were resynchronised for a third round by repeating the resynchrony treatment starting on Day 46 and inseminating cows on detection of oestrus for 4 days. In Experiment 2 the same oestrous synchronisation and resynchronisation treatments were used, but the timing of treatments differed. The cows had their cycles either presynchronised (treatment start Day -23) without AI and then resynchronised, starting on Day 0, for the first round of AI for AI at detected oestrus for 4 days, or they were synchronised (treatment start Day 0) for the first round of AI. In Experiment 1, 91.4% (64/70) and 92.6% (63/68) (P = 0.79) of cows in the I and NI treatments, respectively, were detected in oestrus after the initial synchronisation. At the second round of AI, submission rates for insemination were lower in the I group compared to the NI cows (74.5%, 35/47 versus 92.6%, 63/68, respectively; P = 0.007). Pregnancy rates (proportion treated that were classified as becoming pregnant) in I and NI cows 4 weeks (61.4%, 43/70 versus 63.2%, 43/68) and 7 weeks (77.1%, 54/70 versus 69.1%, 47/68) after the AI start date (AISD) did not differ significantly between treatments. In Experiment 2, presynchronisation and then resynchronisation of oestrous cycles before the first round of AI did not affect oestrous detection rates at the first round of AI (100%, 44/44 versus 98.0%, 50/51; P = 0.54), or pregnancy rates 1 week (63.6%, 28/44 versus 60.8%, 31/51; P = 0.70), 4 weeks (72.7%, 32/44 versus 76.5%, 39/51; P = 0.76) and 7 weeks (81.8%, 36/44 versus 88.2%, 45/51; P = 0.40) after AISD compared to cows that had their cycles synchronised for the first round of AI. These findings support our hypothesis that a reduction in submission rates at a resynchronised oestrus is associated with AI at the first synchronised oestrus and not due to a resynchrony treatment involving IVDs and ODB. This study supports the concept that early embryonic loss following AI at a synchronised oestrus could cause a reduction in submission rates following resynchronisation of oestrus, although investigation of the effect of passing an AI catheter or semen components were not studied per se.     

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 2mg EB plus 50mg P4 (EB+P4 group) or with an injection of 100 microg GnRH (GnRH group) at the beginning of the experiment (day 0). Thereafter, all received PGF(2alpha) 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.     

Resynchronization of ovulation and timed insemination in lactating dairy cows III. Administration of GnRH 23 days post AI and ultrasonography for nonpregnancy diagnosis on day 30

The objective was to compare pregnancy rates to resynchronization and timed AI (TAI) protocols in lactating dairy cows that received GnRH at 23 d and were diagnosed not pregnant at 30 d after the pre-enrollment AI. Nonpregnant cows (624) at ultrasonography on day 30 (study day 0) were classified as diestrus (74.8%), metestrus (5.6%) and without a CL (19.5%). Cows in diestrus were assigned either to the GnRH group (PGF2alpha on day 0, GnRH on day 2 and TAI 16 h later, n = 238) or the estradiol cypionate (ECP) group (PGF2alpha on day 0, ECP on day 1, and TAI 36 h later, n = 229). Cows in metestrus were assigned to the Modified Heatsynch Group (GnRH on day 0, PGF(2alpha) on day 7, ECP on day 8 and TAI on day 9, n = 35). Cows without a CL (n = 122) were classified either as proestrus (10.6%), ovarian cysts (7.5%) or anestrus (1.4%), and assigned to factorial treatments (i.e., use of GnRH versus CIDR) to either the GnRH group (GnRH on day 0, PGF2alpha on day 7, GnRH on day 9 and TAI 16 h later, n = 28), the CIDR group (CIDR insert from days 0 to 7, PGF2alpha on day 7, GnRH on day 9 and TAI 16 h later, n = 34), the GnRH + CIDR group (GnRH on day 0, CIDR insert from days 0 to 7, PGF2alpha on day 7, GnRH on day 9 and TAI 16h later, n = 32), and the control group (PGF2alpha on day 7, GnRH on day 9 and TAI 16 h later, n = 28). For cows without a CL, plasma P4 concentrations were determined on days 0, 7, 10 and 17 and ovarian structures determined on days 0, 7 and 17. Pregnancy rates were evaluated at 30, 55 and 90 d after the resynchronized AI. For cows in diestrus, there were no differences in pregnancy rates on days 30, 55 and 90 for cows in the GnRH (27.5, 26.5 and 24.2%) or ECP (29.1, 25.5 and 24.1%) groups. In addition, there were no differences in pregnancy losses between days 30 and 55 and 55 and 90 between the GnRH (7.0 and 8.6%) and ECP (9.8 and 5.4%) groups. For cows without a CL, GnRH on day 0 increased the proportion of cows with a CL on days 7 and 17 and plasma P4 concentration on day 17 in cows with ovarian cysts but not for cows in proestrus. The CIDR insert increased pregnancy rate in cows with ovarian cysts but reduced pregnancy rate for cows in proestrus.     

Strategic use of gonadotrophin-releasing hormone (GnRH) to increase pregnancy rate and reduce pregnancy loss in lactating dairy cows subjected to synchronization of ovulation and timed insemination

The objective of this study was to determine the effect of GnRH (100 microg i.m.) treatment 5 and 15 days after timed insemination (TAI) on pregnancy rate and pregnancy loss in lactating dairy cows subjected to synchronization of ovulation. The study included 831 lactating dairy cows subjected to a Presynch-Ovsynch protocol for first service. On the day of TAI (Day 0), cows were randomly assigned to one of four experimental groups. Cows in Group 1 (n = 214) were treated with GnRH on Day 5; cows in Group 2 (n = 209) were treated with GnRH on Day 15; cows in Group 3 (n = 212) were treated with GnRH on both Day 5 and Day 15; cows in Group 4 (n = 196) were not treated. Pregnancy rate was evaluated at Day 27 and Day 45 after TAI. The interestrus interval and the proportion of cows diagnosed not pregnant based on expression of estrus and insemination before pregnancy diagnosis on Day 27 were determined. The results of this study are: (1) GnRH treatment on Day 5 or Day 15 did not increase pregnancy rate, or reduce pregnancy loss between Day 27 and Day 55 after TAI; (2) cows treated with GnRH on both Day 5 and Day 15 had a lower (P < 0.01) proportion of cows diagnosed not pregnant based on expression of estrus before ultrasonography on Day 27 (26.5%) compared to control cows (52.9%), and these cows had an extended (P = 0.05) interestrus interval (23.4 days vs. 21.5 days); and (3) GnRH treatment on both Day 5 and Day 15 after TAI reduced pregnancy rate on Day 27 (36.8% vs. 44.4% for control cows; P < 0.03) and Day 55 (28.3% vs. 36.2% for control cows; P < 0.01). Therefore, strategies to stimulate CL function using multiple doses of GnRH during the luteal phase need to consider potential negative effects.     

Efficacy of four synchronization protocols on the estrus behavior and conception in native Korean cattle (Hanwoo)

Ineffective estrus detection is the foremost limiting factor in the fertility of farmed cattle worldwide. Failure to detect estrus or erroneous diagnosis of estrus results in great economic losses in Korea each year. This study was carried out in order to comprehensively describe the estrus behaviors and conception rates of different estrus synchronization protocols applied to 40 cycling native Korean cattle (Hanwoo). The cows were grouped into four (n = 10) and treated with the following protocols: (1) Day -15: controlled intravaginal drug-releasing device (CIDR) for 12 days; Day -5: prostaglandin F_2α (PGF_2α), (2) ovulation synchronization (OVS): Day -15: GnRH; Day -6: PGF_2α; Day -4: GnRH, (3) Day -15: progesterone-releasing intravaginal device for 12 days; Day -5: PGF_2α; and (4) Day -15: PGF_2α; Day -4: PGF_2α. Artificial insemination was performed 12 hours after the detection of estrus using frozen-thawed semen. Estrus signs were compared using a charge-coupled device camera (CCDC) and a control method (direct visual observation). The pregnancy of the cows was determined by transrectal ultrasonography at Days 25 to 30 postinsemination. The results indicated that the day of estrus return was significantly earlier using the CCDC method compared with direct visualization (P < 0.05). Mounting of other cows was the most predominant sign of estrus among the flock (P < 0.05), as analyzed using the CCDC. In the OVS group, a lower rate of mounting was observed than in the other three groups. Moreover, significantly fewer estrus behaviors were noticed in the OVS protocol group (P < 0.05). Both first service conception and overall conception rates were significantly higher (P < 0.05) in the CIDR and OVS treatment groups. In conclusion, the CIDR and OVS protocols appear to be the best practice for the synchronization of estrus for reproductive competence through the CCDC in Hanwoo cows. However, CIDR has a practical advantage over OVS with respect to estrus detection.     

The effect of a progesterone (P4) intravaginal device (CIDR) on resynchronisation of oestrus and embryonic loss in previously timed inseminated dairy heifers

A study was done to evaluate the effect of using progesterone (P4) intravaginal device (CIDR: controlled internal drug-releasing dispenser) to synchronise the return to oestrus of previously timed inseminated (TAI) dairy heifers, and to evaluate embryo survival and pregnancy rate (PR) in the return to oestrus heifers. At the onset of the artificial insemination (AI) breeding period (day -9), heifers were randomly assigned into two groups (treated group CGPG, n = 79) and (control group GPG, n = 83). Every heifer in both groups was injected with gonadotropin-releasing hormone (GnRH) agonist and prostaglandin F2-alpha (PGF2α) as follows: GnRH on day -9; PGF2α on day -2; GnRH and TAI on day 0. Heifers in both groups received TAI within 30 min after the second GnRH injection. Artificial insemination at first breeding was conducted for all heifers during 55 days from day 0. On day 14 after timed insemination, every heifer in the CGPG group received CIDR device for 6 days. Within 3 days after CIDR removal, more heifers in CGPG group showed oestrus within 1.9 days compared to heifers that showed oestrus within 2.9 days in the control. Within 10 days after CIDR removal, more heifers in the CGPG group showed oestrus within 2.4 days compared to heifers that showed oestrus within 6.7 days in the control. PRs on days 30 and 55 were not different between both groups, while PR on day 55 during September were higher (P = 0.032) in CGPG group (58.0%) than GPG group (37.0%). In addition, PR from first to second AI was higher (P = 0.037) for CGPG group (79.8%) than for GPG group (65.1%) but it was similar after that. Pregnancy losses between days 30 and 55 tended to be lower (P = 0.089) for the CGPG group (12.7%) compared to 25.1% for the GPG group. Interval between first and second AI was lower (P = 0.052) for the CGPG group (27.5 ± 1.6 days) compared to 31.6 ± 1.3 days for heifers in the GPG group but no differences were detected for intervals from second to third AI and from third to fourth AI between the two groups. Number of services per pregnancy was not different between CGPG and GPG groups. Results indicate that the CIDR device improved synchronisation to return to oestrus and increased PR to first AI during high temperature months by reducing embryonic losses.     

Ovarian function in nutritionally induced anoestrous cows: effect of exogenous gonadotrophin-releasing hormone in vivo and effect of insulin and insulin-like growth factor I in vitro

Ovarian function of nutritionally induced anoestrus cows was evaluated in vivo (Expt 1) and in vitro (Expt 2). In Expt 1, 32 nutritionally induced anoestrous beef cows were divided into four treatment groups receiving: (1) saline infusions at one pulse every 4 h for 13 days (control); (2) 2 micrograms GnRH at one pulse every 4 h (2 micrograms infused in 1.8 ml saline over 5 min) for 13 days (GnRH-4); (3) 2 micrograms GnRH at one pulse every 1 h for 13 days (GnRH-1); and (4) continuous infusion of 2 micrograms GnRH (a total of 2 micrograms in 34 ml h-1) for 13 days (GnRH-C). On the last day of treatment, cows were killed, ovaries were removed and follicular fluid samples (n = 149) were collected. The percentage of cows with luteal activity on day 13 was significantly different (P < 0.01) among treatments (0, 25, 75 and 25% for control, GnRH-4, GnRH-1 and GnRH-C cows, respectively). Owing to the large percentage of ovulatory cows in the GnRH-1 group (n = 6), anovulatory cows (n = 2) were removed from this treatment group for statistical analysis, as were cows with luteal tissue from the GnRH-4 (n = 2) and GnRH-C (n = 2) groups. The numbers of small (1.0-4.9 mm) and medium plus large (> or = 5 mm) follicles were not affected (P > 0.10) by treatment. However, GnRH-4 cows (n = 6) had greater (P < 0.05) concentrations of oestradiol in follicular fluid than did control (n = 8) but not GnRH-1 (n = 6) or GnRH-C (n = 6) cows. Concentrations of insulin-like growth factor I were greater (P < 0.05) in the follicular fluid of GnRH-1 cows than in all other treatment groups. Concentrations of androstenedione and progesterone in follicular fluid were not affected (P > 0.10) by treatment or follicle size. The binding activity of insulin-like growth factor binding proteins was not affected by GnRH treatment. However, the binding activity of insulin-like growth factor binding protein 2, 29-32 kDa and 22 kDa insulin-like growth factor binding proteins were greater (P < 0.05) in small versus medium plus large follicles. In Expt 2, granulosa cells were collected from nutritionally anoestrous cows to determine whether ovarian cells from anoestrous cows have the capacity to respond to insulin-like growth factor I or insulin in vitro. Both insulin-like growth factor I (20 and 200 ng ml-1) and insulin (10, 100 and 1000 ng ml-1) increased (P < 0.05) granulosa cell proliferation and progesterone production. In conclusion, pulsatile infusion of 2 micrograms GnRH (every 1 or 4 h) for 13 days into nutritionally induced anoestrous cows results in increased intrafollicular oestradiol and insulin-like growth factor I concentrations and can stimulate ovulation without markedly affecting concentrations of androstenedione or progesterone, or the binding activity of insulin-like growth factor binding proteins, in follicular fluid. In addition, granulosa cells from nutritionally induced anoestrous cows have the capacity to respond to insulin-like growth factor I and insulin in vitro, indicating that the decrease in trophic factors observed with restricted feeding does not reduce the response of the ovary to insulin-like growth factor I and insulin.     

Pregnancy rate following GnRH + PGF 2alpha treatment of low body condition, anestrous Bos taurus by Bos indicus crossbred cows during the summer months in a tropical environment

Anestrous and lactating Bos taurus by Bos indicus crossbred cows with minimum body condition were studied to determine the efficacy of GnRH+PGF 2alpha combinations for induction of estrus and/or ovulation on pregnancy rate during the months of the year when temperatures are greater. On day 0 (start of treatment), cows were assigned randomly to either treatment or control groups. Treated cows (n = 74) received i.m. 200 microg of GnRH on day 0 and 150 microg of PGF 2alpha 7 days later (day 7). On day 7, treated cows were equally distributed to each of three protocols: (1) Select Synch (n = 25), artificial insemination (AI) 12 h after exhibiting estrus from day 7 (PGF 2alpha injection) until day 12; (2) Ovsynch (n = 24), 200 microg of GnRH at 48 h after PGF 2alpha (day 9) + timed-AI (TAI) 16-20 h later; (3) CO-Synch (n = 25), 200 microg of GnRH + TAI at 48 h after PGF 2alpha (day 9). Control cows (n = 25) received no treatment + AI 12 h after exhibiting estrus from days 0 to 12. Detection of estrus was performed daily during the early morning and evening hours from days 0 to 7 in all the cows, and from days 7 to 12 in the cows treated with Select Synch and in the control group, with the aid of a sterilized bull. Palpation per rectum and transrectal ultrasonography were used on days -30, -20, -10 and 0 to confirm anestrus (absence of CL and no signs of estrus at each evaluation) but with ovarian follicles > or = 10 mm on day 0. Pregnancy rate was 0% for Select Synch, 21% for Ovsynch and 28% for CO-Synch (P < 0.05). In conclusion, the Ovsynch and CO-Synch protocols resulted in greater pregnancy rates compared with the Select Synch protocol in Bos taurus/Bos indicus cows with minimum body condition that were anestrous and lactating during the summer months in a tropical environment.     

Incidence of premature estrus in lactating dairy cows and conception rates to standing estrus or fixed-time inseminations after synchronization using GnRH and PGF(2alpha).

Fixed-time AI (TAI) after GnRH-PGF(2alpha)-GnRH treatment is a method to achieve pregnancies in dairy herds without estrous detection. However, cows that fail to respond to the initial GnRH may have compromised TAI conception rates due to asynchronous ovarian response. This study documented the percentage of GnRH-treated Holstein cows (n=345) in two herds that displayed estrus at an inopportune time for optimum TAI conception rate (< or =48h post-PGF(2alpha); premature estrus (PE)) and compared conception rates of two TAI protocols in cows that did not display PE. At biweekly herd health exams, cows diagnosed as not pregnant to a previous AI and cows >80 days postpartum with no AI were treated with 100 microg GnRH (day -7) and 25mg PGF(2alpha) (day 0). Cows detected in PE by twice-daily visual observation from day -7 to day 2 were bred by AI 8-12h later. Cows not detected in PE were randomly assigned by parity, body condition score, and postpartum interval to receive either: (1) 100microg GnRH at 48h after PGF(2alpha) and TAI 16 to 18h later (Ovsynch); or (2) TAI at 72h post-PGF(2alpha) and a concurrent 100 microg GnRH injection to those cows not detected in estrus between 48 and 72h post-PGF(2alpha) (modified Ovsynch (MOV)). All hormone injections were im. Twenty percent (68/345) of the cows were detected in estrus before 48 after PGF(2alpha), of which 5% (17/345) were detected in estrus before PGF(2alpha) (< or =day 0). Herd influenced the percentage of cows in the PE group (herd A versus herd B; 25% versus 14%; P<0.05). Conception rates were not affected by treatment (PE versus Ovsynch versus MOV; 32% (21/65) versus 30% (37/125) versus 32% (47/145); P>0.10). However, within MOV-treated cows, conception rates were greater (P<0.05) in cows detected in estrus (46% (23/50)) compared with cows not detected in estrus (25% (24/95)). In conclusion, 20% of GnRH-treated cows displayed PE and necessitates estrous detection during this period if maximal pregnancy rates are to be achieved. Although additional estrous detection is required compared to Ovsynch, reduced cow handling and hormone usage, efficient use of expensive semen through greater conception rates in cows detected in estrus, and comparable TAI conception rates, suggests the MOV protocol may be a cost effective alternative to Ovsynch in many dairy herd reproductive management programs.     

Effects of medroxyprogesterone acetate (MAP) on ovarian antral follicle development, gonadotrophin secretion and response to ovulation induction with gonadotrophin-releasing hormone (GnRH) in seasonally anoestrous ewes

When ovulation is induced with gonadotrophin-releasing hormone (GnRH) in anoestrous ewes, a proportion of animals fail to form normal (full-lifespan) corpora lutea (CL). Progesterone treatment before GnRH prevents luteal inadequacy. It remains uncertain whether a similar effect, achieved with medroxyprogesterone acetate (MAP) from intravaginal sponges, is mediated by influences on growing ovarian follicles and/or secretion of gonadotrophic hormones, before and after GnRH treatment. Two experiments were performed, on 13 and 11 anoestrous Western white-faced ewes, respectively. Seven and six ewes, respectively, received MAP-containing sponges (60 mg) for 14 days; the remaining ewes served as untreated controls. To test the effect of timing of GnRH administration after pre-treatment with MAP-releasing sponges, GnRH injections (250 ng every 2h for 24h followed by a bolus injection of 125 microg of GnRH i.v.) were given either immediately (Experiment 1) or 24h after sponge removal in the treated ewes (Experiment 2). Ovarian follicular dynamics (follicles reaching >or=5mm in size) and development of luteal structures were monitored using transrectal ultrasonography. In Experiment 1, the mean ovulation rate (0.7+/-0.3 and 1.0+/-0.4) and proportion of ovulating ewes (57 and 67%, respectively) did not vary (P>0.05) between MAP-treated and control ewes. Normal (full-lifespan) CL were detected in 29% of treated and 67% of control ewes (P>0.05). In Experiment 2, the mean ovulation rate (2.3+/-0.2 and 1.2+/-0.6; P<0.05) and percentage of ewes with normal (full-lifespan) CL (100 and 40%, respectively; P<0.10) were greater in the treated compared to control ewes. In Experiment 1, the mean peak concentration of the GnRH-induced LH surge was lower (P<0.05) in MAP-treated than in control ewes. There were no significant differences between MAP-treated and control ewes in the characteristics of follicular waves, mean daily serum FSH concentrations, and secretory parameters of LH/FSH, based on intensive blood sampling conducted 1 day before sponging and 1 day before sponge removal. It is concluded that treatment with MAP has no effect on the tonic secretion of LH/FSH or follicular wave development in anoestrous ewes. However, the GnRH-stimulated LH discharge was attenuated in the ewes that received MAP-impregnated sponges for 14 days and were treated with GnRH immediately after sponge withdrawal. Ovulatory response and CL formation were increased when GnRH was administered 24 h after sponge removal.     

Resynchronization of ovulation and timed insemination in lactating dairy cows I: use of the Ovsynch and Heatsynch protocols after non-pregnancy diagnosis by ultrasonography

The objective was to compare pregnancy rates and pregnancy losses in lactating dairy cows that were diagnosed not pregnant and re-inseminated following either the Ovsynch or Heatsynch protocols. Also evaluated were the effects of stages of the estrous cycle, ovarian cysts and anestrus on pregnancy rates for both treatments. Non-pregnant cows (n = 332) as determined by ultrasonography on day 27 post-AI (study day 0) were divided into two groups. Cows in the Ovsynch group (n = 166) received GnRH on day 0, PGF2alpha on day 7, GnRH on day 9, and timed AI (TAI) 16 h later (day 10). Cows in the Heatsynch group (n = 166) received GnRH on day 0, PGF2alpha on day 7, estradiol cypionate (ECP) on day 8, and TAI 48 h later (day 10). Cows detected in estrus on days 8 and 9 were inseminated and included in the study. On day 0, cows were classified according to different stages of the estrous cycle, or presence of ovarian cysts or anestrus. Pregnancy rates were evaluated 27, 45 and 90 days after resynchronized AI. Overall, there was no difference in pregnancy rates on days 27, 45 and 90 between cows in the Ovsynch (25.2, 17.5, and 13.9%) and Heatsynch (25.8, 19.9, and 16.1%) groups. There was no difference in pregnancy losses from days 27 to 45 and days 45 to 90 for cows in the Ovsynch (25.0 and 17.9%) and Heatsynch (14.7 and 10.3%) groups. However, pregnancy rates were increased when cows in metestrus were subjected to the Heatsynch protocol and cows with ovarian cysts were subjected to the Ovsynch protocol.     

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 microg GnRH or with an injection of 4 mg EB. Thereafter, all received PGF(2 alpha) 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.     

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(2alpha) injection at the time of CIDR removal on Day 7, GnRH injection on Day 9, and TAI 16h 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(2alpha) 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.     

Exogenous GnRH induces ovulation in seasonally anoestrous lactating goats (Capra hircus)

A specific sheep LH radioimmunoassay was validated for the measurement of goat LH, and used to monitor luteal-phase LH episodes and the preavulatory LH surge in progestagen sponge-synchronized cycling goats. No luteal-phase LH episodes were detected during 12 h of frequent (15-min) blood sampling in 2 goats. A preovulatory LH surge was recorded in 5/5 goats, with a mean amplitude of 45.4 +/- 7.2 ng/ml and a mean time of onset of 38.4 +/- 1.2 h after removal of a progestagen-impregnated sponge. In anoestrous goats, single i.v. injections of 1000 and 2000 ng GnRH induced LH episodes with a mean amplitude of 2.04 +/- 0.11 and 3.67 +/- 0.06 ng/ml respectively, but injections of 250 or 500 ng did not consistently elevate LH concentrations. Progestagen-primed, seasonally anoestrous lactating goats were treated with repeated injections of 1500 ng GnRH (every 2 h for 52 or 78 h) in May 1985 or 1986. All 10 had kidded in March of the same year, and were consequently at peak lactation at the time of GnRH treatment. A preovulatory LH surge was detected in 9 goats with a mean time of onset of 59.5 +/- 2.9 h (1985) or 39.6 +/- 3.3 h (1986) after vaginal sponge removal. All animals displayed oestrus and ovulated, and 9 of the goats were mated: in 5 of these animals pregnancies were successfully carried to term. The results show episodic LH release in response to GnRH and indicate that ovulation can be induced in seasonally anoestrous goats, even at peak lactation, and normal pregnancies may result.     

Luteinizing hormone, oestrogen and progesterone levels in peripheral serum of anoestrous and cyclic ewes as determined by radioimmunoassay.

Jugular vein blood was collected daily from four mature ewes throughout anoestrus and the first oestrous cycle of the breeding season until 4 days after the second oestrus. The levels of oestrogen, progesterone and LH were determined by radioimmunoassay. There were fluctuations in the LH level throughout most of the observed anoestrous period with a mean plus or minus S.E. value of 2-3 plus or minus 0-9 ng/ml. High LH values of 20-0, 41-2 and 137-5 ng/ml were observed in three ewes on Day - 24 of anoestrus. A brief minor rise in progesterone level was also observed around this period. Progesterone levels were consistently low (0.11 plus or minus 0-01 ng/ml) before Day - 25 of anoestrus. A major rise occurred on Day - 12 of anoestrous and this was followed by patterns similar to those that have been previously reported for the oestrous cycle of the ewe. Random fluctuations of oestrogens deviating from a mean level of 4-40 plus or minus 0-1 pg/ml were observed during anoestrus and the mean level during the period from the first to the second oestrus was 5-2 plus or minus 0-3 pg/ml. A well-defined peak of 13-3 plus or minus 0-7 pg/ml was seen in all ewes on the day of the second oestrus. Results of the present study suggest that episodic releases of LH occur during anoestrus and periods of low luteal activity. The fluctuations in LH levels, as observed during the period of low luteal activity, i.e. before Day - 25 of anoestrus, were less pronounced during the periods of high luteal activity. The view that luteal activity precedes the first behavioural oestrus of the breeding season is supported.     

Effects of pre-synchronization using combinations PGF(2alpha) and (or) GnRH on pregnancy rates of Ovsynch- and Cosynch-treated lactating Holstein cows

In Experiment 1, the effects of two pre-synchronization treatments on synchronized AI pregnancy rates of lactating dairy cattle were compared. Lactating Holstein cows (n=159) received 100 microg of GnRH (im) on day -7 and 25mg of PGF(2alpha) (im) on day 0 and were observed once daily for signs of estrus from day -3 to day 3. Cows detected in standing estrus and those that had lost significant amounts of tail-chalk in the previous 24h were immediately inseminated in a once-daily observation/AI program. Cows not detected in estrus by 72 h after PGF(2alpha) received fixed-time AI (TAI) and a concurrent 100 microg injection of GnRH (im). Cows were randomly assigned by parity and calving date to receive one of the following pre-synchronization treatments: (1) 25mg of PGF(2alpha) (im) on day -35 and day -21 (PGF-PGF) or (2) 100 microg of GnRH (im) on day -14 (GnRH). Fewer (P<0.05) GnRH- (49%, 41/84) than PGF-PGF-pretreated cows (65%, 49/75) were detected in estrus, however, overall pregnancy rates were not affected by pre-synchronization treatment (30 versus 32%, respectively). In Experiment 2, lactating Holstein cows received 100 microg of GnRH (im) on day -7, 25mg of PGF(2alpha) (im) on day 0 and TAI at 60-64 h after PGF(2alpha). Cows were randomized by parity and postpartum interval into pre- and post-synchronization treatments in a 2 x 2 factorial design. Pre-synchronization treatments included: (1) 25mg of PGF(2alpha) (im) on day -35 and on day -21 (PGF-PGF; n=168) or (2) 25mg of PGF(2alpha) (im) on day -21 and 100 microg of GnRH (im) on day -14 (PGF-GnRH; n=180). Within each pre-synchronization treatment, cows were further allocated by parity and postpartum interval to receive as a post-synchronization treatment 100 microg of GnRH (im) at either 48 h (Ovsynch; n=175) or 60-64 h (Cosynch; n=173) after PGF(2alpha). Pregnancy rates at TAI were not affected by pre- (PGF-PGF=26%, 44/168 versus PGF-GnRH=24%, 44/180) or post-synchronization treatments (Ovsynch=29%, 50/175 versus Cosynch=22%, 38/173). However, the numeric shift towards reduced pregnancy rates in Cosynch-treated cows suggests the 12h interval between GnRH and AI may be important to optimize conception rates in GnRH-PGF(2alpha)-based TAI protocols in dairy cattle. In conclusion, each of the pre-synchronization protocols evaluated in present study performed with comparable efficacy. Although the Cosynch protocol facilitates more efficient labor utilization, numeric trends toward reduced conception warrants further investigation.