Ovulation Synchronization Protocol Research Articles

Injectable progesterone in timed artificial insemination programs in beef cows.

The aims of this study were I) to compare the follicular diameter, corpus luteum diameter and serum progesterone (P4) concentrations in cows treated with conventional protocol vs. injectable P4 protocol; II) to determine the serum P4 profile in ovariectomized heifers; and III) to compare pregnancy rate between protocols. In experiment I, multiparous cows received a protocol for ovulation synchronization with an intravaginal P4 device (n = 38; device + EB day 0; device removal + PGF2α + eCG + EC day 8) or injectable P4 (n = 38; injection + EB day 0; PGF2α + eCG + EC day 8). In experiment II, ovariectomized heifers (n = 8) were treated with injectable P4 and blood samples were collected to determine the serum P4 profile. In experiment III, multiparous cows were timed AI with two different P4 approaches, intravaginal P4 device (n = 48) or injectable P4 (n = 47). In the first experiment, cows treated with P4 device had higher (P < 0.05) diameter of dominant follicle after ovulation induction (11.6 ± 1.8 vs.10.3 ± 1.8 mm) and ovulation rate (97%, 37/38 vs. 47.3%, 18/38) than cows treated with injectable P4. But, the follicular growth daily was higher (P < 0.05) in cows treated with injectable P4 than intravaginal device (1.3 ± 0.4 vs. 1.0 ± 0.3 mm/day, respectively). In experiment II, the P4 concentration peak occurred within 48 hours (6.54 ng/mL) and decreased after 96 hours (P < 0.05) after P4 injection. In experiment III, cows with P4 device had higher (P < 0.05) pregnancy rate than the injectable P4 group (60.4 vs. 34.0%, respectively). These results demonstrate that although the intravaginal P4 devices showed a higher pregnancy rate, a protocol with injectable P4 represents an easier method and a promising alternative for TAI in cattle.

Efeito da prostaglandina F2α no início do protocolo de sincronização da ovulação em novilhas leiteiras Bos indicus, Bos taurus e Bos indicus x Bos taurus

The objective of the present study was to evaluate the effect of treatment with prostaglandin F2α (PGF2α) at the beginning of the protocol for ovulation synchronization on follicular dynamics in Bos indicus (Gyr; n=11), Bos taurus (Holstein Black and White, HBW; n=10), and crossbred animals (Gyr x HBW; n=12). On a random day of the estrous cycles (day 0, D0), the animals received 2.0 mg estradiol benzoate (EB) intramuscularly plus an intravaginal progesterone (P4) device, which was maintained for 8 days (day 8, D8). Half the heifers of each group received a dose of 25 mg PGF2α intramuscularly at the time of insertion of the intravaginal P4 device. When the intravaginal device was removed (D8), all animals received another dose of 25 mg PGF2α intramuscularly, followed by intramuscular injection of 1.0 mg EB 24 h later (day 9, D9). Ultrasonographic evaluations were performed at intervals of 24 hours from D0 to D8 and at intervals of 12 hours from removal of the P4 device to 96 hours thereafter. Samples were collected on days 0, 3, 6, 8, 10 and 22 for the measurement of P4. The mean maximum diameter of the dominant follicle (DF) was smaller (P=0.01) in Gyr heifers (10.0 ± 0.8 mm) than in Gyr x HBW (13.0 ± 0.6 mm) or HBW (12.5 ± 0.8 mm). Furthermore, treatment with PGF2α on D0 increased (P=0.02) the maximum diameter of DF (12.9 ± 0.5 vs. 10.9 ± 0.7 mm) in the three genetic groups evaluated. The growth rate of the DF was lower (P=0.008) in Gyr heifers (0.8 ± 0.1 mm/day) than in crossbred heifers (1.3 ± 0.1 mm/day) or HBW (1.2 ± 0.1 mm/day). Heifers of the three genetic groups treated with PGF2α on D0 had higher (P=0.002) growth rates of DF (1.3 ± 0.1 vs. 0.9 ± 0.1 mm/day). The ovulation rate was lower (P=0.02) in Gyr heifers (36.4%) than in crossbred heifers (83.3%), but did not differ from HBW heifers (70.0%). However, higher (P<0.01) ovulation rates (93.7% vs. 35.3%) were observed in heifers treated with PGF2α on D0. The circulating concentration of P4 on removal of the intravaginal device (D8) was higher (P<0.05) in Gyr heifers (3.8 ± 2.2 ng/ml) than in crossbred heifers (2.2 ± 1.2 ng/ml), but no significant contrast was observed in HBW heifers (2.4 ± 1.6 ng/ml). Throughout the treatment period, the circulating concentrations of P4 were lower (P< 0.05) in heifers treated with PGF2α compared to untreated animals. Gyr heifers exhibited a lower growth rate and smaller maximum diameter of DF and a tendency towards a lower ovulation rate compared to HBW heifers. Treatment with PGF2α on the day of insertion of the intravaginal P4 device reduces circulating P4 concentrations and increases the growth rate and maximum diameter of DF, as well as ovulation rate.

Comparación de dos protocolos para sincronizar ovulación e implementar inseminación artificial en vaquillonas

Se efectuaron dos experimentos (EI y EII) en vaquillonas Bos taurus de 20-24 meses de edad y 3-3,5 de condición corporal (escala 1 a 5). El objetivo fue comparar dos protocolos de sincronización de la ovulación (PSO), utilizando dispositivos intravaginales con progesterona (DISP) combinados con cipionato de estradiol (CPE) administrado al momento de retirar el DISP o benzoato de estradiol (BE) 24 h más tarde. En el día 0, las vaquillonas (EI, n=16; EII, n=173) recibieron un DISP (1 g de progesterona) más 2 mg BE; en el día 8 se retiró el DISP, se administraron 0,150 mg de D-Cloprostenol y se aplicó, a sendos PSO, una inyección de 1 mg de CPE en dicho momento o 1 mg de BE 24 h más tarde. En EI, se efectuaron ecografías (días 0, 8 y 9 y desde este último momento cada 12 h hasta el día 11) y muestreos sanguíneos para determinar progesterona plasmática (P4; días 8, 9, 10, 11 y 21); se determinó porcentaje de vaquillonas con cuerpo lúteo (días 0 y 8), los diámetros de los folículos dominante (FD, día 8) y ovulatorio. En EII, se realizó IATF (día 10) y se determinó preñez (día 35). Los análisis estadísticos se realizaron por SAS. Los diámetros del FD (13,1±2,4 mm) y ovulatorio (15,4±2,2 mm) y el intervalo retiro DISP-ovulación (65,3±5,3 h) no difirieron entre PSO (p&gt;0,05); se observó un efecto del día sobre el nivel de P4 (p&lt;0,05), no así del PSO o interacción PSO x día (p&gt;0,05), el nivel de P4 al día 8 (4,6±4,4 ng/ml) disminuyó a valores &lt;1ng/ml post retiro del DISP. La preñez fue similar entre PSO (60,7%; p&gt;0,05). Se concluye que en vaquillonas Bos taurus, ambos PSO generan similares cambios ováricos, variaciones en el nivel de P4 y porcentajes de preñez.

1066 Effect of GnRH removal at CIDR insertion in the 5 d CO-Synch + CIDR ovulation synchronization protocol on ovarian function in beef cows

1066 Effect of GnRH removal at CIDR insertion in the 5 d CO-Synch + CIDR ovulation synchronization protocol on ovarian function in beef cows

Impact of parity on the efficiency of ovulation synchronization protocols in Holstein cows

The objective of this study was to elucidate the impact of parity on the efficiency of three different protocols to synchronize time of ovulation in Holstein cows. All cows enrolled in this trial were categorized into primiparous and multiparous (M1 = 2–3 and M2 ≥3 parities). Conception (P/AI at Day 28) and pregnancy (P/AI at Day 75) rates in the Presynch and CIDRsynch (31.7% and 35.5%; 26.3% and 28.4%, respectively) groups were significantly greater than that in spontaneous estrus (SE; 24.7 and 20.4%, respectively) group (P = 0.048 and 0.024; 0.041 and 0.011, respectively); however, no significant differences were detected between the SE and Ovsynch group for conception, pregnancy, and embryonic loss rates. Conception and pregnancy rates in the Presynch group decreased from 37.8% and 33.5%, respectively in primiparous cows to 29.6% and 23.1%, respectively in M1 cows (P = 0.022 and 0.007, respectively). However, conception and pregnancy rates using the CIDRsynch regimen were increased from 31.1% and 23.8% in primiparous cows to 41.4% and 34.7% in M1 cows (P = 0.017 and 0.008, respectively), and 40.9% and 33.6% in M2 cows (P = 0.021 and 0.019, respectively). Embryonic loss rate using the CIDRsynch protocol was decreased from 22.9% in primiparous cows to 15.1% and 18.2% in M1 and M2 cows (P = 0.013 and 0.130, respectively). On the contrary, embryonic loss rate using the Ovsynch protocol was increased from 11.5% in primiparous cows to 22.1% and 21.8% in M1 and M2 cows (P = 0.001 and 0.003, respectively). The Cox proportional-hazards model of embryonic loss showed significant associations for parity and season of calving with the hazard of embryonic loss (P = 0.001 and 0.016, respectively). Multiparous cows (M1 and M2) had a higher risk of embryonic loss than primiparous cows (Hazard ratio = 1.32 and 1.89, respectively). Our results indicate that use of the CIDRsynch regimen may achieve satisfactory conception and pregnancy rates in multiparous Holstein cows. However, synchronizing time of ovulation in primiparous cows with use of the Presynch treatment increases the fertility indices.

Efficacy of the 5-day CO-Synch ovulation synchronization protocol with or without the inclusion of exogenous progesterone in beef cows

ABSTRACT Fixed timed-AI (TAI) pregnancy rates were compared in suckled beef cows (n = 883; 5 replications) synchronized using the 5-d CO-Synch protocol with (CDR) or without (NCDR) the inclusion of exogenous progesterone (EAZI-BREED CIDR insert; CIDR). Cows were assigned to either the CDR (n = 445) or NCDR (n = 438) treatment by breed, parity, and days postpartum. Blood samples were collected 10 d before and immediately before CIDR insertion (d 0) to determine cyclic status. On d 0 all cows received gonadotropin-releasing hormone (100 μg), and cows in the CDR treatment received a CIDR. On d 5, CIDR were removed in CDR treatment and all cows received 2 separate doses of prostaglandin F 2α (25 mg/dose). Cows were TAI 72 h after CIDR removal (d 8), concurrent with gonadotropin-releasing hormone (100 μg). The proportion of females determined to be cyclic before estrous synchronization was 87.1% (757/869). Timed-AI pregnancy rates were greater ( P = 0.05) in CDR (62.3%, n = 438) than NCDR (50.7%, n = 436) treatment. However, a treatment × parity interaction ( P = 0.08) was noted relative to TAI. Although CDR obtained greater ( P ≤ 0.01) TAI pregnancy rates than NCDR in both primiparous and multiparous groups, difference between treatments was greater in primiparous females (69.0 vs. 46.3% for CDR and NCDR, respectively) than multiparous females (60.7 vs. 51.7% for CDR and NCDR, respectively). To optimize TAI pregnancy rates in beef cows synchronized with the 5-d CO-Synch protocol, inclusion of a CIDR is recommended.

A comparison of timed artificial insemination and automated activity monitoring with hormone intervention in 3 commercial dairy herds

The objective of this study was to compare the reproductive performance of cows inseminated based on automated activity monitoring with hormone intervention (AAM) to cows from the same herds inseminated using only an intensive timed artificial insemination (TAI) program. Cows (n=523) from 3 commercial dairy herds participated in this study. To be considered eligible for participation, cows must have been classified with a body condition score of at least 2.50, but no more than 3.50, passed a reproductive tract examination, and experienced no incidences of clinical, recorded metabolic diseases in the current lactation. Within each herd, cows were balanced for parity and predicted milk yield, then randomly assigned to 1 of 2 treatments: TAI or AAM. Cows assigned to the TAI group were subjected to an ovulation synchronization protocol consisting of presynchronization, Ovsynch, and Resynch for up to 3 inseminations. Cows assigned to the AAM treatment were fitted with a leg-mounted accelerometer (AfiAct Pedometer Plus, Afimilk, Kibbutz Afikim, Israel) at least 10d before the end of the herd voluntary waiting period (VWP). Cows in the AAM treatment were inseminated at times indicated by the automated alert system for up to 90d after the VWP. If an open cow experienced no AAM alert for a 39±7-d period (beginning at the end of the VWP), hormone intervention in the form of a single injection of either PGF2α or GnRH (no TAI) was permitted as directed by the herd veterinarian. Subsequent to hormone intervention, cows were inseminated when alerted in estrus by the AAM system. Pregnancy was diagnosed by ultrasound 33 to 46d after insemination. Pregnancy loss was determined via a second ultrasound after 60d pregnant. Timed artificial insemination cows experienced a median 11.0d shorter time to first service. Automated activity-monitored cows experienced a median 17.5-d shorter service interval. No treatment difference in probability of pregnancy to first AI, probability of pregnancy to repeat AI, pregnancy loss, time to pregnancy, or proportion of pregnant cows at 90d past the VWP existed. Based on these results, inseminating cows using AAM with hormone intervention can achieve a level of reproductive performance comparable to TAI. Considering the strict cow selection criteria used in this study, interpretation of results for on-farm implementation should be performed cautiously; the results cannot be directly extrapolated to whole herds of cows.

Comparison of Two Different Programmes of Ovulation Synchronization in the Treatment of Ovarian Cysts in Dairy Cows

It was the aim of this field study to evaluate two different protocols of ovulation synchronization for the treatment of ovarian cysts and their effect on reproductive performance in dairy cows. In addition, factors with a possible influence on treatment success and pregnancy outcome as well as costs per pregnancy were analysed. The study was performed with 130 German Holsteins with ovarian cysts diagnosed on days 55 to 60 postpartum. Cows belonging to group 1 (n = 65) received a modified ovsynch protocol [day 0: 0.15 mg cloprostenol (PGF) + 0.02 mg buserelin acetate (GnRH); day 14: PGF; day 16: GnRH]. Group 2 (n = 65) was treated with the conventional ovsynch protocol (day 0: GnRH; day 7: PGF; day 9: GnRH). Timed artificial insemination was performed 20 to 24 h later. Cows without ovarian cysts served as controls. Treatment success (disappearance of the ovarian cyst) after the first ovsynch cycle was higher in group 1 (66.2%) than in group 2 (23.1%, p < 0.05). Reproductive measures in group 1 were comparable with those of the control group and, compared with group 2, were conspicuously better (66.2%, 76.9%, 83.1%, 59.5% vs. 40.0%, 50.7%, 60.0%, 27.5% for cumulative pregnancy rate after treatment cycle 1 to 3 and second service conception rate, respectively, p < 0.05). Overconditioned cows and cows with larger ovarian cysts showed a diminished treatment and pregnancy success. In group 1, costs per pregnancy were only slightly higher than in the control group (group 1: €352.44, group 2: €484.59, control group: €333.77). In conclusion, our results suggest that ovsynch protocols can be used in the treatment of ovarian cysts. The modified ovsynch protocol led to a better cure rate as well as a better reproductive performance, and was economically beneficial compared with a conventional ovsynch protocol.

Effects of administration of prostaglandin F at initiation of the seven-day CO-Synch+controlled internal drug release ovulation synchronization protocol for suckled beef cows and replacement beef heifers.

Two experiments were conducted to determine the effect of administering PGF at the initiation of the 7-d CO-Synch+controlled internal drug release (CIDR) fixed-timed AI (TAI) protocol on pregnancy rates of suckled beef cows and replacement heifers. Within location, cows were stratified by days postpartum (DPP), BCS, and parity (Exp. 1; = 1,551) and heifers were stratified by BCS (Exp. 2; = 999) and randomly assigned to 1 of 2 treatments: 1) CO-Synch+CIDR (100-μg injection of GnRH at CIDR insertion [d -10] with a 25-mg injection of PGF at CIDR removal [d -3] followed by injection of GnRH and TAI on d 0) or 2) PG-CO-Synch+CIDR (a 25-mg injection of PGF on d -10 of the CO-Synch+CIDR protocol). Follicle diameter and corpus luteum (CL) development were assessed on d -10 and -3, and pregnancy status was determined on d 30 to 35. Blood was collected on d -20, -10, -3, and 0 relative to TAI to determine concentrations of progesterone (P4). In Exp. 1, TAI pregnancy rates did not differ ( = 0.667) between treatments and were affected by BCS ( = 0.003) and DPP ( = 0.006). Concentrations of P4 were greater ( < 0.0001) on d -3 for CO-Synch+CIDR than for PG-CO-Synch+CIDR (4.1 ± 0.2 and 3.4 ± 0.2 ng/mL, respectively). Follicle diameter on d -3 differed ( = 0.05) between PG-CO-Synch+CIDR (13.4 ± 0.3 mm) and CO-Synch+CIDR (12.5 ± 0.3 mm) treatments. Cows with P4 > 2.5 ng/mL on d -10 had greater ( = 0.024) pregnancy rate to TAI (56.5%) compared with cows with 2.5 ng/mL < P4 > 1 (43.0%), whereas cows with P4 < 1 ng/mL were intermediate (51.6%). Cows with a CL on d -10 had greater ( = 0.012) pregnancy rates to TAI than cows without a CL (66.3 vs. 39.4%, respectively). In Exp. 2, TAI pregnancy rates did not differ ( = 0.316) between treatments. Concentrations of P4 differed ( < 0.0001) on d -3 with greater concentrations of P4 for CO-Synch+CIDR than for PG-CO-Synch+CIDR (3.75 ± 0.20 ng/mL and 3.60 ± 0.21 ng/mL, respectively). Follicle diameter was similar ( = 0.749) between treatments on d -10 and -3. Regardless of treatment, cyclic status tended ( = 0.062) to improve pregnancy rates to TAI (55 vs. 45%, for cycling and noncycling heifers, respectively). We concluded that addition of PGF to the 7-d CO-Synch+CIDR protocol decreased concentrations of P4 in cows and heifers and increased follicle diameter at CIDR removal in cows but failed to increase TAI pregnancy rates.

Factors affecting the size of ovulatory follicles and conception rate in high-yielding dairy cows

Two studies were designed to determine (1) the effects of Heatsynch and Ovsynch protocols versus spontaneous ovulation and (2) the effects of calving problems, clinical uterine infections, and clinical mastitis on the size of the ovulatory follicle, conception rate, and embryonic/fetal (E/F) death in high-yielding dairy cows. In study 1, cows without the history of calving problems, clinical uterine infections, and clinical mastitis were randomly allocated to either an Ovsynch (n = 45) or Heatsynch (n = 39) ovulation synchronization protocol or spontaneous ovulation (n = 43) groups. Blood samples were collected on the day of artificial insemination (AI) to measure progesterone (P4), estradiol-17β, and insulin-like growth factor 1 (IGF-1) and 7 days later to measure P4. Study 2 consisted of cows (n = 351) with or without the history of calving problems, clinical uterine infections, and clinical mastitis which were artificially inseminated after a 55-day voluntary waiting period. Transrectal ultrasonography was performed at the time of AI to measure the ovulatory follicle size and on Days 30 and 68 after AI to diagnose pregnancy in both studies. In study 1, the mean (±standard error of the mean) diameter of the ovulatory follicle was greater (P = 0.0005) and E/F mortality was lower (P = 0.007) for the spontaneous ovulation group compared with Ovsynch and Heatsynch groups. Serum concentration of P4 on Day 7 after AI was correlated with the size of the ovulatory follicle (P = 0.007). Conception rate at Days 30 and 68 was not significantly different between the three experimental groups in study 1. Cows with serum IGF-1 concentrations greater than 55 ng/mL at AI had significantly higher Day 68 conception rate (50% vs. 24%) and lower E/F death (16.6% vs. 40%) compared to cows with serum IGF-1 concentrations lower than 56 ng/mL at AI. The conception rate on Days 30 and 68 for follicles of 10 to 14 mm in diameter (34% and 21.8%) was significantly lower than follicles of 14.1 to 19 mm in diameter (60% and 50%), respectively (P < 0.05). In study 2, the ovulatory follicle in cows with clinical uterine infections was smaller than that in cows without clinical uterine infections (16.4 vs. 17.1 mm; P = 0.04). In conclusion, the size of the ovulatory follicle is affected by ovulation synchronizing protocols and postpartum clinical uterine infections. In addition, cows with higher serum IGF-1 concentrations on the day of AI had higher Day 68 conception rate and lower E/F death.

Impact of thermal stress on the efficiency of ovulation synchronization protocols in Holstein cows

The objective of this study was to evaluate the impact of thermal stress on the efficiency of three different protocols to synchronize time of ovulation in purebred Holstein cows under subtropical Egyptian conditions. The influence of temperature humidity index (THI) on the conception, pregnancy, embryonic loss and early abortion rates were investigated. Conception and pregnancy rates using the CIDRsynch and Presynch (37.5% and 33.9%; 29.5 and 29. 6%, respectively) were significantly greater than that for cows expressing spontaneous estrus (SE) and with use of the Ovsynch (28.5% and 24.3%; 21.6% and 24.6%, respectively) treatment regimen. Conception and pregnancy rates using the Ovsynch protocol were significantly decreased from 31.6% and 26.3% at the lesser THI to 11.5% and 9.9%, respectively than at the greater THI [crude odds ratio (COR)=0.28 and 0.32; P=0.001 and 0.004, respectively]. However, conception (P/AI at 28 days) and pregnancy (P/AI at 75 days) rates using the Presynch protocol were significantly reduced at either the lesser or greater THI (COR=0.47 and 0.42; 0.48 and 0.34, respectively). Embryonic loss rate with the Presynch group was significantly increased from 11.5% at the lesser THI to 22.2% at the greater THI (COR=2.28; P=0.039). In contrast, conception, pregnancy and embryonic loss rates did not differ significantly (P>0.05) with the CIDRsynch protocol at the different THI. Results from the present study indicate that use of the CIDRsynch protocol may provide consistent and satisfactory conception and pregnancy rates in Holstein cows under subtropical environmental conditions.

Desenvolvimento folicular e pico de LH em fêmeas Nelore (Bos taurus indicus) com ovulação sincronizada*

The objective with this work was to monitor ovarian activity and the moment of LH pre-ovulatory peak in Nellore heifers and cows submitted to a hormonal protocol for ovulation synchronization with norgestomet (NOR), estradiol benzoate (EB) and cloprostenol. In experiment 1, five cows and five heifers received application of 2.0 mg of EB and implant of NOR on day zero (D0), with removal on D8 following application of 0.5 mg of cloprostenol. On D9 1.0 mg of EB was applied, performing ultrasound monitoring of ovarian activity since the beginning of the protocol until ovulation. In experiment 2, six females in each category were submitted to the same treatment. Twenty seven hours after BE blood was collected every 15 minutes, over a six hours period, for determination of LH serum levels. The mean diameter of the ovulatory follicle was 8.02±0.39 mm in heifers and 9.10±0.24 mm in cows (P

Diameter of the ovulatory follicle at timed artificial insemination as a predictor of pregnancy status in lactating dairy cows subjected to GnRH-based protocols

Ovulation of an early-stage dominant follicle induced by exogenous GnRH reportedly results in a reduced ovulatory follicle size and fertility in beef and dairy cattle. Objectives were to examine factors associated with ovulatory follicle diameter and the relationship between ovulatory follicle diameter and pregnancy per artificial insemination (P/AI) and pregnancy loss in lactating dairy cows subjected to GnRH-based programs for timed artificial insemination (TAI). A total of 1048 ovulations from 1576 breedings of cows that had or had not been presynchronized and subjected to a 5- or a 7-day GnRH-based protocol with or without progesterone supplementation between initial GnRH and PGF2α were analyzed. Ultrasonography was used to determine cyclicity, ovulation, and pregnancy status and to measure diameter of the ovulatory follicle at the time of TAI. Mean (±standard error) diameter of the ovulatory follicle was 16.4 ± 0.1 mm (range, 11–25 mm; n = 1048); the most common diameters were 15 (n = 170), 16 (n = 169), and 17 mm (n = 170). Multiparous cows and those subjected to a 7-day protocol had larger ovulatory follicles (P < 0.05). On average, multiparous cows that did not ovulate after the initial GnRH had the largest ovulatory follicles (17.0 ± 0.1 mm; n = 290), whereas all cows that ovulated after the initial GnRH and were subjected to a 5-day GnRH-based protocol had the smallest ovulatory follicles (15.6 ± 0.2 mm; n = 207). The associations between ovulatory follicle diameter and P/AI at 32 and 60 days after TAI were not significant. However, a significant linear relationship between ovulatory follicle diameter and pregnancy loss between 32 and 60 days after TAI was observed, with an increased (P < 0.05) probability of pregnancy loss in cows with an ovulatory follicle greater than 20 mm in diameter. In summary, the diameter of the ovulatory follicle preceding TAI was affected by interactions between ovulatory response to initial GnRH and parity and between ovulatory response to initial GnRH and the length of ovulation synchronization protocol. Ovulatory follicle diameter was not associated with P/AI at 32 or 60 days, but large ovulatory follicle size was identified as a predictor of pregnancy loss in lactating dairy cows subjected to GnRH-based protocols for TAI.

A review of recent developments in buffalo reproduction - a review.

The buffalo is an important livestock resource in several countries of South Asia and the Mediterranean regions. However, reproductive efficiency is compromised due to known problems of biological and management origins, such as lack of animal selection and poor nutrition. Under optimal conditions puberty is attained at 15 to 18 months in river buffalo, 21 to 24 months in swamp buffalo and is influenced by genotype, nutrition, management and climate. However, under field conditions these values deteriorate up to a significant extant. To improve reproductive efficiency, several protocols of oestrus and ovulation synchronization have been adopted from their use in commercial cattle production. These protocols yield encouraging pregnancy rates of (30% to 50%), which are comparable to those achieved in buffaloes bred at natural oestrus. The use of sexed semen in buffalo heifers also showed promising pregnancy rates (50%) when compared with conventional non-sexed semen. Assisted reproductive technologies have been transferred and adapted to buffalo but the efficiency of these technologies are low. However, these latest technologies offer the opportunity to accelerate the genetic gain in the buffalo industry after improving the technology and reducing its cost. Most buffaloes are kept under the small holder farming system in developing countries. Hence, future research should focus on simple, adoptable and impact- oriented approaches which identify the factors determining low fertility and oestrus behaviour in this species. Furthermore, role of kisspeptin needs to be explored in buffalo.

Fertility after implementation of long- and short-term progesterone-based ovulation synchronization protocols for fixed-time artificial insemination in beef heifers

Two experiments were conducted to evaluate the effect of long-term (LT; a 14-day controlled internal drug release insert [CIDR]–PGF2α [PGF]–GnRH) and short-term (ST; 5-day CO-Synch + CIDR) progesterone-based protocols on pregnancy rate to fixed-time artificial insemination (FTAI) in beef heifers. In experiment 1, Angus cross beef heifers (N = 1887) at nine locations received a body condition score and a reproductive tract score (RTS). Within the herd, heifers were randomly assigned to LT-72 and ST-56 protocol groups. Heifers in the LT-72 group received a CIDR from Days 0 to 14, followed by 25 mg of PGF 16 days later (Day 30). Heifers in the ST-56 group received a CIDR and 100 μg of gonadorelin hydrochloride (GnRH) on Day 25 followed by 25 mg of PGF at CIDR removal on Day 30 and a second dose of PGF 6 hours later (Day 30). Artificial insemination was performed at 56 hours (Day 32) after CIDR removal for the ST-56 group and at 72 hours (Day 33) after CIDR removal for the LT-72 group, and all heifers were given GnRH (100 μg, intramuscular) at the time of AI. In experiment 2, Angus cross beef heifers (N = 718) at four locations received a body condition score and an RTS. Within the herd, heifers were randomly assigned to LT-72 and ST-72 protocol groups. The protocol was similar to experiment 1 except that AI was performed at 72 hours after CIDR removal for both LT-72 and ST-72 groups. In experiment 1, no difference in AI pregnancy rates between the LT-72 and ST-56 groups was observed (54.5% [489 of 897] and 55.5% [549 of 990], respectively; P = 0.92) after accounting for the RTS. The AI pregnancy rates for heifers with RTS 3 or less, 4, and 5 were 52.6%, 53.6%, and 59.9%, respectively (P < 0.05). In experiment 2, controlling for the RTS, no difference in AI pregnancy rates was observed between the LT-72 and ST-72 groups, 56.9% (198 of 347) and 57.8% (214 of 371), respectively (P = 0.87). The AI pregnancy rates for heifers with RTS 3 or less, 4, and 5 were 49.3%, 58.4%, and 62.1%, respectively (P < 0.05). In conclusion, heifers synchronized for fixed-time AI with LT and ST protocols resulted in a similar AI pregnancy rate. Approximately, 55% of the herd was pregnant to one insemination in 33 days with the LT protocol compared with just 8 days with the ST protocol.

8 COMBINATION OF OESTRUS DETECTION AND FIXED-TIME ARTIFICIAL INSEMINATION IN BEEF HEIFERS FOLLOWING A SHORTENED OESTRADIOL-BASED PROTOCOL THAT PROVIDES FOR A LENGTHENED PROESTRUS

Studies have shown that gonadotropin-releasing hormone-based protocols that reduce the period of progestin insertion and prolong the period from progestin removal to gonadotropin-releasing hormone and fixed-time AI (FTAI; named 5-day Co-Synch) results in similar or higher pregnancy rates than the conventional 7-day Co-Synch protocol in beef cows and heifers (Bridges et al. 2008 Theriogenology 69, 843–851). Similar findings have been reported following the use of an oestradiol-based protocol that also provides for a longer period of proestrus (named J-Synch; de la Mata and Bó 2012 Taurus 55, 17–23). An experiment was designed to compare the J-Synch protocol for synchronization of ovulation that allows for a prolonged proestrus with a conventional 7-day oestradiol-based protocol for FTAI in heifers. Cycling 18-month old Angus and Hereford heifers (n = 208) with a body condition score of 6 to 7 (scale of 1 to 9) were randomly allocated to 1 of 2 treatment groups. Heifers in the 7-day EB group (n = 105) received a progesterone (P4) device (DIB 0.5 g of P4, Syntex SA, Buenos Aires, Argentina) and 2 mg of oestradiol benzoate (EB, Syntex SA) on Day 0 and 500 μg of cloprostenol (PGF; Ciclase DL, Syntex SA) and 0.5 mg oestradiol cypionate (Cipiosyn, Syntex SA) on the day of DIB removal (Day 7). Heifers were also tail painted at the time of DIB removal and observed for signs of oestrus (i.e. tail paint rubbed off). Those with the tail paint rubbed off by 36 h after DIB removal were inseminated 12 h later, whereas those not showing oestrus by 36 h were FTAI at 54 h. Heifers in the J-Synch group (n = 103) received DIB and 2 mg of EB on Day 0 and PGF on the day of DIB removal (Day 6). Heifers in this group were also tail painted at DIB removal, and those with their tail paint rubbed off by 48 h were inseminated 12 h later; those not showing oestrus by 60 h received 100 μg of gonadorelin acetate (gonadotropin-releasing hormone, Gonasyn gdr, Syntex SA) and were FTAI at 72 h after DIB removal. Pregnancy was diagnosed by ultrasonography at 55 days after FTAI (Honda 101V, 5.0-MHz transducer). Data were analysed by logistic regression. Oestrus detection rate and pregnancy rate to FTAI did not differ (P &gt; 0.1) between groups (38.8%, 40/103 and 60.3%, 38/ 63 for heifers in the J-Synch group v. 28.5%, 30/105 and 45.3%, 34/75 for those in the 7-day EB group). However, pregnancy rates to observed oestrus tended (P &lt; 0.09) to be higher and the overall pregnancy rate was significantly higher (P &lt; 0.01) in heifers in the J-Synch group (80.0%, 32/40 and 67.9%, 70 /103) compared with those in 7-day EB group (50%, 15/30 and 46.6%, 49/105). Furthermore, heifers within the J-Synch group that had their tail paint rubbed off by 48 h after DIB removal and were AI 12 h later (i.e. 60 h) had higher (P &lt; 0.05) pregnancy rate than those in the same group that were FTAI. In conclusion, reducing the time of progestin device insertion and lengthening the proestrus period, as in the J-Synch protocol, results in higher pregnancy rates than with the conventional oestradiol-based protocol. Furthermore, the combination of oestrus detection and FTAI would appear to improve the pregnancy outcome even more.

102 SUPPLEMENTATION WITH ESTRADIOL CYPIONATE AT THE ONSET OF A SYNCHRONIZED PROESTRUS ALTERS THE UTERINE GENE EXPRESSION OF SUCKLED ANESTROUS BEEF COWS

The present study evaluated the effect of oestradiol cypionate (ECP) supplementation at the onset of a proestrus [i.e. at progesterone (P4) device removal of the synchronization of ovulation protocol] on the global endometrial gene expression of suckled anestrous beef cows. A total of 12 suckled cows presenting absence of corpus luteum detected by ultrasound received 2 mg of oestradiol benzoate IM and an intravaginal P4 device. Eight days later, P4 devices were removed, and the cows received 500 mg of sodium cloprostenol IM. Cows were blocked according to body condition score and diameter of largest follicle (LF) at P4 device removal and were randomly assigned to receive an IM treatment with 1 mg of ECP (ECP, n = 6) or not (CON, n = 6) at the P4 device removal. All cows received 10 μg of buserelin acetate 48 h after P4 device removal and were timed AI immediately after. Cows presenting a new corpus luteum formed 6 days after the gonadotropin-releasing hormone treatment had an endometrial fragment collected by transcervical biopsy. RNA-Seq analysis was performed and the transcriptome profile was obtained. The significance of differential gene expression was assessed with the package DESEqn 2 v.1.2.10 and the differential expression estimation was based on the GLM followed by the Wald test. The significance threshold was established as an FDR- Benjamini-Hochberg-adjusted P-value of &lt;0.1. The integrated analysis was performed using DAVID database. In total, 135 transcripts were differentially expressed between ECP and CON groups, of which 73 genes were up-regulated by ECP supplementation and 62 genes were up-regulated in the CON cows. Two pathways were overrepresented by the ECP-induced transcripts: pathways in cancer (n = 5 genes) and small cell lung cancer (n = 3 genes). On the other hand, ECP-inhibited transcripts indicated the enrichment of 3 pathways: Parkinson's disease (n = 3 genes), oxidative phosphorylation (n = 3 genes), and Alzheimer's disease (n = 3 genes). More specifically, ECP-induced transcripts associated with pathways in cancer [gene symbol (fold change); respectively] were LAMC3 (1.55), PTCH1 (1.51), PTCH2 (1.52), PIK3R3 (1.22), and PIAS1 (1.18), whereas ECP-inhibited transcripts associated with oxidative phosphorylation were ATP5F1 (1.18), ATP5J (1.24), and NDUFB3 (1.37). Therefore, ECP supplementation at onset of the synchronized proestrous slightly alters the uterine transcriptome. The enriched pathways affected by the ECP supplementation described in this work need to be studied more but these results show candidate pathways that can be associated with uterine environment and receptivity and with possible regulation by oestradiol supplementation given at the onset of the proestrous.

Effect of 2 ovulation synchronization protocols on reproductive performance of May-calving cows

<h2>ABSTRACT</h2> A 2-yr experiment was conducted using Red Angus×Simmental cows (yr 1, n=145; yr 2, n=162). Cows were randomly assigned to 1 of 2 treatments: (1) cows received gonadotropin-releasing hormone (GnRH; 100μg, i.m.) on d 0, prostaglandin F_2α (PGF_2α; 25mg, i.m.) on d 7, and GnRH (100μg, i.m.) with fixed-time AI (TAI) 48h after PGF_2α (CO-Synch); or (2) cows received GnRH (100μg, i.m.) and controlled internal drug release device (CIDR) insertion on d 0, PGF_2α (25mg, i.m.) and CIDR removal on d 7, and GnRH (100μg, i.m.) with TAI 60h after PGF_2α (CO-Synch+CIDR). Five days after TAI, bulls were placed with cows for 45 d. Cows synchronized with the CO-Synch+CIDR protocol had increased (P<0.01) AI and overall pregnancy rates compared with cows synchronized utilizing the CO-Synch protocol. Due to increased AI pregnancy rates, CO-Synch+CIDR cows calved 5 d (±1 d) earlier (P<0.01), resulting in a greater (P<0.01) proportion of cows calving within the first 21 d of the calving season compared with CO-Synch cows. Calf crop weaned per cow exposed was increased (P=0.02) for CO-Synch+CIDR. Weaning BW per cow exposed was also greater (P=0.04) for CO-Synch+CIDR. In conclusion, pregnancy rates were greater for CO-Synch+CIDR compared with the CO-Synch synchronization protocol, resulting in more calves born earlier in the calving season and a $55.22/cow increased net return utilizing the CO-Synch+CIDR protocol.

2014 protocols for synchronization of estrus and ovulation in beef cows and heifers

Biotechnology presents beef producers with an unprecedented opportunity to improve herd genetics. Producers have more precise tools for genetic selection. Research has led to a better understanding of methods to induce and synchronize estrus and ovulation in postpartum cows and replacement heifers. These improvements enable producers to expand their use of artificial insemination (AI) and make it possible to inseminate cows at predetermined times and to achieve pregnancy rates comparable to those gained after several days of detecting heat. Many options exist for synchronization of estrus and ovulation. This short list of protocols, based on research and field use by reproductive physiologists, veterinarians, and professionals in related industries, is intended to help you select an appropriate synchronization option.

Pregnancy rate in lactating Bos indicus cows subjected to fixed-time artificial insemination and treated with different follicular growth inducers

The objective of this experiment was to evaluate the effects of replacing eCG with FSH or FSH/LH on the diameter of ovulatory follicles (DOF) and the pregnancy rates (PR) of lactating Bos indicus cows subjected to a synchronization of ovulation protocol and fixed-time artificial insemination (FTAI) based on progesterone, estradiol benzoate (EB), PGF2α, and estradiol cypionate (EC). On day 0, primiparous and multiparous Nellore cows (n = 329) at 68 days postpartum were body condition scored (BCS) and received a P4 implant (PRIMER 1.0 g P4) plus 2 mg EB intramuscularly (IM). At day 8, the implant was removed, and 250 μg cloprostenol were injected IM along with 0.5 mg EC. At the time of implant removal, the animals were divided into one of four treatments: cows received (G1) 1 mL of saline solution IM (Control; n = 80); (G2) 300 IU eCG IM (ECG300; n = 84); (G3) 15 mg FSH IM (Folltropin; n = 82); and (G4) 30 IU FSH/LH IM (Pluset; n = 83); all cows were subjected to FTAI 48-54 h after implant removal (day 10). Transrectal ultrasonography was performed to measure the DOF to FTAI and to estimate the pregnancy rate on day 35. A statistical analysis examined the effects of the treatment, technician, semen, BCS, calf age and parity on PR to FTAI. There was no significant difference in PR and DOF among the treatment groups (G1, 41.3%, 13.1 mm; G2, 46.4%, 14.5 mm; G3, 46.3%, 14.2 mm; and G4, 48.2%, 14.3 mm), but PR was higher in multiparous than in primiparous cows. Commercial FSH solutions (Pluset or Folltropin) do not promote increases in PR or DOF of lactating Nellore cows and are equal to eCG in promoting growth in preovulatory follicles and elevating the PR in Nellore cows with a moderate BCS subjected to a progesterone-based FTAI protocol with EC.