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

Luteal Function and Pregnancy Rate in Bos taurus Heifers Treated With GnRH Prior to Timed Artificial Insemination

The study aimed to evaluate the effects of GnRH given 34 h after progesterone (P4) intravaginal device (IVD) removal in a timed artificial insemination (TAI) protocol. In Experiment 1, 17 Hereford and Braford heifers (control, n = 7; GnRH34; n = 10) received 2 mg estradiol benzoate (EB) and a 1 g P4 IVD on Day 0 (D0). On D8, IVDs were removed and 150 μg d-cloprostenol (PGF) and 1 mg estradiol cypionate (EC) were administered. In the GnRH34 group, animals received 25 μg lecirelin 34 h after the IVD removal (D9). TAI was performed in both groups on D10 (48 h after IVD removal). Follicular dynamics were evaluated from D8 until ovulation; blood samples were collected 7 and 12 days after TAI. In Experiment 2, to evaluate the effect of GnRH34 on pregnancy rates (control, n = 187; GnRH34; n = 203), heifers were subjected to the TAI protocols described in Experiment 1. No significant differences were observed in preovulatory follicle (POF) diameter on D10, follicular growth and ovulation rates until 72 h and P4 concentrations on days 7 and 12 after TAI (p > 0.05). Pregnancy rates (PR) were similar between groups (Control = 50.2%; GnRH34 = 50.2%; p = 0.65). A significant effect of body weight (BW) and body condition score (BCS) on PR was observed for control (p< 0.05), but not for GnRH34. In conclusion, GnRH 34 h after the IVD removal in beef heifers previously treated with EC had no effect on luteal function and fertility.

Reproductive outcomes in Holstein heifers synchronized with timed-AI protocols that provide for a lengthened proestrus

This study compared reproductive outcomes among two protocols for synchronization of ovulation that provide for a lengthened proestrus with the conventional oestradiol-based protocol currently used for timed-AI (TAI). Holstein heifers (13-15 months) at one location were assigned randomly to one of three TAI protocols. Heifers (n = 150) in the 7-day oestradiol benzoate (EB) group received a progesterone device (Cue-Mate) and 2 mg EB on Day 0; 500 μg of cloprostenol (PGF) and Cue-Mate removal on Day 7; 1 mg of EB on Day 8 and TAI on Day 9 (54 h after Cue-Mate removal). Heifers (n = 150) in the 5-day CO-Synch (CO) group received a Cue-Mate and 100 μg of gonadotropin-releasing hormone (GnRH) on Day 2; Cue-Mate removal and PGF (twice, 12 h apart) on Day 7; and GnRH along with TAI on Day 10 (72 h after Cue-Mate removal). Heifers (n = 150) in the J-Synch (JS) group received a Cue-Mate and 2 mg of EB on Day 1; PGF and Cue-Mate removal on Day 7; GnRH and TAI on Day 10 (72 h after Cue-Mate removal). Heifers were inseminated by one technician with frozen-thawed conventional semen from one of four commercially available sires. Plasma progesterone (P4) concentrations (ng/mL) were determined at Cue-Mate removal and TAI. Ovarian ultrasonography was done in a subset of 217 heifers at the initiation of protocols, at Cue-Mate removal; TAI; and 7 days after TAI. Approximately, 28 and 50 days after TAI pregnancy status was determined by ultrasonography. Mean (±SEM) plasma P4 concentration at Cue-Mate removal was greater (p < .01) in CO (6.02 ± 0.2) and JS (6.51 ± 0.2) compared to EB heifers (4.53 ± 0.2). Mean (±SEM) plasma P4 concentration at TAI was lowest in the JS (0.28 ± 0.05), intermediate in CO (0.46 ± 0.02), and greatest in EB heifers (0.66 ± 0.05, p < .01). The diameter of the ovulatory follicle (mean ± SEM) was the smallest in the JS group compared to that in the CO and EB groups (15.8 ± 0.5; 13.9 ± 0.5; and 12.7 ± 0.5 mm for EB, CO and JS, respectively). More (p < .01) heifers in the JS group had their oestrous cycle synchronized (50.0, 78.8 and 82.4% for EB, CO and JS groups), and were pregnant at 28 (40.3, 51.3 and 63.3% for EB, CO and JS groups) and 50 days after TAI (32.6, 46.0 and 60.0% for EB, CO and JS groups). In summary, heifers subjected to the J-Synch TAI protocol had lower P4 at TAI, and better overall response to hormonal treatments, which resulted in increased P/AI at 28 and 50 days after TAI compared to those heifers subjected to either a 7-day EB protocol or a 5-day CO-synch protocol.

Is estradiol valerate an alternative to estradiol benzoate in promoting the synchronization of ovulation and timed artificial insemination in suckled Bos indicus beef cows?

The objective of the present study was to evaluate the effect of estradiol valerate administered at the beginning of the ovulation synchronization protocol on the pregnancy rate of Bos indicus cows. In the experiments, the following products from MSD, Sao Paulo, Brazil were used: estradiol valerate (EV), estradiol benzoate (EB), intravaginal progesterone device (P4), estradiol cypionate (EC), equine chorionic gonadotropin (eCG) and cloprostenol (PGF). In Experiment 1, Bos indicus cows (n=899) with a body condition score (BCS) of 2.76 ± 0.01 were included in a 3 (device) × 2 (protocol: 5 mg of EV or 2 mg of EB) factorial design. There were three types of P4 devices: a new device (New), a device previously used for 9 days (1×), and a device previously used for 18 days (2×). Nine days later (D9), the P4 device was removed, and cows received 300 IU of eCG. In addition, cows in the EB group received 1 mg of EC and 265 μg of PGF. Timed artificial insemination (TAI) was performed 48 h after P4 device removal in the EB group (TAI48) and 54 h after P4 device removal in the EV group (TAI54). In Experiment 2, Bos indicus cows (n=434) with a BCS of 2.62 ± 0.01 received a new P4 device or one previously used for 9 days and 5 mg of EV. On D9, all cows received 300 IU of eCG, and the P4 devices were removed and distributed in TAI48 and TAI54 cows. In Experiment 3, Bos indicus cows (n=429) with a BCS of 2.80 ± 0.01 were divided into the control and EV/EC groups. All cows received a P4 device. In addition, cows in the control group received 2 mg of EB, and cows in the EV/EC group received 5 mg of EV on D0. On D9, all cows received 1 mg of EC and 300 IU of eCG, and the P4 devices were removed. Cows in the control group also received 265 μg of PGF. All cows were inseminated 48 h after the removal of the P4 device. In Experiment 1, there was no effect of the interaction between protocol and P4 device on the occurrence of estrus (P=0.45) or on the pregnancy per artificial insemination ratio (P/AI; P=0.30). In addition, the occurrence of estrus and P/AI were not different between in the two estradiol groups (P=0.12 and P=0.82) and across the types of intravaginal P4 device (P=0.91 and P=0.47). In Experiment 2, the pregnancy rate was lower (tendency) in TAI48 cows (P=0.07). In Experiment 3, the estrus rate (P=0.12) and P/AI (P=0.56) were similar between the experimental groups. In summary, protocols using estradiol valerate without exogenous ovulation induction require adjustments in the timing of AI from 48 to 54 h after P4 device removal. However, a combination of estradiol valerate at the beginning of the protocol and estradiol cypionate nine days later successfully induced ovulation in Bos indicus cows inseminated 48 h after P4 device removal.

Prohibition of hormones in animal reproduction: what to expect and what to do?

As our understanding of ovarian function in cattle has improved, our ability to control it has also increased. The development of Fixed-Time Artificial Insemination (FTAI) protocols at the end of the 20th century has increased exponentially the number of animals inseminated over the last 20 years. The main reasons for this growth were the possibility of obtaining acceptable pregnancy rates without heat detection and, above all, the induction of cyclicity in suckled cows in postpartum anestrus and prepubertal heifers at the beginning of the breeding season. Most FTAI treatments in South America have been based on the use of progesterone (P4) releasing devices and estradiol to synchronize both follicular wave emergence and ovulation, with pregnancy rates ranging from 40 to 60%. These protocols are implemented on a regular basis, allowing producers access to high-quality genetics, and increasing the overall pregnancy rates during the breeding season. In addition, it provided the professionals involved in these programs with a new source of income and the diversification of their practices into activities other than their usual clinical work. Many of these practices are now apparently at risk from restrictions on the use of estradiol by the European Union (EU) and other countries. However, the development of alternative protocols based on GnRH, with P4 devices and eCG and other new products that are not in the market yet will allow us to adapt to the new times that are coming. Logically, the challenge has already been raised and we must learn to use alternative protocols to try to continue increasing the use of this technology in beef and dairy herds. The objective of the present review is to describe the main aspects of banning estradiol in livestock production, the negative impacts on reproductive efficiency, and to present some alternative FTAI protocols for dairy and beef cattle.

Morphologic, Steroidogenic, and Transcriptomic Assessment of the Corpus Luteum in Holstein Cows after Spontaneous or Hormone-Induced Ovulation

There is evidence that replacing the gonadotropin-releasing hormone (GnRH) with porcine luteinizing hormone (pLH) to synchronize ovulation prior to artificial insemination (AI) increased pregnancy per AI in dairy cows without affecting blood progesterone (P₄) concentrations. Whether morphologic, steroidogenic, and transcriptomic differences exist among corpora lutea (CL) formed after ovulation induced by GnRH and pLH is unclear. Our main objective, therefore, was to compare CL characteristics between GnRH- and pLH-induced CL. In 24 non-lactating Holstein cows, ovulations were spontaneous (Spont-Ov) or induced with 100 µg GnRH, 25 mg pLH, or 1 mg estradiol benzoate (EB), with CL excised 12 d after ovulation. In pLH- versus GnRH-treated cows, the duration of elevated LH (above baseline) was prolonged (10 versus 6 h, respectively, p < 0.01), but CL dimensions, pixel intensity of CL images, proportions of steroidogenic and non-steroidogenic luteal cells, and mean plasma LH did not significantly differ. Post-ovulation mean plasma P₄ (ng/mL) did not differ among Spont-Ov (3.0) pLH (3.1) or GnRH (3.0) cows but were lower in EB cows (2.0). In vitro P₄ concentration was greater in luteal explants of pLH-treated cows than in all other groups (combined means, 16.0 vs. 12.3 µg/mL, p < 0.02). Relative abundance of mRNA for oxytocin receptor (OXTR) was 2-fold higher (p < 0.01) in CL of pLH vs. GnRH cows and highest in Spont-Ov CL. In summary, pLH-treated cows had a longer LH peak, and greatest luteal tissue concentrations and in vitro production of P₄. We inferred that increased P₄ concentrations at the ovarian-uterine level in pLH-treated cows could have promoted embryo development and increased pregnancy per AI.

Estradiol Priming Potentiates the Kisspeptin-Induced Release of LH in Ovariectomized Cows

The present study examined whether priming with estradiol benzoate (EB) for 12 h increased both the peak and duration of LH release in response to kisspeptin (KISS1, KP) in cows. In a Latin square design, ovariectomized Nelore cows (n = 8) received: Control, i.m. 4 mL of 0.9% saline; KP, i.m. 4 mg murine KISS1-10; EBKP, i.m. 4 mg KISS1-10 + i.m. 2 mg EB simultaneously; EB12KP, i.m. 4 mg KISS1-10 + i.m. 2 mg EB 12 h before KISS1-10. Concentrations of LH were determined in blood samples obtained at time 0 (treatment), 20, 40, 60, 90, 120, 150, 180, 210 and 270 min. Concentrations of LH were analyzed by Proc GLIMMIX for repeated measures. In case of significance, the adjusted Tukey test was used to test for differences among treatments. GraphPad 8.0 PRISM® was used to determine the area under the LH-response curve (AUC) after injection of KISS1-10. Plasma LH remained relatively constant throughout sampling after treatment with saline. The peak in LH after injection of KISS1-10 occurred at 20 min in Groups KP and EBKP and at 40 min in Group EB12KP. The peak LH response (∆LH, ng/mL) was greater (p < 0.01) in Group EB12KP (5.6 ± 0.9) than in Groups KP (2.4 ± 0.9) and EBKP (3.5 ± 0.9), which did not differ. AUC (LH ng/mL*min) was greater (p = 0.02) in Group EB12KP (439 ± 73) than in Groups KP (176 ± 73) and EBKP (241 ± 73), with the latter two groups not differing. The findings indicated that 12 h priming with EB increased both the peak and duration of the LH response to treatment with KISS1. The incorporation of EB priming and KISS1 could improve the efficiency of estrus synchronization with fixed-time AI in cows. This would have an important practical application in assisted breeding in beef and dairy cattle.

Estrus synchronization and artificial insemination in Korean black goat (Capra hircus coreanae) using frozen-thawed semen

Presently, there is an increased demand for livestock products all over the world which has led to more devotion on improving livestock population. Although goats have been bred for a long time in Korea, but there is not much research conducted on traditional Korean black goat (Capra hircus coreanae) compared to other livestock populations. Mutton consumption has been dramatically changing from medicinal use to edible meat and this trend directs the black goat populations declining and also mutton import quantities are increasing consistently. The present study introduced a new estrus synchronizing technique with subsequent artificial insemination (AI) for Korean black goats to enable crossbreeding with non-native breeds for the small or subsistent farmers. Our data highlighted that, the percentage of motile sperm from the electro-ejaculated samples declined significantly after freezing and melting. In addition, the sperm motility significantly declined with regard to sperm incubation period (0, 5, 60, and 120 min at 37°C) and was negatively correlated (64.2 ± 7.9%, 63.3 ± 5.8%, 49.9 ± 6.3%, and 35.9 ± 7.6%, respectively) in frozen-thawed sperm samples. Moreover, the E2 levels were unchanged even 24 h after controlled internal drug releas (CIDR) withdrawal. But, 48 h and 72 h after CIDR removal, E2 levels increased significantly. These data helps us to consider the two time points for AI; CIDR removal after 24 h, at which E2 decreases, and after 48 h, as the time at which progesterone increases. Additionally, the AI after 48 h of CIDR removal group exhibited significantly higher pregnancy and parturition rates (42.9%) compared to AI after 24 h after CIDR removal 28.6% group. In conclusion, these studies will propose an optimal estrus synchronisation process with subsequent timing of AI and also will promote the Korean black goat breeding industry.

Estradiol-17β Injection Induces Ovulation in Llamas

This study aimed to investigate the effect of three different doses of estradiol-17β on ovulation and subsequent luteal development and function in llamas. Twenty-three llamas were examined daily by transrectal ultrasonography until the detection of an ovulatory follicle (≥8 mm). Thereafter, animals were divided into five groups: Control (n = 3; treated with 1.6 ml of saline solution), GnRH group (n = 6, treated with an intravenous injection of 8.4 μg Buserelin), and estradiol groups that received 0.6 mg (E1, n = 4), 1 mg (E2, n = 4), or 1.6 mg (E3, n = 6) of estradiol-17β intravenously. Detection of ovulation was based on ultrasonographic visualization of disappearance of the largest follicle and subsequent presence of a newly formed corpus luteum (CL) and progesterone concentration exceeding 1 ng ml⁻¹. Daily blood samples were collected to determine plasma progesterone concentration. Ovulation rate was 0% for control and E1 groups, 25% for E2 group, and 100% for GnRH and E3 groups. Differences in the mean CL diameter between GnRH and E3 groups were not statistically significant. Plasma progesterone concentration was similar between groups during the different days in ovulated animals. However, the day that the plasma progesterone concentration was above 1 ng ml⁻¹ and the day that the highest plasma progesterone concentration was achieved differed among E3 and GnRH groups, occurring later in females treated with estradiol. In conclusion, an injection of estradiol-17β is capable of inducing ovulation in llamas and the response depends on the dose used. Most of the animals required the highest tested dose (1.6 mg) to induce the ovulatory process. Although the CL diameter in females induced to ovulate with estradiol was similar to that in llamas induced to ovulate with a GnRH analog, the rise in plasma progesterone concentration above 1 ng ml⁻¹ and the peak progesterone concentration were attained 1 day later in the estradiol treated females.

Treatment with estradiol cypionate at progesterone withdrawal reduces handling without compromising the pregnancy rate to timed-AI in buffalo

The aim of this study was to determine if treatment with estradiol cypionate (EC) at the time of P4 withdrawal induced ovulation in a synchronization/timed-AI (TAI) protocol in buffalo. In Experiment 1, 56 buffaloes received an intravaginal P4 device (1.0 g) plus estradiol benzoate (EB, 2.0 mg im) on Day 0 (D0). On Day 9, the P4 device was removed and buffaloes were given PGF_2α (0.53 mg im sodium cloprostenol) plus eCG (400 IU im). Buffaloes were then randomly allocated to one of two groups: Group GEC (n = 29), treated with EC (1.0 mg im) at P4 device removal; Group GEB (n = 27), treated with EB (1.0 mg im) 24 h after P4 device removal. Ovarian ultrasound was undertaken on: D0, to ascertain general ovarian status; D9 to D11 (every 24 h), to measure diameter of the largest follicle (LF) and follicular growth rate; D11 to D13 (every 12 h for 72 h), to determine the time of ovulation and ovulation rate. Following P4 device removal, Groups GEC and GEB had a similar follicular growth rate (0.9 ± 0.1 and 1.1 ± 0.1 mm/day, respectively; P = 0.15) and similar LF diameter on D11 (11.4 ± 0.6 and 12.5 ± 0.5 mm; P = 0.12). Groups GEC and GEB also had a similar diameter of the ovulatory follicle (13.0 ± 0.5 and 13.4 ± 0.6 mm; P = 0.52), interval from P4 device removal to ovulation (68.2 ± 2.8 and 71.1 ± 1.4 h; P = 0.41) and ovulation rate (62.1% and 70.4%; P = 0.44). In Experiment 2, 199 buffaloes were assigned to the two treatments in Experiment 1 (GEC, n = 100; GEB, n = 99). All animals underwent TAI 56 h after P4 device removal and pregnancy diagnosis was preformed on D41. The pregnancy rate was similar for Groups GEC and GEB (50.0 and 45.5%, respectively; P = 0.45). The findings indicate that treatment with EC at the time of P4 withdrawal induces ovulation and achieves the same pregnancy rate to TAI as treatment with EB 24 h after P4 removal. The use of EC requires one less handling which is highly important in facilitating practical adoption of TAI in assisted breeding and genetic improvement in buffalo.

A simple and practical short-term timed artificial insemination protocol using estradiol benzoate with prostaglandin F2α in lactating dairy cows

To minimize costs and labor for short-term ovulation synchronization protocol, we developed one wherein each treatment-drug administration and timed artificial insemination (TAI)-was performed 24 h apart. The objective of the present study was to evaluate this short-term ovulation synchronization protocol in lactating dairy cows. Data were derived from 133 inseminations performed in 120 cows (32 primiparous and 88 multiparous), and the ovaries of these cows were scanned using ultrasound. The cows detected to have a functional corpus luteum (CL) received prostaglandin F2α (PGF) as a luteolytic agent. The cows were randomly assigned to two treatment groups: (1) treatment with estradiol benzoate (EB) 24 h after PGF treatment, and TAI 24-28 h after EB treatment (EB group); and (2) treatment with gonadotropin-releasing hormone agonist (GnRH) 56 h after PGF treatment, and TAI 16-20 h after GnRH treatment (GnRH group). As a luteolytic agent, either dinoprost (DP; 25 mg) or D-cloprostenol (DCLP; 0.15 mg) was administered intramuscularly in each treatment group. Pregnancy per AI (P/AI) was significantly higher in the DP- or DCLP-treated cows in the EB group when compared with their counterparts in the GnRH group (64.5% vs. 33.3%, P = 0.03 in the DP-treated cows and 51.1% vs. 27.3%, P = 0.04 in the DCLP-treated cows, respectively). Regarding parity, multiparous cows had greater P/AI in the EB group than in the GnRH group (52.8% vs. 26.7%, P = 0.01), whereas primiparous cows showed no significant intergroup difference (65.2% vs. 41.7%, P = 0.28). To conclude, the use of a convenient synchronization protocol comprising the administration of PGF and EB 24 h apart, rather than PGF and GnRH 56 h apart, has greater potential to improve pregnancy rates after TAI in lactating dairy cows given that a functional CL was accurately detected. This beneficial effect of the protocol using EB was clearly demonstrated in multiparous cows.

Infrared thermography and behavioral biometrics associated with estrus indicators and ovulation in estrus-synchronized dairy cows housed in tiestalls

Most Canadian dairy herds operate in tiestall housing (61%), where average estrus detection rates may be lower than 54%. The objective of this study was to evaluate infrared thermography and behavioral biometrics as indicators of estrus in dairy cows. Eighteen cyclic multiparous cows (Synch) were subjected to an estrus synchronization protocol, and 18 pregnant cows (control) received a sham protocol on the same schedule and frequency as the cyclic cow treatment. A decline in plasma concentrations of progesterone and the appearance of a dominant follicle using transrectal ultrasonography were used as indirect indicators of estrus, and the disappearance of a dominant follicle was used to confirm ovulation. All cows were monitored via visual cameras to determine the frequency of treading, drinking, neighbor interaction, tail movement, lying, and shifting behaviors. Infrared thermograms were recorded at the eye, muzzle, cheek, neck, front right foot, front left foot, rump, flank, vulva area, tail head, and withers. To evaluate the accuracy of behavioral and thermal parameters, a predefined minimum acceptable value (i.e., threshold) for estrus alerts (>0.30 Youden J index and >0.60 area under the curve) was used. Ovulation was confirmed in 14 (77.7%) out of 18 Synch cows. Eye, cheek, neck, rump, flank, vulva area, and wither thermograms exhibited higher temperatures at 48 h [cycle threshold (Δt) = +0.30 to 1.20°C] and 24 h before ovulation compared with 4 d prior to ovulation (Δt = 0.06 to 0.11°C) and during ovulation day (Δt = 0.03 to 0.32°C) in the Synch group. In addition, control cows exhibited greater treading activity per day compared with Synch cows (20.84 ± 0.39 vs. 16.35 events/5 min ± 0.34), and tail movement frequency was greater in Synch cows compared with control cows (14.84 ± 2.7 vs. 10.11 ± 4.7 events/5 min). However, within Synch cows, tail movement was the only behavior that significantly increased in frequency 2 d before ovulation (11.81 ± 1.71 events/5 min) followed by a decrease in frequency 1 d before ovulation (4.67 ± 1.05 events/5 min) compared with ovulation day (0 d; 6.10 ± 1.25 events/5 min) and during luteolysis (3 d before ovulation; 6.01 ± 1.25 events/5 min). Upon evaluation of all variables (thermograms and behavior frequencies) as estrus indicators at 48 and 24 h before ovulation, treading and tail movements before milking and 9 thermal locations satisfied the predefined minimum acceptable value for estrus alerts. This study demonstrates that fluctuations in radiated temperature measured at specific anatomical locations and the frequency of tail movements and treading behaviors can be used as a noninvasive estrus alerts in multiparous cows housed in a tiestall system.

Effect of Exogenous Progesterone or Flunixin Meglumine After AI on Serum Progesterone Concentration and Pregnancy per AI in Lactating Dairy Cows

The objective of this study was to determine the effect of post AI administration of exogenous progesterone (P₄) or a prostaglandin F2α (PGF2α) synthesis inhibitor agent on serum P₄ concentrations and pregnancy per AI (P/AI) in lactating dairy cows. Eighty lactating cows were randomly allocated to one of four treatment groups: 1) CON (control), received 5 mL of saline solution on d 6 and 14 post AI; 2) IP4 (injection of P ₄), received 125 mg of P₄ im on d 6 and 14 post AI; 3) CIDR, received a controlled internal drug release insert containing 1.38g of P₄ from d 6 to 20 post AI; and 4) FM (Flunixin Meglumine), received 0.625 g of Flunixin Meglumine, a nonsteroidal anti-inflammatory drug, twice daily on d 15 and 19 post AI. Blood samples were taken on d 0, 6, 14, 17 and 20 post AI to determine P₄ concentrations. Transrectal palpation was performed between 40 and 45 d post AI to determine pregnancy status. All treatment groups (i.e. IP4, CIDR and FM) resulted in greater serum P₄ concentration on d 17 and 20 post AI compared to CON (P < 0.05). Cows given a CIDR insert had greater concentrations of P ₄ on d 17 and 20 than IP4 and FM cows (P < 0.05). However, no significant difference was found between IP4 and FM groups for serum P₄ concentrations. The P/AI was greater (P < 0.05) in CIDR-treated cows (55%, 11/20) than CON (25%, 5/20), and intermediate in IP4 (40%, 8/20) and FM (35%, 7/20) cows. In summary, treatment with exogenous P₄ (i.e. CIDR and IP4) or FM increased serum P₄ concentrations in lactating dairy cows. However, results suggest that only CIDR administration would improve P/AI.

Hormonal strategy to reduce suckled beef cow handling for timed artificial insemination with sex-sorted semen

Two experiments were conducted to assess a hormonal strategy developed to reduce animal handling for timed artificial insemination (TAI) with sex-sorted semen. Four-hundred ninety-one (491) suckled beef cows received a progesterone (P4) intravaginal device and 2 mg intramuscular (im) injection of estradiol benzoate (EB) on a randomly chosen day of the estrus cycle (Day 0) in Experiment 1. Cows were treated with 500 μg of sodic cloprostenol (PGF2α) and with 300 IU of eCG at P4 device removal (Day 8); these cows were also randomly assigned to receive 1 mg of estradiol cypionate (EC) administered at P4 device removal (treatment EC-0h) or 1 mg of EB 24 h after P4 device removal (treatment EB-24h). Both treatments were timed inseminated (TAI) with sex-sorted semen 60 h after P4 device removal. Cows treated with EC-0h presented higher pregnancy rate per AI (P/AI) [45.0% (113/251)] than the ones treated with EB-24h [35.4% (85/240); P = 0.03)]. A subset of cows (n = 26) were subjected to ultrasound examination every 12 h after P4 device removal for 96 h in the row in order to determine the time of ovulation. Similar interval between device removal and ovulation was recorded for EB-24h = 70.0 ± 2.9 h vs. EC-0h = 66.0 ± 2.8 h (P = 0.52). Five-hundred ninety-one (591) cows were subjected to the same synchronization protocols and treatments (EC-0h or EB-24h). In addition, they were randomly assigned to a 2 × 2 factorial arrangement aiming at determining the effects of treatment with estradiol (EC-0h vs. EB-24h) and of semen type (Sex-sorted vs. Non-sex-sorted semen). All animals were timed inseminated 60 h after P4 device removal. There was no interaction (P = 0.07) between the ovulation inducer and semen type. The EC protocol led to greater P/AI than EB (P = 0.03). Greater (P = 0.01) P/AI was achieved through treatments with non-sex-sorted semen rather than with sex-sorted semen [sex-sorted (EB-24h = 49.0%; EC-0h = 51.0%) vs. non-sex-sorted semen (EB-24h = 52.4%; EC-0h = 68.2%)]. Therefore, EC administered at P4 device removal resulted in greater P/AI. Furthermore, the EC-0h protocol allowed reducing suckled beef cow handing for timed artificial insemination with sex-sorted semen.

Ovarian response and conception rate following oestrus synchronization using three protocols in Egyptian buffalo heifers

Objective: The aim of this study was to monitor the ovarian response and conception rate following estrous synchronization using CIDR, Ovsynch and double prostaglandin F2α protocols in Egyptian buffalo heifers. Material and methods: A total of 80 cyclic buffalo heifers were divided into four equal groups: CIDR (intravaginal progesterone releasing device, EAZI-BREEDTM CIDR®), Ovsynch (GnRH, PGF2α, GnRH injections), PGF (double PGF2α doses) and control. Timed artificial insemination (TAI) was performed in all heifers. All animals were exa - mined using ultrasound and blood samples were collected for measurement of progesterone. Results: A new follicular wave occurred earlier in the Ovsynch and PGF groups than in the CIDR group (p < 0.05). The mean diameter of the ovulatory follicle was smaller in the CIDR group than in the Ovsynch and PGF groups (p < 0.05). The ovulation rate was 100% in the CIDR group, 75% in the Ovsynch group and 70% in the PGF group. In the control group a lower pregnancy rate (20%) was determined in than in the CIDR (35%), Ovsynch (40%) and PGF (35%) groups. Progesterone concentrations were numerically higher in pregnant heifers of the CIDR group but the difference was non-significantly compared to the Ovsynch, PGF and control groups (p > 0.05). Conclusion and clinical relevance: EAZIBREEDTM CIDR®, Ovsynch-based TAI and PGF protocols were effective in synchronizing oestrus and resulted in nearly similar pregnancy rates in Egyptian buffalo heifers.

Characterization of blood flow and the effects of exogenous estradiol benzoate on residual follicles formed after ultrasound-guided transvaginal follicle aspiration in cattle

BACKGROUND

Removal of the follicular content by ultrasound-guided transvaginal follicle aspiration (TVFA) may fail to induce immediate atresia and loss of function, resulting in the occurrence of residual follicles (RF). The aims of this study were to characterize the blood flow in RF and to determine the effects of the treatment with estradiol benzoate on RF fate. Lactating, cyclic Holstein-Gir crossbred cows were used. In Experiment 1, follicular wave emergence (D0) was synchronized in cows (n = 10) and follicular growth was then monitored by transrectal ultrasonography from D0 to D8, followed by TVFA of the largest follicle present on the ovaries 24 h later. Color Doppler ultrasound imaging was used to examine blood flow on the follicular wall, which was recorded immediately before and every 12 h after TVFA, up to 72 h. In experiment 2, cows (n = 22) were randomly allocated to receive either 2 mL of saline i.m. (Control group, n = 11) or 2 mL estradiol benzoate i.m. (EB group, n = 11) immediately after TVFA. Ovaries were scanned every 12 h to confirm the presence and to measure the diameter of RF. The contents of the RF, if present, were collected 72 h after the first TVFA, using the same aspiration procedures. Follicular fluid from original follicles and RF were stored at -20 °C until hormonal assays.

RESULTS

In Experiment 1, there was no reduction (P > 0.05) of blood flow in the remaining follicle walls after TVFA and maximum blood flow values were observed at 49.5 ± 19.7 h post-TVFA. In Experiment 2, formation of RF after TVFA was proportionally similar between Controls (5/9) and EB (5/10) cows. Also, RF diameter did not differ between groups (P > 0.05). Nonetheless, the content of RF from cows in the EB group had lower (P = 0.0004) estradiol (E2) concentration and lower (P = 0.0005) E2:P4 ratio compared with Controls.

CONCLUSIONS

In conclusion, 1) the persistence of vascularization in the remaining follicle wall may contribute to the formation of RF after follicle aspiration, and 2) the treatment with estradiol benzoate does not prevent formation of RF, but does reduce their estradiol production.

Follicular-phase concentrations of progesterone, estradiol-17β, LH, FSH, and a PGF2α metabolite and daily clustering of prolactin pulses, based on hourly blood sampling and hourly detection of ovulation in heifers

Circulating concentrations of hormones were determined each hour in 13 heifers from the end of the luteolytic period to ovulation (follicular phase, 3.5 days). Diameter of the preovulatory follicle was determined every 8 hours, and the time of ovulation was determined hourly. The diameter of the preovulatory follicle decreased 0.8 ± 0.1 mm/h in heifers when there was 1 to 3 hours between the last two diameter measurements before ovulation. The concentration of progesterone (P4) after the end of the luteolytic period (P4 < 1 ng/mL) changed (P < 0.0001), as shown by a continued decrease until Hour -57 (Hour 0 = ovulation), then was maintained at approximately 0.2 ng/mL until 2 hours before the peak of the LH surge at Hour -26, and then a decrease to 0.1 ng/mL along with a decrease in estradiol-17β. Concentrations of LH gradually increased (P < 0.007) and concentrations of FSH gradually decreased (P < 0.0001) after the end of luteolysis until the beginning nadirs of the respective preovulatory surges. A cluster of prolactin (PRL) pulses occurred (P < 0.0001) each day with approximately 24 hours between the maximum value of successive clusters. Hourly concentrations of a PGF2α metabolite decreased (P < 0.007) until Hour -40, but did not differ among hours thereafter. Novel observations included the gradual increase in LH and decrease in FSH until the beginning of the preovulatory surges and follicle diameter decrease a few hours before ovulation. Results supported the following hypotheses: (1) change in the low circulating P4 concentrations during the follicular phase are temporally associated with change in LH concentrations; and (2) PRL pulses occur in a cluster each day during the follicular phase of the estrous cycle.

Synchronization using PGF(2α) and estradiol with or without GnRH for timed artificial insemination in dairy cows

This study examined the use of PGF_2α and estradiol benzoate (EB) either with or without GnRH to synchronize estrus in dairy cows for timed artificial insemination (TAI) under field conditions. First, Holstein dairy cows with a corpus luteum (CL) received 500 μg cloprostenol and were then randomly allocated to three groups: no further treatment (control, n=236); treatment with 1 mg EB 56 h after cloprostenol (EB group, n=339); or treatment with 1 mg EB 56 h after cloprostenol followed by treatment with 100 μg gonadorelin 24 h later (EB + GnRH group, n=216). All cows received TAI 80 h after the cloprostenol injection. In a second experiment, Holstein dairy cows with a CL received 500 μg cloprostenol and were then randomly allocated to two groups: treatment with 2 mg EB 36 h later (EB group, n=284) or treatment with 2 mg EB 36 h after cloprostenol followed by 100 μg gonadorelin 24 h later (EB + GnRH group, n=229). All cows received TAI 24 h after the EB injection. Logistic analyses revealed that the odds ratio for the probability of pregnancy when 1 mg EB was administered 56 h following cloprostenol was 1.9 and 2.0 times (P<0.001) higher in the EB (39.5%) and EB + GnRH groups (40.7%), respectively, compared with the control group (25.8%). However, pregnancy rates in cows receiving 2 mg EB 24 h following cloprostenol showed no difference compared with cows treated with EB only (32.4%) or with EB + GnRH (35.8%). These results indicate that a synchronization protocol comprising PGF_2α and EB could be used for TAI in dairy herds under field conditions.

Effects of two estradiol esters (benzoate and cypionate) on the induction of synchronized ovulations in Bos indicus cows submitted to a timed artificial insemination protocol

The effects of estradiol benzoate (EB) and estradiol cypionate (EC) on induction of ovulation after a synchronized LH surge and on fertility of Bos indicus females submitted to timed AI (TAI) were evaluated. In Experiment 1, ovariectomized Nelore heifers were used to evaluate the effect of EB (n = 5) and EC (n = 5) on the circulating LH profile. The LH surge timing (19.6 and 50.5 h; P = 0.001), magnitude (20.5 and 9.4 ng/mL; P = 0.005), duration (8.6 and 16.5 h; P = 0.001), and area under the LH curve (158.6 and 339.4 ng/mL; P = 0.01) differed between the EB and EC treatments, respectively. In Experiment 2 (follicular responses; n = 60) and 3 (pregnancy per AI; P/AI; n = 953) suckled Bos indicus beef cows submitted to an estradiol/progesterone-based synchronization protocol were assigned to receive one of two treatments to induce synchronized ovulation: 1 mg of EB im 24 h after progesterone (P4) device removal or 1 mg of EC im at P4 device removal. There was no difference (P > 0.05) between EB and EC treatments on follicular responses (maximum diameter of the ovulatory follicle, 13.1 vs. 13.9 mm; interval from progesterone device removal to ovulation, 70.2 vs. 68.5 h; and ovulation rate, 77.8 vs. 82.8%, respectively). In addition, P/AI was similar (P < 0.22) between the cows treated with EB (57.5%; 277/482) and EC (61.8%; 291/471). In conclusion, despite pharmacologic differences, both esters of estradiol administered either at P4 device removal (EC) or 24 h later (EB) were effective in inducing an LH surge which resulted in synchronized ovulations and similar P/AI in suckled Bos indicus beef cows submitted to TAI.

High-pressure steam sterilization of previously used CIDR inserts enhances the magnitude of the acute increase in circulating progesterone after insertion in cows

Objectives were to compare serum concentrations of progesterone (P4) in ovariectomized cows receiving (1) new, (2) re-used disinfected (DIS), and (3) re-used autoclaved (AC) controlled internal drug release (CIDR) inserts. Five ovariectomized (OVX) beef cows were used in a replicated 3 x 3 Latin square design. Each experimental period was 7 days, with at least 48 h between periods. All re-used CIDR had been inserted previously in beef cows for 7 days. Upon removal, CIDR used for the DIS treatment were washed thoroughly and soaked in a chlorhexidine gluconate solution (0.03%) for 2h, rinsed thoroughly with water and air-dried. For the AC treatment, CIDR were not soaked in disinfectant but were steam sterilized at 121 degrees C and 724 mmHg for 20 min before use. Blood samples were collected at 0, 10, 30, 60, 180, and 480 min relative to time of insertion of CIDR, daily until day 7, and at 30, 60, and 180 min relative to time of removal for radioimmunoassay of P4. Mean serum concentrations (ng/mL) of P4 during the 7-day period of insertion were greater (P<0.03) for new (3.7+/-0.2) and AC (3.4+/-0.3) than for DIS CIDR (2.8+/-0.2). These effects were created primarily by differences occurring during the first 8h after CIDR insertion. Within this interval, mean concentrations (ng/mL) differed (P<0.05) among all groups, but values for AC (6.0+/-0.7) exceeded both new (4.6+/-0.5) and DIS (2.7+/-0.3) markedly. Autoclaving may be the best option when re-using CIDR inserts because it creates greater concentrations of P4 immediately after insertion and reduces maximally the risk of disease transmission.

Negative Effect of Estradiol on Luteinizing Hormone Throughout the Ovulatory Luteinizing Hormone Surge in Mares1

The negative effect of estradiol-17beta (E2) on LH, based on exogenous E2 treatments, and the reciprocal effect of LH on endogenous E2, based on hCG treatments, were studied throughout the ovulatory follicular wave during a total of 103 equine estrous cycles in seven experiments. An initial study developed E2 treatment protocols that approximated physiologic E2 concentrations during the estrous cycle. On Day 13 (ovulation = Day 0), when basal concentrations of E2 and LH precede the ovulatory surges, exogenous E2 significantly depressed LH concentrations to below basal levels. Ablation of all follicles > or = 10 mm when the largest was > or =20 mm resulted in an increase in percentage change in LH concentration within 8 h that was greater (P < 0.03) than for controls or E2-treated/follicle-ablated mares. Significant decreases in LH occurred when E2 was given when the largest follicle was either > or =25 mm, > or =28 mm, > or =35 mm, or near ovulation. Treatment with 200 or 2000 IU of hCG did not affect E2 concentrations during the initial portion of the LH surge (largest follicle, > or =25 mm), but 2000 IU significantly depressed E2 concentrations before ovulation (largest follicle, > or =35 mm). Results indicated a continuous negative effect of E2 on LH throughout the ovulatory follicular wave and may be related to the long LH surge and the long follicular phase in mares. Results also indicated that a reciprocal negative effect of LH on E2 does not develop until the E2 surge reaches a peak.