Bovine somatotropin increases the pregnancy rate in fixed-time artificial insemination in beef cattle.

This study evaluated the effect of bovine somatotropin (bST) on pregnancy rate (PR) and size of the dominant follicle (DF) on the day of intravaginal progesterone (P4) removal in protocols for fixed-time artificial insemination (FTAI). Bos indicus (Nellore) females (n = 392) were distributed into three groups. The control group (CG; n = 92) received an intravaginal P4 device + estradiol benzoate on day (d)0; prostaglandin F2α on d7 (first application); removal of P4 + estradiol cypionate (EC) + PGF2α (second application) + ultrasound (US) of the DF on d9; the FTAI was performed on d11; and pregnancy diagnosis (PD) was performed on d45. The bST group (bSTG; n = 142) underwent the same protocol as the CG, except that the animals received 125 mg of bST on d7. The equine chorionic gonadotropin (eCG) group (eCGG; n = 158) underwent the same protocol as the CG, except that the animals received 300 IU of eCG on d9. The PRs of the bSTG, eCGG, and CG were 48%, 48%, and 35%, respectively (p < .05); the bSTG and eCGG showed greater PRs, with follicles 6-7.9 mm (p < .05) and 8-8.9 mm in diameter, respectively. The bSTG exhibited a greater dimension of the DF on d9 of the protocol (p < .05). The eCGG had higher PRs with a body condition score (BCS) of 2.5, and the bSTG had a BCS of 3.0 (p < .05). It was concluded that bST increased PR, bST showed better performance in smaller DF and larger follicular diameter on d9 of the protocol, eCG acted better on animals with lower BCSs, and bST can be used in FTAI.

Timed-artificial insemination protocols for Bos indicus beef heifers: Evaluation of protocol length and variations in prostaglandin F2α treatments.

The aim was to compare reproductive outcomes of Nelore heifers submitted to timed AI (TAI) protocols, with 7 or 9 d of permanence of the intravaginal progesterone (P4) device and different times of prostaglandin F2α (PGF) administration, for first (n = 935) and second (n = 530) services. On Day -24, heifers without corpus luteum (CL) underwent a protocol for induction of ovulation. On Day 0, heifers received a P4 device (0.5 g) and 1.5 mg estradiol (E2) benzoate. In order for the TAI to be carried out on the same day, these treatments were performed 2 d later on the heifers treated with the 7-d protocol. Additionally, heifers received 0.5 mg PGF at different times, resulting in four experimental groups: 9dP4-PGFd9 (n = 365); 9dP4-PGFd7 (n = 369); 9dP4-PGFd0&9 (n = 364); 7dP4-PGFd0&7 (n = 367). These nomenclatures indicate for how many d the P4 device was kept and the specific day on which PGF was given. At P4 removal, all heifers received 0.5 mg E2 cypionate and 200 IU eCG, and TAI was performed 2 d later. Effects were considered significant when P ≤ 0.05 (superscript letters a,b) whereas a tendency was assumed when 0.05 < P ≤ 0.10. Groups 9dP4-PGFd0&9 and 7dP4-PGFd0&7 had lower percentage of heifers with CL at P4 removal. The diameter (mm) of the dominant follicle (DF) was affected by treatment at P4 removal (9dP4-PGFd9: 11.3 ± 0.3b; 9dP4-PGFd7: 11.8 ± 0.2ab; 9dP4-PGFd0&9: 12.6 ± 0.2a; 7dP4-PGFd0&7: 10.8 ± 0.2c) and at TAI (9dP4-PGFd9: 12.7 ± 0.3ab; 9dP4-PGFd7: 13.2 ± 0.2a; 9dP4-PGFd0&9: 13.4 ± 0.2a; 7dP4-PGFd0&7: 12.4 ± 0.3b). Expression of estrus (%) was affected by treatment (9dP4-PGFd9: 89.6a; 9dP4-PGFd7: 93.5a; 9dP4-PGFd0&9: 88.2ab; 7dP4-PGFd0&7: 85.6b). There were no differences among treatments for P/AI on Day 40 (30-35 d post AI), final P/AI (between Day 70 and parturition) and pregnancy loss (between Day 40 and final P/AI). When the permanence of the P4 device was compared, regardless of PGF treatments, 9-d protocols resulted in greater DF diameter at P4 removal and at TAI, and greater expression of estrus (90.4 vs. 85.6%) than the 7-d protocol. Despite that, the 7-d protocol resulted in greater P/AI on Day 40 (55.3 vs. 49.1%). In addition, there was an interaction between protocol duration and body weight, in which heavier heifers (≥ 307 kg) had greater P/AI when treated with the 7-d protocol, in comparison to 9-d. In conclusion, longer TAI protocols (9 d of P4 device duration) resulted in greater DF diameter and expression of estrus. However, the shorter TAI protocol (7 d of P4 device duration) produced greater P/AI on Day 40, particularly in heavier heifers. Within 9-d protocols, the additional dose of PGF on Day 0 or the anticipation of the PGF to Day 7 did not influence fertility.

Prostaglandin F2α treatment does not hasten ovulation in weaned sows.

This study evaluated the efficiency of prostaglandin F2α (PGF) to hasten ovulation in weaned sows. In experiment I, weaned sows detected in estrus (0 h) received: no hormone (Control; n = 56); 0.5 mg PGF IM at 0 h and 2 h (PGF0; n = 56); or 0.5 mg PGF IM at 24 h and 26 h (PGF24; n = 55). In experiment II, weaned sows that did not express estrus signs until 72 h after weaning (0 h) were assigned to: no hormone (Control; n = 45); 10 µg buserelin acetate IM at 0 h (Buserelin; n = 43); 0.5 mg PGF IM at 34 h and 36 h (PGF; n = 44); or 10 µg buserelin acetate IM at 0 h plus 0.5 mg PGF IM at 34 h and 36 h (Buserelin + PGF; n = 45). In experiment I, no effect of PGF on the interval treatment onset to ovulation was observed (P > 0.05), and no treatment effect was observed on the relative or cumulative proportion of females that ovulated post-treatment onset (P > 0.05). In experiment II, treatment onset to ovulation interval was shorter for Buserelin group than for PGF group (P < 0.05), and a higher cumulative percentage of Buserelin treated sows ovulated up to 48 h compared to PGF and Control groups (P < 0.01), with no differences from Buserelin + PGF. Treatments did not affect total number of piglets born in both experiments (P > 0.05). In conclusion, PGF did not hasten ovulation timing or affect litter size in weaned sows.

Effects of equine chorionic gonadotropin dosage and its splitting in different days on reproductive performance of Nellore cows synchronized for timed-artificial insemination.

This study evaluated the effects of dose of equine chorionic gonadotropin (eCG) and its splitting in different days of the synchronization protocol on reproductive performance of primiparous and multiparous Nellore cows. In the present study, 2,536 Nellore cows (1,634 primiparous and 902 multiparous) were assigned to receive in a 2 × 2 factorial design 1) an intravaginal progesterone (P4) device and 2.0 mg of estradiol benzoate (EB) on day -11, 12.5 mg (i.m.) of dinoprost tromethamine (PGF), 300 IU (i.m.) of eCG, 0.6 mg (i.m.) of estradiol cypionate (ECP), and P4 device withdrawal on day -2, followed by TAI on day 0 (n = 632 cows, being 409 primiparous and 223 multiparous; 300-2), 2) 300 IU (i.m) of eCG administered on days -4 and -2 (150 IU of eCG/day; n = 637 cows, being 412 primiparous and 225 multiparous; 300-4-2), 3) 400 IU (i.m.) of eCG administered on day -2 (n = 633 cows, being 406 primiparous and 227 multiparous; 400-2), and 4) 400 IU (i.m) of eCG administered on days -4 and -2 (200 IU of eCG/day; n = 634 cows, being 407 primiparous and 227 multiparous; 400-4-2). Individual cow BCS was assessed on days -11, 0 (timed-AI), and 31 of the study. Body condition score of the animals was classified into LOW or HIGH using the threshold of 2.75 (≤2.75 = LOW; >2.75 = HIGH). For primiparous cows, an eCG splitting effect was observed on follicle size, as cows receiving eCG on days -4 and -2 of the synchronization protocol had a larger follicle than cows administered eCG only on day -2. For day 31 P/AI, primiparous cows receiving 400-4-2, regardless of BCS, had a greater P/AI than cows from other treatments. Administering 400-4-2 to LOW BCS cows also resulted in greater P/AI than all other treatments assigned to LOW BCS cows. For multiparous cows, no treatment effect was observed for follicle size, estrus expression, and day 31 P/AI (P ≥ 0.21). In summary, increasing the dose and splitting the dose of eCG positively impacted the pregnancy rates of primiparous cows under a BCS ≤2.75, but no effects were detected on multiparous cows.

GnRH analogs induce a LH peak and increase pregnancy per timed-AI in ewes.

To date, there have been no studies testing the capacity of GnRH analogs and respective doses to induce a LH peak in sheep. In this sense, the present study aimed to evaluate the capacity of different synthetic forms and doses of GnRH in inducing LH release in sheep, and the effect of GnRH administration at timed artificial insemination (TAI) on pregnancy per timed-AI. In experiment 1, ewes (n = 40) received an intravaginal device (IVD) of medroxyprogesterone acetate (MPA; 60 mg) for 7 d and prostaglandin F2α analog on Day 5. On Day 7, the ewes were allocated randomly into one of eight groups (n = 5/group), which received a GnRH analog at a specific dose, as follows: lecirelin (12.5 or 25 µg), gonadorelin (50 or 100 µg), buserelin acetate (4.2 or 8.4 µg), or deslorelin (375 or 750 µg). Blood samples for LH determination were obtained at 0, 2, 4, and 6 h after GnRH and the IVDs were removed after the last blood collection. The maximal LH concentration induced by gonadorelin at doses of 50 µg and 100 µg (12.0 ± 2.4 ng/mL and 28.6 ± 7.1 ng/mL, respectively) was lower (P < 0.05) than serum LH induced by 8.4 µg of buserelin (78.9 ± 12.9 ng/mL), 375 µg and 750 µg of deslorelin (75.6 ± 7.4 ng/mL and 72.1 ± 10.6 ng/mL, respectively) and 12.5 µg and 25 µg of lecirelin (73.3 ± 17.8 ng/mL and 61.6 ± 5.9 ng/mL, respectively). However, the maximal LH concentration induced by 4.2 µg of buserelin (49.4 ± 5.9 ng/mL) was similar (P > 0.05) to the 100 µg of gonadorelin. The total release of LH (area under the curve - AUC) after treatment with 50 µg of gonadorelin (31.7 ± 5.9 ng h/mL) was lower (P < 0.05) than after other agonists. In a second experiment, 330 ewes were treated with IVD containing MPA for 7 d. Simultaneously with IVD removal, 250 µg of cloprostenol and 200 IU of eCG were administered. Then, ewes were assigned randomly to either no further treatment (control); or to receive 4.2 µg of buserelin acetate (GnRH group) at cervical TAI, which was performed with fresh semen 54 h after IVD withdrawal in all the animals. Higher pregnancy per timed-AI was observed for GnRH (50.3 %) compared to control (40.7 %). We conclude that buserelin acetate (8.4 µg), lecirelin (12.5 and 25 µg) and deslorelin (375 and 750 µg) induced a greater stimulatory effect on LH secretion than gonadorelin treatment. Furthermore, buserelin acetate treatment at TAI increased pregnancy per timed-AI in ewes previously treated with MPA and eCG.

Effect of recombinant bovine somatotropin on the reproductive efficiency of beef cows subjected to differently timed-artificial insemination protocols.

This study aimed to verify the reproductive efficiency of beef cows treated with recombinant bovine somatotropin (rbST). Study 1, Bos indicus cows were distributed (three groups). The control group (CG) was subjected: on day zero (d0), the animals received a CIDR and oestradiol benzoate (EB); on (d8, CIDR was removed, and PGF2α and oestradiol cypionate (EC) were administered; on d10, timed Artificial Insemination (TAI) was performed; on d45, pregnancy diagnosis was made. The rbST on d0 group (bST0G) was subjected to an identical protocol as CG, except for the addition of 250 mg rbST on d0. The rbST on d8 group (bST8G) was subjected to the same protocol as bST0G, except that the rbST was administered on d8 rather. In study 2, the animals followed the same design which was used in Bos taurus cows. The follicular growth rate (FGR) was calculated between d8 and d10. In study 1, pregnancy/artificial insemination (P/AI) did not differ among the treatments. FGR in bST8G was higher than in other groups. In study 2, bST0G showed higher Pregnancy/Artificial Insemination (P/AI) (p < .05) when compared with other groups. bST0G showed a different FGR (p < .0001) than the other groups. In conclusion, rbST (Bos indicus cows) did not increase P/AI, but it did promote follicular growth when administered on d8; the rbST administered on d0 improved P/AI (p < .05) and the FGR in Bos taurus cows.

Effects of estradiol cypionate dosage and body condition on reproductive performance of Nellore cattle synchronized for timed-artificial insemination.

This experiment was designed to evaluate the effects of increasing doses of estradiol cypionate (ECP) and different body condition score (BCS) on reproductive performance of Bos indicus beef females assigned to a timed-artificial insemination (TAI) management. In this experiment, 1683 Bos indicus Nellore cows were blocked by parity and assigned to receive 1) an intravaginal P4 device (1.9 g of P4) and 2.0 mg of estradiol benzoate on day -11, 12.5 mg (i.m.) of dinoprost tromethamine, 300 IU (i.m.) of equine chorionic gonadotrophin, 0.6 mg (i.m.) of estradiol cypionate and CIDR withdrawal on day -2, followed by TAI on day 0 (n = 849; 0.6ECP) or 2) the same synchronization protocol with 1.0 mg of ECP on day -2 (n = 834; 1.0ECP). In both treatments, estrus expression was measured between days -2 and 0. Body condition score (BCS) was evaluated on days -11, 31, and 71 of the experiment and the BCS variation (Δ) was also determined between these timepoints. Transrectal ultrasonography was performed on days 31, 71, and 111 for pregnancy rate determination. All binary data were analyzed using cow as the experimental unit with GLIMMIX, whereas continuous variables were analyzed with the MIXED procedure of SAS. No treatment effects were observed on estrus expression rate. Treatment × BCS interactions were observed for pregnancy rates in all time points (days 31, 71, and 111), as 1.0ECP cows with a LOW BCS also had a greater P/AI than cows assigned to 0.6ECP. In summary, increasing the dose of ECP benefited the reproductive performance of Nellore beef cows with a reduced BCS (≤2.75), whereas no benefits were seen when the BCS was considered adequate (>2.75).

Attempts for increasing Astyanax altiparanae spawning rates and percentage of responsive oocytes.

In this study, we aimed to propose changes in the protocol of cultured Astyanax altiparanae hypophysation to increase the maximum ovulation rate of 60% registered previously. To that two consecutive experiments were conducted. In the first experiment, three carp pituitary homogenate (CPH) doses (3, 6, and 9 mg/kg) were administered in a single injection, while in the second experiment, the 6 mg/kg CPH dose was tested either in single or double injections. In the first experiment, a single injection of 3 mg/kg CPH did not induce final oocyte maturation or spawning, while a dose of 6 mg/kg CPH resulted in an increase in the plasma level of prostaglandin (PGF2α) at ovulation. The single higher dose of 9 mg/kg CPH did not improve reproductive performance and even though anticipated the resumption of meiosis it was detrimental to the spawning rate. In the second experiment, the dose of 6 mg/kg CPH fractionated into two injections led to a higher spawning rate, spawning volume per female body mass, frequency of post-ovulatory complexes, and PGF2α concentration at ovulation compared to the single injection. The most effective treatment remained the 6 mg/kg of CPH fractionated into two injections, but still providing very low proportion of ovulated females (∼40 %). Overall, this study indicates that the spawning protocols for this species need to be improved to induce ovulation in a larger number of females and be more potent in those females that respond positively.

Effect of increased serum progesterone on luteal morphology and function, pregnancy, and gestational loss in Nelore cows.

The aim of the present study was to determine the impact of different strategies for increasing the level of serum progesterone (P4) on luteal morphology and function in bovine females. The effects of increasing P4 on pregnancy rate and gestational loss (GL) in Nelore cows subjected to timed artificial insemination (TAI) were also evaluated. A total of 939 cows were divided into three groups: P4LA (n = 305), 150 mg of long-acting injectable P4 7 days after TAI; GnRH (n = 306), 10 µg of buserelin acetate 7 days after TAI; and control (n = 328), no hormone treatment after TAI. Doppler ultrasound assessments and P4 measurements were performed on days 7 and 16 after TAI. The pregnancy rate and GL as a function of treatment were compared using the SAS GLIMMIX procedure. Corpus luteum (CL) vascular perfusion, volume, and plasma P4 concentration were analysed using the SAS PROC MIXED procedure. No significant difference was found among the treatments in terms of volume, number of pixels, and CL intensity or in the serum P4 concentration at 7 days after ovulation. The CL blood flow at 16 days after ovulation was lower in the P4LA and GnRH groups than that in the control group (p < .01). Serum concentrations of P4 at 16 days after ovulation were higher in the P4LA and GnRH groups than those in the control group (p = .04). A difference in the pregnancy rate (p = .003) and a trend in GL (p = .07) as a function of treatment were found. Overall, long-acting injectable P4 supplementation on day 7 after TAI or GnRH administration affected CL vascularization and increased the serum concentrations of P4 16 days after ovulation, promoting better pregnancy rates than the control.

Current knowledge about the processes of luteolysis and maternal recognition of pregnancy in camelids.

Camelids have many unique reproductive features that considerably differ from those of other domestic species. Females are induced ovulators with subsequent development of a corpus luteum (CL) with a short lifespan. Plasma progesterone concentration starts to increase on day 4, peaks on day 8-9 and, in non-pregnant animals, basal concentration is reached around day 10-11 post-induction of ovulation. Luteolytic pulses of prostaglandin F2α (PGF2α ) are firstly detected on day 7 or 8 (approximately on day 5-6 after ovulation), with maximal luteolytic peaks observed between days 9 and 11 post-mating, in coincidence with a high endometrial expression of cyclooxygenase 2, a limiting enzyme in prostaglandins synthesis. Unlike other species, oxytocin seems not to be involved in the luteolytic process in these species. The CL is the main source of progesterone secretion, and its function is required to support pregnancy. Despite constant research efforts, aspects of reproduction and maternal recognition of pregnancy in camelids remain not fully understood. A transient decrease and subsequent recovery in plasma progesterone concentration are observed after day 9 post-mating in pregnant animals in association with a pulsatile release of PGF2α and a transitory decrease in CL vascularization. Thus, embryo recognition should occur between days 8 and 12 post-mating. In camels, conceptus tissues exhibit aromatizing activity with the capacity to synthesize large amounts of oestradiol. Similarly, llama blastocysts secrete oestradiol-17ß during the preimplantation stage, with a higher production during the elongation period. An increase in the endometrial expression of oestrogen receptor α is also observed on day 12 post-mating. All these evidences suggest that oestrogen could be the signal released by the embryo at the time of its recognition in camelids. Besides, nearly 98% of pregnancies are carried out in the left horn. A decrease in the endometrial expression of mucin 1 and 16 genes has been reported, suggesting that these changes are crucial for successful embryo implantation; however, no differences have been observed between horns. Thus, maternal recognition of pregnancy in camelids is a particularly complex process that must occur in a concise time to allow the rescue of the CL and embryo survival.

Effects of additional gonadotropin-releasing hormone and prostaglandin F2α treatment to an estradiol/progesterone-based embryo transfer protocol for recipient lactating dairy cows.

This study was designed to evaluate whether the utilization of a second PGF2α treatment at the end of an estradiol/progesterone (E2/P4)-based protocol with or without GnRH at the beginning of the protocol would improve pregnancy rates of lactating Holstein cows assigned to timed embryo transfer. A total of 501 lactating Holstein cows in 5 farms were enrolled in the experiment. Within farm, cows were blocked by parity and, within block, were assigned randomly to (1) insertion of an intravaginal P4 device (controlled internal drug-releasing device; CIDR) and estradiol benzoate on d -11, PGF2α on d -4, CIDR withdrawal and an injection of estradiol cypionate on d -2, and timed embryo transfer on d 7 (1-PGF; n = 164); (2) the same treatments as 1-PGF, but with PGF2α administered on d -4 and -2 (2-PGF; n = 171); and (3) 2-PGF with the addition of a GnRH treatment on d -11 (GnRH+2-PGF; n = 166). Ovaries were scanned by transrectal ultrasonography on d -11, -4, and 7, and blood samples were collected on d -11, -4, 0, and 7 for P4 determination. Treatment comparisons were performed using contrasts. The proportion of cows with a new corpus luteum on d -4 was greater in GnRH+2-PGF cows. Cows in 1-PGF had a greater P4 concentration on d 0 but lesser P4 on d 7 compared with cows in the other groups. Cows assigned to receive 2-PGF (2-PGF and GnRH+2-PGF) had greater estrus expression, and a greater proportion of cows ovulated to estradiol cypionate. No further contrast effects were observed for follicle diameter, double ovulation rate, pregnancy per embryo transfer (P/ET) on d 32 and 60, or pregnancy loss. As P4 concentration on d -4 increased, P/ET on d 60 tended to increase. Cows with P4 ≥3.66 ng/mL on d -4 had greater P/ET on d 32 and 60 than those with P4 below that threshold. Regardless of treatment, cows with P4 concentration ≥3.66 ng/mL also had a greater pregnancy per synchronized protocol (P/SP) on d 60. Also, a P4 concentration on d -4 (low or high) × follicle diameter (continuous) interaction tendency was observed when evaluating P/ET. Although P/ET did not differ among cows with different follicles sizes with reduced P4 concentration on d -4 (<3.66 ng/mL), it increased in cows with larger follicles exposed to increased P4 concentration (≥3.66 ng/mL). When P4 on d 0 was evaluated, P/ET on d 32 and 60 was greater for cows with low (≤0.09 ng/mL) versus high (>0.21 ng/mL) P4; as P4 concentration on d 0 increased, P/ET linearly decreased. In summary, cows with increased P4 concentrations during growth of the ovulatory follicular wave had improved P/ET. Administering a second PGF2α dose reduced P4 concentration on d 0 and increased ovulatory response to the protocol, but no benefits were observed on P/ET or P/SP.

Fertility of Holstein cows and heifers submitted to timed artificial insemination and receiving one or two doses (12 h apart) of semen.

The objective of this retrospective study was to assess the effect of receiving a single (n = 50,285) or double (n = 4392) artificial insemination (AI), 12 h apart, within a timed artificial insemination protocol on pregnancy per AI (P/AI) in nulliparous heifers (inseminated with either sex-sorted or conventional semen) and pluriparous Holstein cows in a commercial dairy herd. Also, this study aimed to investigate the relationship between temperature-humidity index (THI) and time of the first AI and fertility. Fertility of cows receiving two AI with normothermia (THI <68) was higher (p < .05) than cows receiving a single AI (42.9% vs. 36.4%). P/AI of cows receiving two AI with severe heat stress (THI >85) was higher (p < .05) than cows receiving a single AI (21.0% vs. 12.6%). Regardless of heat stress conditions, applying the first AI in the morning increased (p < .05) P/AI in cows with double AI than in cows whose first AI occurred in the afternoon (38.4 vs. 33.3%). With moderate heat stress, and sexed-sorted semen, P/AI to timed AI was higher (65.0 vs. 51.9%; p < .05) in heifers receiving double AI than those serviced once. It was concluded that double AI, 12 h apart, enhanced fertility at timed AI than herd mates with a single AI, particularly with heat stress at breeding.

Intravaginal devices impregnated with medroxyprogesterone acetate avoid early parturition and synchronize farrowing in sows.

Two experiments were performed to evaluate the use of an intravaginal device (IVD) impregnated with medroxyprogesterone acetate (MPA) to avoid early parturition and synchronize farrowing in sows. In both experiments with IVDs, the gestation length, stillbirth rate, birth weight, colostrum yield, lactational litter performance, and subsequent reproductive performance of sows were assessed. In Experiment 1 (Exp. 1; n = 91), sows were assigned to four treatments to evaluate the minimum required MPA dose: without IVD (CONT; control), 400 mg (MPA400), 600 mg (MPA600), and 800 mg (MPA800) of MPA in the IVD. The IVD was inserted on day 110 of gestation and removed on day 115. No sows farrowed during IVD treatment. Gestation length was increased in treatments with MPA (116.4 days) compared to the control (CONT; 114.9 days; P < 0.01), without effects on piglet birth weight (P = 0.98). A lower percentage of deaths around the farrow (P = 0.02) was observed in the CONT (1.8%) compared to MPA treatments (6.8%). The dose of 400 mg of MPA, validated in Exp. 1, was used in Experiment 2 (Exp. 2; n = 84) to evaluate the performance of sows and piglets in a sow farrowing synchronization protocol. Sows were treated with MPA from days 110-114 of gestation with or without 0.168 mg of cloprostenol sodium (PGF2α), for luteolysis induction, at IVD removal. Thus, four treatments were considered: CONT - without MPA or luteolysis induction (no interventions); PGF2α - luteolysis induction on day 114 of gestation without MPA; MPA114 - MPA treatment till 114 days of gestation without luteolysis induction; MPA114 + PGF2α - MPA treatment and luteolysis induction on day 114 of gestation. The gestation length in treatments with IVDs was longer (P < 0.01) than CONT without a difference for PGF2α treatment (P = 0.46). No impact of IVD use on piglet birth weight (P = 0.67) and deaths around the farrow (P = 0.50) were observed. The colostrum yield (P = 0.65), immunocrit (P = 0.72), piglet performance during lactation (P = 0.81), and weaning-to-estrus interval (P = 0.21) were similar among treatments. In conclusion, the use of IVDs impregnated with 400 mg of MPA between days 110 and 114 of gestation prevented early parturition with no implications for piglet survival at birth, colostrum yield, or litter performance.

Early maturation of corpus luteum in rabbits - effect of sildenafil citrate on luteolytic capacity in the early luteal period

Background: Prostaglandin F2 alpha (PGF2 α) binds to the specific receptor (PTGFR) on the corpus luteum (CL) in mammals, inducing regression of the CL structure (luteolysis) and initiating a new cycle. While PGF2 α is effective only on mature CL, the immature CL structure (early luteal phase) resists PGF2 α. In this study, sildenafil citrate, which is used to increase blood flow in the genital organs for treating specific pregnancy issues in women, was administered during the early luteal phase in a rabbit model to test the hypothesis of enhancing blood flow to the CL, thereby promoting earlier maturation and enabling a response to PGF2 α. Materials, Methods & Results: The study was conducted in 2 sub-studies: clinical and molecular. A large number of rabbits were initially included in the sub-studies to ensure a sufficient number of pseudo-pregnant rabbits. Ovulation in rabbits was induced with buserelin acetate and was considered as day 0 of the study. The sub-studies were continued with rabbits whose pseudo-pregnancies were confirmed according to progesterone (P4 ) results. As a result, the studies were continued with a total of 41 pseudo-pregnant New Zealand female rabbits, 21 of which were included in the clinical sub-study and 20 in the molecular sub-study. In both sub-studies, on day 3 of the luteal period, rabbits in the treatment group received 5 mg/kg sildenafil citrate and all rabbits received a single dose of exogenous PGF2 α on day 4 to induce luteolysis. In the clinical sub-study, echotexture and intraovarian blood flow changes in the ovaries were determined by ultrasonography (USG) examination. In the molecular sub-study, the expression changes of Hypoxia Inducible Factor 1 Alpha (HIF1A) and Vascular Endothelial Growth Factor (VEGF) related to angiogenesis, Steroidogenic Acute Regulatory Protein (StAR) related to P4 metabolism, Prostaglandin-Endoperoxide Synthase 2 (PTGS2) related to prostaglandin (PG) mechanism and 15-Hydroxyprostaglandin Dehydrogenase (HPGD) genes at mRNA level were determined using Real Time Polymerase Chain Reaction (RT-PCR) in CL tissues obtained with ovariohysterectomy (OVH) at 1 and 12 h after PGF2 α injection. In addition, blood samples were collected for determine P4 levels from all rabbits. In the clinical sub-study; there was no difference between the groups in mean gray values (MGV), whereas there was a significant decrease in both pulsatile index (PI) and resistance index (RI) values at 40 min after PGF2 α injection (P < 0.05). In the molecular sub-study, it was determined that sildenafil citrate had no significant effect (P > 0.05) on the expression levels 1 and 12 h after PGF2 α injection. According to the results of the molecular sub-study, no significant effect of sildenafil citrate on the mRNA expression levels in the investigated genes was detected (P > 0.05). However, within each group, differences were found according to OVH time after PGF2 α injection. It was observed that PTGS2 and HPGD mRNA expressions decreased at the 12th h compared to the 1st h, while HIF1A expression increased (P < 0.05). Discussion: According to the results obtained from clinical and molecular sub-studies, it was determined that a single dose of sildenafil citrate (5 mg/kg) applied on the 3rd day of the luteal period did not contribute to the maturation process of the CL, did not increase blood flow, and was insufficient to break the resistance of the CL against PGF2 α applied on the 4th day of the luteal period. However, a significant decrease in the PI value at the 40th min after PGF2 α injection suggests that sildenafil citrate has a supportive effect, and that this decrease is also seen in the RI value, suggesting that its effect is insufficient against the vasoconstrictive effect of PGF2 α.

Abordagem terapêutica hormonal para cistos foliculares ovarianos em vacas leiteiras - relato de casos / Hormonal therapeutic approach for ovarian follicular cysts in dairy cattle - case reports / Enfoque terapéutico hormonal para quistes foliculares ováricos en vacas lecheras - informe de casos

Vacas de alta produção de leite estão mais sujeitas a desequilíbrios metabólicos pós-parto, influenciando na performance reprodutiva subsequente. Alterações relacionadas a funcionalidade do ovário podem desencadear desequilíbrios hormonais e desordens reprodutivas, como a formação de cistos ovarianos, os quais podem interferir no processo de ovulação e impactar substancialmente na eficiência reprodutiva. Neste estudo de caso em específico, sete vacas leiteiras foram diagnosticadas com a presença de cistos foliculares ovarianos. Foram submetidas a terapia hormonal envolvendo o uso de análogos de Hormônio Liberador de Gonadotrofinas (GnRH) e prostaglandina-F2a (PGF-2a), a qual apresentou resultados satisfatórios. A abordagem terapêutica hormonal tem sido amplamente utilizada devido à sua efetividade na resolução dos cistos ováricos e melhoria da função reprodutiva. É fundamental que o médico veterinário tenha conhecimento clínico sobre a abordagem adequada de cistos ovarianos, a fim de proporcionar saúde e bem-estar aos animais, garantindo bons índices em produção de leite e desempenho reprodutivo.

High milk production cows are more likely to postpartum metabolic imbalances, which may influence subsequent reproductive performance. Changes in ovarian functionality can trigger hormonal alterations and reproductive disorders, such as the formation of ovarian cysts, which can interfere with the ovulation process and substantially impact reproductive efficiency. In this specific case study, seven dairy cows were diagnosed with the presence of ovarian follicular cysts. They were submitted to hormonal therapy involving the use of Gonadotropin-Releasing Hormone (GnRH) and prostaglandin F2a (PGF-2a) analogs, which presented satisfactory results. Hormonal therapeutic approaches have been widely employed due to their effectiveness in resolving ovarian cysts and improving reproductive function. It is essential for the veterinarian to have clinical knowledge about the appropriate management of ovarian cysts in order to provide the health and welfare of the animals, ensuring suitable rates in milk production and reproductive performance.

Las vacas de alta producción de leche tienen mayor probabilidad de desequilibrios metabólicos posparto, lo cual puede influir en el rendimiento reproductivo posterior. Los cambios en la funcionalidad ovárica pueden desencadenar alteraciones hormonales y trastornos reproductivos, como la formación de quistes ováricos, que pueden interferir en el proceso de ovulación y afectar sustancialmente la eficiencia reproductiva. En este estudio de caso específico, se diagnosticó la presencia de quistes foliculares ováricos en siete vacas lecheras. Se sometieron a terapia hormonal que incluyó el uso de análogos de Hormona Liberadora de Gonadotropinas (GnRH) y prostaglandina F2α (PGF-2a), lo cual arrojó resultados satisfactorios. Los enfoques terapéuticos hormonales se han utilizado ampliamente debido a su efectividad en la resolución de quistes ováricos y la mejora de la función reproductiva. Es fundamental que el médico veterinario tenga conocimiento clínico sobre el manejo adecuado de los quistes ováricos para garantizar la salud y el bienestar de los animales, asegurando adecuadas tasas de producción de leche y rendimiento reproductivo.

Prostaglandin F2α treatment concurrent with artificial insemination does not affect bovine embryo production / Administração de prostaglandina F2 alfa no momento da inseminação artificial não afeta a produção de embriões bovinos

Treatment with prostaglandin F2α (PGF) induces ovulation and increases conception rates in cows, while improving embryo production in buffalos. However, its effect on superovulated cows is unknown. This study verified whether single PGF administration concurrent with artificial insemination (AI) improves fertilization and embryo production rates in superovulated cows. In each replicate, embryo donor cows were equally allocated to two groups: the untreated control and PGF groups. The latter of which received 482 µg of cloprostenol concurrent with the first AI. Each cow (n = 35) was subjected to two superovulations (SOV) in a crossover design (total = 70 embryo collections). In the control and PGF groups, respectively, the observed responses were [median (95% CI)]: 12 (10-18) and 15 (12-18) total structures, 9 (7-11) and 7 (6-10) viable embryos, 1 (0-1) and 1 (1-3) degenerated embryos, and 1 (0-3) and 2 (0-5) oocytes (P > 0.05). In conclusion, single PGF treatment concurrent with the first AI did not affect embryo production in superovulated cows.

A prostaglandina F2α (PGF) pode induzir a ovulação e melhorar tanto a concepção em vacas, como a produção de embriões em búfalas, mas o efeito em vacas superovuladas é desconhecido. Esse estudo teve como objetivo verificar se a administração de uma dose de PGF na inseminação artificial (IA) após a superovulação (SOV) melhora as taxas de fecundação e produção embrionária em vacas. Em cada replicação, vacas doadoras de embriões foram equilibradamente alocadas em dois grupos: controle, não tratado, ou PGF, que recebeu 482 µg de cloprostenol no momento da primeira IA. Cada doadora (n = 35) foi submetida a duas SOV em um delineamento crossover (total = 70 coletas de embriões). Nos grupos controle e PGF, respectivamente, foram observados [medianas (IC 95%)]: 12 (10-18) e 15 (12-18) estruturas totais; 9 (7-11) e 7 (6-10) embriões viáveis; 1 (0-1) e 1 (1-3) embriões degenerados; e 1 (0-3) e 2 (0-5) ovócitos (P > 0,05). Conclui-se que uma única administração de PGF no momento da primeira IA não afeta a produção embrionária de vacas superovuladas.

Disruption of multiple copies of the Prostaglandin F2alpha synthase gene affects oxidative stress response and infectivity in Trypanosoma cruzi.

Chagas disease, caused by the protozoan Trypanosoma cruzi, is a serious chronic parasitic disease, currently treated with Nifurtimox (NFX) and Benznidazole (BZ). In addition to high toxicity, these drugs have low healing efficacy, especially in the chronic phase of the disease. The existence of drug-resistant T. cruzi strains and the occurrence of cross-resistance between BZ and NFX have also been described. In this context, it is urgent to study the metabolism of these drugs in T. cruzi, to better understand the mechanisms of resistance. Prostaglandin F2α synthase (PGFS) is an enzyme that has been correlated with parasite resistance to BZ, but the mechanism by which resistance occurs is still unclear. Our results show that the genome of the CL Brener clone of T. cruzi, contains five PGFS sequences and three potential pseudogenes. Using CRISPR/Cas9 we generated knockout cell lines in which all PGFS sequences were disrupted, as shown by PCR and western blotting analyses. The PGFS deletion did not alter the growth of the parasites or their susceptibility to BZ and NFX when compared to wild-type (WT) parasites. Interestingly, NTR-1 transcripts were shown to be upregulated in ΔPGFS mutants. Furthermore, the ΔPGFS parasites were 1.6 to 1.7-fold less tolerant to oxidative stress generated by menadione, presented lower levels of lipid bodies than the control parasites during the stationary phase, and were less infective than control parasites.

Mitigation of low pregnancy rate in excitable Nellore cows by administration of GnRH or P4.

This research aimed to determine the effect of temperament on reproductive parameters including cortisol and progesterone (P4) in Nellore cows. Additionally, two methods for increasing plasma progesterone (P4) levels in excitable animals to enhance pregnancy rate (P/AI) and reduce pregnancy loss were investigated. In total, 939 cows were subjected to timed artificial insemination (TAI) and divided into three groups: (P4LA; n = 305) 150 mg of injectable long-acting progestogen 7 days after TAI; (GnRH; n = 306), 10 µg of buserelin acetate on day 7 after TAI; control group (CG; n = 328) without hormonal treatment. In 213 cows, randomly chosen from each group, ultrasound evaluations of the preovulatory follicle (Mode B) were performed on the day of insemination and of the corpus luteum (Color Doppler) 7 and 16 days after TAI. Blood samples were obtained from 20% of the 939 animals, randomly chosen from each group, on the day of insemination and after 7 and 16 days to measure cortisol and progesterone, respectively. At the time of insemination, subjective temperament evaluations were performed with the animals being classified as excitable (EXC) or adequate (ADQ). The SAS GLIMMIX procedure was used to compare the pregnancy rate (P/AI) and gestational loss within each temperament for the three experimental groups. Continuous variables were analyzed utilizing SAS PROC MIXED procedure. Cortisol concentration was higher and POF (preovulatory follicle) and CL (corpus luteum) volumes at the time of insemination and 7 days after AI, respectively, were lower in EXC animals than in ADQ. No significant difference was observed between the number of pixels, CL intensity, and plasma concentration of P4, 7 days after TAI. However, 16 days post-insemination, among the animals classified as EXC, higher concentrations of P4 were observed in the GnRH and P4LA groups than in the control. Regarding P4 concentrations, there was a tendency to be lower in animals classified as EXC than in ADQ within the control group (P = 0.06), while rate of blood flow from the CL was lower in EXC animals than in ADQ animals (P = 0.04). Among the ADQ animals, the GnRH and P4LA groups showed a lower CL flow rate than that observed in the control (P = 0.04), 16 days after the TAI. Among EXC animals, a higher pregnancy rate was observed in the GnRH and P4LA groups than in the control group (P = 0.01). In the control group, the pregnancy rate (P/AI) of the ADQ animals was higher than that of the EXC animals (P = 0.05). No statistically significant differences were observed between gestational losses when the treatments or temperaments were compared. In conclusion, the use of GnRH or P4LA, 7 days after insemination, improves pregnancy rates in excitable animals and is a viable alternative to minimize the negative impact of stress and improve reproductive efficiency in beef cattle.

The effect of progesterone length in timed AI in ewes.

This study aimed to evaluate the reproductive performance of ewes submitted to timed AI protocol with 7 (D7) or 9 (D9) days of progesterone. A total of 220 crossbred ewes (Doper × Santa Ines) were distributed in the treatments according to body weight (52.67 ± 11.76 kg), body condition score (2.5 ± 0.8; scale of 1-5), and the female category (multiparous, nulliparous and primiparous). Ewes received an intravaginal device of 0.3 g of progesterone (CIDR® Easy breed) on day 0, keeping in ewes for 7 or 9 days, which were the experimental treatments. At the time of P4 withdrawal, ewes received 300 IU of eCG (Novormon®) and 6.70 mg of dinoprost tromethamine (Lutalyse®). Insemination by laparoscopy was performed between 46 and 59 h after device removal, lasting from 1 to 5 min/ewe, which did not differ between protocols. The estrus detection rate was higher in the 9-day protocol compared to the 7-day protocol (82% and 65%, respectively, P = 0.0096). However, the 7-day protocol tended to increase pregnancy rate on the TAI compared to the 9-day protocol (45% and 33%, respectively, P = 0.09). The plasma concentration of progesterone at device removal was higher in the 7-day protocol than in the 9-day protocol (2.35 and 1.22 ng/mL, respectively, P = 0.04). We conclude that reducing the length of the estrus synchronization protocol to 7 days is recommended, which improved the reproductive response in ewes.

Effect of the addition of GnRH and a second prostaglandin F2α treatment on pregnancy per artificial insemination in lactating dairy cows submitted to an estradiol/progesterone-based timed-AI protocol.

Two experiments determined whether the addition of GnRH at the beginning of an estradiol (E2)/progesterone (P4)- based synchronization protocol and/or a second dose of prostaglandin F2α (PGF2α) the day before P4 device removal improves pregnancy rate in lactating dairy cows. On Day 0, all cows received a CIDR-B device and 2 mg i.m. estradiol benzoate, and half received 200 µg i.m. gonadorelin acetate (GnRH). On Day 7, cows were further subdivided to receive PGF2α (500 µg i.m. cloprostenol) or no PGF2α treatment. On Day 8, CIDR-B were removed, and all cows received PGF2α, 1 mg estradiol cypionate and 400 IU eCG i.m., and an estrus detection aid. Experiment 1 was designed to evaluate the effect of treatments on follicular development from P4 device removal to ovulation, expression of estrus, time of ovulation and serum P4 concentrations. Cows (n = 76) were examined by ultrasonography and bled for serum P4 determinations every 12 h from the time of P4 device removal but were not inseminated. In Experiment 2, all cows (n = 1036) were inseminated based on estrus detection using tail-paint. Cows with >50% of the paint rubbed-off by 48 h after P4 device removal were inseminated at that time, whereas those not in estrus received 100 µg i.m. of GnRH and were inseminated 12 h later. In Experiment 1, the interval from P4 device removal to ovulation was 71.7 ± 1.5 h and did not differ among groups. However, cows that received 2 injections of PGF2α had a greater (P < 0.01) estrus rate and lower (P < 0.01) P4 concentrations at 48 h after P4 device removal than those that received 1 PGF2α (estrus rate: 86.8% vs 68.4% and P4 concentration: 0.12 ± 0.01 vs 0.36 ± 0.07, for 2 and 1 PGF2α, respectively). In Experiment 2, estrus rate was also influenced by the number of PGF2α treatments, regardless of whether cows received or did not receive GnRH on Day 0 (2 PGF2α: 84.7%, 438/517 vs 1 PGF2α: 65.7%, 341/519; P < 0.01). Furthermore, there was a GnRH treatment by number of PGF2α treatments interaction (P < 0.05) on P/AI that was attributed to greater (P < 0.05) P/AI in cows that received GnRH on Day 0 and 2 PGF2α than in the other three treatment groups (EB+1 PGF2α: 45.2%, 119/263; EB+2 PGF2α: 45.8%, 119/260; EB + GnRH + 1 PGF2α: 45.7%, 117/256 and EB + GnRH + 2 PGF2α: 57.2%, 147/257). It was concluded that the addition of GnRH on Day 0 and a second dose of PGF2α the day before P4 device removal improves P/AI in lactating dairy cows synchronized with an estradiol/P4-based protocol.