LH and FSH concentration and follicular development in Nellore heifers submitted to fixed-time artificial insemination protocols with different progesterone concentrations

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Neither plasma progesterone concentrations nor exogenous eCG affects rates of ovulation or pregnancy in fixed-time artificial insemination (FTAI) protocols for puberal Nellore heifers

The objective was to evaluate the effects of plasma progesterone (P4) concentrations and exogenous eCG on ovulation and pregnancy rates of pubertal Nellore heifers in fixed-time artificial insemination (FTAI) protocols. In Experiment 1 (Exp. 1), on Day 0 (7 d after ovulation), heifers (n = 15) were given 2 mg of estradiol benzoate (EB) im and randomly allocated to receive: an intravaginal progesterone-releasing device containing 0.558 g of P4 (group 0.5G, n = 4); an intravaginal device containing 1 g of P4 (group 1G, n = 4); 0.558 g of P4 and PGF2α (PGF; 150 μg d-cloprostenol, group 0.5G/PGF, n = 4); or 1 g of P4 and PGF (group 1G/PGF, n = 3). On Day 8, PGF was given to all heifers and intravaginal devices removed; 24 h later (Day 9), all heifers were given 1 mg EB im. In Exp. 2, pubertal Nellore heifers (n = 292) were treated as in Exp. 1, with FTAI on Day 10 (30 to 36 h after EB). In Exp. 3, pubertal heifers (n = 459) received the treatments described for groups 0.5G/PGF and 1G/PGF and were also given 300 IU of eCG im (groups 0.5G/PGF/eCG and 1G/PGF/eCG) at device removal (Day 8). In Exp. 1, plasma P4 concentrations were significantly higher in heifers that received 1.0 vs 0.588 g P4, and were significantly lower in heifers that received PGF on Day 0. In Exp. 2 and 3, there were no significant differences among groups in rates of ovulation (65-77%) or pregnancy (Exp. 2: 26-33%; Exp. 3: 39-43%). In Exp. 3, diameter of the dominant ovarian follicle on Day 9 was larger in heifers given 0.558 g vs 1.0 g P4 (10.3 ± 0.2 vs 9.3 ± 0.2 mm; P < 0.01). In conclusion, lesser amounts of P4 in the intravaginal device or PGF on Day 0 decreased plasma P4 from Days 1 to 8 and increased diameter of the dominant follicle on Day 9. However, neither of these nor 300 IU of eCG on Day 8 significantly increased rates of ovulation or pregnancy. © 2011.

Use of cooled bull semen as a strategy to increase the pregnancy rate in fixed-time artificial insemination programs-case report

Semen cryopreservation is still considered suboptimal due to lower fertility when compared to fresh semen. The reasons for the loss of fertility are various and related to irreversible damage caused to the cells during the freeze-thaw process. An alternative to conventional cryopreservation represents the use of chilled bull semen, preventing the damage associated with freezing, thereby guaranteeing greater sperm viability. The aim of this study was to describe the use of cooled bull semen as a strategy to increase the pregnancy for Fixed-Time Artificial Insemination (FTAI) of Nellore (Bos indicus) cows. One ejaculate of a select Nellore bull obtained by electroejaculation was used; the semen sample was fractioned into two aliquots: one diluted in Botu-Bov® extender containing 6.4% glycerol for cryopreservation (BB-F, frozen group) and one diluted in the same extender, free from cryoprotectants and used for cooling (BB-C, cooled semen group). The samples in the BB-C group were chilled to 5°C using an isothermic box and maintained for 24 h prior to use. A total of 349 lactating Nellore cows (70-90 days after birth) were synchronized by the insertion of a progesterone releasing device (1.0 g) and estradiol benzoate (2.0 mg i.m.) on a random day of the estrous cycle (Day 0); FTAI was performed 44-48 h after the removal of the device. The pregnancy rates were 45.71 and 61.49% (P<0.05), respectively, for the cryopreserved or chilled bovine semen groups. In conclusion, the use of bull semen cooled for 24 h represents an alternative to conventionally cryopreserved semen, as determined by the increase the pregnancy per artificial insemination in bovine herds. © 2012 Science Publication.

Timing of prostaglandin F2α treatment in an estrogen-based protocol for timed artificial insemination or timed embryo transfer in lactating dairy cows

Objectives were to investigate progesterone concentrations and fertility comparing 2 different intervals from PGF2α treatment and induced ovulation in an estrogen-based ovulation synchronization protocol for timed artificial insemination (TAI) or timed embryo transfer (TET) in lactating dairy cows. A total of 1,058 lactating Holstein cows [primiparous (n=371) and multiparous (n=687)], yielding 34.1±0.33 kg of milk/d at various days in milk were randomly assigned to receive treatment with PGF2α on either d 7 or 8 of the following protocol: d 0: 2mg of estradiol benzoate + controlled internal drug release device; d 8: controlled internal drug release device removal + 1.0mg of estradiol cypionate; d 10: TAI or d 17: TET. Only cows with a corpus luteum at d 17 received an embryo and all cows received GnRH at TET. Pregnancy diagnoses were performed by detection (transrectal ultrasonography) of an embryo on d 28 or a fetus on d 60. Fertility [pregnancy per artificial insemination (P/AI) or pregnancy per embryo transfer (P/ET)] was affected by breeding technique (AI vs. ET) and time of PGF2α treatment (d 7 vs. 8) at the 28-d pregnancy diagnosis for TAI [32.9% (238) vs. 20.6% (168)] and TET cows [47% (243) vs. 40.7% (244)] and at the 60-d pregnancy diagnosis for TAI [30% (238) vs. 19.2% (168)] and TET cows [37.9% (243) vs. 33.5% (244)]. The progesterone (P4) concentration at d 10 altered fertility in TAI cows, with higher P/AI in cows with P4 concentration <0.1 ng/mL compared with cows with P4 concentration ≥0.1 ng/mL, and in ET cows, with higher P/ET in cows with P4 concentration <0.22 ng/mL compared with cows with P4 concentration ≥0.22 ng/mL. Prostaglandin F2α treatment at d 7 increased the percentage of cows with P4 <0.1 ng/mL on d 10 [39.4 (85) vs. 23.2 (54)]. Reducing the period between PGF2α and TAI from 72 to 48h in dairy cows resulted in a clear reduction in fertility in cows bred by TAI and a subtle negative effect in cows that received TET. The earlier PGF2α treatment benefits are most likely mediated through gamete transport, fertilization, or early embryo development and a more subtle effect of earlier PGF2α treatment that may be mediated through changes in the uterine or hormonal environment that manifests itself after ET on d 7. © 2013 American Dairy Science Association.

Estrus synchronization and fixed time artificial insemination (FTAI) in dairy buffaloes during seasonal anestrus

The aim of this work was to study estrus synchronization and fixed time artificial insemination (FTAI) in dairy buffaloes during season anestrus. One hundred thirty-nine dairy buffaloes in seasonal anestrus were divided in two groups as G1(n=66) and G2(n=73). The protocols for both the groups were the same until day (D)14:D0 administration of 2.0 mg estradiol benzoate and implantation of progesterone device (P4) for 14 days; D14 removal of P4 plus 150 mg of cloprostenol and 400 IU of equine chorionic gonadotropin. On D16, G1 received 10 mg of buserelin and G2 100 mg deslorelin acetate. On D17, both the groups were submitted to FTAI. Ultrasonographic examinations of ovaries were performed on D0, D14, D16 and D17. Results showed that pregnancy rates in G1 and G2 were 20 and 41% (p<0.05) and the ovulation rates were 16.6 and 37%, respectively (p<0.05). The dominant follicle (DF) diameter on D16 was 7.9 mm in G1 and 8.9 mm in G2 (p>0.05). Thirty-five percent of the animals in G1 and 54.1% in G2 showed a diameter DF greater than 8.0 mm on D16 (p>0.05). Thus, it could be concluded that the protocols synchronized the estrus, leading the concentration of the parturitions in the period of low milk production. Deslorelin was more efficient than buserelin due the higher percentage of DF ovulation and higher pregnancy rates.

Effect of progesterone concentrations, follicle diameter, timing of artificial insemination, and ovulatory stimulus on pregnancy rate to synchronized artificial insemination in postpubertal Nellore heifers

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Increasing length of an estradiol and progesterone timed artificial insemination protocol decreases pregnancy losses in lactating dairy cows

Our hypothesis was that increasing the length of an estradiol and progesterone (P4) timed artificial insemination (TAI) protocol would improve pregnancy per artificial insemination (P/AI). Lactating Holstein cows (n = 759) yielding 31 +/- 0.30 kg of milk/d with a detectable corpus luteum (CL) at d - 11 were randomly assigned to receive TAI (d 0) following 1 of 2 treatments: (8d) d - 10 controlled internal drug release (CIDR) and 2.0 mg of estradiol benzoate, d - 3 = PGF(2 alpha) (25 mg of dinoprost tromethamine), d - 2 = CIDR removal and 1.0 mg of estradiol cypionate, d 0 = TAI; or (9d) d - 11 = CIDR and estradiol benzoate, d -4 = PGF(2 alpha), d -2 CIDR removal and estradiol cypionate, d 0 TAI. Cows were considered to have their estrous cycle synchronized in response to the protocol by the absence of a CL at artificial insemination (d 0) and presence of a CL on d 7. Pregnancy diagnoses were performed on d 32 and 60. The ovulatory follicle diameter at TAI (d 0) did not differ between treatments (14.7 +/- 0.39 vs. 15.0 +/- 0.40 mm for 8 and 9 d, respectively). The 9d cows tended to have greater P4 concentrations on d 7 in synchronized cows (3.14 +/- 0.18 ng/mL) than the 8d cows (3.05 +/- 0.18 ng/mL). Although the P/AI at d 32 [45 (175/385) vs. 43.9% (166/374) for 8d and 9d, respectively] and 60 [38.1 (150/385) vs. 40.4% (154/374) for 8d and 9d, respectively] was not different, the 9d cows had lower pregnancy losses [7.6% (12/166)] than 8d cows [14.7% (25/175)]. The cows in the 9d program were more likely to be detected in estrus [72.0% (269/374)] compared with 8d cows [62% (240/385)]. Expression of estrus improved synchronization [97.4 (489/501) vs. 81% (202/248)], P4 concentrations at d 7 (3.22 +/- 0.16 vs. 2.77 +/- 0.17 ng/mL), P/AI at d 32 [51.2 (252/489) vs. 39.4% (81/202)], P/AI at d 60 [46.3 (230/489) vs. 31.1% (66/202)], and decreased pregnancy loss [9.3 (22/252) vs. 19.8% (15/81)] compared with cows that did not show estrus, respectively. Cows not detected in estrus with small (<11 mm) or large follicles (>17 mm) had greater pregnancy loss; however, in cows detected in estrus, no effect of follicle diameter on pregnancy loss was observed. In conclusion, increasing the length of the protocol for TAI increased the percentage of cows detected in estrus and decreased pregnancy loss.

The influence of insemination dose on pregnancy per fixed-time artificial insemination in beef cows is affected by semen extender

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Prostaglandin treatment at the onset of norgestomet and estradiol-based synchronization protocols did not alter the ovarian follicular dynamics or pregnancy per timed artificial insemination in cyclic Bos indicus heifers

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Inferences of body energy reserves on conception rate of suckled Zebu beef cows subjected to timed artificial insemination followed by natural mating

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effect of adding a gonadotropin-releasing-hormone treatment at the beginning and a second prostaglandin F-2 alpha treatment at the end of an estradiol-based protocol for timed artificial insemination in lactating dairy cows during cool or hot seasons of the year

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Impact of the temperament of Nellore cows on the quality of handling and pregnancy rates in fixed-time artificial insemination

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)