Pregnancy Rates to Fixed Embryo Transfer of Vitrified IVP Bos indicus, Bos taurus or Bos indicus × Bos taurus Embryos.

The pregnancy rates obtained after the transfer of cryopreserved in vitro-produced (IVP) embryos are usually low and/or inconsistent. The objective of this study was to evaluate the pregnancy rates of Holstein, Gyr and Holstein × Gyr cattle after the transfer of vitrified IVP embryos produced with X-sorted sperm. Seventy-two Gyr and 703 Holstein females were subjected to ovum pickup (OPU) sessions, followed by in vitro embryo production using semen from sires of the same breeds. Embryos (1636 Holstein, 241 Gyr and 1515 Holstein × Gyr) were exposed to forskolin for 48 h prior to vitrification. The pregnancy rate achieved with Gyr dam and sire was 46.1%, which was similar (p = 0.11) to that of Holstein dam and Gyr sire (40.3%). Crossing Gyr dams with Holstein sires resulted in a pregnancy rate of 38.9% and did not differ (p = 0.58) from the pregnancy rate obtained with the cross between Holstein dams and Gyr sires. The rate obtained with Holstein dam and sire was 32.5%. The average pregnancy rate was 36.6%, and no difference was found in the proportion of female foetuses (88.8%, in average) among breeds (p > 0.05). In conclusion, transfer of cryopreserved X-sorted embryos represents an interesting choice for dairy cattle. Despite the small differences between pregnancy rates, we highlight the efficiency of this strategy for all of the racial groups studied.

Improvement of development of equine preantral follicles after 6 days of in vitro culture with ascorbic acid supplementation.

The aim of this study was to evaluate the effects of different concentrations of ascorbic acid (25, 50, and 100 µg/mL) in supplemented minimum essential medium (MEM+) on the development of equine preantral follicles that were cultured in vitro for 2 or 6 days. The contralateral ovaries (n = 5) from five mares in seasonal anestrus were collected from a local abattoir. Nine ovarian tissue fragments of approximately 5 × 5 × 1 mm were obtained from each animal. One fragment was immediately fixed and subjected to histologic analysis (control group; Day 0), and the other eight were placed in PBS supplemented with penicillin (200 IU/mL) and streptomycin (200 mg/mL) at 4 °C for 1 hour (during transport to the laboratory). The fragments were cultured in situ for 2 days (D2) or 6 days (D6) in MEM+ or MEM+ plus ascorbic acid at three different concentrations, establishing the following nine groups: control; MEM+ (D2); MEM+ (D6); MEM+ 25 µg/mL of ascorbic acid (D2); MEM+ 25 µg/mL of ascorbic acid (D6); MEM+ 50 µg/mL of ascorbic acid (D2); MEM+ 50 µg/mL of ascorbic acid (D6); MEM+ 100 µg/mL of ascorbic acid (D2); and MEM+ 100 µg/mL of ascorbic acid (D6). The preantral follicles were classified according to their stage (primordial, primary, secondary, or antral) and their morphology (normal or abnormal). Slides (n = 951) including 4450 histologic sections were evaluated. Follicles were observed in only 4.85% (216 of 4450) of the histologic sections. Of the 407 follicles evaluated, 120 were in the primordial stage and 287 were in different developmental stages; additionally, 43.5% were morphologically normal. After 6 days of culture, the groups cultured with 50 and 100 µg/mL of ascorbic acid differed in terms of follicular development compared with the other groups. On the basis of occurrence of follicular development and the presence of viable follicles, it can be concluded that a positive effect of culture for 6 days in MEM+ supplemented with 50 and 100 µg/mL of ascorbic acid was observed on equine ovarian fragments.

Resynchronization of estrous cycle with eCG and temporary calf removal in lactating Bos indicus cows.

The aim of this study was to compare four methods of estrus resynchronization performed 23 days after timed artificial insemination (TAI) plus estrus observation in Bos indicus cows. Eight hundred fourteen lactating Nelore cows were submitted to TAI and then randomly assigned to one of the five following treatments: R23 (resynchronization without eCG), R23/200 (resynchronization with 200 IU of eCG), R23/300 (resynchronization with 300 IU of eCG), R23/TCR (resynchronization with temporary calf removal [TCR]), and a control group, with estrus observation followed by AI (with no resynchronization). Treatment consisted of a progesterone device plus administration of estradiol benzoate on Day 0; on Day 8, the device was removed and cloprostenol was applied, together with estradiol cypionate. Also on Day 8, either eCG was administered or TCR was performed in the resynchronized groups, except for R23. The females were inseminated 48 hours after device removal or TCR (33 days after the first TAI). The control group was kept under estrus observation from 18 to 23 days after the first TAI and was inseminated 12 hours after detection of estrus. The first pregnancy evaluation was performed using ultrasound examination 31 days after the first TAI. After 30 days of the resynchronization, a second pregnancy evaluation was performed and the animals in the R23/300 and R23/TCR groups achieved the highest conception rates, 76.6% and 74.0%, respectively (P < 0.05). There were no differences between the conception rates of the animals in the R23/200 (63.3%), R23 (61.3%), and control (54.3%) groups (P > 0.05). These results suggest that estrus resynchronization at 23 days after TAI can effectively improve the conception rate of lactating Bos indicus cows in a short time period. Furthermore, resynchronization with 300 IU of eCG or with TCR provided the best results.

Cryosurvival and pregnancy rates after exposure of IVF-derived Bos indicus embryos to forskolin before vitrification.

In vitro-produced (IVP) bovine embryos are more sensitive to cryopreservation than their in vivo counterparts due to their higher lipid concentrations, whereas Bos indicus IVP embryos are even more sensitive than Bos taurus IVP embryos. To examine the effects of a lipolytic agent, before vitrification of Bos indicus IVP embryos, on embryo survival, viability, and pregnancy rates, two experiments were conducted. In experiment 1, Bos indicus (Nelore) embryos were produced from abattoir-derived ovaries and allocated into two groups. In the treatment group, 10 µM of forskolin was added to the in vitro culture medium on Day 5 and incubated for 48 hours. On Day 7 of culture, IVP-expanded blastocysts from both the control (n = 101) and treatment (n = 112) groups were vitrified with ethylene glycol and DMSO via the Cryotop procedure. Although there was no significant difference between the rates of blastocoel reexpansion and hatching of the embryos exposed to forskolin (87.5% and 70.5%, respectively) compared with the control embryos (79.2% and 63.3%, respectively), the numerically superior rates of the embryos exposed to forskolin led to another experiment. In experiment 2, blastocysts produced from the ovum pick up were exposed or not exposed to the lipolytic agent and vitrified as in experiment 1. Embryos treated with forskolin had higher pregnancy rates than the control group (48.8% vs. 18.5%). In view of these results, 1908 Bos indicus embryos were produced from ovum pick up, exposed to the lipolytic agent, and blastocysts were transferred to recipients, and the pregnancy rates of the embryos of various breeds were compared. The mean pregnancy rate obtained was 43.2%. All data were analyzed by chi-square or by binary logistic regression (P ≤ 0.05). In conclusion, treatment with forskolin before vitrification improved cryotolerance of Bos indicus IVP embryos, resulting in good post-transfer pregnancy rates.

Internal artificial vagina (IAV) to assess breeding behavior of young Bos taurus and Bos indicus bulls.

Bull breeding soundness evaluation (BBSE) usually neglects the libido and mating ability evaluation. The internal artificial vagina (IAV) permits semen sampling, as well as mating ability evaluation. Few studies have been performed using IAV with young bulls and there are none with Bos indicus bulls. The present study evaluated sexual behavior, mating ability and semen quality in young Bos taurus (Devon) and B. indicus (Nellore) bulls using the IAV device. In the first experiment, 52 Devon bulls, 18-25 months old were observed, and the behavior and mating ability recorded over a 10-min period within a restrained mount-cow with an IAV inserted. In the second experiment, 20 Nellore bulls, 20-30 months old were evaluated over a 20 min period. Of the 52 Devon bulls, 45 (86.5%) had semen recovered with the IAV, 31 (69.0%) were considered satisfactory. Nellore bulls exhibited a different sexual behavior, with 10 bulls not showing any interest in the females. Four bulls demonstrated sexual interest only once, e.g., sniffing, two showed interest on more than one occasion, and four had more than two mounts or mounting attempts. None out of the Nellore bulls was collected with IAV. The IAV was an effective and welfare-promoting animal technology for the evaluation of semen quality and mating ability of B. taurus bulls. However, the IAV was not adequate for young Nellore bulls, probably due to their quiescent sexual behavior and delayed sexual maturity. Further studies are needed to evaluate the performance of the IAV for older Nellore bulls.