Fresh or Frozen Embryo Selection in Embryo Transfer: Live Birth Rates and Obstetric and Fetal/Neonatal Results

: Assisted reproductive techniques used in the treatment of infertility have been promising methods for infertile individuals. Embryo selection and embryo transfer are an important part of assisting reproductive techniques. The selection of the embryo to be transferred is important for the implantation and clinical pregnancy success. In addition, whether to use a fresh embryo or frozen embryo for embryo transfer is a controversial issue. While the fresh embryo transfer technique is widely used, the frozen embryo transfer technique has become widespread. The main factor in choosing the method of freezing the embryos is to avoid the negative effects of controlled ovarian hyperstimulation on endometrial receptivity. Therefore, it is thought that the use of frozen embryos can improve pregnancy outcomes and reduce the risk of developing obstetric and perinatal problems. However, in the embryo freezing technique, there are problems such as the risk of developing degeneration in the embryo during freezing or thawing process and postponing the transfer. In addition, adverse conditions have been reported such as an increased risk of developing hypertensive disorders in the mother and macrosomia in the baby.

A Nonsurgical Embryo Transfer Technique for Fresh and Cultured Blastocysts in Rats

The use of a nonsurgical embryo transfer technique in rodents eliminates the potential pain, distress, and health complications that may result from a surgical procedure and as such, represents a refinement in rodent assisted reproductive techniques. A nonsurgical technique has not been previously developed for use with rat embryos. Here we describe an efficient method to deliver either fresh or cultured blastocyst stage embryos to the uterine horn of pseudopregnant female rats using a rat nonsurgical embryo transfer (rNSET) device. The rNSET device is composed of a Teflon catheter and a hub that attaches to a 2 μL pipette. Oxytocin is used to dilate the cervix before the delivery of blastocysts, allowing passage of the rNSET catheter directly into the uterine horn for embryo delivery. The efficiency of recovery of pups after nonsurgical embryo transfer is similar to the efficiency after surgical embryo transfer. Furthermore, the technique is not stressful to the subjects, as demonstrated by the absence of a decrease in weight or increase in fecal corticosterone level in recipients of embryos delivered nonsurgically, without the use of anesthesia or analgesia.

Effect of rectal temperature on efficiency of artificial insemination and embryo transfer technique in dairy cattle during hot season

This study aimed to evaluate the effects of rectal temperature (RT) as well as artificial insemination (AI) technique on pregnancy rates in Holstein cows and artificial insemination or embryo transfer (ET) techniques in Holstein heifers during summer. The experiments were conducted on five dairy farms in Hungary, where 1 631 data were examined. The RT was measured immediately before reproductive techniques using a digital thermometer. The effects of animal group and month on RT were analysed. The enhancement of RT until September can be seen in heifers, but the highest RT of cows occurred during July. In line with the enhancement of RT the pregnancy rate decreased in all groups; the lowest (cows) and the highest (heifers) value was observed in July. Moderate to high negative coefficients of correlation were detected between rectal temperature and pregnancy rate for particular groups (r = −0.3 – −0.7). More than 92% of ET, 48% and 16% of inseminated heifers and cows were pregnant up to the category of 39.1°C of RT, above this it did not change considerably in the inseminated groups. In inseminated animals with RT higher than 39.1 °C significantly higher services per conception could be observed contrary to ET heifers. ET may become a more effective strategy to improve pregnancy success in heifers compared to AI during summer.

Frequencies of genotypes and alleles of rs41256848 in the LHCGR gene in the population of black-and-white holsteinized cattle

Embryo transfer technique is one of the key in accelerated reproduction of cattle. One of the most important stages is the selection of donor cows that are most sensitive to the procedure of hormonal stimulation of ovulation. One of the promising genetic markers of the reproductive status of cattle is currently the gene encoding the luteinizing hormone / choriogonadotropin receptor (LHCGR). One of the SNP in the LHCGR gene of cattle has already been described in the literature as associated with the number of oocytes and the quality of embryos - rs41256848 (c.1401G> T, p.Trp467Cys). The purpose of this work was to estimate the frequencies of genotypes and alleles of this substitution in the population of Black-and-White holsteinized cattle (190 cows). Genotyping was performed by PCR-RFLP method. In the studied population of cattle, the frequency of the G allele associated with higher rates in the total number of oocytes and the number of embryos survived after transplantation, as well as with the least number of unfertilized oocytes, is 63.2%.