The influence of transfer gun passage time through the uterine cervix on pregnancy rate in recipient heifers

Abstract

The influence of passage time of the transfer gun through the uterine cervix and body to the embryo insertion site on pregnancy rate was analysed in 248 recipient heifers (mean age: 15-17 months). Embryos (90 fresh and/or 88 and 70 frozen in glycerol and ethylene glycol, respectively, grades 4 and 5, stage 1 or 2) were transferred to the ipsilateral uterine horn on day 7. Two different transfer guns were used in this experiment: a sterilisable steel transfer instrument to be used without sheaths with a removable tip made of gold-plated stainless steel (Wörrlein Minitüb) or a transfer stylet with sheaths with a metal tip and a side opening (Cassou gun, IMV Technologies). The time of passage of the instruments through the uterine cervix and body to the site of embryo deposition in the uterine horn was measured in the study. In order to randomise the risk of errors, all manipulations were carried out by the same experienced operator. The average time needed for the insertion of embryos into the uterus was 50.6 seconds (s) and it was longer for the transfer gun with sheaths than for the metal-tipped transfer gun (60.1 and 40.8 s, respectively) (P < 0.001). The average conception rate was 45.6%. If the time needed to insert embryos into the uterus was 10-60 s, the conception rate was 53.4% (up to 20, 21-30, 31-40, 41-50 and 51-60 s - 57.7, 52.5, 50, 51.5 and 50%, respectively). In contrast, if the time needed to insert the embryo in the uterine horn was longer than 60 s, the conception rate was 20.4% (61-80, 80.1-120 and > 120 s - 28.0, 6.0 and 24.9%, respectively). Thus, it cannot be excluded that the type of the applied transfer gun may influence pregnancy rate in recipient cows due to its effect on cervical passage time.

The incompletely fulfilled promise of embryo transfer in cattle—why aren’t pregnancy rates greater and what can we do about it?

“…That one or more of insults to the reproductive tract are potentially deleterious to pregnancy establishment is indicated by observations that the difficulty in passing the cervix and depositing the embryo in the uterus is negatively associated with P/ET ( Jaśkowski et al, 2010 ; Kasimanickam et al, 2018 , 2019 ; Alkan et al, 2020 ). Moreover, the physical characteristics of the transfer instrument have been reported to affect pregnancy success.…”

“…Moreover, the physical characteristics of the transfer instrument have been reported to affect pregnancy success. The P/ET was higher when embryos were transferred using a steel instrument with a gold-plated tip and no plastic sheath than when using a instrument covered with plastic sheath ( Jaśkowski et al, 2010 ). Treatment of recipients with flunixin meglumine, an inhibitor of prostaglandin F 2α synthesis, improved P/ET in several experiments ( Purcell et al, 2005 ; Scenna et al, 2005 ; Kasimanickam et al, 2018 , 2019 ).…”

“…Rather than simply relying on what already exists, often designed for other purposes (Petri dishes and Foley catheters), there are opportunities to devise tools that are optimized for use with embryo technologies. Some of these new tools can be simple, as for the above-mentioned example of new ET pipettes ( Jaśkowski et al, 2010 ). Others can be much more sophisticated.…”

Effectiveness of embryo transfer in cows - risk factors including in vivo derived and in vitro produced embryos

“…Worse results of pregnancies are obtained in the case of embryo transfer in cows than in the case of heifers [18,50]. It is suspected that one of the reasons is a longer TTIGP and larger uterus size [18,51]. Similarly, the multiple use of a female as a recipient reduces the likelihood of pregnancy after embryo transfer.…”

A Critical Overview on Prostaglandin Inhibitors and Their Influence on Pregnancy Results after Insemination and Embryo Transfer in Cows

“…Assisted reproductive techniques, such as artificial insemination (AI) or embryo transfer (ET) in cows, have been used in veterinary practice for many decades. The effectiveness of ET depends on a number of conditions, including individual, environmental, technical, and technological ones [1,2]. While the number of embryos transferred is relatively constant worldwide, the results of ET have not improved over the years despite improvements in the welfare of recipients, in technical skills, and in methods of cryopreservation and embryo production.…”