Abstract
This study was undertaken to produce trophoblastic vesicles (TVs) by using blastocysts of in vitro origin and to estimate the effect on the interestrous interval after transfer of 4 TVs into the uteri of heifers on Day 7. Morphological examination under a stereoscopic microscope revealed that the total formation rate of TVs prepared from IVP expanded blastocysts was 80.5% and that there was no difference in the formation rates of TVs derived from blastocysts between Day 7 (83.5%) and Day 8 (78.5%). After intrauterine transfer of TVs, observation of the corpus luteum (CL) by transrectal ultrasonography together with measurement of the plasma progesterone concentration confirmed that 2 of 4 recipients (50%) had a longer interestrous interval, 33.5 and 35.0 days, while the other 2 recipients had normal cycles, 20.0 and 24.5 days. In the control group transferred D-PBS, all 4 heifers had a normal cycles, 24.0-24.5 days. Consequently, the average number of days after intrauterine transfer of TVs compared with the 2 consecutive cycles just before the treatment was longer than in the controls (6.1 ± 2.4 days vs. -0.8 ± 1.1 days, P<0.05). These results indicate that preparation of TVs from blastocysts of in vitro origin is a useable method and that TVs from blastocysts may have the capacity to maintain CL function after intrauterine transfer.
