Abstract
This study was to investigate the influence of key parameters (donor parity, milk production, post-parturient day, season, and milk recording data) associated with efficiency of embryo recovery (ER) in Holstein cattle. Elite Holstein cows and heifers were selected for ER while Holstein heifers were used as recipients. The numbers of transferrable embryos (TEs) produced were not significantly different when analyzed in terms of donor parity, milk production, postparturient day, and season. However, the numbers of TEs were significantly increased when the milk protein (%; P) / fat (%; F) ratio was over 0.95 and/or the milk urea nitrogen (MUN) was between 12 and 18 dl/ml. The results from ET showed no differences in pregnancy rates among Holstein heifers receiving another type, developmental stage code and quality grade of embryos. The mean interval from ER to artificial insemination was 60.6 days. Moreover, 19 offspring that had milk recording data showed a similar milk yield performance to that of the donor cows. In conclusion, this study has shown that in Holstein cows, embryos were recovered and, transferred, and resulted in production of viable calves. Furthermore, using P/F ratio and MUN could be candidates for choosing donor cows for selecting high-efficiency donor cows.
