16 EFFECT OF DONOR CELL AND TRICHOSTATIN A ON DEVELOPMENT OF CLONED DAIRY CATTLE EMBRYOS

The objective of present study was to investigate the effects of treatments to donor cells with fresh digestion (FD), cryopreservation/thawing (CT), trichostatin A (TSA) and durations of culture using TSA-CR1aa medium on in vitro development of dairy cow cloned embryos. In addition, some somatic cell cloned embryos were transferred to surrogates in heat to evaluate the in vivo developmental competence. The results (Table 1) showed that pretreatment of donor cells using TSA could significantly increase both cleavage and blastocyst rates of embryos (P < 0.05) compared with FD and CT group, whereas no significant difference was found between FD and CT group. When cloned embryos were subjected to TSA treatment in CR1aa for different times (0, 24, 48 and 60 h), the results showed that the blastocyst rate in the 60-h group was the highest (36.11 ± 1.78%) compared with the other groups (P < 0.05). Whereas the reconstructed embryos derived from donor cells treated with TSA for 24 h were continually cultured in TSA for different times (24, 48 and 60 h), the results showed that the blastocyst rate (37.39 ± 1.78%) in the 60-h group was significantly higher than that of the 24-h (25.48 ± 1.34%) group (P < 0.05). Finally, when the cloned embryos from different groups were respectively transferred to 40 natural oestrus recipients, no significant difference in terms of pregnancy rate among groups was found; however, a viable cloned calf was successfully obtained from TSA-treated donor cells and cloned embryo. Therefore, cloned embryos treated with optimized methods can develop to term. Table 1. Pregnancy results established from embryos of different origins