FARROWING RATE AND LITTER SIZE AFTER TRANSCERVICAL EMBRYO-TRANSFER IN SOWS

A transcervical embryo-transfer procedure was evaluated in two experiments with synchronized donor and recipient sows. In Experiment 1, the recovery of the transferred embryos was determined 3 h after transfer. In Experiment 2, farrowing rate and litter size were determined. In Experiment 1 in six sows, the average (XBAR +/- SD) recovery of the transferred embryos was 74 +/- 18%. In Experiment 2 (n = 21), farrowing rate was 33%. When the transfers were differentiated according to the developmental stage of the transferred embryos (morulae in the presence (n = 11) or absence (n = 10) of blastocysts), the pregnancy rate was 55% (6 out of 11) in the case of transfers with blastocysts, and 10% (1/10) in the case of transfers with only morula-stage embryos (p = 0.06). Litter size was 6.7 +/- 1.6. Of the 14 recipients which were not pregnant, six showed a prolonged estrus interval of 25-29 days. It is concluded that, in this experiment, the pregnancy rate after non-surgical embryo transfer depended on the developmental stage of the transferred embryos. The possibility of increasing embryonic survival and pregnancy rate by a correct choice of developmental stages of the transferred embryos and/or synchrony of recipients is discussed.