Relationships between oxygen consumption rate, viability, and subsequent development of in vivo–derived porcine embryos

Oxygen consumption rate of in vivo–derived porcine embryos was measured, and its value as an objective method for the assessment of embryo quality was evaluated. Embryos were surgically collected 5 or 6 days after artificial insemination (AI), and oxygen consumption rate of embryos was measured using an embryo respirometer. The average oxygen consumption rate (F × 1014/mol s−1) of the embryos that developed to the compacted morula stage on Day 5 (Day 0 = the day of artificial insemination) was 0.58 ± 0.03 (mean ± standard error of the mean). The Day-6 embryos had consumption rates of 0.56 ± 0.13, 0.87 ± 0.06, and 1.13 ± 0.07 at the early blastocyst, blastocyst, and expanded blastocyst stages, respectively, showing a gradual increase as the embryos developed. Just after collection, the average oxygen consumption rates of embryos that hatched and of those that did not hatch after culture were 0.60 ± 0.04 and 0.50 ± 0.04 for Day 5 (P = 0.08) and 1.05 ± 0.09 and 0.77 ± 0.05 for Day 6 (P < 0.05), respectively. The value and probability of discrimination by measuring the oxygen consumption rates of embryos to predict their hatching ability after culture were 0.56 and 63.6% for Day-5 embryos and 0.91 and 68.4% for Day-6 blastocysts, respectively. When Day-5 embryos were classified based on the oxygen consumption rate and then transferred non-surgically to recipient sows, three of the seven sows, to which embryos having a high oxygen consumption rate (≥0.59) were transferred, became pregnant and farrowed a total of 20 piglets. However, none of the four sows, to which embryos having low oxygen consumption rate (<0.59) were transferred, became pregnant. These results suggest that the viability of in vivo–derived porcine embryos and subsequent development can be estimated by measuring the oxygen consumption rate.