抄録
The study on cryopreservation of porcine embryos were conducted to determine an effect of dietary intake of polyunsaturated fatty acid by donor gilts on embryo survival after freezing and thawing. Linoleic acid and a-tocopherol were supplemented to a conventional concentrated diet at the rate of 3.75% and 600 ppm, respectively. The diet was given to 5 pubertal gilts with an initial age of 6 months old for approximately 4 months (2 to 3 kg/head/day). From at least 70 days after starting of feeding of the experimental diet, embryo collections were performed. The control embryos were obtained from pubertal gilts given only the conventional concentrated diet. Embryos were surgically collected by flushing both uteri of donors on day 6 (day 1=the last day of estrus). Expanded blastocysts were used immediately for experiment, after measuring the diameter by an ocular micrometer. The younger-stage embryos were cultured in vitro in Ham's F-12 supplemented with 12 mg/ml BSA fraction V in 5% CO2 in air at 38.5 C up to expanded blastocyst stage with more than 200 μm in diameter. The embryos were equilibrated with 10% ethylene glycol solution containing 0.2 M trehalose for 5 min at room temperature. The embryos loaded into 0.25-ml plastic straws were immersed in alcohol bath at -7 C, seeded at -7 C, cooled to -30 C at the rate of 0.4 C/min and plunged directly into liquid nitrogen. After being thawed in air, the embryos were subjected to count the viable nuclei following a two-step dilution of the cryoprotectant with 0.5 M trehalose solution. As a result of counting the viable nuclei of frozen-thawed embryos, the mean number of viable nuclei of the embryos derived from gilts given the linoleic-acid supplemented diet was larger (P=0.0553) than that of the embryos derived from gilts given the control diet. The result of the present study suggests that dietary linoleic acid intake by embryo donor gilts is likely to have a potential effect on enhancement of freezing tolerance in porcine embryos.
