Improvement of superovulatory response and pregnancy rate after transfer of embryos recovered from Japanese Black cows fed rumen bypass polyunsaturated fatty acids.

Feeding rumen bypass polyunsaturated fatty acids (PUFA) affects to Japanese Black cows affects their reproduction, though its influence on superovulatory response in donor cows and conception in recipient cattle has not been well studied. Here, we investigated the effects of feeding PUFA to Japanese Black cows on blood biochemistry, the numbers of ova and embryos or transferable embryos and pregnancy rate following embryo transfer (ET) to recipient Holstein heifers. PUFA (40% linoleic acid) was fed at 300 g/day in the experimental group from the last day of estrus until the day of artificial insemination for superovulatory treatment. Blood was collected on the first day of follicle-stimulating hormone administration. Total cholesterol level was significantly higher in the 15- to 19-day feeding group (117.4 mg/dl) than in the control group (95.0 mg/dl). The numbers of ova and embryos or transferable embryos were significantly higher in the 15- to 19-day feeding group than in the control group. The numbers of transferable embryos in the 15- to 19-day feeding group were significantly higher than in the 10- to 14-day feeding group. The pregnancy rate at day 60 was significantly higher in the experimental group (66.7 and 57.1%) than in the control group (51.1 and 44.0%) after transfer of fresh and frozen-thawed embryos, respectively. In conclusion, the numbers of ova and embryos or transferable embryos after superovulatory treatment increased, and the pregnancy rate after ET was higher in Japanese Black cows fed PUFA than in the control group.