Abstract

The increased use of assisted reproductive technologies (ARTs), increase the risks of erroneous prostaglandin F_2α (PGF_2α) administration. The objective of this study was to determine if pregnancies could be maintained if P₄ was administered after PGF_2α administration. A total of seven pregnant heifers between 30 - 40 days of gestation and 19 pregnant cows between 30 to 40 (n=12) or 80 to 90 (n=7) days of gestation were used. All females were administered a maintenance dose of P₄ or progestin at either 2, 6, 8, 10, 12 or 18 hours post-PGF_2α for 7 days. A total of 18 of 25 (72%) pregnancies were maintained for a minimum of 7 days. The success rate for cows and heifers receiving P₄ or progestin 2, 6, 10, 12 or 18 hours after PGF_2α was 4/6 (75%), 6/6 (100%), 2/3 (67%), 2/4 (50%), 1/2 (50%) and 3/4 (75%), respectively. Maintenance P₄ or progestin was continued on selected females (12 of the 18) and they were examined via ultrasonography 2 to 3 times weekly until a follicle ≥10 mm developed on the ovary ipsilateral to the gravid uterine horn, at which time hCG (2,500 IU) was administered. Luteal tissue was successfully induced in 10 of the 12 (83%) and 8 of these calved (80%). These results indicate that it is possible to maintain a bovine pregnancy by administering maintenance dose of P₄ from 2 to 18 hours post-PGF_2α.

Keywords: Cattle, abortion, induced luteal tissue, pregnancy, progesterone