Plasma hormone levels and fertility in pigs induced to superovulate with PMSG

Abstract

Seventy one mature gilts were allocated to a 3x2x2 factorial experiment consisting of three doses of pregnant mare serum gonadotropin (PMSG) (0, 600 or 1200 i.u.), two levels of food intake on the 1st day of estrus (none or double the normal daily amount of food), and two times of autopsy after mating (Day 6 or Day 24). The PMSG was administered by a single subcutaneous injection on Day 15 of the estrous cycle and animals were mated on the first 2 days of the subsequent estrus. Blood samples were collected in order to assess the effects of PMSG and superovulation on the secretion of estrogen, luteinizing hormone (LH) and progesterone. Ovulation rate was significantly increased by PMSG treatment (P≤0.001), but was not affected by food intake at estrus. The number of normal embryos at slaughter on Day 6 or Day 24 after mating was significantly increased by PMSG treatment compared to that in the control animals, but embryonic losses by Day 24 were greatly increased in the gilts treated with PMSG. The plasma estrogen concentration before ostrus was increased by PMSG treatment. The magnitude of the LH surge on the 1st day of estrus was not affected by PMSG, but estrus and the preovulatory LH surge were advanced by about 1 day. Mean plasma progesterone concentrations after mating were increased by PMSG treatment.