Peripheral plasma levels of progesterone and fertility after prostaglandin-2alpha induced oestrus in heifers.
Sixteen heifers of the Swedish Red and White Breed were given 25 mg PGF2 alpha as tromethamine salt intramuscularly or subcutaneously either on day 8 or day 14 of the oestrus cycle. The injection of PGF2 alpha caused a marked reduction of the size of the corpus luteum in 24 hours. Irrespective of day of injection standing heat occurred 48-96 hours after administration of PGF2 alpha. In the heifers injected on day 8 of the oestrus cycle the midcycle follicle continued to grow and appeared to be the one which was ovulated. Inheifers injected on day 14 a new follicle could be palpated within two days. Eleven of the 16 heifers (69%) became pregnant during the induced heat period. All heifers showed a marked decrease of the peripheral plasma level of progesterone on the day after treatment. The mean progesterone level at the day of first insemination was 80 pg/ml and at the day of second insemination where applied 46 pg/ml. It is concluded that intramuscular or subcutaneous administration of PFG2 alpha on days 8 and 14 of the oestrus cycle results in luteolysis of the cyclic corpus luteum, follicular growth, ovulation and normal pregnancy result after artificial insemination.
D000818:Animals; D002417:Cattle / Q000502:physiology*; D004971:Estrus / Q000187:drug effects*; D005260:Female; D005298:Fertility; D007315:Insemination, Artificial / Q000662:veterinary; D010060:Ovulation; D011247:Pregnancy; D011374:Progesterone / Q000097:blood*; D011453:Prostaglandins / Q000494:pharmacology*; D013997:Time Factors
D011453:Prostaglandins; D011374:Progesterone