Short-term relationships between plasma LH, FSH and progesterone concentrations in post-partum dairy cows and the effect of Gn-RH injection.
Jugular venous blood samples were obtained from 7 dairy cows every 10 min for 10-19 h during the early- or mid-luteal phase of the oestrous cycle, and each cow was given 1 or 2 i.v. injections of 100 micrograms synthetic Gn-RH. Four of these cows were also sampled in a different cycle with no treatment being administered. Peaks of plasma LH, FHS and progesterone were detected in each animal in the absence of treatment; those of LH and progesterone often occurred in parallel. Injection of Gn-RH was always followed by a significant increase in plasma LH and progesterone concentrations and in most cases by a significant FSH increase. There was a significant temporal relationship between the peaks of all 3 hormones. A further 8 cows were sampled during the first 10 days post partum when the mean plasma progesterone concentration was low. An i.v. injection of 200 micrograms synthetic Gn-RH was given to each animal and this resulted in a significant increase in plasma LH and FSH concentrations, but in only one cow was the Gn-RH injection followed by a significant increase in plasma progesterone concentration. The LH response to Gn-RH injection was significantly less in cows injected on or before Day 5 post partum than in cows injected on Days 7-10 post partum.
D000818:Animals; D002417:Cattle / Q000097:blood*; D004971:Estrus; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood*; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology*; D007986:Luteinizing Hormone / Q000097:blood*; D049590:Postpartum Period / Q000187:drug effects*; D011247:Pregnancy; D011374:Progesterone / Q000097:blood*; D013268:Stimulation, Chemical
D007987:Gonadotropin-Releasing Hormone; D011374:Progesterone; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone