Plasma LH concentrations after single or double injections of synthetic LH-RH in dairy cows

Abstract

Milked Friesian dairy cows were given 1 or 2 i.v. injections of synthetic LH[lutropin]-RH[luliberin]. The second of 2 injections of LH-RH given 1.5 h apart induced a significantly greater release of LH than the 1st. The response to this injection was also significantly greater than that caused by injections given 6 h apart. There was no significant difference between the LH responses to the 2 injections given 6 h apart. The total LH release produced by the 2 injections of 100 .mu.g synthetic LH-RH given 1.5 h apart was significantly greater than that produced by single injection of 200 .mu.g synthetic LH-RH. There may be a short-term increase in the responsiveness of the bovine pituitary gland to LH-RH after an initial LH-RH stimulus.