The Effect of Progesterone on Ovulation Time in Dairy Heifers

Evidence for the existence of a nervous mechanism in the release of luteinizing hormone and ovulation in the cow recently has been presented In these experiments the parasympathetic blocking drug, atropine, administered to heifers at the beginning of estrus, was found to block ovulation. However, when atropine and chorionic gonadotrophin (as a source of luteinizing hormone) were administered concurrently to heifers at the beginning of estrus, ovulation occurred at the normal time or earlier. These results were interpreted to indicate the existence of a neural mechanism having a parasympathetic component involved in luteinizing hormone release and ovulation in the cow.