Hormone Levels in Pre- and Post-Parturient Beef Cows

Abstract

Levels of luteinizing hormone (LH), prolactin, estrogens, progestins and corticosteroids were measured in three multiparous beef cows from 3 to 4 weeks prepartum through the second postpartum estrus. Blood was collected daily except at parturition and estrus, when they were collected at 4-hr. intervals from silastic cannulas in the jugular Vein. All cows were suckled following calving. Parturition to postpartum estrus averaged 98 days. LH levels were between 1 and 1.5 ng/ml prepartum; periodic increases up to 3 ng/ml occurred after 2 weeks postpartum until estrus, when a peak of 42 ng/ml occurred 27 hr. before ovulation and declined to between 0.5 to 1.7 ng/ml until the peak at the subsequent estrus. Prolactin levels were below 50 ng/ml during pregnancy but fluctuated from this value to above 300 ng/ml from 2 to 4 days prepartum to 20 days postpartum, remaining between 100 to 200 ng/ml for the rest of the postpartum period studied. Progestins declined gradually from 10 ng/ml at 3 weeks prepartum to about 2 ng/ml at parturition, fluctuating around 1 ng/ml through most of the postpartum period. Estrogens, in the last 20 days prepartum ranged between 870 and 1,300, fell to 500 pg/ml at parturition and decreased postpartum to about 200 pg/ml and peaked at 500 pg/ml at 2 days before estrus. During the cycle, estrogens fluctuated between 50 and 500 pg/ml with a high at day 5. Corticosteroids varied from 10 to 80 ng/ml between 6 and 21 days prepartum, rising gradually to 116 ng/ml at parturition and falling to 25 ng/ml at 1 day postpartum. Postpartum levels did not appear to be associated with estrus activity. Copyright © 1974. American Society of Animal Science. Copyright 1974 by American Society of Animal Science.