Hormone Induced Lactation in the Bovine. I. Lactational Performance Following Injections of 17β-Estradiol and Progesterone

Abstract

Injection of 17β-estradiol (.1 mg per kg body weight per day) and progesterone (.25 mg per kg body weight per day) for 7 days initiated lactation in 7 of 10 treated cows. Lactations began 11 to 21 days after the first 17β-estradiol-progesterone injection. Lactations were characterized by a rapid increase (1.32 ± .15 kg per day) in daily yield the first 10 days after milking began. Peak lactation occurred 30 to 50 days after lactations began, and persistency of lactations approximated normal. The mean 305-day yield of fat-corrected milk for the seven lactations was 5,069 ± 462 kg. This average was 95% of the best recorded hormone induced lactation. Maximum actual yield of milk and fat for 305 days was 6,773 kg of milk and 266 kg of fat, and the highest daily yield recorded was 40.9 kg. The treatment described for initiation of lactation in the bovine shares with previous techniques the disadvantages of variability in response to treatment and increased estrous activity following hormone injections. Estrous activity in all treated animals appeared to be transient in all but two. Estrous cycles of normal length started 30 to 50 days after lactation began in three of the animals, and all three became pregnant. One aborted at approximately 120 days of gestation, one has been pregnant 150 days, and one has completed a normal gestation and calved normally. © 1973, American Dairy Science Association. All rights reserved.