Pregnancy rates in lactating dairy cattle following supplementation of progesterone after artificial insemination

• Published in: Animal reproduction science 2007-11, Vol.102 (1), p.172-179
• Main Authors: Larson, Sandra F., Butler, W.R., Currie, W. Bruce
• Format: Article
• Language: English
• Subjects: Animals; artificial insemination; biomarkers; Cattle; conception; Dairy cattle; dairy cows; Dairying; dosage; dose response; Drug Administration Schedule; Drug Implants; Female; female reproductive system; Fertility Agents, Female - administration & dosage; Fertility Agents, Female - pharmacology; Growth Hormone - pharmacology; hormonal regulation; Insemination, Artificial - veterinary; Lactation; milk; ovulation; Ovulation Induction; Pregnancy; pregnancy outcome; Pregnancy Rate; Progesterone; Progesterone - administration & dosage; Progesterone - pharmacology; protective effect
• ISSN: 0378-4320; 1873-2232
• DOI: 10.1016/j.anireprosci.2007.02.023

Poor conception rates in highly productive lactating cattle is especially prevalent in large, intensively-managed commercial herds. One of the causative factors is sub-optimal pre-implantation embryonic development which appears to result from inadequate circulating concentrations of progesterone. In the present study, the efficacy of very modest progesterone supplementation, between Days 3.5 and 10 post-AI, on pregnancy rates was determined in a commercial herd where bovine somatotropin (bST) was used as a management tool. All lactating cattle that were deemed to be in estrus and inseminated over a 4-week period were randomly assigned to either a control group (no treatment) or CIDR-1.9 g (previously used for estrous synchronization) treatment from Day 3.5 to Day 10 post-AI. Milk samples were collected four times: on the day of AI, at Day 2 or 3, at Day 4 and at Day 22 post-AI and were analyzed for progesterone content. Data from a total of 130 breedings were used in the final analysis. The CIDR treatment increased circulating concentrations of progesterone in treated animals over those of control animals on Day 4 by 0.7 ng/ml ( P < 0.05) and increased pregnancy rate from 35% (22/63) to 48% (32/67) ( P = 0.068). The effect of treatment was greater in first and second lactation cows, where pregnancy rates were 33% (18/55) in controls and 51% (31/61) in treated animals ( P = 0.03). The results of this study indicate that the timing of onset of the progesterone influence is important for successful pregnancy outcome, particularly in first and second lactation cows.