Submitted to: Research Update for Fort Keogh Livestock and Range Research Laboratory
Publication Type: Popular Publication
Publication Acceptance Date: October 1, 2002
Publication Date: January 15, 2003
Repository URL: http://www.larrl.ars.usda.gov
Citation: GEARY, T.W. DEVELOPMENT OF NEW ESTROUS AND OVULATION SYNCHRONIZATION PROTOCOLS FOR USE IN BEEF COWS. RESEARCH UPDATE FOR FORT KEOGH LIVESTOCK AND RANGE RESEARCH LABORATORY. p. 35-36. 2003. Interpretive Summary: Less than 6% of the beef cattle in the United States are bred by artificial insemination (AI) each year. The primary reason that so few cattle are artificially inseminated is due to the time and labor involved with detection of estrus. Estrous synchronization decreases the amount of time required for detection of estrus and facilitates the use of AI. To a producer, a good synchronization protocol must be cheap, easy to administer, effective on the majority of the cows in a herd (must induce estrous cycles), and results in high pregnancy rates.
Technical Abstract: Study 1. Beef cows (n=404) received the CO-Synch ovulation synchronization protocol with either 50 or 100 µg of GnRH the first and/or second GnRH injection. Pregnancy rates for cows treated with either a 50 or 100 µg dose of GnRH at either the first and/or second injection in the CO-Synch protocol were not different Z(51, 49, 50, and 45% for cows receiving 50:50, 50:100, 100:50, 100:100 µg GnRH, respectively). Study 2. Pregnancy rates for CO-Synch treated cows receiving bST at 1st GnRH, PGF, 2nd GnRH, or control cows were 30.0%, 26.9%, 33.1%, and 27.1%, respectively, and were not different. Bovine somatotropin had no effect on pregnancy rates in the CO-Synch ovulation synchronization protocol. In the Select Synch trial, pregnancy rates were higher for cows receiving bST at the time of GnRH injection and control cows than for those receiving bST at PGF.