Submitted to: Research Update for Fort Keogh Livestock and Range Research Laboratory
Publication Type: Popular Publication
Publication Acceptance Date: 10/1/2002
Publication Date: 1/15/2003
Citation: GEARY, T.W. USE OF TIMED ARTIFICIAL INSEMINATION WITH GONADOTROPIN-RELEASING HORMONE/PROSTAGLANDIN ESTROUS AND OVULATION SYNCHRONIZATION PROTOCOLS FOR USE IN BEEF COWS. RESEARCH UPDATE FOR FORT KEOGH LIVESTOCK AND RANGE RESEARCH LABORATORY. p. 37-38. 2003. Interpretive Summary: Artificial insemination (AI) with semen from genetically proven sires provides the quickest means for genetic improvement and selection of economically important traits. However, less than 6% of the beef cattle in the United States are artificially inseminated each year. The primary reason that so few cattle are artificially inseminated is due to the time and labor involved with detection of estrus. Artificial insemination is used in a higher percentage of beef heifers (~30%) than beef cows (~3%). The primary reasons for the greater use among heifers is due to the availability of an estrous synchronization protocol that works well in heifers but not cows, and because suckled cows represent extra work in the form of calf handling and care. Current estrous synchronization protocols minimize the amount of time spent observing cattle for signs of estrus to approximately 5 days. Development of inexpensive estrous synchronization protocols for both cows and heifers that allow timed insemination with minimal or no estrous detection would increase the use of AI by beef producers.
Technical Abstract: Moving the time of insemination and second GnRH injection of the CO-Synch protocol which includes the first two injections of the Select Synch protocol and timed insemination with a second GnRH injection at 48 hours after PGF to 64 hours after PGF resulted in higher pregnancy rates in some herds and lower pregnancy rates in other herds (unpublished data). We interpret this to mean that in some herds, we have lost the opportunity to induce a fertile ovulation with a second GnRH injection by moving the GnRH injection later than 48 hours after PGF injection. When estrous detection efficiency is high during the time period from -30 to 72 hours after PGF (0 hours), breeding by estrus until 72 hours coupled with timed AI at 72 hours should result in high pregnancy rates. However, when estrous detection efficiency is low or in herds that have not had a high estrous response (> 50%) by 72 hours after PGF, it might be more economical to continue to observe cows and AI following observation of estrus for an additional 2 days rather than mass inseminating cows. We conclude that incorporating a timed AI at 72 hours after PGF for cows synchronized with the Select Synch protocol may be feasible if the 72-hour estrous response is high, but caution against timed AI at 72 hours in herds when the 72-hour estrous response is low. Also, addition of a second injection of GnRH at 72 hours is not necessary.