ARS | Publication request: Utilizing Natural Service with Estrous Synchronization in Conjunction with Timed Artificial Insemination

Submitted to: Extension Fact Sheets
Publication Type: Popular Publication
Publication Acceptance Date: March 25, 2007
Publication Date: March 26, 2007
Citation: Torell, R., Geary, T.W., Bohnert, D., Ahola, J. 2007. Utilizing Natural Service with Estrous Synchronization in Conjunction with Timed Artificial Insemination. University of Nevada Cooperative Extension; Fact Sheet 07-25:1-4.

Interpretive Summary: Beef producers could benefit from estrous synchronization protocols that allow high success with timed AI. This study evaluated the incorporation of bulls into estrous synchronization and timed artificial insemination protocols to achieve high first-service pregnancy rates without detection of estrus. More than 1200 well developed and cycling yearling beef heifers were synchronized and bred on four cooperating commercial ranches. Two protocols were examined including the CO-Synch + CIDR or CO-Synch protocol with exposure to fertile bulls (1 bull to 15 heifers) from time of prostaglandin injection to 48 hours later and again at 84 hours. Timed AI breeding occurred at 65 to 70 hours instead of the standard 54 ± 2 hours recommended for the CO-Synch + CIDR protocol because heifers exhibiting estrus before 48 h and after 84 h received natural service. At two locations, producers saved semen costs by identifying heifers in estrus at 48 h and removing them from the timed AI breeding. Calving results suggest that first service conception rates for both protocols ranged from 50 to 70 percent. One potential drawback to this system is that it does not allow simple identification of AI or natural service produced calves. Identification of AI sired calves might be possible with use of a heat detection aid, accurate breeding records, and early ultrasound diagnosis of pregnancy.

Technical Abstract: Objectives of this study were to evaluate the incorporation of bulls into estrous synchronization and timed artificial insemination protocols to achieve high first-service pregnancy rates without detection of estrus. More than 1200 well developed and cycling yearling beef heifers were synchronized and bred on four cooperating commercial ranches. Two protocols were examined including the CO-Synch + CIDR or CO-Synch protocol with exposure to fertile bulls (1 bull to 15 heifers) from time of prostaglandin injection to 48 hours later and again at 84 hours. Timed AI breeding occurred at 65 to 70 hours instead of the standard 54 ± 2 hours recommended for the CO-Synch + CIDR protocol because heifers exhibiting estrus before 48 h and after 84 h received natural service. Calving results suggest that first service conception rates for both protocols ranged from 50 to 70 percent.