Timing of Artificial Insemination
Dr. Glen Selk
Oklahoma State University
Traditional methods to determine when to inseminate beef cows depend on accurate detection of heat. A common practice used to inseminate cows is the AM/PM. rule. With this method, cows detected in estrus in the morning are inseminated in the evening, and cows first exhibiting estrus in the evening are inseminated the following morning. Twice daily visual observation of cows and tail marking do not allow precise detection of the onset of estrus. OSU researchers have examined the length of heat and number of mounts that occur in beef cattle using an electronic heat detection system called HeatWatchTM. Cows were in heat 17 – 18 hours in the summer time and about 14 hours in the winter. They were mounted about 70 times in winter but only 44 times in the summer. There is tremendous variation among cows around these average numbers.