When Should Dairy Cows Be Inseminated?

INTRODUCTION Reproductive efficiency of the dairy herd is important for the economic success of the dairy operation. One of the most important reproductive technologies of the dairy industry is artificial insemination (AI). Artificial insemination reduces the incidence of sexually transmitted diseases among cattle and increases the use of genetically superior sires to improve performance of the herd. Standing estrus, or “heat,” is the most reliable indication that a cow is going to ovulate and release an ovum or “egg.” Estrous behavior is used to determine when a cow should be inseminated. A brief window of opportunity exists to fertilize the ovum and impregnate the cow. Senger (1994) estimated that the U.S. dairy industry loses more than $300 million annually due to failure and/or misdiagnosis of estrus. De Vries (2007) reported that a one percentage point increase in pregnancy rate (PR; defined as the number of eligible cows that become pregnant in each 21-day cycle) is valued between $22 and $35 per cow per year when PR varied from 15 to 19%, respectively. The average value of a new pregnancy was $278 in a simulated herd based generally on Holstein cow performance and prices in the United States (De Vries, 2006). The value of a pregnancy changes with different levels of production and with changing milk prices; the value goes up with higher milk prices and at higher milk production levels. Thus, efficiently and accurately detecting estrus and inseminating at the proper time are of utmost importance if dairy producers want to increase reproductive efficiency of the herd.