Once vs Twice Daily Insemination Schedules
Mel DeJarnette, reproductive specialist, Select Sires
Questions have surfaced regarding the fertility of once vs twice daily insemination schedules. To interpret studies evaluating once vs twice daily insemination, you must keep in mind; there is a clear distinction between time of initial standing estrus and first observed standing estrus.
In order for the AM/PM rule of insemination timing to be successful, you must first have an accurate estimation of when standing heat began. In a Pennsylvania study, 63% of the herds observed cows for signs of estrus only twice per day or less, therefore, the accuracy of determining time of initial standing heat was lower in these herds than in herds with more intense estrous detection programs. Also, the time interval from initial standing heat to first observed standing heat is longer in herds with low intensity estrous detection. For herds where heat detection is less than optimal, breeding cows soon after they are observed in estrus is as good a guess as any. In fact, due to the longer time interval from initial standing heat to first observed standing heat in these herds, many animals inseminated shortly after estrus is first noted are probably being inseminated fairly close to when they should, according to the AM/PM rule. Trying to predict proper timing of insemination using the AM/PM rule without intense estrous detection programs and accurate estimations of time of initial standing heat is just kidding yourself.
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