Detecting standing heat or estrus in beef and dairy cattle can be a critical aspect to the success of an artificial insemination (AI) program. Time and dedication to observing cattle throughout the day and evening are essential in accurately detecting estrus. A Colorado State University study indicated that 95% of animals monitored constantly were observed exhibiting standing heat, while only 56% of the animals were observed using a twice a day method. Compiled studies have indicated that 56% of animals in these studies came into standing heat through the evening hours and into the early morning hours. These studies indicate that persons checking for heat that do not spend several observation periods throughout both the day and evening are missing as many as 40% of the females exhibiting estrus. For this reason, many producers have implemented synchronization programs that rely on timed breeding; however, this management strategy is not easily implemented on cows that do not conceive on first breeding and AI is used for subsequent breedings.
For the sake of this article the terms standing heat and estrus will be used interchangeably. Standing heat indicates the cow or heifer will stand for mounting and is receptive to breeding. Ideally cows will be artificially inseminated 12 hours after to onset of standing heat. Cattle that are exhibiting estrus will also show signs of nervousness, frequently ride other cattle, have a moist and swollen vulva and may have a clear mucous discharge. But remember the true sign is standing to be mounted.
Because accurate detection of estrus can be difficult, understanding of secondary estrus signs are important to identify. Cattle actively riding other cows may be either coming into estrus or just recently were in estrus. Also, roughed tail head hair, mud dirt or roughed hairs over the ribs are other indicators that an individual was recently in standing heat. Keeping accurate records and recording the signs of estrus can greatly improve determination of the onset of estrus. Not all individuals will be observed standing to be ridden, the true indicator of standing heat. Recording signs of estrus over time can assist in determining an approximation for the onset of estrus.
Heat detection aids can be used to aid detection of secondary sings of estrus. Applying paint or marking chalk to the tail head of cows is the least expensive method. Observers look for paint that has been rubbed off. Another form is patches can be glued to the tailhead. These patches either contain a vessel of dye that is broken during mounting to release the dye or are a scratch-off. The scratch-off patch has a neutral cover over a bright color that is scratched off during mounting to reveal a brightly marked patch. Chin ball marker is an apparatus that is fastened by straps to the head of a vasectomized bull. The marker is filled with paint to mark the backs of cows during mounting. Electronic devices are much more expensive and in addition to the cost of the devices, computer software and equipment are used to record estrus activity.
Other consideration should also be considered during estrus detection. Cattle will exhibit fewer signs of estrus while other activities are taking place. For example, cattle will show fewer signs just after feed delivery or in confined areas such as in moving into the milking parlor. Cattle with poor footing, exhibiting heat stress or seeking shelter from cold, rain or wind will exhibit fewer signs of standing heat. Producers using heat detection need to commit time to the process and read the signs.
Source: Frank Wardynski, Michigan State University Extension