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Historically, a key to a successful artificial insemination (AI) program has been accurate detection of estrus. Even with utilization of currently available estrus synchronization programs and timed AI, estrus detection is important as a tool to evaluate the efficacy of the protocol, troubleshoot problems in real time, and identify outliers that can be bred outside the prescribed “AI window.”

Several estrus detection methods exist, including tailhead paint, mount detectors, self‐adhesive heat detection patches, and visual observation. All these methods depend on female cattle standing for mounting during estrus. Thus these methods might miss females with weak or short estrus behavior [1]. By far the most efficient estrus detector is the bull, with the caveat that there is the benefit of male presence [2]. Therefore utilization of a teaser bull (intact sterilized male) is the most reliable method of estrus detection in the utilization of an AI program.

Several factors need to be considered when choosing a teaser bull procedure and each producer will have different needs and expectations. Besides the obvious need to render the bull sterile, other considerations would include herd status (open or closed herd). If an open herd, venereal disease transmission is an important factor to consider and prevention of intromission during mounting will be an important factor when choosing a teaser bull surgical procedure. Additionally, expected longevity needs to be discussed with the producer. On average, teaser bulls will last one to three years within a herd [1]. Decreased libido is the most common reason for culling, with excessive size and aggression being the next most common culling reasons [3]. To summarize, the main goals of surgical preparation of teaser bulls are to render him sterile, prevent intromission and therefore the transmission of venereal disease, and avoid excessive libido reduction [4, 5].

Proper bull selection is also an important aspect of teaser bull preparation. The ideal bull needs to be of moderate size, mild temperament, and easily handled. This bull also needs to be free of transmissible diseases. Of course, the bull also needs strong libido, but this can be difficult to assess in yearling bulls [4]. Teaser bull surgery should be performed well before the breeding season to allot time for healing and recovery from surgery. Ideally, the procedure should be performed on bulls less than 272 kg, primarily for ease of handling and decreased hemorrhage during surgery [4].

Teaser bull procedures can be divided into two categories: those that block semen flow and deliver sterility (vasectomy, epididymectomy) and those that prevent penile penetration (penile–prepuce translocation, penopexy, preputial pouch). Depending on the needs and expectations of the producer, any one or a combination of these procedures can be used for preparation of a teaser bull.