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as needed. Much like the finger‐electrodes, the intent of this probe design is to enable stimulation of specific areas with minimal stimulation of non‐target tissue [12]. The caudal segment is used to achieve erection and then the middle segment is used to achieve ejaculation. In some bulls, the activation of the cranial segment may be required to cause ejaculation [12]. The segmented probe is no longer popular due, at least in part, to its being complicated to use. In comparison with a conventional rectal probe it was shown that it was much easier to obtain full penile protrusion using the conventional probe, but ultimately both probe types were equally effective for obtaining semen emission. In a study comparing the pain response associated with the use of a conventional three‐electrode probe and the segmented probe for an equal number of stimulations, and with the segments activated according to the operator’s manual, no differences in cortisol or progesterone release were detected [13]. Weighted probes and probes with two longitudinal electrodes are now available. The intent of these design changes is to target the appropriate nerves with as little stimulation of surrounding tissue as possible. No critical studies have been done comparing weighted and two‐electrode probes to conventional (three‐electrode, no additional weight) probes; however, the clinical impressions of the author are that they are at least as effective as conventional probes yet appear to be more comfortable for the bull.
Electroejaculator probes are inserted into the rectum with the electrodes oriented ventrally and rotation of the probe is prevented by a U‐shaped tail cradle or yoke. The tail cradle helps to maintain the probe in the rectum, properly oriented with the electrodes down. Until the sequence of electrical stimulation is begun it is a good idea to hold the probe in place simply by pressing the tail into its relaxed position. Horizontal or vertically (upright) oriented yokes are available. Damage to the electrical cord connecting the probe to the electroejaculator is less likely with the upright yoke in the event that bull lies down during the collection procedure, whereas horizontal yokes invariably catch on the butt bar often at the electrical connection. Upright yokes are also easy to grasp, facilitating probe extraction. Figure 9.1 shows a Lane Pulsator V and the two‐electrode probe with upright yoke.
Figure 9.1 Lane Pulsator V and two‐electrode probe with vertical yoke.
Source: Courtesy of Lane Manufacturing, Inc.
Modern electroejaculators use a sine‐wave pulse at a frequency of 20–30 cycles per second [14, 15]. Other wave forms and frequencies have been tried but have been proven less effective [14]. The maximum voltage of a very common electroejaculator in use today, the Lane Pulsator IV (Lane Manufacturing, Denver, CO, USA), is 16 with a maximum current of 900 mA [12]. With this machine, ejaculation occurs with electrical impulses less than 8 or 9 V [12]; however, some bulls, usually older bulls, may require more electrical intensity to elicit ejaculation.
Electroejaculation Technique
Before attempting to electroejaculate a bull ensure that the electroejaculator is in good working order. Electrical cords and connections are most likely to be the cause if the electroejaculator unit is functioning and the probe is in place yet the bull is not responding to stimulation. Always turn the electroejaculator off before making even the slightest adjustments to trouble‐shoot electrical connections. A suddenly restored connection, even if the electrical intensity is relatively low, will unduly startle the bull. The rectal probe selected should be of sufficient diameter to enable full contact with the rectal mucosa, but not so large as to prevent its insertion. Usually, a probe with a diameter of 6.5–7.5 cm will suffice. Very large (>900 kg) or older animals may require a 9‐cm probe to ensure contact with the rectal mucosa [16]; 6‐ to 6.5‐cm yearling probes are available and are much easier to use on smaller bulls [17]. Bulls must be suitably restrained to prevent side–side and back–forth motion and should not be handled in such a way as to cause excitement. Overly excited animals tend to vocalize more during the procedure [18] and are more difficult to collect [16]. Cattle squeezes generally work very well for BBSE provided there is enough room for larger bulls to fit into them. Earlier models were designed mainly for use with cows and often are not long enough to accommodate a mature bull. A post, often referred to as a butt bar or kick post, placed horizontally across the chute immediately behind the bull will prevent the bull from moving backward or kicking the examiner. Ideally, the butt bar should be placed immediately behind the bull so that any kick action is softened, yet at a level that enables examination of the scrotum and testes. Modern hydraulic squeezes are the author's preferred system for examining bulls. Side–side pressure is infinitely variable and easy to apply, virtually eliminating any kicking. The side–side squeeze pressure and squeeze pressure on the neck must be relaxed prior to beginning the EEJ process. Failure to obtain a semen sample, bulls lying down in the chute, and poor quality ejaculates have all been caused by excessive squeeze pressure. Giving bulls room to move and to get their feet placed under them will go a long way toward shortening the duration of the EEJ procedure and yielding good quality samples.
A per rectum examination of the bull's ampullae, seminal vesicles, prostate, pelvic urethra, and inguinal rings should be conducted accompanied by a thorough clean‐out of feces from the rectum. Massage of the pelvic urethra and accessory sex organs lasting 30–60 seconds will provide sexual simulation for the bull and relaxation of the anal sphincter to enable insertion of the probe. An elbow to wrist, back and forth rectal massage with immediate insertion of the probe following arm removal works best, coupled with the smallest probe that is still effective for the size of bull being collected. The smaller yearling probes have proven effective in at least 9 out of 10 mature bulls when matched with well‐designed, late‐model electroejaculators. Lubrication of the probe with palpation sleeve lube or even water will facilitate insertion and enhance contact with the rectal mucosa [16].
Electroejaculators available today are similar in function with features that appeal to a variety of users. Advances in electrical circuitry and battery technology have been adopted by manufacturers, resulting in enhanced portability without the need for a constant electrical supply. Machines available today may be used to electroejaculate over 100 bulls on a single charge (Bob Green, Lane Manufacturing Inc., personal communication). A significant innovation has been preprogrammed, automated EEJ sequences that increase electrical voltage in a step‐wise fashion, bridging the gap between the art and science of collecting a bull. Manual control of voltage intensity is still available via a rheostat knob and step‐wise control buttons, allowing the operator to use the machine according to personal preferences. Experience is a great teacher when collecting semen from bulls using EEJ. Effective stimulation sequences vary with the breed, age, size, temperament, handling system, weather, and individual animal. For the novice a great deal can be learned by using the preprogrammed sequences, then try to emulate a sequence using the manual controls. Learn to watch the response of the bull not the indicator systems on the machine. The initial application of electrical stimulation must be applied carefully while observing the response of the bull. The operator should increase the electrical intensity just enough to cause a slight contraction of the muscles of the hind limb. Thereafter, with each successive stimulation the intensity of the voltage should be increased slightly and should last 1–2 seconds followed by ½−1 second of rest until erection, then ejaculation occurs [12, 16]. Some bulls are more difficult to collect than others for a variety of reasons. Common problems are inadequate contact between the probe and the rectal mucosa (excess feces, small probe, or a buildup of dried mucus or lube on the electrodes); insufficient voltage; bulls that have been recently used for breeding [16]; and excessive squeezing pressure on the neck or sides of the bull. Even when these potential problems are addressed, EEJ may still be unsuccessful with a small number of normal, fertile bulls.
Semen collection handles are useful for safely extending the operator's reach to obtain a sample. Disposable, single‐use, funnel‐shaped collection cones have largely replaced reusable latex rubber cones and are designed so that the wide end