9 Evaluation of Breeding Soundness: The Spermiogram

       Colin W. Palmer

       Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK, Canada

Introduction

      The cost of purchasing and maintaining a bull is substantial yet is easily overshadowed when a group of cycling female cattle fail to become pregnant and a complete calf crop is lost. Fortunately, this worst case scenario is a relatively rare occurrence but can have financial implications on a par with any unforeseen natural disaster. Especially in single‐sire breeding systems, this should be reason enough to have a breeding soundness evaluation prior to every breeding season; however, the most costly losses associated with poor fertility are much more insidious. Profit margins in the cow‐calf sector continue to shrink; therefore all producers must look for ways to improve productivity. In well‐managed herds, it is expected that 95% of the breeding females will become pregnant in a 60‐day breeding season, with 65% pregnant during the first 21 days. Anything less than this may be considered subfertility. Most mature beef bulls are expected to successfully mate with at least 25 cows, with lower ratios of one bull to 30, 35, and even 40 or more being used in an effort to improve efficiency while capitalizing on superior genetics. To achieve these goals, bulls must meet a set of standards below which subfertility is likely to occur.

      The Society for Theriogenology (SFT) has developed a set of standards for bull breeding soundness examination (BBSE) based on available scientific data combined with input from veterinary practitioners. The SFT standards, including how the breeding potential of the bull is classified, differ almost unnoticeably from the standards adopted in other countries [1, 2]. The intent of this chapter is to provide an overview of the semen collection and evaluation in the bull. For a more indepth review, readers are encouraged to access a breeding soundness examination manual identified in the references and to review other chapters in this textbook.

      Utilizing the SFT classification system, following a BBSE the animal may be classified as (i) a Satisfactory Potential Breeder, also known as “Passing” the BBSE; (ii) Classification Deferred; or (iii) an Unsatisfactory Potential Breeder. The BBSE focuses on three major categories: (i) physical soundness; (ii) scrotal circumference; and (iii) semen quality. To be classified as a Satisfactory Potential Breeder a bull must meet the described standards for all of the categories. Exceeding the standard in one category does not supersede failing the standard in another [1].

      The number‐one reason bulls do not receive a satisfactory classification is because of semen quality, specifically, abnormal sperm morphology.

Semen Collection

Evaluating semen quality is an integral part of a BBSE. Electroejaculation (EEJ) has been a reliable method of obtaining a semen sample for many years. Alternatives to EEJ include using an artificial vagina (AV), transrectal massage (TM) of the accessory sex glands, and aspiration of semen from the vagina of a cow following a recent natural service. Compared to these other techniques, EEJ is fast and efficient, eliminating the need for mount animals, animal training, and specialized laboratory and animal handling equipment. Nearly anyone can be trained to use an electroejaculator, and in recent years automated machines that use a preprogrammed series of electrical stimulation have been developed, enabling even the most inexperienced individual to operate with confidence. The one significant disadvantage of EEJ, however, is the widely held misperception that it is painful. Due to this its use has been forbidden in several countries. [3]

      In the USA, EEJ is still widely used to collect semen from bulls for presale or prebreeding breeding soundness evaluations, but as is the case with many other previously accepted management practices, the potential discomfort of animals enduring these procedures is being increasingly scrutinized. At the core of the problem has been lack of widely disseminated critical knowledge to determine if EEJ is painful and to quantify the intensity of the pain. Certainly it was known that EEJ without anesthesia was painful for humans [4, 5]; therefore it must also be painful for bulls [3]. (Editor's note: see also [6].)

      The first published report on the use of EEJ in domestic animals was in 1936 [7–9]. Rams were the first animals experimented with, and although attempts to electroejaculate most species of animals have been made, the technique has been most successful with rams and bulls [9]. Electroejaculators are designed to use AC or DC power and consist of a box containing a step‐down transformer to reduce the source current and a variable transformer to enable the electrical stimulation to be modified [10]. Electrical stimulation must be carried to the pelvic nerves; specifically, the pudendal nerve, located near the prostate over the pelvic urethra responsible for erection; and the hemorrhoidal nerves, located in the area of the ampullae and seminal vesicles responsible for ejaculation [9]. To accomplish this task, a solid rectal probe at least 30 cm long and at least 6 cm in diameter containing bipolar electrodes is used. Rectal probes on early models consisted of alternating, bipolar electrode strips or rings capable of providing electrical stimulation over their entire circumference. This design resulted in unnecessary stimulation of the muscles of the hindquarters reportedly causing undue discomfort and temporary paralysis in some animals [11]. This led to the development of finger‐electrodes in which bipolar rings were fitted to the index and middle fingers in such a way as to avoid them coming in contact with each other. This device enabled the operator to apply electrical stimulation specifically to the urethral muscles to cause erection, followed by stimulation of the seminal vesicles to achieve ejaculation [11]. A disadvantage of the finger‐electrode system was that two persons were needed to coordinate semen collection because the principal operator was unable to see if erection had occurred and when stimulation should be moved to the seminal vesicles [9].

      Most probes in use today have three longitudinal electrodes. Probes with the electrodes divided into three segments have also been developed and are referred to as segmented probes. There are three caudal electrodes, three