8 Evaluation of Breeding Soundness: The Physical Examination

       Mike Thompson1 and James Alexander2

       1 Willow Bend Animal Clinic, Holly Springs, MS, USA

       2 Alexander Veterinary Services, Bentonia, MS, USA

Introduction

      When a bull breeding soundness examination (BBSE) is performed for the purpose of evaluating a bull's potential to breed in a natural service situation, the physical component takes on paramount significance. In fact, as soon as any physical abnormality that would impede natural service is observed, or the bull does not meet the minimum standards for scrotal circumference (SC), the examination need not proceed to evaluation of semen characteristics. Thus, goals of the physical examination portion of a BBSE are the identification of undesirable genetic traits, structural or physical impediments to breeding, and pathology of the reproductive tract. Even though it is common for inadequacies to exist in this area of the BBSE, it is often ignored or rushed through without attention to detail or in a consistent systematic manner. Therefore it is of utmost importance that the physical examination be done using a consistent protocol. Additionally, the SC, which is an indirect metric for testicle size and thus sperm production potential, must be measured and meet minimum standards.

History

      The history can be addressed prior to or during the physical examination. The history can provide the examiner with insight into genetics, condition, management, vaccination, any disease testing programs, and history of disease in the herd. The breed or breed composition should be obtained to help establish what genetic abnormalities or which conformation traits, maturity rates, and age of puberty may be common to that breed. The ration fed previously and at present should be established as well as the level of each ingredient in the rations and the poundage fed to each bull. The veterinarian needs to determine what body condition scores were attained at different stages of development. Management practices should be established with regard to large or small group facilities, parasite control, pasture or dry lot, through space, and water availability. These management practices can influence the level of foot problems and increased incidence of diseases such as vesiculitis. The herd vaccination program should be ascertained, if for no other reason than for buyer information. Information on disease control programs should be established for buyer information and the reason for those programs. The history of disease in the herd may explain the results of the BBSE examination and again be useful information to the herd owner and/or buyer.

Basic Physical Examination

      For a bull to survive and function as a natural service sire (pasture or range environment), he must be able to walk, eat, see, and bear weight on his back legs. Thus, a basic examination should begin with a history, examination at a distance, and an assessment of a bull's conformation, gait, and overall appearance.

      Examination at a Distance

If possible, the bulls should be observed from the fence of the holding pen while they are standing quietly. This is a good time to observe their conformation, and overall appearance. Bull identification numbers are collected for those that will need closer examination for any problems that may be seen. Move through the bulls slowly while noting any other problems. This is a good time to observe each bull's gait, possible foot issues, sight deficiencies, and bilateral symmetry. If they are being unloaded at a veterinary facility for BBSE, watch them as they are being unloaded as stepping off a trailer can exacerbate lameness signs that you can check more closely. The absence of bilateral symmetry is the examiner's guide to areas of potential abnormalities.

      Conformation

Selection for conformation has been influenced by judges for show purposes and is not always the conformation most desirable for durability of the bull in a pasture or range environment. Because a bull is required to cover large areas and mount and lunge multiple times in a single day, feet and legs are often the trait that determines his ability to service cattle and his longevity as a sire. Hoof and hock abnormalities lead to lameness, which affects his ability to accomplish this purpose, as well as lowering sperm quality. Screw claw, chronic laminitis, and interdigital fibromas are common. The incidence of screw claw (Figure 8.1) appears to be increasing in beef breeds and is considered heritable by the American Association of Bovine Practitioners Lameness Committee [1]. Moving up the legs, stifle and hock injuries such as collateral ligament rupture, meniscal injuries, and anterior cruciate ligament (ACL) rupture should all be investigated as they will interfere with copulation and fertility [2]. Less common and sometimes more difficult to diagnose are shoulder injuries and spinal injuries or disease [2]. These abnormalities should be recorded in the feet and legs section of the BBSE form. Defects that may be inherited should be listed in the comment block with a statement that recommends use in a terminal cross only. Research has shown that animals with shorter hoof length and greater dorsal hoof angle develop less hoof lameness [3]. Dorsal hoof angles of 50 and 55° in the rear and front hooves, respectively, appear to be the more desirable. The angle of the hock should be between 155 and 170° – this being based on information derived from the Conformation Determination System (CDS), which was a method of relating hock angles of dairy heifers with other anatomical landmarks and then correlating those metrics with the incidence of future unsoundness [4].