By: Glen L. Jensen, DVM

A complete bull breeding soundness exam is potentially one of the best investments cattle producers can make to insure a high level of reproductive efficiency. Reproductive efficiency has been shown to be 5 times more important than growth and ten times more important than carcass traits towards the profitability of cattle production.
A bull breeding soundness exam is not only supposed to find the infertile bulls but also the subfertile bulls. Subfertile bulls can and will get cows pregnant. The difference is that they will have a lower conception rate, meaning less cattle will become pregnant during each cycle. One of the sometimes overlooked, yet very important, aspects of reproductive efficiency is to have very high percent of cows calving during the first 21 days of the calving season and having a short calving season. A bull with as little as a 10% lower conception rate will cost a producer up to $15,000 over a five year period on just 30 head of cows. These losses include decreased weaning weights, a slightly decreased calf crop, increased culling rates, and higher replacement costs. If a bull has a lower normal sperm count at the time of turn out it will have the very potential to cost in lower conception rates.

Understanding the results of a bull breeding soundness exam is very important. For a bull to pass a breeding soundness exam it needs to have a minimum sperm motility of fair and 70% normal morphology (cell structure) in order to pass. The bull also needs to be free of any injuries or abnormalities to any part of the reproductive track including the testicles, prepuce, penis, and internal accessory sex glands. The legs, feet and eyes have to be free from anything that could jeopardize the bull’s ability to breed.

The process of spermatogenesis (creating sperm cells) takes about 61 days, then it takes another 7 -13 days of maturation and transportation through the epididymis. Many bulls that do not pass are classified as differed. This is done because some damage to the testicles can change or heal. For instance if a bull had a fever or was in a very hot environment it will jeopardize the production of normal spermatozoa. It would take up to 74 days after the insult or injury to insure that the bull cannot or is not returning to normal. So rechecking at the end of 74 days or just before bull turn out would be optimal.

Young bulls that are not yet completely sexually mature may also have a lower normal cell count, some of these bulls, but not all of them, may improve as they continue to mature and have normal sperm production. “Only about 35, 60, and 95% of 12-, 14-, and 16-monthold bulls, respectively, are reproductively mature and produce good quality semen (Barth 2000).” – See more at: http://www.thebeefsite.com/articles/1491/reproductive-fertility-in-herd-bulls/#sthash.Bra4lFVt.dpuf

Older bulls, 4 or 5 years and up will often start a slow process called testicular degeneration. In these bulls they will continue to go downhill and are very unlikely to ever improve.  It is estimated that at least 5% of older bulls will fail their bull breeding soundness exam. Turning bulls out without checking for the infertile and sub-fertile bulls can cost a producer thousands of dollars. Make this a routine every year. The best time to do this is as close to bull turn out as you can, just give yourself time and a way to get any replacements if needed. Remember that a breeding soundness exam does not evaluate libido (the bulls desire to breed). It is important to observe bulls often for libido and injuries during the entire breeding season.