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Interesting article on Bulls from the Western Producer

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Well-known member
Feb 10, 2005
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Southern Manitoba

By Roy Lewis DVM

One of the most frustrating conditions to hit our herd sires is testicular degeneration (testicles shrinking up). It often strikes without warning or reason. It causes headaches for both purebred breeders with bulls they have sold and for insurance companies with bulls they have insured.

In this article I will go over some known causes and what to be observant for. Often we cannot prevent this condition however early recognition of warning signs may prevent the economic ramifications it brings.

The scrotum and it's muscular attachments has the ability to expand and contract and in so doing raise and lower the testicles depending on the ambient temperature and body temperature of the bull. The scrotal temperature is normally lower than body temperature and must be maintained at that for normal sperm production. Anything that alters this greatly will affect normal sperm production and could over the long-term lead to testicular degeneration. It is important to note when even a temporary increase in scrotal temperature (say 1o C for 10 days) will affect sperm production for four to five months. Recovery will take a long time, which often as a producer you do not have the luxury of.

Any condition, which causes increased temperature in the scrotal area, must be guarded against. Severe clinical disease, swelling in the area as a result of trauma (stepped on or bunted in the scrotal area), testicular torsion all may result in degeneration over time. Extremely fat bulls have too much insulation in their scrotum raising the internal temperature. Frostbite will initially cause the damage freezing brings but as healing occurs inflammatory processes set up and these can cause local temperatures to rise. Most of these conditions may have been long past and may not have even been recognized before testicular degeneration is picked up at semen evaluation time.

The body also has a unique mechanism when it comes to the testicles. Any situation where sperm mix into the bloodstream causes the equivalent of organ rejection. The bull's body produces antisperm antibodies, which fight sperm production causing the testicles to degenerate. This could happen in any traumatic incident or with a testicular torsion. If surgery is necessary to remove a damaged testicle: if precautions are not taken the remaining testicle could degenerate as a result of either inflammation or sperm getting into the bulls blood supply.

There is a huge misconception out there that treating a bull with antibiotics will hurt sperm production. It is far, far worse to leave a medical condition untreated running the risk of increased body temperature than it is to quickly treat the condition. Having said that treatment with anabolic steroids or implanting can have devastating effects on the testicles because of alterations in hormone production.

Degeneration can happen to any bull at any stage in his life. That's why it's important to semen evaluate close to the breeding season in case anything has gone undetected over the winter. Testicles with degeneration will feel a lot softer and will measure much smaller than they did before. Sometimes only one testicle will degenerate such as from a bunt to only one side of the scrotum. If the other testicle is fully functional you will even see it hypertrophy (get bigger) and it may produce more sperm to compensate for the loss of the other testicle. These bulls will have somewhat reduced capacity but still may be fertile enough to use.

The most obvious clinical signs of degeneration are of course shriveled testicles and the scrotal hair will often grow longer. If you suspect degeneration or if the testicles are markedly swollen or frostbitten it is wise to have a semen evaluation performed. As mentioned before regeneration can take place but it is a rarer event. Plus this may take several months and depending on the season of the year you may not be able to afford the time. Anytime bulls are fighting excessively or you notice even slightly swollen testicles document it especially if the bull is insured. The insurance companies will need some form of documentation because testicular degeneration is such a gray area when it comes to insurance. Primarily because we often don't know what the initiating cause is.

Spontaneous degeneration can occur at anytime in a bull's life but is more common in older age (> 5 years). That is why it is imperative to semen test all older bulls yearly. If you have a past history of scrotal size you can pick up degeneration in the early stages and eliminate the bull. It is not uncommon for scrotal size to vary up to 2cm depending on fat cover and season of year. An experienced veterinarian will pick up the palpable softness of the testicles along with the multitude of sperm defects, which accompany degenerating testicles.

The bull's testicles are one of the most important anatomical organs when it comes to breeding ability and fertility always keep a close eye on this investment. Diligent observation and subsequent testing can eliminate potential disasters in your breeding program when a bull degenerates.

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