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Toxic sperm - a hidden problem

Did you know that it takes up to about 70 days to make, package and deliver sperm from the time the cell first divides in the testicle until it fertilizes an egg?

This has serious implications. If I did something that stopped the formation of new sperm for a week, the result would be a lack of sperm in the ejaculate for a week. The trouble is, that this week of infertility might not occur for another 60-70 days, long after the insult I gave to the bull was forgotten.

Similarly, If I did something to the bull that killed off all the sperm undergoing formation in the testicles, there would be no viable sperm for up to 70 days!

It’s quite difficult to kill off all the sperm undergoing formation in a testicle, but it’s really easy to damage sperm slightly, and believe it or not damaged sperm is more dangerous to herd fertility than dead sperm.

As part of sperm formation, several feet of DNA must be very carefully folded and packaged down to a minute size and stored in the sperm cell. This takes a long time (weeks) and the process is very delicate. If there is an interruption when the sperm is being packed up, chances are that it will not unpack correctly either. This is called “Toxic Sperm”. These sperm are quite capable of swimming and fertilizing an egg, but the egg so fertilized will never produce a calf – it will die when it gets to the DNA unpacking phase of development.

These “toxic sperm” are dangerous because they waste eggs.  Eggs can only be fertilized once !

If you have two bulls in a paddock, and one is releasing toxic sperm, then every egg  that bull fertilizes is a guaranteed non-pregnancy.  The other bull cannot compensate in the way that he perhaps could if the first bull had a penile injury and was unable to serve cows at all.

So, what causes toxic sperm ?

Here lies the problem.  It is minor insults that damage sperm enough to make it toxic, while major insults will tend to kill it off altogether.  Sperm that is damaged in a major way (and for example cannot swim or fertilize an egg) can easily be compensated for by good sperm.  Minor damage can cause bigger herd fertility problems than major damage !

“Insults” that can cause toxic sperm include:

  • prolonged stress (cortisone is released into the blood and this causes toxic sperm)
  • High Temperatures (testicles hang down for a reason) caused by fever or sitting down too much
  • Diet(especially high grain diets) and various toxins

At a practical level, toxic sperm causes might include prolonged transport, the stress of moving farm into a new social group, disease, lameness, and high grain diets.  After these events, the bull will look perfectly normal, and may not start to produce toxic sperm for several weeks.

I worry that this a vastly under diagnosed problem.

Lets say Farmer Fred purchases a bull, and in hot weather ships it to his new farm (which takes 2 days) where it is bashed around for a week by the senior bulls after arrival.  This might cause a toxic sperm event such that there will be a 2 week period of toxic sperm starting in 40 days.  This is very likely to be during the joining period.


Preventing toxic sperm

Here are two ways to help avoid toxic sperm causing problems on your farm:

  1. Own and have control of the bull for 70 days before joining.
    This will give the Bull time to settle in, and if the bull is in your control for that time, you should be able to identify any likely “Toxic Sperm Events” that might occur.
  2. If a bull has a potential “Toxic Sperm Event” (i.e. the bull gets sick, lame etc.) give him 70 days off.
    Remember that a Bull that was lame for a week is likely to be at best infertile or at worst toxic at some unknown time in the next few weeks. Better safe than Sorry !

– David S. Beggs BVScMVS