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On Feed - March 22, 2019

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The New Herd Bull

Sale season is here and in full swing and if you haven’t purchased your next herd bull already, you may still be planning on it.  So after you write the check and load him up, there are things you can do to make sure that your new bull lives up to your expectations and his genetic potential.

Most of the bulls sold are just yearlings.  They are far from done growing and we need to remember that when we haul him home and put him in back 40 until we are done calving.  These bulls need to be maintained on a high level of nutrition, including protein, energy, vitamins and minerals in order for him to be a successful breeder in a couple of months.  Protein required for young bulls will vary but around 10-13% protein would be necessary to keep him growing, putting on muscle, and priming the immune system.  Energy required is going to be the most variable nutrient.  If we get the bulls overly fat, then the fat in scrotum can negatively impact semen quality.  However, if the bulls are underfed, they don’t grow properly and won’t have the body condition necessary to make it through the breeding season as an active breeder or be able to cover all of the cows you expect he should.  Bulls could lose 100-200 lbs during the breeding season, so  we want those bulls to be in AT LEAST a BCS 5 prior to turn out.

In a Nutshell

  • We need to supply good nutrition to young bulls
  • Young bulls need at least 10-13% protein in a ration *Bulls should be in at least a BCS 5 prior to turnout
  • Trace mineral nutrition is critical for bulls
  • Complexed trace minerals improve bull fertility
  • Breeding Soundness Exams help determine fertility
  • Consider bedding bulls to maintain fertility

Trace mineral nutrition is a critical component of bull nutrition. 

Zinc in particular is required for semen production and a lack of that mineral could result in more deformed or immature cells and poor motility at semen testing.  Zinc and copper are both important for foot health, and there isn’t much that will cause more problems with getting cows bred than lame or injured bulls.  Remember, semen production occurs 60 days prior to breeding and so we need to have those quality trace minerals in BEFORE bull turnout.  And, if you test your bulls, you want to have good nutrition prior to that so you have the most accurate sample for evaluation.

Trace mineral source can impact fertility. 

A higher quality mineral source, like complexed trace minerals from Zinpro, help overcome mineral antagonism that can happen when we have high sulfates, iron, or molybdenum.  Zinpro has conducted studies evaluating semen quality and found that bulls supplemented with the complexed trace minerals had more motile sperm and a greater percentage of motile sperm with rapid motility than bulls supplemented with standard minerals (like zinc sulfate and copper chloride).   Products like Ultimate Breeder 8 and Stress Tubs supply Availa-4 trace mineral nutrition.

Comparison of Standard vs Availa-4 Minerals on Semen Quality Chart

It is a good idea to have all of your bulls undergo a Breeding Soundness Exam to help ensure a successful breeding season. 

A Breeding Soundness Exam will include physical examination of the bull, examination of the reproductive tract of the bull, measurement of scrotal circumference, and semen collection and evaluation.  Bulls that fail to pass a BSE are sub-fertile and will likely have an impact on the percentage of open cows that you get at pregnancy testing.  If your bulls pass a semen test, there is a better chance that your cows will get bred.   And, bulls should pass a BSE every year because their status can change because of injury, weather stress, or age.  The veterinarian testing your bulls should be able to explain to you the criteria they use to determine whether they pass or fail a bull based on a Breeding Soundness Exam.  Research by Wiltbank and Parrish  (in the table below) evaluated pregnancy rates for over 2,000 cows mated to bulls known to pass a BSE or untested bulls and found a 5-6% increase in pregnancy rates when bulls passed a BSE.  That may not seem like a high percentage, but when you think about the difference in the number of open cows you could have and the difference in value between open and bred cows right now, 5% is a big number.  If you hear that the bull has some motile sperm and that he will breed some cows, be aware having a sub-fertile bull isn’t going to do us a lot of good.  You should also talk to your vet about any vaccinations you should give and a deworming program for your bulls.


Pregnancy Rate after 90 days


All bulls passed BSE

Untested Bulls

Year 1



Year 2



Adapted from Wiltbank and Parrish, 1986

Bedding the bulls ...

... when the temperature starts to drop is another thing you can do to help ensure fertility of your bulls.  The extreme conditions this winter may mean the bulls will have decreased fertility.  When breeding soundness exams are done, it is not uncommon to find scabs on the scrotum.  That is an indication of damage to the testes that can have a negative impact on fertility.  The duration of impact on semen quality after that injury like frostbite is almost impossible to estimate, so put out some bedding to keep the bulls more comfortable when the weather goes downhill.  Remember that extreme heat during the breeding season can also impact fertility during the breeding season.

Bulls comprise a huge amount of the genetics of your herd for the years to come.  With the investment that we make in purchasing bulls for our herds, we need to hold up our end of the deal and take care of the bulls nutritionally so they can perform to their full genetic potential. 

Roxanne Knock, PhD

Mineral Promotion ends March 29th

What do you need to be thinking about this time of year?

  • Get prepared for calving- get chains, OB sleeves, lube, and calf puller in place and colostrum replacement on hand
  • Think about ramping up your mineral program for cows prior to calving, ask about Ultimate Breeder 8
  • Consider having Land O’Lakes Electrolyte Complete or Calf Insure on hand for stressed or scouring calves
  • Scrape pens when possible to help avoid foot problems
  • Set up an implanting protocol for calves to finish
  • Get Stress tubs for the first and second calf heifers
  • Feed Rumensin to the cows to improve feed efficiency and to limit environmental coccidia prior to calving
  • Remember to get MGA if you are planning to use a synchronization protocol for your heifers to calve early

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