South Africa

Health Care

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Preparing Bulls for the Breeding Season Part 2

(This is article 2 of 2 articles on this topic)

Bulls do not always get the necessary attention in preparation for the breeding season. The importance of the genetic contribution to the herd, the costs associated in the buying of quality bulls, and the necessity to optimize reproduction, forces us to attend to the well being and preparation of bulls to be performance ready!

The following areas should get the necessary attention (Areas 1 & 2 discussed in Part 1):

3. Vaccinations

3.1 Modified ”live” vaccines - 

Vaccination of live vaccines should be completed at least 60 days before the start of the breeding season as they can induce a fever reaction that could be detrimental to fertility. Vaccines that should be avoided includes:

  • Modified live BRD complex vaccines (BVD, IBR, PI₃, BRSV)
  • Rift Valley Fever
  • Lumpy-skin
  • Three-day Stiff-sickness

3.2 Inactivated (“dead”) vaccines -

Can / should be given closer to the breeding season:

  • Vibriosis
  • “Pinkeye”

4. Trace minerals 

Trace minerals plays an important role in bull fertility, especially Zn, Mn,Cu and Se. Sperm takes about 61 days to develop into mature sperm. Supplementation before breeding is critical to reduce oxidative stress and optimize semen quality and quantity.

An injectable trace mineral supplement (Multimin) should be given as a TOP UP over and above normal oral supplementation (licks):

  • 8 weeks before the start of the mating season. It supports optimal sperm development as demonstrated by Dr Ferreira (2015). Various semen parameters were significantly improved (P=0.05), whilst other were numerically improved. Don’t forget the synergistic Vit A & E support supplementation. 

  • Repeat supplementation at the start of breeding season to last the 3 month breeding season.

5. Parasite control

5.1 Internal parasites:

Internal parasites in cattle are generally seen as “less important”. Although not always as “visible” as with sheep, internal parasites could have a negative effect on the condition and performance of bulls.



Liver fluke in particular, can result in huge economic losses. In addition to all the other essential functions of the liver, it also regulates hormone production - which is critical in this pre-breeding period!


5.2 External parasites: 

Treat external parasites (ticks) as and when needed to prevent/reduce the transmission of tick borne diseases and mechanical damage of the scrotum and sheath. A tick burden can also effect negatively the appetite of cattle. Fly control will also reduce irritation that negatively impact on growth and condition.

6. General management

The following general management aspects can optimise the effectiveness of bulls during the breeding season:

  • Determine the number of bulls needed well in advance!
    • Cows: 1 bull per 25-35 cows 
    • Heifers: 1 bull per 15-20 heifers
    • Be prepared to replace bulls that become injured or sick
  • Newly bought bulls should be kept in quarantine and observed for at least 2 weeks before introduction to the bull herd or cows.
  • Observe new bulls after introduction to the bull herd to prevent excessive fighting and injuries. Keep separate if needed.
  • Use experienced bulls on heifers (signs of estrus not always as strong as with cows and last for a shorter time)
  • Fitness:
    • Train bulls daily - walk at brisk pace
    • Start slow/shorter time and increase for up to 30-25 minutes per day - especially those “over conditioned” auction bulls
    • Identify bulls with injuries, hoof and joint problems

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