Completing a bull 'NCT' ahead of breeding

We are now in April and while there is still a focus on getting the last of the cows safely calved, we should now also be looking at next year’s crop of calves. One very important half of this equation is the stock bull.

Only 5% of stock bulls are infertile; however, 25% can be or become sub-fertile. The causes of sub-fertility in bulls are numerous – infection (either viral or bacterial, e.g. IBR), lameness, fatness, injury, etc. Therefore, it is critical that your stock bull is checked in advance of the breeding season. There are a number of important factors to consider in terms of stock bull functionality. These include:

• Daily sperm production and semen quality are related to scrotal circumference;
• The semen used to inseminate a cow today would have begun to be produced almost 10-11 weeks ago;
• Infections and viruses can cause sub-fertility;
• Bull mobility issues reduce conception rates.

The bull 'NCT'

The key areas to check when examining your bull as part of the annual ‘NCT’ include:

• Feet should be sound. Lameness will reduce his ability to mount and may be the result of an infection, which could cause a rise in body temperature and thus cause the bull to be sub-fertile.
• Ensure the bull is walking well. Mobility issues will reduce his ability to mate.
• Check the scrotum is clean and without deformities. A bull’s virility is directly related to the size of his scrotum, the bigger the better within reason. A mature bull should have a scrotal circumference of at least 34cm, while a young 17-month-old bull should be at least 31cm. The scrotum should feel like a bicep muscle, the testes should be balanced in size and all should be free from deformities.
• Check the penis is free from swellings and discharges.
• Give all vaccinations and any doses well in advance of the breeding season.
• Avoid stress as this can weaken the immune system, which may lead to viruses or disease, a rise in body temperature and thus reduced fertility.

Bulls should have been on a good plane of nutrition prior to the breeding season, as body reserves will be utilised when turned out with cows in the coming weeks. However, there is a fine line and bulls need to be fit and not fat. If sufficient time is available, a fertility test can be completed 6-8 weeks pre-breeding.

Once a bull has been turned out with the cows, observation is key. Record matings and watch for repeats. If there are several, you need to act quickly by removing the bull and instead use a different bull or AI. If you are selling weanlings, every cycle missed could be worth €100 per cow due to the sale of a lighter weanling (28 days x 1.2kg x €3/kg).

This article first appeared in the April edition of the Future Beef newsletter. For further information on the programme and to sign-up to the programme’s monthly newsletter click here.

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