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Age of Your Bulls

THE AGE OF YOUR BULLS is a factor that can affect bull fertility and performance.

Young bulls [23]

Some cattle producers with experience in managing yearlings often say that they prefer them because they settle in better, mix with other cattle more easily and are easier to handle than older bulls. They are free of the structural problems that beset older bulls and there is potential to extend the working lives of the bulls by a year or more, thereby lowering the bull costs of a herd. However, yearling bulls are usually sexually inexperienced, are more likely to be sexually immature, and their health and body condition are far more sensitive to poor nutrition. Although poor management can reduce calving percentages, compromise animal welfare and limit their lifetime potential, yearling bulls have much to offer, both genetically and financially.

Younger bulls are best joined with their own group. Younger bulls are very prone to injury, especially the prepuce and penis, due to overzealous serving behaviour. Do not over-mate younger bulls (12–15 months) (maximum: 25–30 females).

In order to harness the potential of yearling bulls, consider:[23]

  • 1joining them either alone or with bulls of the same age. Mixing ages of bulls in mating groups or mixing bulls shortly before or during mating may cause low bull fertility and conception as a result of establishing dominance within the herd[20 ]
  • join yearling bulls for 6–8 weeks (2 cycles) only, then spell them for at least 3 months
  • after removing yearling bulls from their joining groups, place them on high quality feed in specially prepared paddocks

TIPS


Bulls that are well grown at 15 months of age can be used lightly over 15–20 females (usually heifers), provided there is no large disparity in height in favour of the females.[12]


Yearling bulls are usually sexually inexperienced and may be a little clumsy and awkward. The learning phase may cause minor delays to the start of calving.


Newly purchased young bulls should not be multiple joined with older herd bulls. They will not be allowed to work much and in keeping them away from the cows, the older, dominant bull will knock them around.[8]



Older bulls[8]

Older working bulls also need special care and attention before mating begins.

They should be tested or checked every year for physical soundness, testicle tone, and serving ability. All bulls to be used must be free-moving, active and in good store condition. Working bulls may need supplementary feeding before the joining season to bring up condition.

All bulls should be drenched, treated for lice, vaccinated with 7-in-1 (leptospirosis and key clostridial diseases) and for vibriosis and pestivirus annually. They may need vaccinating against three-day sickness in some areas.

Older bulls (>5 years of age) are more prone to diseases than younger bulls. They should be checked to ensure they can be retained in the herd.

A pre-joining bull breeding soundness examination should be conducted.