With the breeding season in motion on spring calving suckler herds, it is important to keep an eye on the stock bulls that are currently in action.
Completing bull fertility tests before the breeding season begins is advised, as issues can be identified and therefore any threat of a surprising issue occurring during breeding will be reduced.
One issue that can be an problem during the breeding season is subfertility in breeding bulls.
According to Teagasc, subfertility is estimated to affect 20–25% of bulls, and is an insidious condition with an economic significance, given that it cannot be readily identified during a typical bull breeding soundness evaluation (BBSE).
Causes of subfertility
There are a few potential factors that may result in a level of subfertility which includes; a bull having a low libido, sperm defects, or physical factors affecting bull mobility or mating ability.
In terms of the impacts that reduced fertility can have, it may lead to a longer calving period if not identified – while also creating an economic loss and distress to herd owners.
Keeping in mind that a subfertile bull may still be capable of getting some cows pregnant, Teagasc has highlighted that the condition will result in low pregnancy rates, an extended calving interval, reduced calf weaning weights and higher involuntary culling of cows for barrenness – unless the bull is operating within a herd with a very low cow-bull ratio.
On many occasions, it is not until it comes to the scanning of cows that a subfertile bulls is identified, and this stage of the year has most likely progressed by the target breeding season period.
There is no guarantee that a bull will retain his fertility from season to season, or even within a season.
Therefore, farmers need to cast a watchful eye and be vigilant for potential fertility problems. The retention of breeding records from when when cows are bred, will aid in the monitoring of potential issues.