Bull Fertility - the importance of bull testing
It is often said that the bull or ram is worth half the herd/flock. However, when it comes to poor fertility it can actually be worth so much more. Studies have demonstrated that approximately 1 in 5 bulls are sub- or in-fertile, the significance of which can be significant.
A 136 cow commercial, spring calving Hereford-X suckler herd running 4 continental bulls decided to change the breeding policy to satisfy a supermarket contract, replacing 2 of the bulls. The herd received their annual BVD and Leptospirosis vaccine prior to being split in to 2 groups and put to the bulls for 9 wks. The results of the PD session are shown below:
No. of cows
2 x original bulls
2 x new bulls
In herds with good control of infectious diseases, pregnancy rates of 90% in a 9 week period should be the lower threshold. In this herd, you can see that the original bulls have achieved this desired level while the replacement bulls have fallen well short. Fertility testing of these new bulls revealed a large proportion of dead sperm and very poor motility of the live sperm. This herd was heavily impacted by the poor fertility of the newly purchased bulls, leading to the sale of 54 additional barren cows and the purchase of in-calf replacements in order to maintain numbers. At the time, this cost £13k in replacement costs alone, without taking into account the cost of biosecurity measures and initiating vaccination programmes with the replacement stock.
This case demonstrates several important points:
• Good fertility should not be assumed
• Utilising the vet helps to prevent and detect problems (fertility testing the bulls would have prevented these issues, pregnancy testing the cows allowed action to be taken early)
• Maintaining good records allow performance to be monitored and improvements made