Most spring-calving herds are in week five of the 2022 breeding season, with many farmers about to turn out the bull – some, might have done so already.
The breeding season so far has gone quite well on farms, with grass growth coming at the right time for farmers.
But there has been a slight decrease in the amount of artificial insemination (AI) being used this year.
A number of factors have potentially contributed to this, such as better conception rates to first service, less cows being bred and farmers turning out their bulls earlier.
Farmers must be aware however, that turning out bulls too early could have a significant impact on a herd’s fertility performance.
This is because turning out the bull too early can result in him being overworked and potentially having a reduced level of fertility.
Speaking to Agriland, George Ramsbottom, a dairy specialist with Teagasc, said: “Turning out the bull while there is still a lot of heat activity will lead to him being overworked and result in poor fertility performance.
“This could result in an increased number of repeats later in the season and potentially a larger number of cows not being in-calf at the end of the season.”
Continuing, George said: “Farmers should hold off letting the bull out until week six or seven.
“Every three weeks that the bull is delayed being turned out, the number of cows not in-calf is halved.
“Farmers should continue to use beef AI for the next number of weeks until enough cows are in-calf, leaving the bull with a number of cows not in-calf that he can handle.”
So, before considering turning out the bull with the cows, it’s is important to have an idea of how many cows may actually be in-calf.
The target is to have a 90% submission rate after three weeks of breeding; of this, a 50% conception rate to first service should be the aim.
That would mean that on a 100-cow farm where all cows are being bred, 90 cows should have been submitted for breeding and 45 of them will hopefully have held to first service.
This means after three weeks of breeding that 45 out of 100 cows should be in-calf, but that also means that 55 cows are not.
If you turned out the bull after three weeks he has 55 cows to cover and a mature bull will struggle to breed that many cows.
So, waiting until week seven of breeding, where more than half of the remaining 55 cows should be in-calf, would leave a mature bull with a number of cows that he can handle.
This should result in a more compact calving and fewer empty cows at the ending of the breeding season.