19 May 2025
Will you have enough heifers in 2027?
With a significant drop in dairy heifer calf numbers in recent years, Stuart Childs, Joe Patton, and Laurence Shalloo stress the importance of breeding enough replacements to meet herd needs, urging farmers to plan ahead.
Recent statistics show that there has been a significant drop in the number of dairy heifer calves in recent years. For the period January to May 2025 there were 62,000 fewer dairy heifer calves born compared 2023 (ICBF).
It is recommended to maintain an 18-20% replacement rate annually, with 9-10% arising from cows not in calf at the end of the breeding season and allowing for a further 9-10% voluntary culling. For herds with performance issues such somatic cell count, herd fertility or low milk solids, a target replacement rate of 25% may be required in the medium term to allow for a higher culling rate.
Herds with capacity for growth should allow for production of dairy heifers surplus to the planned herd replacement rate, possibly producing 30-35 heifers per 100 cows depending on the circumstances. It is important to consider the implications for nitrates calculations in this case.
Additionally, with the increased incidence of TB nationally, having a slight surplus of heifers on the ground could allow herds return to normal numbers without the need to purchase stock thus maintaining a closed herd against other diseases. Therefore, it is important that dairy farmers ensure that they breed enough dairy replacements to meet their requirements.
Getting the desired number of heifer calves born in 2026
ICBF figures also show that only 78% of heifers calve down at the desired 2 years of age. This means that 22% of the heifer calves born don’t make the parlour at the correct age. This needs to be factored into the breeding plan to ensure that there are enough dairy heifers on the farm each year.
Scenario A: Normal Herd Fertility – 20% replacement rate
100 cows x 20% replacement rate = 20 heifers entering the parlour in 2027.
If 20 heifers entering the parlour in 2027 represents 78% of the heifers born then the number of heifers born needs to be 25 to still be able to bring through 20 heifers in 2027.
This can be done in several ways;
- Sexed Semen Only – Need at least 2 sexed dairy straws per heifer calf
- 25 x 2 = 50 sexed semen dairy straws to be used
- Conventional Semen Only – Need at least 4 dairy straws per heifer calf
- 25 x 4 = 100 conventional dairy straws must be used
- A combination of both sexed and conventional straws to generate the heifers
- 40% sexed and 60% Conventional – 25 Heifer calves x 40% = 10 heifer calves from sexed straws – 10 x 2 = 20 sexed dairy semen straws
- 25 heifer calves x 60% = 15 heifer calves from conventional inseminations – 15 x 4 = 60 conventional dairy straws required.
Then the dairy farmer should switch to fulltime beef AI.
Scenario B: Suboptimal Herd Performance
Firstly, the underlying reason(s) for poor herd performance needs to be identified and addressed. Adding more heifers to the system each year will not resolve the issue, and is not sustainable in the long term. However, affected animals (e.g. late calvers, low EBI cows, chronically mastitis-infected cows) will still need to be culled so a higher number of heifers is be needed as part of addressing the issue.
In this example, a 30% replacement rate with a 20% loss of heifers between birth and first milking applied will mean 36 heifer calves need to be born.
- Conventional Semen Only – Need at least 4 dairy straws per heifer calf
- 36 x 4 = 144 conventional dairy straws must be used
- Sexed Semen Only – if you have poor herd fertility, the use of sexed semen may be questionable in your herd in the absence of identification of the reasons for suboptimal fertility.
Summary
- Dairy farmers need to plan to have sufficient heifer calves born to meet the replacement rate requirements of their own herd and consideration should be given to risk of losses associated with a potential TB outbreak.
- Farmers should use 2 sexed dairy semen straws or 4 conventional dairy straws per heifer calf required to ensure they will have adequate numbers of heifer calves born in 2026.