With many people interested in using sexed semen for the upcoming breeding season, many are probably wondering how many straws they will need to achieve their target number of female dairy bred calves.
In this video, Dr Stephen Butler, Teagasc Moorepark gives an overview of how you make the calculation, based on the size of your herd.
The calculation, by Dr Butler, of how many dairy heifer calves you can expect to achieve from the 25 heifers is as follows:
- Targeting 30 dairy heifer calves from a herd of 100 cows and 25 maiden heifers;
- All 25 maiden heifers are eligible for sexed semen;
- Beef semen or a stock bull to be used after the first round of AI;
- Heifers have 60% conception rate to sexed semen, whereas cows only have 50%;
- Sexed semen has a 90% sex bias.
- = 13.5 dairy heifer calves from 25 maiden heifers
This calculation means that a further 16.5 dairy heifer calves are needed from the cows. The calculation for how many sexed semen straws you will need, as explained by Dr Butler, is as follows:
- Assumed that all will be given conventional AI after first round of servicing;
- 50% conception rate for cows;
- 90% sex bias in sexed semen;
- = 37 straws needed for cows.
Total number of straws needed = 62