Teagasc researchers have been investigating if there is a role for using so-called “sexed” semen to expand the Irish dairy herd.
In the dairy industry, female offspring are more desirable than male offspring, particularly with the impending removal of the milk quota regime.
The principal benefit for dairy farmers of using semen specifically enriched with sperm containing X chromosomes is increased numbers of heifer calves born.
This can lead to approximately 90% of successful pregnancies resulting in a heifer calf.
Dr Stephen Butler of Teagasc said the subsequent increased availability of replacement heifers could form a pivotal component of the 50% increase in milk output targeted by the Government and the dairy industry.
Other benefits of sexed semen use include reduced incidence of calving difficulty, as heifer calves are smaller than male calves.
This allows farmers to expand herd size by generating greater numbers of heifers while maintaining a biosecure closed herd, and reducing the number of low-value male dairy calves born.
The current technology used to sort sperm containing X or Y chromosomes has a number of limitations.
Dr Butler said only 10 to 15% of the original sperm population entering the flow cytometer are recovered as marketable sexed semen.
Furthermore, he said, conception rates in heifers for frozen-thawed sexed semen are assumed to be 53%, compared to figures of 70% for conventional frozen-thawed semen and 66% for fresh sexed semen.
