Artificial insemination using female-specific semen may be used to enhance the Irish dairy herd.
Teagasc researchers are running trials to examine any benefits to be gained from using ‘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 — ‘sexed semen’ — is increased numbers of heifer calves born, with approximately 90% of successful pregnancies resulting in a heifer calf.
Dr Stephen Butler is leading the trials at the Teagasc Animal and Grassland Research and& Innovation Centre at Moorepark, Co Cork.
“The subsequent increased availability of replacement heifers could form a pivotal component of the 50% increase in milk output targeted in Food Harvest 2020,” he said.
Other benefits of sexed semen use include reduced incidence of calving difficulty, as heifer calves are smaller than male calves, allowing 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. “Only 10% to 15% of the original sperm population entering the flow cytometer are recovered as marketable sexed semen,” said Dr Butler. Furthermore, 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.
Dr Butler explained: “Data from recently published studies conducted in the US, Denmark, Switzerland and China indicate that conception rates achieved with frozen-thawed sexed semen in maiden heifers are approximately 75% of those achieved with conventional semen. For example, this means a conception rate of 70% for conventional semen vs 52.5% for sexed semen.
“The reduction in fertility observed when using frozen-thawed sexed semen has, to date, restricted its use to inseminations on maiden heifers.”
Sexed semen is more expensive than conventional semen (€12 to €20 more per straw) and fertility performance will likely be poorer. Research is currently being undertaken to model the economic impact of using sexed semen in heifers and lactating cows on Irish dairy farms.
Initial observations suggest that use of sexed semen could have important implications for the rate of national herd expansion after the quota regime is removed.
Further results of the study can be found in the spring 2012 issue of TResearch, which is also available on www.teagasc.ie.
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