Up to 90% heifer calves claim
Conception rates on a par with conventional semen are now claimed, resulting in between 60% and 90% of heifer calves being born — with conception claims depending on the company marketing it.
AI companies say using sexed semen could make for easier calving — by producing heifers from heifers.
Better genetic progress can come from breeding from the best of the herd, and sexed semen also makes it easier to operate a closed herd.
Sale of surplus heifers offers extra income.
Attention to detail and careful handling of semen are seen as key to conception rates from sexed semen.
Secure handling is needed for ease of management and more accurate insemination.
Pre-warmed AI equipment must be kept insulated until insemination. Use of an electric thawer, which takes 40 seconds to thaw one straw, at 37 degrees, is recommended.
Only one straw at a time should be removed for thawing, using tweezers, and thawed immediately.
Operators are instructed to thoroughly dry the straw, because just one drop of water can kill the sperm, and to use a clean, sharp scissors to cut off the sealed end.
They should inseminate within five minutes of removing the semen from the tank, and should not re-freeze semen.
As with all AI, the recipient cow should be in good health, stress-free, and gaining condition, and should be treated at the optimum time for insemination, which is 12 hours from the onset of standing oestrus.
Cows milking heavily or in a negative energy balance are less likely to go in calf.
It is not recommended to use high value sexed semen on cows with other problems.
Sexed semen has been adopted fairly widely in the US, where breeders are generally promised a 90% success rate.
Surprisingly, it is only just catching on in New Zealand, often a leader in dairy technology.
LIC genetics manager Peter Gatley expects it will take several years for demand to build up.
