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Efficacy of a New Post-thaw Method for Altering the Sex Ratio

Posted: June 20, 2008

The Heifer-Plus™ kit has become commercially available for treating bovine semen immediately post-thaw to alter the sex ratio of offspring.

Recently a kit has become commercially available for treating bovine semen immediately post-thaw to alter the sex ratio of offspring. It is called Heifer-Plus™. Several inquires have been made about the efficacy of this methodology that can be used on the farm. Based upon the results from trials conducted by the company using a very limited number of animals it was concluded that this method altered the sex ratio of the calves born. More recently results from three research trials reported at the Annual Conference of the International Embryo Transfer Society in January 2008 (Proceedings of the conference published in the journal Reproduction, Fertility and Development) showed there was no numerical or statistical alteration of the sex ratio using this method.

In the first experiment involving 265 embryos, the control semen group (not treated with Heifer-Plus) actually generated a significantly greater number of female embryos (65%) compared to the Heifer-Plus treated semen samples (43%). In the two subsequent trials using artificial insemination of synchronized cows there was no statistical alteration in the sex ratio as determined by fetal sexing via ultrasonography or calving records.

In addition, based upon computer assisted evaluation of sperm motility of semen from six bulls there was no difference in progressive sperm motility between control semen or Heifer-Plus™ treated samples.

In summary, to our knowledge there is no commercially reliable method to treat semen following thawing to alter the sex ratio. Remember proper handling of frozen semen prior to and following thaw is critical to achieving success with artificial insemination.

Mike O’Connor, Dairy and Animal Science Extension and Jon Oatley, Assistant Professor of Reproductive Biology, Department of Dairy and Animal Science
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