How does semen sexing work?

Whether a cow calf or bull calf is created is decided in the fertilisation when an X-chromosome is added to a sperm (produces a cow calf) or a Y-chromosome is added (produces a bull calf). The objective is to enrich the sperms with the desired sex chromosomes (X or Y) and to remove the others, or at least to impede them.

The principle of semen sexing

A new generation sorter (of which there are 4 in Mülligen), can produce approximately 10 sexed semen doses per hour each with about 2 million sperm. To date it has not been possible to significantly increase the performance of the sorter. On the other hand, a reliable enrichment of X-sperm to over 90% has been achieved with this method.

Terms

Chromosome

Structure in the cell nucleus that contains the genetic substance (DNA). Chromosomes occur in pairs apart from in gametes and originate half from the father and half from the mother. In cattle there are a further 2 x 29 normal chromosomes in addition to the two sex chromosomes X and Y. 
Female animals receive two X chromosomes and male animals receive one X and one Y chromosome in their cells.

DNA

Abbreviation of the term DesoxyriboNucleic Acid. 
A thread-like molecule in the cell nucleus in the form of a double-strand. 
DNA contains the genetic code. 

Flow cytometry

Procedure for counting, examining and sorting cells and other microscopic particles in a liquid flow. The particles are marked here with a fluorescent dye.