Mazza, Serena (2009) Sessaggio del seme bovino, tecniche e prospettive di mercato. [Laurea triennale]
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From years the possibility of offspring sex pre-selection has been a dream for breeders, mainly for dairy farms’ owners, with the aim to plan exactly the animals quota for the farm replacement. Besides, in this way, there would be the opportunity to use the remaining animals for inseminations with beef cattle bulls or embryos, having, in this way, another income. To obtain as result the separation between X- and Y- spermatozoa, during last years lot and different technologies were studied, also due the discovery of the exact difference of DNA content between male and female spermatozoa. Between these technologies it’s possible to mention electrophoresis, use of H-Y antigen, centrifugation with albumin columns or Percoll density gradient, and gel-filtration in Sephadex columns. However these procedures had relevant limits, as the lost of spermatozoa motility, a semen purity level not suitable for a satisfactory insemination and, last but not least, a lower conception rate. In order to reach the more convenient possible results, for semen purity and also from economical point of view, during years lot of efforts were done to improve the only technique today considered valid for sexing procedure: flow cytometry. This technique uses fluorescent matters that, linked with spermatozoa, give more or less fluorescence in relation with DNA content, with more “light” for X-spermatozoa, as they are bigger with more DNA, and less for Y- one. Actually, also this mechanism shows lot of limitations, as: procedure slowness; less spermatozoa concentration in the final product, due an high loss of these, because not well oriented in order to show the fluorescence; less fertilizing capacity. Despite all above, as regards with all techniques to be considered up today obsolete, flow cytometry allows about 90% of sexed semen purity. For this reason it is considered the only efficient procedure for sex pre-selection. However, all breeders who decide to use sexed semen must strictly follow the insemination procedures and some guide lines in order to obtain the maximum result despite the less spermatozoa concentration. The commercial availability of cryo-preserved sexed sperm for bovines represent a very important innovation in managing this species reproduction. 4 Unfortunately, sexed semen doses have still a very high cost in comparison to the conventional one: for sure this is the main reason why we still see a limited use of this product. Probably, a better evaluation of costs/benefits ratio will bring to a totally different development of this interesting procedure.
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