The aim of the present report is to describe the procedure followed for sexing embryos on the field using the french DNA probe (INRA patented). The procedure was first tested in conjuction with Rhone Merieux (G. Kohen), the biopsies were performed in farms and sent to the Central Laboratory of ours in Maisons Alfort for sexing. The second step which started in early 1991 is to sex the embryos in laboratories included in the AI Centers facilities, close to the farms, where the embryos are collected and biopsied. The results reported here however are essentially issued from the first step of the experiment. From 241 biopsied embryos, 88% had their sex determined in the laboratory, and 8% were questionable at that stage. The accuracy of unquestionable sex determined embryos was under these circumstances 100%. The sex ratio from the 212 sexed embryos was 48% females, 52% males. From the 61 biopsied embryos that were since then born, the calving rate was 54% (fresh embryos). In addition, some in vitro fertilized embryos (n = 53) were also sexed and 36% of them were females.
