Setting time of artificial insemination of superovulated lactating holstein cows with sex-sorted sperm

The embryo production results after use of sex-sorted sperm to inseminate superovulated cows (SOV) have not been very encouraging so far, due to the low quantity of sperms used as well as their short half- life. In a previous study conducted in Brazil in Holstein cows, it was shown that using the protocol of SOV P36/Lh60 and inseminating with sexsorted sperm at 18 and 30h (interval of 12hs between the two inseminations) after application of the inductor of ovulation it was obtained a similar quantity of transferable structures than inseminating at the 12 and 24h with non-sorted sperm. The aim of this investigation was to adjust the moment of the artificial insemination (AI) in superovulated and inseminated cows with sex-sorted sperm to achieve better synchrony with ovulations and by this way to increase the quantity of transferable embryos obtained. For this, we evaluated 2 moments of AI in which the interval between both were of 6hs. We used 30 lactating Holstein cows treated with the protocol P36/LH60 and, at insemination, were divided at random in three groups: 1-group AI18/30 (control group; n=10), the AI were carried out at the 18 and 30h after application of the inductor of the ovulation (GnRH); 2- group AI18/24 (n=10) the AI inseminations were made at 18 and 24 h after GnRH and 3- group AI24/30(n=10) the AI were made at 24 and 30h. In all cases, each insemination was doing with 2.1 x 106 sex-sorted sperm. The results between groups were no different in the quantity of transferable embryos (1,9±0,6;4,1±1,5 and 1,3±0,4respectively; p>0,05) nor in the proportion of transferable from total structures (38,8%; 60,1% y 34,1% respectively). In conclusion, the low number of cows in each group and the high variability of responses do not permit to conclude on significant differences in the alternatives evaluated. However, the numerical results lead to propose new studies to increase the number of animals treated and so, reevaluate these results