Today, achieving to the premium female calves is an important issue in the dairy industry. Therefore, the use of biological relationship and new technologies can make it possible to achieve this goal. One of the methods that can be used today to identify eligible cows is the relationship between the level of various amino acids in the blood and the amount of blastocyst production per female animal. Therefore, the present study aimed to investigate the relationship between blood amino acid concentrations at ovulation and in-vivo embryo production. For this purpose, 50 Holstein heifers of age (10±2 month) and weight (250±50 kg) were used. All heifers fed the same diet during experiment.. This study was conducted in FKA Dairy complex during winter and spring of 2019. Iheifers were divided into two groups at the time of ovulation in a completely randomized design based on the rate of blastocyst production and amino acid concentration: A) heifers that did not produce blastocysts and B) heifers that produced blastocysts. The heifers were then classified into three groups in order to determine the association of blood amino acid concentrations with different percentages of blastocysts: group 1) ovulated heifers that did not produce blastocysts; 2)group 1 that produced blastocysts, 3) heifers that produced 40 to 80 percent of blastocysts. Heifers entered the estrus and ovulate by injecting FSH. The ovums were then inoculated with OPU in vitro and the percentage of blastocysts formed per heifer was recorded on day 7 after breeding. concurrently, blood samples were taken from each heifer after OPU and the amount of essential, semi-essential and non essentialamino acids was measured. The results showed that the concentration of glutamic, histidine, glycine, tyrosine, asparagine, citrulline, threonine and isoleucine, valine, phenylalanine, leucine, lysine, ornithine was directly and positively correlated with blastocyst production (P 0.05). Compared with group 1, it was found that the concentrations of lysine, threonine and ornithine amino acids in blood were significantly (P 0.05) hiigher in the group 3. Also, Animals with the highest levels of blastocyst production had the lower concentrations of glutamate, histidine, glycine, tyrosine, lysine, leucine, ornithine, valine and phenylalanine, asparagine, asparagine. This findings showed that the increase in the level of some amino acids in the blood was significantly correlated with the level of blastocyst production (P 0.05). The results show that blood amino acid index can be used to predict embryo production. Keywords: Blastocyst, Essential amino acid, Holstein heifer's embryo, Embryo transfer
