In the higher standards of milk production, the priority in modern breeding is keeping dairy cows in high lactation and healthy. It is known that highly productive animals compared to those who produce less are in a more or less negative energy status. The negative energy status mostly appears during three situations: in late pregnancy, in the first weeks of lactation, and during disease. Thus, priority for higher milk production is prevention of metabolic disorders and other diseases. According to animal nutrition experts, to prevent a negative energy balance, particularly during the transition period, fat supplement can be used. Fat supplements used in this study; granulate fat soybean meal that was added to the concentrate part. This study was performed at the Animal Husbandary, Unit, College of Agriculture, Isfahan University of Technology, located 40km western south of Isfahan, Iran. Twenty-four two and multiparous Holstein cows (with mean body weight 700 ± 50 kg in first period) were used in a randomized complete design experiment to determination effect of Supplemental fat on gene expression, composition and milk yield and liver function in transition period. Cows before calving were divided into two group and one group received control diet (include %73.3 corn silage, %7.2 alfalfa hay, %2 wheat straw and %20.5 concentrate) and another group fat supplement (include %59.5 corn silage, %8.4 alfalfa hay, %8.6 wheat straw and %23.5 concentrate include %2.5 fat soybean meal). In after parturition cows divided two group again, and one group received control diet (include %65.5 corn silage, %5.5 alfalfa hay, and %34 concentrate) and another group fat supplement (include %59 corn silage, %7.5 alfalfa hay and %33.5 concentrate include %3.5 , fat soybean meal) as cows under experiment were included four groups: 1. Group fed with control diet pre and postpartum. 2. Group fed with control diet pre and fat diet postpartum. 3. Group fed with fat diet pre and control diet postpartum. 4. Group fed with fat diet pre and postpartum. Milk production was recorded at each milking. Samples were obtained the end of every week during the experimental period and analyzed for determination milk component. Blood samples were obtained before morning feeding as weekly of 14d before the expected day of parturition until 28 d after parturition. Data were analyzed using repeated measures of the mixed procedure of SAS. In this study, was assessed calcitonin gene related peptide (CGRP) gene expression and It was found that this gene in liver tissue of dairy cows (up to 60 days of lactation) the ability of expression, but is probably based on the research findings in liver tissue bulls and cows dry period is capable of expression. As variety of amino acids this gene had most homology in cattle with the sheep, mice, rats and dogs, thus if needed can be determined as this factor in the blood ¬ bovine function can increase cattle performance.